September 8, 2023 • 49 mins
Joe McCormick and Jonathan continue their discussion about radio waves, transmitters and radio direction finding. How can you locate a transmitter and what is fox hunting?
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Episode Transcript
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Speaker 1 (00:04):
Welcome to tech Stuff, a production from iHeartRadio. Hey there,
and welcome to tech Stuff. I'm your host Jonathan Strickland.
I'm an executive producer with iHeartRadio. And how the tech
are you? It's time for another tech Stuff classic. This
time we are concluding a discussion that we started last
(00:26):
Friday with tech Stuff Goes Transmitter Hunting Part two. Joe
McCormick joined me for this episode Joe as a host
of Stuff to Blow your Mind, and we had a
discussion about transmitter hunting that I hope you will find enjoyable.
Take it away past Jonathan and Joe. So we need
(00:47):
to move into more of a discussion about radio specifically,
because even though radio is a subset of electromagnetic radiation,
it covers an enormous range of frequencies and therefore.
Speaker 2 (01:00):
And not all frequencies behave the same on Earth.
Speaker 1 (01:03):
True.
Speaker 2 (01:04):
Yeah, so you've got different bands you might have You've
seen terms like HF or VHF, FEU HF. These are
specific subbands of frequencies on the electromagnetic spectrum, all what
we would call radio frequencies. But so yeah, you've got
like high frequency, very high frequency, and a lot of
what we're going to be talking about today is going
(01:25):
to be in the VHF part of the spectrum.
Speaker 1 (01:27):
Yeah, that very high frequency. So yeah, this radio spectrum
is pretty broad and it goes well beyond the types
of radio that the typical person can listen into, unless
you happen to be one of those folks who you know,
maybe you operate a maritime radio to help with navigation,
in which case you are using frequencies most of us
don't touch. But or maybe you are a doctor working
(01:48):
with experimental medical imaging equipment, in which case you're using
radio frequencies on the opposite end of the spectrum, because
maritime radio uses very low frequency radio waves, whereas medical
imaging uses extremely high frequency radio waves. So the range
goes from the bottom is that like three herts, which
(02:12):
means you get three waves passing a given point in
a second, all the way up to tremendously high frequency,
which is three thousand gigaherts or three trillion hurts, meaning
three trillion waves pass a given point within a second. Actually,
I like extremely low frequency more because the acronym is
elf so elves. Elves communicate kind of like ense very
(02:38):
long wave forms. The elves at the bottom of the ocean. Yeah,
that's where we've stuck them. So again, you know, we
talked about how all these waves are traveling at the
speed of light, so it's really just the number of
waves that pass a given point in a second that
tells you a frequency, not speed of transmission, because that's
going to remain the same no matter what. So a
(02:59):
three hurts frequent and see wave will tell you that
the wavelength for that particular wave has to be a
one hundred thousand kilometers in length. That's a long radio wave,
one hundred thousand kilometers. Meanwhile, and the opposite end of
the spectrum, if you go all the way to that
three thousand gigahertz wave, you're talking about one hundred micrometers
in length. So teeny tiny micrometers are very tiny, huge
(03:24):
difference obviously in the length of these waves. So that's
why you know, the whole frequency wavelength relationship is important.
So we use the different frequencies for very specific purposes.
It's also important to point out that this is not universal.
There are usually some sort of governing body within a
(03:44):
country that designates what frequencies can be used for what purposes.
In the US we have the FCC. So if you're
looking at the terror hertz side of things, that's that
ultra ultra high or terribly high frequency as is some
sometimes referred to. It's for medical imaging, that kind of stuff,
(04:06):
also molecular dynamics measurements, and other high tech information. The
extremely low frequency would be like radio communication with submarines.
Can't You can't use very high frequency when communicating with
stuff that's underwater. The waves attenue are the radio waves
get attenuated by the ocean water, and that creates problems
with communication, But it's less of a problem with extremely
(04:30):
low frequency and very long wavelength radio transmissions.
Speaker 2 (04:33):
Now, what about the kind of radio we think of
as standard radio, as in radio accessible to the average
consumer AM FM. That kind of stuff, so AM would
be in the medium frequency. Medium frequency ranges from three
hundred killer hertz to three thousand kill herts or three
megaherts if you prefer AM radio specifically in the United
States is in an even more narrow range than that, right,
(04:56):
that's all of medium frequency AM radio in the US
goes from five hundred third five killer hurts to one thousand,
seven hundred killer hurts or one point seven mega hurts.
If you wanted to talk about short wave radio, that's
from five point nine mega hurts to twenty six point
one mega hurts.
Speaker 1 (05:11):
CB goes to twenty six point ninety six mega hurts
to twenty seven point four one mega hurts, and so
on and so forth.
Speaker 2 (05:18):
So so FM radio is going to be that's mega hurts, right,
So it's going to be around around one hundred mega.
Speaker 1 (05:23):
Hurts, yes, exactly. So yeah, because power ninety nine, that
would be at ninety nine mega hurts right, ninety nine
point one I think originally maybe.
Speaker 2 (05:32):
Starts high eighties, I think, yeah, and.
Speaker 1 (05:34):
Goes up to like one oh seven I think somewhere
around there. So different countries have allocated their broad broadcast
spectrum in different ways, so not everyone follows those exact
same rules. There's usually some overlap. Now, when you know
something about the wavelength of the radio frequency, that tells
you what you need, how you need to build your
(05:56):
antenna right, Because the length of your antenna is dependent
upon the frequencies you're looking for. You want your antenna
to be the right length to resonate properly with the
radio frequencies you're searching for. There's no such thing as
really a perfect universal antenna that can equally pick up
all frequencies across the radio range. Now, you might wonder,
(06:21):
how can you have like a pocket AM radio, because
if AM radio is broadcasting in the medium frequency and
has pretty long radio waves, and you need to have
an antenna that is the right length to pick that up.
Typically we're talking about half the length of the wavelength
(06:41):
of the radio frequency you're looking at right, So if
you're talking about like a wavelength that's one hundred meters long,
then you're looking at a radio antenna that's between forty
and fifty meters. How the heck do you fit that
on like that? That seems ridiculous. Well, the antenna for
AM radios are typical wire that are and that wire
(07:02):
is wrapped around the core. Because it doesn't matter if
the wire's straight or not straight or whatever, you can
you can coil it inside a device and have it
completely housed within the radio. So if you were to
open up an AM radio, chances are you'd find a
wire where one end is not attached to anything and
it's just wrapped around around around around around a core
(07:23):
of some sort. That's the antenna. It's it's not like
it's providing any sort of electrical stimulation apart from convert
you know, pulling in radio waves and having that induce
an electric current. So that's why AM radios don't necessarily
have a visible, incredibly long antenna. And this is important
(07:47):
when it comes to things like transmitter hunting.
Speaker 2 (07:49):
Yeah, because if you look at transmitter hunting sites and
we'll get into the specifics of the sport here in
a minute, you see a lot of jargon that obviously
has to do with stuff about like antenna length and
frequencies and stuff like that. One of the common things
you'll see is like the idea of a two meter hunt. Yes,
the two meter arena is often considered the sweet spot
(08:12):
for transmitter hunting. Now what does that mean When a
HAM radio enthusiast talks about two meters.
Speaker 1 (08:18):
They're telling you specifically about the size of the antenna
that they are using. To two meters is a pretty
decent sized antenna, right, like you know, a meter's like
here in the United States, we don't necessarily think in
terms of meters that frequently because we're not on the
metric system. But yeah, that's the reason is because the
frequencies that are being used by ham radio enthusiasts are
(08:41):
falling in the VHF radio frequency band, that very high frequency. Now,
that frequency band goes from thirty mega hurts to three
hundred megaherts, and the radio wavelengths go from ten meters
down to one meter. And we're using descending sizes because
remember as frequency increases, the wavelength decreases, right, So if
(09:03):
you're if you're hunting for a radio signal that's somewhere
in that that four to five meter range, you need
a two meter antenna in order to pick them up
effectively to have it be particularly sensitive to those transmissions. Now,
(09:23):
the specific range within VHF designated for amateur radio use
is in the United States one hundred and forty four
megahurts tow one hundred and forty eight megahertz. It's a
little different in Europe where it's one forty four to
one forty six.
Speaker 2 (09:37):
So stingy with it over there and not quite as
wide a range. Give us our two megaherts come on, yeah.
Speaker 1 (09:43):
And well, to be fair though, it's not the only
band for amateur radio. Amateur radio actually has bands and
several different frequency ranges. It's just for the VHF frequency range.
It's this specific UH range of frequencies from eight in
the US one forty four to one forty six in Europe.
But you can also find amateur radio frequency bands in low, medium,
(10:07):
and high frequency as well as all the way up
to like terribly fast, terribly high frequency. You can find
them up there too. Now, because of the wavelengths involved,
that two meter antenna is best able to pick up
those transmissions because it resonates more readily with transmissions in
that frequency. Yeah, like it can pick up stuff outside
of it, but not as effectively as the stuff it
(10:27):
was designed for. It's that's the sweet spot. So you
can build your own if you wanted to. There are
a lot of different resources, both online and in libraries
that will teach you how to build an antenna. I
watched one that actually was so cool that I think
I might do it as a project here at how
stuff works and do a video about it. What kind
of antenna was it would be? It would be a
(10:48):
quad antenna. I'll talk about a little bit a little
bit later.
Speaker 2 (10:50):
Mostly guys, now, I've been thinking about trying to build
a yacky antenna.
Speaker 1 (10:53):
Yeah, well, that would be great, both of them.
Speaker 2 (10:55):
As some of the Hams pronounce it, yaggy yaggy.
Speaker 1 (10:59):
Yeah, I think that that project would be really kind
of fun. And also I like the way a quad
antenna can look. I'll talk more about that in a
little bit.
Speaker 2 (11:12):
Anyway, Well, well, I challenge you to an antenna built off.
Speaker 1 (11:15):
That sounds great. Yeah, let's do it. Totally do it.
To be fair, it's way easier to do it now
than it was in the old hobbyist days, where you
had to do all the calculations by hand. Now there
are so many online tools that will allow you to
just plug in what you're an attempting to do, and
they'll tell you exactly how long each element.
Speaker 2 (11:33):
I've been to exactly one of these calculators. I found
one online that says like, Okay, here's the frequency I
want to look for, here's the decibel gain I want. Yeah,
and then it'll tell you the relative size of your
of your elements for your antenna.
Speaker 1 (11:48):
Yeah. So, if you are a transmitter hunter, chances are
you have multiple antenna or as I put, a veritable
array of antenna, oh, perhaps a literal arrayna's, depending upon
what you're depending upon how much money and time you
have to put into the hobby.
Speaker 2 (12:06):
Uh.
Speaker 1 (12:06):
But then we also have another element that you put
in our notes. Yeah, they're a question. Yeah.
Speaker 2 (12:12):
So sometimes you'll hear or you'll read about people in
the transmitter hunting community talking about harmonics. Yeah, you know,
so they'll say, maybe, oh, I got very close to
the transmitter and I was I was overwhelmed.
Speaker 1 (12:26):
What could I do?
Speaker 2 (12:27):
You know, I suddenly I couldn't isolate the direction of
the signal anymore. And somebody else might say, well, try
looking for the third harmonic. I love that because it
sounds very cryptic and in the know.
Speaker 1 (12:40):
Yeah, sounds a little Star Trek esque in a way.
So harmonics are integer multiples of the fundamental frequency, which
is a fancy way of saying you start with whatever
frequency you're looking for, because generally speaking, transmitter hunters there's
a specific frequency that they know they are searching for,
Otherwise it would be needle in a haystack. Right. Plus
(13:03):
they're limited anyway by the range that amateur operators are
allowed to use. So you start with whatever the target
frequency is and you multiply it by integers in order
to get the harmonics. So the first harmonic is the
fundamental frequency, because you just multiply by one, got it. So,
third harmonic you multiply by three. Fifth harmonic you multiply
(13:26):
by five. Both of those are particularly useful in transmitter hunting.
So the typical frequency you'd be hunting for is one
forty six point five six y five mega hurts. Now,
if you want to find the third harmonic, you multiply
that number by three. That gives you four hundred thirty
nine points six ninety five megahurts. The fifth harmonic you
(13:48):
multiply by five. That gives you seven hundred and thirty
two point eight two five megahertz. Now, each of those
harmonics has a weaker signal than the fundamental frequency.
Speaker 2 (13:57):
But it would be related to the fundamental.
Speaker 1 (13:59):
Three related to it. But it is a weaker signal. Now,
if you're when you get close to one of these transmitters,
chances are the signal strength is such that you are
it's hard for you to get any useful information.
Speaker 2 (14:12):
Yeah, right, Like, say you might if you have a
directional antenna, which we'll talk about in a minute. Yeah,
you might be sweeping it all around and you're just
maxing out your receiver no matter what direction you pointed in, right, because.
Speaker 1 (14:22):
The signal it's not like you're right on top of
the transmitter, but you're close enough where the directionality is
no longer useful. It's kind of like you can hear
someone yelling off in the distance and you're blindfolded, so
you know generally what direction they're in, but as you
get really close and they're yelling and it's an echoe area,
(14:42):
you can't really tell where the noise is coming from necessarily.
It's kind of like that as an analogy. So if
you're able to switch to one of these harmonics because
it's a weaker signal, you can get a little more
precise with that directionality. You can use it. If you
have an antenna that can switch to one of these signals,
or you have an antenna specifically made to detect those harmonics,
(15:04):
then you are able to switch to a weaker signal
which is not going to overwhelm your antenna so quickly,
and you can hone in on the direction a little
more precisely than you would if you had to rely
on your chief two meter antenna.
Speaker 2 (15:21):
Right.
Speaker 1 (15:21):
Yeah, So that's why harmonics are important. Uh, and we'll
talk a little bit more about the Yaggi antennas in
a second. Yagi antenna more formally is the yagi Uda antenna,
which sounds like it should be a Star Wars character, right,
yagi Uda? Oh you seek yagy udah. Yeah, it's a
(15:43):
directional antenna that looks kind of like one of those
old TV antennas, like the old aerols that you would
see on top of houses, typically in the movie like
Willy Wonka and the Chocolate Factory.
Speaker 2 (15:54):
Yeah, it has it has one long boom in the
middle as well. Yeah, to a central pole on which
are mounted parallel elements. And these elements are what does
the shaping and receiving of the signal or transmitting. You
can have a transmitter or receiver.
Speaker 1 (16:09):
Sure, yeah, antenna they're meant to be both transmitters and receivers, right.
Typically the antenna that I use and most people use,
I would imagine are simply used as receivers, except when
you get into things like phones and stuff. Obviously, any
phone type device has both a transmitter and receiver. Otherwise
it's just a radio, so not terribly useful if you
(16:31):
want to make a call, not that anyone does anymore,
but I digress.
Speaker 2 (16:33):
Well, anyway, we'll talk about the specific centementute. But the
point of these parallel elements on the Agie antenna is
to create this directional effect. Yes, where a signal is
detected if you are pointing right at it, but it
is killed if you are pointing perpendicular to it right right.
Speaker 1 (16:53):
So the idea being that if you turn to your
right and the signal suddenly drops out, you know that
the the direction to the right is not the way
to go. You start turning to the left and you
find where the signal drops out, you can eliminate that.
It narrows down the range where the transmission can actually originate.
And since transmitter hunting is all about finding that transmitter,
(17:17):
that's important. And we're going to talk more about transmitter
hunting and really dive into the hobby and the sport
in just a moment, But first let's take another quick
break to thank our sponsor. All Right, we're back, and Joe,
(17:41):
I want you to tell me more about this sport
of transmitter hunting, a sport I did not know existed
until you brought this topic to my attention.
Speaker 2 (17:53):
Yeah, so I at some point want to try this.
I've never done it myself, but I've been reading about
it over the past couple months, and I've watched a
few videos of people trying it out on YouTube and
it looks very interesting. So the sport is known as
transmitter hunting, also t hunting or fox hunting, and a
(18:15):
standard game goes like this. You got one participant who
is the hider. This is sort of the dungeon master
of the fox hunt. Gotcha, and the hider puts together
a radio transmitter appropriate for the scale of the hunt.
So you might use a small handheld transmitter stashed inside
an old ammunition can for a small scale hunt on
(18:37):
foot or in a small several mile area with cars.
And in this scenario, you would set the transmitter to
repeat a signal at steady intervals, so it might be like.
Speaker 1 (18:49):
Bpity beep beep beep, bpit beep, beep beep, gotcha.
Speaker 2 (18:54):
And then you'd hide it somewhere, maybe in a public
park or another a reasonably small search area. For large
scale hunts, you could actually build a powerful antenna capable
of transmitting miles and miles across state lines. There are
people who do this in you know, these long all
day car hunts. Where they're going a really long way
to try to find a transmitter somewhere out in the
(19:14):
desert or something. It looks like a lot of fun
and you use it. You hunt it using cars or
maybe fan boats. Wow, you know, so.
Speaker 1 (19:22):
You can you can do this in the Everglades. I
would That's just the way I would like to do it. Yeah,
I just all I can imagine is now we talked
earlier about possibly making a movie. This movie would now
have to star Burt Reynolds.
Speaker 2 (19:36):
But if you are hiding a transmitter, there are some
social and safety concerns you probably want to keep in mind.
Speaker 1 (19:42):
Makes sense.
Speaker 2 (19:43):
Imagine, for example, you are out at a public park
with your children and you see some creepy loaner with
an antenna attached to their van pull up beside the
park and then put a bunch of electronics inside an
ammunition can and hide it in the bushes next to
the sandbox.
Speaker 1 (19:59):
I would say that that would raise at least one,
possibly two red flags.
Speaker 2 (20:03):
Right, So you probably first of all, need to be
careful where you hide your transmitters. You need to if
it's you know, in a place where you would need permission,
get permission first. In any case, if you're doing transmitter hunting,
I've heard that it is a good idea to notify
the police ahead of time that there are going to
be people running around with antenna's and that you're going
to be hiding a thing and let the police know
(20:26):
where you're hiding it so that it doesn't get mistaken
for a bomb or some other nefarious device. Yeah, it
also looks like it's a good idea to put some
writing on the device warning people that it's not dangerous.
Speaker 1 (20:39):
Right, although honestly you wouldn't believe it. Yeah, I mean,
I like if I were if I were the type
to make a device that was intended to be harmful
to people, I can't imagine that I would have the
ethics to avoid writing this totally will not harm you.
Speaker 2 (20:58):
It's like, I'm pretty sure a box of hot pocket
says this is not.
Speaker 1 (21:01):
Dangerous on it. Yeah, I mean it, but it was
trust them, but definitely go to that extra effort. Yeah,
we were talking offline about this before we came in
here to record the episode, and the world is a
very different place than what it was when. Uh. Transmitter
hunting was really one of those hobbies that that people
(21:23):
could essentially go anywhere and play. No one really noticed
because they didn't even It was just be beneath the
public consciousness. Joe found a book and lent it to
me that I got to read, and in it they
describe a situation where one person who was hiding a
transmitter didn't have the time to actually do it himself,
(21:44):
and so entrusted the transmitter to two other people who said, oh, yeah,
we'll totally hide it where you told us, and instead
they went and hit it under an overpass. And I
thought those days are over. You would get into so
much trouble now because you.
Speaker 2 (21:59):
Rememberary prank back then now freaks people out.
Speaker 1 (22:02):
Yeah, you remember the Moononites. Those are characters from Aquitine
Hunger Force, where they Cartoon Network had done this promotional
stunt where they put very simple led displays of the
Moononites over certain bridges and it freaked people out. They
thought perhaps it was like a weird warning about an
(22:22):
explosive that had been attached to said overpasses. Turned out,
of course, no, it was just a promotional stunt, but
no one knew that at the time, and in the
world that we live in today, it's probably better to
take those extra precautions and to let whatever authority oversees
the area that you're planting the transmitter in to know
about it ahead of time, get approval, that kind of thing,
(22:45):
and take these extra steps to make sure you don't
inside a panic.
Speaker 2 (22:49):
By the way, you mentioned this book, and I just
wanted to throw out the name of it, sure, because
I was looking at this too.
Speaker 1 (22:55):
It's a book I order.
Speaker 2 (22:56):
Called Transmitter Hunting Radio Direction find being simplified. It's from
the late nineteen eighties and it is a radio hobbyist
manual by Joseph Moell and Thomas in Curly.
Speaker 1 (23:09):
An exhaustive hobbyist manual.
Speaker 2 (23:11):
Well, they've got a lot of projects and stuff back
then for building different antenna types, but also just sort
of an overview of what the sport looks like, you know,
when people practice it. Sure, so when you get into
a transmitter hunt, you've got the transmitter hidden somewhere, yeah,
and you've got some boundaries established, and then the players.
Speaker 1 (23:30):
Are set loose.
Speaker 2 (23:32):
They're like the dogs on a fox hunt, which I
assume is where the name comes from and not some
other counterintuitive naming scheme. But they know what to listen for,
so they've got the frequency established, they know what the
signal is, but they've got to somehow find the physical
location of the transmitter.
Speaker 1 (23:49):
Yep.
Speaker 2 (23:49):
Now, once you think you have isolated the direction from
which a signal is coming, and in just a second,
we'll talk about ways you could do that, some different
equipment you could have. Typically you'll have some kind of
antenna or device that gets you a bearing, so you've
got a line to where you think the signal is
coming from, and then from there there are a couple
(24:10):
of primary ways you can hunt. One is the simple way,
which is just chasing the bearing. Even this is not
as simple as it sounds.
Speaker 1 (24:18):
Idea is that you found you've found a direction, and
you're like, okay, well the transmission is coming from the southeast,
so let's just get in the car and travel as
close to southeast as we possibly can for a while,
and then we'll jump out and check again.
Speaker 2 (24:34):
Yeah, so you just follow it and then keep checking
the signal. The other way would be what's known as triangulation.
And so there imagine you would need a map.
Speaker 1 (24:45):
For this, Yes, an actual physical paper map would probably.
Speaker 2 (24:48):
You're going to make marks on as accurate distances and measurements.
So you get a bearing from one known location. You
know where you are, You mark your location on the
map and then you get a bearing. So you draw
a line on the map, saying, okay, it's coming from
this direction. Then you go to another place on the
map and you mark your location there and you get
a bearing again. You say, okay, it's coming from this direction.
(25:11):
Draw another line. Then you go to a third place,
get a bearing again, and maybe do that another time. So,
if everything is working correctly, those three or more lines
should begin to intersect right the location of the transmitter.
Speaker 1 (25:24):
There should be a convergence around the general area. Now,
it may be because of geography and buildings and such
that the signal you're picking up is a reflected signal
and not really indicative of the actual source of transmission.
Right Like, let's say that the source of the transmission
is off by a few degrees from where you get
(25:45):
your bearing because of this reflection. Well, as you do
your triangulation, you might notice that that this intersection is
a little weird, like, not all the it's not like
all the lines are converging on a single point. It
might be that they create a trapezoid of possible, and
then the idea is that, all right, well, now we're
going to need to get further closer to that trapezoid
(26:06):
because we know that the transmitter is most likely within
that area somewhere, but we have to narrow it down
from there.
Speaker 2 (26:12):
Either way you go, if you're just homing in on
a bearing or if you're trying to do triangulation, it's
not as easy as it sounds, because, as you alluded to,
the propagation of radio waves can be affected by all
kinds of stuff, many variables like terrain, presence of water,
reflective obstacles like fences, power lines, or even concrete buildings.
(26:34):
So a hill can block your line of sight to
a transmitter. Yeah, so the hill, a hill can be
in the way. You might jump out of.
Speaker 1 (26:42):
Your vehicle and you're trying to pick up the signal
and you can't pick up anything or whatever. You pay
so a week that you can't really get a reading
on where it's coming from, and instead of freaking out,
it just may mean that you have to travel a
little bit further to get the hill out of the way.
Speaker 2 (26:56):
Also, apparently, sometimes water and shorelines can change the apparent
direction from which a signal is coming. So if the
signals coming at you over water and then there's a shoreline,
it can sort of shear the direction of it. There
are some obviously, things like metal fences, power lines, buildings
can create these reflective surfaces that will bounce the signal around.
(27:20):
Some environments, like cities are absolutely jammed with radio reflective objects.
So if you're in a city, the very buildings around
you are just like bouncing the signal back and forth
like a pinball, and this can create what's known as
a multipath environment. So multipath is going to be one
of the biggest problems to overcome if you are looking
(27:42):
for a hidden transmitter, especially in a city or other
area crowded with reflective obstacles, and it just means that
you're getting the signal, you're tracking from multiple different directions,
and you've got to have some experience and knowledge of
how exactly to work around problems like that. Yeah, so
(28:08):
a good hunter needs to have experience and skill, but
they also are going to need, not necessarily need, but
it really helps to have some specialized equipment, including special
antennas and receivers.
Speaker 1 (28:21):
Now, as the authors of that book, Joe mentioned point
out multiple times, and experienced and skillful hunter can use
seemingly inferior equipment and still produce a better result than
someone who has lots of money and has dropped it
on a bunch of high tech equipment but has little
(28:42):
to no experience actually using set equipment. So there is
a lot of art to this. It's not just science.
There's a bit where you know, knowing kind of having
an intuition about how radio waves work and the geography
that you are in, and kind of getting an idea
of how that could be affecting what you are receiving.
(29:02):
It might be way more helpful than just a high
tech antenna that is the costs a lot of money.
Speaker 2 (29:09):
Yeah, I have read the authors of this book say,
and it does seem true to me based also on
other things I've read that one of the most important
pieces of equipment in a transmitter hunt is a map. Yes,
it's having a good map, especially like a topographical map
that includes surface features and buildings.
Speaker 1 (29:27):
And they also say that, you know, it can become
incredibly challenging because the game doesn't necessarily confine itself to
the area of any given map, so you might need
multiple maps and that also becomes a bit of a
challenge because unless the maps are both produced at the
same scale, you can't just overlay them, you know, and
(29:50):
tape them together or whatever it may be. That it
requires a lot of math on your part. Yeah, so
that's a strike against it for me. Well, let's do
a real brief overview of some of the main types
of antennas you might encounter absolutely transmit on. So we've
mentioned by name several times the yagi or yaggy antenna yep.
(30:12):
So this is a directional antenna. There are a couple
major kinds of directional antennas, but a directional antenna, as
we've said, it is designed to isolate the directionality of
the signals. So if you point it at a right
angle to the signal, you shouldn't be getting much of anything.
Right if you point it in the opposite direction, most
of them should say you know nothing or not much.
(30:35):
But if you finally find the direction of the signal,
the strength of the signal that comes through the antenna
two year receiver should spike yes, and so a yaggi
antenna is made of a series of metal elements arranged
in parallel. So if you're trying to picture this, think
of one long pole could be like a broom handle
or PBC pipe or whatever. And then there are metal
(30:58):
rods or wires of very lengths, and the lengths are
very specific and very important, yes, and they are determined
by the frequency of the signal that you're looking for.
The relationship of the links of the various elements are
very important, depending upon what their job is. Yeah.
Speaker 2 (31:17):
So there is the most important elements. The main one
is the driven element, and this is the electrically active part.
This is the one that connects to the wires that
go down to your receiver handheld radio receiver. This is
what is resonating with that frequency. But then there are
these other elements that are known as the parasitic elements,
(31:37):
and they're not connected to the receiver, but they're there
to manipulate the types of waves that the driven element receives.
Speaker 1 (31:45):
Yeah, this is what gives these directional antenna their directionality. Yeah.
Speaker 2 (31:50):
So there's a reflector element that goes behind the driven element.
So if you're pointing at the signal source, the reflector
element should be closer to you and behind the driven one,
and it reflects the signal back and focuses the reception
field to the direction that the antenna's pointing. And then
there may be multiple director elements, which are more elements
(32:13):
in parallel ahead of the active element to help manipulate
the shape of the wave forms and enforce directionality.
Speaker 1 (32:21):
So if you're looking at these different elements, first of all,
if you're trying to envision this in your head, imagine
that broomstick, all right, the broomstick you are holding out
from yourself. These elements are perpendicular to the broomstat stick,
but parallel with each other, right, So at the closest
end to you, you have this reflector element. It's going
(32:44):
to be the largest of those elements. Then you have
the just slightly not just slightly and not by a
whole lot, and it sort of is acting kind of
like the dish in a satellite dish antenna sort of
in that same style. So it's it's slightly larger than
the driven element. That's the one that you were you know,
is actually hooked up to the sensor so that it's
(33:06):
pulling in the signal. And then at the far end
you have the director elements. These are the shortest of
the elements. And again it's not dramatically shorter, it's just
a little shorter. All of the size sizes of these
depend upon the frequency you're searching for. I mean, if
you want to build a yagi for a very specific purpose,
(33:29):
you would look at the frequency you're looking for, and
there's a mathematical formula you use that gives you the
ideal driven element size, reflector elements size, and director element sizes,
And it's essentially you take a number and you divide.
Also also their distance from each other. That is also Yeah,
(33:50):
the spacing is also important. The spacing between these elements
is very important. You can't just put them anywhere along
that broomstick. You need to have them spaced out properly.
So both of the those things are very important in
order for you to get an antenna that is going
to resonate properly with the frequency you want and therefore
help you narrow down its direction. Yeah.
Speaker 2 (34:11):
So then there's another very popular form of directional antenna
that is accomplishes the same goal but with a different
type of construction, and that's the quad antenna.
Speaker 1 (34:20):
Yeah. They're also typically used to detect frequencies in the
high frequency or very high frequency ranges. So they consist
of the driven element and the direction and a reflective
element or directive elements, I should say, just like the
yagi is, but they're arranged in a slightly different way.
(34:42):
They use loops of wire, these loops that are not
necessarily in a circle, They just need to be closed off.
So the example I saw was a cubicle two element
quad antenna, and actually it's technically a three element, but
because you've got the driven you've got the reflector, and
the the direction one the directive element. I liked it
(35:04):
because it kind of looks like a tie fighter.
Speaker 2 (35:06):
Oh yeah, they look like tie fighter wings the loops do.
Speaker 1 (35:09):
Yeah. Now that's just the cubicle version. There are other
variants of the quad antenna. These are these are slightly
different look, I mean, a very different look from the yagis.
They have a very sensitive directionality to them, and they
also tend to have a slightly higher gain than Yaggi's
(35:30):
by about two decibels. Decibel is a sliding scale, by
the way, it's a logarithmic scale, right, not so two
decibels on its own means nothing. You need to have
another point of reference for you to understand what.
Speaker 2 (35:41):
To decibles, but if you've got a weak signal and
you need to amplify it, that could be important.
Speaker 1 (35:46):
Yeah, So quad antennas are a popular way of trying
to track down a signal, especially if you need a
little bit more sensitivity than you would with a yagi.
So both of these are popular. They also come in
different sizes. I mean, obviously it depends upon what frequencies
you're looking for. The quad antenna is interesting because the
(36:06):
length of the loop is dependent upon the frequency you're
you're searching for. So the squares in the tie fighter,
like the wing size of the tie fighter, are dependent
upon that frequency. And the reflector is actually going to
be slightly larger than the other ones. So I was
watching a video on how to make this, and that's
(36:27):
when I said, I kind of want to make one
of these. And you know, the mobile ones are slightly
smaller than the ones you might mount at your house
if you happen to live out in the country and
you can have a forty meter tall antenna in your backyard.
But they are and it definitely doesn't look like something
that's easy to carry around. I mean, they're not, they're
(36:49):
not small. A lot of people who are serious about
this hobby they have.
Speaker 2 (36:55):
They have mounts attached to their cars.
Speaker 1 (36:57):
Yeah, yeah, so you'll see vans with the things attached
or jeeps that kind of thing, with these things attached
to the vehicles themselves mounted on them, and they're not
meant to be taken off. So that's another popular one.
Another one is the Doppler direction finder.
Speaker 2 (37:14):
Now this is going to be somewhat different than the
directional antennas. It still ultimately establishes directionality, but it makes
use of the eponymous Doppler effect.
Speaker 1 (37:24):
Yes, named after a Christian Doppler who was known for
running down the hallways going e I got Dylan laughing
on that one. Who's just so absurd that Dylan Stern laughing.
It's rare that I get our producer to laugh at something,
but that was one of them. No. So, Doppler was
a nineteenth century physicist, apparently in my world, a slightly
(37:49):
absurd one, and he came up with the equations to
describe the apparent frequency shifts we perceive that happened from
the relative motion of us center of a signal and
the receiver of a signal or a wave. Now you've
heard me talk about this before you probably experienced it.
The easiest way to give an example is with sound waves.
(38:12):
So if you've ever noticed a siren on an approaching
emergency vehicle being much higher pitched than it is when
it passes you, So it's coming at you, it's a
higher pitch noise, it passes you, it's a lower pitch noise.
Or if you happen to be next to it and
the two of you are either motionless or you're moving
at the same speed in the same direction, it may
sound like a pitch that's somewhere in between. That's because
(38:36):
of the Doppler shift. When the vehicles moving towards you,
it is effectively compressing those sound waves. So it's increasing
the frequency, which we perceive as an increase in making
the pitch go up. When it's moving away from you,
it's elongating those sound waves, and so our perception of
that is that it's a lower frequency and the pitch
(38:57):
goes down. Same sort of thing is true with electro
magnetic radiation. Actually it's also true with light I mean,
which technically is part of electromagnetic radiation, but it's not
radio waves. The same thing is true for all of
these things. Yeah, so you shift exactly. Yeah, it's how
we measure how fast we're moving away from or toward
other galaxies, for example. So using a very special type
(39:21):
of antenna you can take advantage of this property of physics.
So Toppler direction finders typically have several rotating elements and
it's usually between three and eight vertically oriented antenna. The
antenna pick up these signals that then are sent to
a processor that determines where is the signal really coming from?
(39:44):
The incoming signal, where is that coming from? And typically
there's like a circular display that it's just a circle
of led lights is the simplest version, and whatever direction
the signal appears to be coming from with respect to
the the front of your vehicle, a light will pop up.
So it's not telling you that, oh, you need to
(40:07):
go northeast. It'll tell you, oh, the signals coming this
many degrees to your right, or this many degrees to
your left, or it's actually coming from behind you. That
kind of thing. So if you were driving due west
and the signal at the three o'clock position or the
light at the three o'clock position on your little circular
display lights up, that would tell you that the signal
(40:27):
is actually coming from the north. Yeah, because to your
right would be true north if you're going due west.
So you look at this signal the circle of lights,
and whichever one is lit up, that's telling you, all right, well,
we need to start changing our bearing toward that direction
if we want to head in the direction of the
transmission itself.
Speaker 2 (40:46):
Now, another type of direction finder that you could use
would be something that's known as a time difference of
arrival antennas. Yeah, and this is another interesting thing. So
it has multiple receips elements arranged in a pattern that
passed the signal along to an electronic or computational core
(41:07):
that compares the time delay between when the different elements
received the same signal pattern.
Speaker 1 (41:14):
Now this is crazy because remember these signals travel at
the speed of light, so the differences are not detectable
by humans, right, Like, there's no way that we humans
would be able to tell the difference.
Speaker 2 (41:26):
And this is obviously easier if you have, you know,
something where there are multiple elements that are very.
Speaker 1 (41:32):
Far away from each other.
Speaker 2 (41:33):
Absolutely installations, sure, sure, but yeah, so you can use
time difference of arrival. Since we know the speed of
radio transmission is constant. We know exactly what the speed is,
and we know the difference between the different elements. We
can use the time delay between when they receive the
signal to calculate the direction the signals coming from.
Speaker 1 (41:55):
All right, So we've talked a lot about antennas and
we've we've mentioned receiver quite a few times. Now. Some
people listening maybe thinking that what you're doing is you
got a pair of cans on your ears and you're
listening really carefully for the beaty beeps. But as it
turns out, most of the time, we're actually talking about
(42:15):
a piece of equipment that indicates when it's receiving a
signal and giving you an idea of how strong that
signal is. Let's talk about that for a second.
Speaker 2 (42:22):
Well, so it is going to be a receiver, radio receiver,
a radio receiver you might be familiar with, but the
most useful ones obviously are going to be ones that
are equipped with what's known as an S meter. So
you've got your antenna and you've got a wire running
from your antenna to the receiver or wires running from
the antenna to the receiver, and the receiver should be
(42:45):
able to translate the signal into something you can make
sense of. That might be sounds, or that might be
a number, and in the case of an S meter,
it would be a number. It's a gauge that gives
you a direct reading in a numerical value of the
strength of the signal. So you're not just relying on
you know, subjective impressions from listening or some other method, right,
(43:08):
so you just find the direction where the number on
the S meter is the highest.
Speaker 1 (43:12):
This makes it a lot easier, and the signal strength
is going to increase the closer you get to the transmitter.
There's actually a very specific amount where you can sit
there and say, like, all right, I look to see
when the strength of the signal has doubled. That gives
me an idea of how much closer I am to
(43:33):
the transmitter. But using you know, describing that requires lots
of calculations and variables that I don't really have the
time to go into right now, But just general rule
of thumb, you know, you look at that signal strength,
and that gives you an idea of how much closer
you are to the transmitter without actually giving you any
sort of units, Like it doesn't tell you, oh, it's
(43:56):
a mile away, or it's a thousand yards away or
anything like that. It just tells you, oh, you have
halved the distance between you and the transmitter. Whether that
distance was ten miles or one mile, who's to say.
It all depends upon the strength of the transmitter.
Speaker 2 (44:12):
So yeah, so you mentioned when you get close. Another
important factor is going to be that most of your
equipment is going to be attuned to weak signals. Yeah,
you want to be able to detect a signal coming
from a long distance.
Speaker 1 (44:29):
Right, But when you get close to something that is,
you know you is no longer a weak signal, it
can overpower your equipment.
Speaker 2 (44:36):
Right, So you might suddenly you've got your receiver and
you've got your directional antenna and you can point it
around in a circle, and no matter what direction you
pointed in, your s meter is maxed out, right.
Speaker 1 (44:47):
Because you're just you're just too close. It's it's it's like,
you know, the water is completely around you. So detecting
where the water is coming from is not easy to do, right.
Speaker 2 (44:57):
So in this case, another piece of equipment that some
people might have that would make a big difference would
be known as an attenuator and so yeah, in this case,
an attenuators and electronic element that can help you knock
down the power of the signals, sort of the opposite
of an amplifier yeap, and so that your equipment can
tell which direction the signals strongest and not just be
(45:19):
maxing out at the top of the s meter.
Speaker 1 (45:21):
Right. This is also when the harmonics can come into play.
Exactly if you can switch to the third harmonic or
the fifth harmonic, then you're using weaker signals and it
is less likely to overwhelm your equipment.
Speaker 2 (45:35):
Now we've been talking about, you know, antenna types and
stuff like that. If you are a HAM hobbyist and
you want to build something or you want to spend
some money and order something on the internet, you can
have these interesting setups that will give you a big advantage.
But some of these hams will talk about how you
don't actually have to have something like that to do
(45:56):
ham hunting. No ham hunting, transmitter hunting.
Speaker 1 (45:59):
You are the hand I've hunted ham before.
Speaker 2 (46:02):
Ham The most dangerous game it was there was There
was this time where I spent with a bunch of
my school friends on an island hunted HAM.
Speaker 1 (46:10):
I don't like to talk about it, though it didn't
turn out well to serve Ham.
Speaker 2 (46:16):
But one example of an interesting hack for crude tea hunting.
If you don't have a directional antenna, but you just
got a standard receiver a handy talkie, you know, is
this thing that I read about called body blocking or
body fading, which doesn't involve tackling somebody. No, but this
is a really interesting idea. So let's say you've just
(46:37):
got a little handy talking The antenna on this thing
is omni directional, right, like a standard radio antenna, It directs,
it listens to all directions equally, right, So if you're.
Speaker 1 (46:47):
Picking up a signal, you can't tell where it's coming from. Hell,
just you just know that you are within range of
that signal.
Speaker 2 (46:53):
But here's what you can do. You take your regular
omni directional antenna and press it tied up again your chest,
hug it to your body. Now, stand in place and
rotate your body slowly. You should find, actually that your
reception will be fine in most directions, but that it
will deteriorate when your back is facing one direction. And
(47:17):
that's because you're suddenly that's the direction where you're putting
your body directly between the transmitter and your receiver.
Speaker 1 (47:25):
So it's called body blocking because you are physically blocking
the signal from getting to the radio effectively.
Speaker 2 (47:31):
Yeah, it's sort of the opposite of a directional antenna here,
because you instead of saying go to where the signal
is strongest, you find the direction where you are most
able to block the antenna from receiving the signal, and
then you know that your butt is facing the transmitter.
Speaker 1 (47:49):
Yeah, as is always the case with me. Yeah, I
like this idea. I like the idea of actually holding
a competition that only allows for that sort of tan.
It's been her hunting. I think it could be really interesting.
It would also be really interesting to see it from afar,
like be able to see at least three or four
Like you're just seeing these people turn around very slowly,
(48:11):
stop and then immediately do a one eighty and start
running in that.
Speaker 2 (48:14):
Direction, passionately embracing their little handy talkies.
Speaker 1 (48:19):
Yeah. When walking. Yeah, and again, like before you brought
this topic up to me, I had never I'm not
a ham radio operator. I've never gotten into amateur radio.
I think it's fascinating, but I've never it's just not
that's never been a world that I've explored, so I
didn't even know that this was a thing when you
brought this up, and learning about it, I'm like, you know,
(48:39):
this is it does appeal to me because just as
geo cashing and letter boxing and those other forms of
of kind of using technology to help hunt down something.
It's kind of cool because that, you know, it does
had that relationship between technology and skill, and that that
desire for us to uncover secrets. I mean, I think
(49:00):
that's something that's kind of innate in humans, right. Yeah,
this desire to the scavenger hunt is a very powerful
thing because it's just it's fun to go through that
experience and to uncover mysteries and stuff. That concludes the
two part episode series about Transmitter of Hunting. I hope
you enjoyed that conversation from twenty seventeen. This episode originally
(49:21):
published March fifteenth, twenty seventeen. And uh yeah, I gotta
get Joe back on the show sometime. It's been a
while since I've had a chat with him. Hope you
all are doing well and I'll talk to you again
really soon. Tech Stuff is an iHeartRadio production. For more
(49:42):
podcasts from iHeartRadio, visit the iHeartRadio app, Apple podcasts, or
wherever you listen to your favorite shows.
Welcome to tech Stuff, a production from iHeartRadio. Hey there,
and welcome to tech Stuff. I'm your host Jonathan Strickland.
I'm an executive producer with iHeartRadio. And how the tech
are you? It's time for another tech Stuff classic. This
time we are concluding a discussion that we started last
(00:26):
Friday with tech Stuff Goes Transmitter Hunting Part two. Joe
McCormick joined me for this episode Joe as a host
of Stuff to Blow your Mind, and we had a
discussion about transmitter hunting that I hope you will find enjoyable.
Take it away past Jonathan and Joe. So we need
(00:47):
to move into more of a discussion about radio specifically,
because even though radio is a subset of electromagnetic radiation,
it covers an enormous range of frequencies and therefore.
Speaker 2 (01:00):
And not all frequencies behave the same on Earth.
Speaker 1 (01:03):
True.
Speaker 2 (01:04):
Yeah, so you've got different bands you might have You've
seen terms like HF or VHF, FEU HF. These are
specific subbands of frequencies on the electromagnetic spectrum, all what
we would call radio frequencies. But so yeah, you've got
like high frequency, very high frequency, and a lot of
what we're going to be talking about today is going
(01:25):
to be in the VHF part of the spectrum.
Speaker 1 (01:27):
Yeah, that very high frequency. So yeah, this radio spectrum
is pretty broad and it goes well beyond the types
of radio that the typical person can listen into, unless
you happen to be one of those folks who you know,
maybe you operate a maritime radio to help with navigation,
in which case you are using frequencies most of us
don't touch. But or maybe you are a doctor working
(01:48):
with experimental medical imaging equipment, in which case you're using
radio frequencies on the opposite end of the spectrum, because
maritime radio uses very low frequency radio waves, whereas medical
imaging uses extremely high frequency radio waves. So the range
goes from the bottom is that like three herts, which
(02:12):
means you get three waves passing a given point in
a second, all the way up to tremendously high frequency,
which is three thousand gigaherts or three trillion hurts, meaning
three trillion waves pass a given point within a second. Actually,
I like extremely low frequency more because the acronym is
elf so elves. Elves communicate kind of like ense very
(02:38):
long wave forms. The elves at the bottom of the ocean. Yeah,
that's where we've stuck them. So again, you know, we
talked about how all these waves are traveling at the
speed of light, so it's really just the number of
waves that pass a given point in a second that
tells you a frequency, not speed of transmission, because that's
going to remain the same no matter what. So a
(02:59):
three hurts frequent and see wave will tell you that
the wavelength for that particular wave has to be a
one hundred thousand kilometers in length. That's a long radio wave,
one hundred thousand kilometers. Meanwhile, and the opposite end of
the spectrum, if you go all the way to that
three thousand gigahertz wave, you're talking about one hundred micrometers
in length. So teeny tiny micrometers are very tiny, huge
(03:24):
difference obviously in the length of these waves. So that's
why you know, the whole frequency wavelength relationship is important.
So we use the different frequencies for very specific purposes.
It's also important to point out that this is not universal.
There are usually some sort of governing body within a
(03:44):
country that designates what frequencies can be used for what purposes.
In the US we have the FCC. So if you're
looking at the terror hertz side of things, that's that
ultra ultra high or terribly high frequency as is some
sometimes referred to. It's for medical imaging, that kind of stuff,
(04:06):
also molecular dynamics measurements, and other high tech information. The
extremely low frequency would be like radio communication with submarines.
Can't You can't use very high frequency when communicating with
stuff that's underwater. The waves attenue are the radio waves
get attenuated by the ocean water, and that creates problems
with communication, But it's less of a problem with extremely
(04:30):
low frequency and very long wavelength radio transmissions.
Speaker 2 (04:33):
Now, what about the kind of radio we think of
as standard radio, as in radio accessible to the average
consumer AM FM. That kind of stuff, so AM would
be in the medium frequency. Medium frequency ranges from three
hundred killer hertz to three thousand kill herts or three
megaherts if you prefer AM radio specifically in the United
States is in an even more narrow range than that, right,
(04:56):
that's all of medium frequency AM radio in the US
goes from five hundred third five killer hurts to one thousand,
seven hundred killer hurts or one point seven mega hurts.
If you wanted to talk about short wave radio, that's
from five point nine mega hurts to twenty six point
one mega hurts.
Speaker 1 (05:11):
CB goes to twenty six point ninety six mega hurts
to twenty seven point four one mega hurts, and so
on and so forth.
Speaker 2 (05:18):
So so FM radio is going to be that's mega hurts, right,
So it's going to be around around one hundred mega.
Speaker 1 (05:23):
Hurts, yes, exactly. So yeah, because power ninety nine, that
would be at ninety nine mega hurts right, ninety nine
point one I think originally maybe.
Speaker 2 (05:32):
Starts high eighties, I think, yeah, and.
Speaker 1 (05:34):
Goes up to like one oh seven I think somewhere
around there. So different countries have allocated their broad broadcast
spectrum in different ways, so not everyone follows those exact
same rules. There's usually some overlap. Now, when you know
something about the wavelength of the radio frequency, that tells
you what you need, how you need to build your
(05:56):
antenna right, Because the length of your antenna is dependent
upon the frequencies you're looking for. You want your antenna
to be the right length to resonate properly with the
radio frequencies you're searching for. There's no such thing as
really a perfect universal antenna that can equally pick up
all frequencies across the radio range. Now, you might wonder,
(06:21):
how can you have like a pocket AM radio, because
if AM radio is broadcasting in the medium frequency and
has pretty long radio waves, and you need to have
an antenna that is the right length to pick that up.
Typically we're talking about half the length of the wavelength
(06:41):
of the radio frequency you're looking at right, So if
you're talking about like a wavelength that's one hundred meters long,
then you're looking at a radio antenna that's between forty
and fifty meters. How the heck do you fit that
on like that? That seems ridiculous. Well, the antenna for
AM radios are typical wire that are and that wire
(07:02):
is wrapped around the core. Because it doesn't matter if
the wire's straight or not straight or whatever, you can
you can coil it inside a device and have it
completely housed within the radio. So if you were to
open up an AM radio, chances are you'd find a
wire where one end is not attached to anything and
it's just wrapped around around around around around a core
(07:23):
of some sort. That's the antenna. It's it's not like
it's providing any sort of electrical stimulation apart from convert
you know, pulling in radio waves and having that induce
an electric current. So that's why AM radios don't necessarily
have a visible, incredibly long antenna. And this is important
(07:47):
when it comes to things like transmitter hunting.
Speaker 2 (07:49):
Yeah, because if you look at transmitter hunting sites and
we'll get into the specifics of the sport here in
a minute, you see a lot of jargon that obviously
has to do with stuff about like antenna length and
frequencies and stuff like that. One of the common things
you'll see is like the idea of a two meter hunt. Yes,
the two meter arena is often considered the sweet spot
(08:12):
for transmitter hunting. Now what does that mean When a
HAM radio enthusiast talks about two meters.
Speaker 1 (08:18):
They're telling you specifically about the size of the antenna
that they are using. To two meters is a pretty
decent sized antenna, right, like you know, a meter's like
here in the United States, we don't necessarily think in
terms of meters that frequently because we're not on the
metric system. But yeah, that's the reason is because the
frequencies that are being used by ham radio enthusiasts are
(08:41):
falling in the VHF radio frequency band, that very high frequency. Now,
that frequency band goes from thirty mega hurts to three
hundred megaherts, and the radio wavelengths go from ten meters
down to one meter. And we're using descending sizes because
remember as frequency increases, the wavelength decreases, right, So if
(09:03):
you're if you're hunting for a radio signal that's somewhere
in that that four to five meter range, you need
a two meter antenna in order to pick them up
effectively to have it be particularly sensitive to those transmissions. Now,
(09:23):
the specific range within VHF designated for amateur radio use
is in the United States one hundred and forty four
megahurts tow one hundred and forty eight megahertz. It's a
little different in Europe where it's one forty four to
one forty six.
Speaker 2 (09:37):
So stingy with it over there and not quite as
wide a range. Give us our two megaherts come on, yeah.
Speaker 1 (09:43):
And well, to be fair though, it's not the only
band for amateur radio. Amateur radio actually has bands and
several different frequency ranges. It's just for the VHF frequency range.
It's this specific UH range of frequencies from eight in
the US one forty four to one forty six in Europe.
But you can also find amateur radio frequency bands in low, medium,
(10:07):
and high frequency as well as all the way up
to like terribly fast, terribly high frequency. You can find
them up there too. Now, because of the wavelengths involved,
that two meter antenna is best able to pick up
those transmissions because it resonates more readily with transmissions in
that frequency. Yeah, like it can pick up stuff outside
of it, but not as effectively as the stuff it
(10:27):
was designed for. It's that's the sweet spot. So you
can build your own if you wanted to. There are
a lot of different resources, both online and in libraries
that will teach you how to build an antenna. I
watched one that actually was so cool that I think
I might do it as a project here at how
stuff works and do a video about it. What kind
of antenna was it would be? It would be a
(10:48):
quad antenna. I'll talk about a little bit a little
bit later.
Speaker 2 (10:50):
Mostly guys, now, I've been thinking about trying to build
a yacky antenna.
Speaker 1 (10:53):
Yeah, well, that would be great, both of them.
Speaker 2 (10:55):
As some of the Hams pronounce it, yaggy yaggy.
Speaker 1 (10:59):
Yeah, I think that that project would be really kind
of fun. And also I like the way a quad
antenna can look. I'll talk more about that in a
little bit.
Speaker 2 (11:12):
Anyway, Well, well, I challenge you to an antenna built off.
Speaker 1 (11:15):
That sounds great. Yeah, let's do it. Totally do it.
To be fair, it's way easier to do it now
than it was in the old hobbyist days, where you
had to do all the calculations by hand. Now there
are so many online tools that will allow you to
just plug in what you're an attempting to do, and
they'll tell you exactly how long each element.
Speaker 2 (11:33):
I've been to exactly one of these calculators. I found
one online that says like, Okay, here's the frequency I
want to look for, here's the decibel gain I want. Yeah,
and then it'll tell you the relative size of your
of your elements for your antenna.
Speaker 1 (11:48):
Yeah. So, if you are a transmitter hunter, chances are
you have multiple antenna or as I put, a veritable
array of antenna, oh, perhaps a literal arrayna's, depending upon
what you're depending upon how much money and time you
have to put into the hobby.
Speaker 2 (12:06):
Uh.
Speaker 1 (12:06):
But then we also have another element that you put
in our notes. Yeah, they're a question. Yeah.
Speaker 2 (12:12):
So sometimes you'll hear or you'll read about people in
the transmitter hunting community talking about harmonics. Yeah, you know,
so they'll say, maybe, oh, I got very close to
the transmitter and I was I was overwhelmed.
Speaker 1 (12:26):
What could I do?
Speaker 2 (12:27):
You know, I suddenly I couldn't isolate the direction of
the signal anymore. And somebody else might say, well, try
looking for the third harmonic. I love that because it
sounds very cryptic and in the know.
Speaker 1 (12:40):
Yeah, sounds a little Star Trek esque in a way.
So harmonics are integer multiples of the fundamental frequency, which
is a fancy way of saying you start with whatever
frequency you're looking for, because generally speaking, transmitter hunters there's
a specific frequency that they know they are searching for,
Otherwise it would be needle in a haystack. Right. Plus
(13:03):
they're limited anyway by the range that amateur operators are
allowed to use. So you start with whatever the target
frequency is and you multiply it by integers in order
to get the harmonics. So the first harmonic is the
fundamental frequency, because you just multiply by one, got it. So,
third harmonic you multiply by three. Fifth harmonic you multiply
(13:26):
by five. Both of those are particularly useful in transmitter hunting.
So the typical frequency you'd be hunting for is one
forty six point five six y five mega hurts. Now,
if you want to find the third harmonic, you multiply
that number by three. That gives you four hundred thirty
nine points six ninety five megahurts. The fifth harmonic you
(13:48):
multiply by five. That gives you seven hundred and thirty
two point eight two five megahertz. Now, each of those
harmonics has a weaker signal than the fundamental frequency.
Speaker 2 (13:57):
But it would be related to the fundamental.
Speaker 1 (13:59):
Three related to it. But it is a weaker signal. Now,
if you're when you get close to one of these transmitters,
chances are the signal strength is such that you are
it's hard for you to get any useful information.
Speaker 2 (14:12):
Yeah, right, Like, say you might if you have a
directional antenna, which we'll talk about in a minute. Yeah,
you might be sweeping it all around and you're just
maxing out your receiver no matter what direction you pointed in, right, because.
Speaker 1 (14:22):
The signal it's not like you're right on top of
the transmitter, but you're close enough where the directionality is
no longer useful. It's kind of like you can hear
someone yelling off in the distance and you're blindfolded, so
you know generally what direction they're in, but as you
get really close and they're yelling and it's an echoe area,
(14:42):
you can't really tell where the noise is coming from necessarily.
It's kind of like that as an analogy. So if
you're able to switch to one of these harmonics because
it's a weaker signal, you can get a little more
precise with that directionality. You can use it. If you
have an antenna that can switch to one of these signals,
or you have an antenna specifically made to detect those harmonics,
(15:04):
then you are able to switch to a weaker signal
which is not going to overwhelm your antenna so quickly,
and you can hone in on the direction a little
more precisely than you would if you had to rely
on your chief two meter antenna.
Speaker 2 (15:21):
Right.
Speaker 1 (15:21):
Yeah, So that's why harmonics are important. Uh, and we'll
talk a little bit more about the Yaggi antennas in
a second. Yagi antenna more formally is the yagi Uda antenna,
which sounds like it should be a Star Wars character, right,
yagi Uda? Oh you seek yagy udah. Yeah, it's a
(15:43):
directional antenna that looks kind of like one of those
old TV antennas, like the old aerols that you would
see on top of houses, typically in the movie like
Willy Wonka and the Chocolate Factory.
Speaker 2 (15:54):
Yeah, it has it has one long boom in the
middle as well. Yeah, to a central pole on which
are mounted parallel elements. And these elements are what does
the shaping and receiving of the signal or transmitting. You
can have a transmitter or receiver.
Speaker 1 (16:09):
Sure, yeah, antenna they're meant to be both transmitters and receivers, right.
Typically the antenna that I use and most people use,
I would imagine are simply used as receivers, except when
you get into things like phones and stuff. Obviously, any
phone type device has both a transmitter and receiver. Otherwise
it's just a radio, so not terribly useful if you
(16:31):
want to make a call, not that anyone does anymore,
but I digress.
Speaker 2 (16:33):
Well, anyway, we'll talk about the specific centementute. But the
point of these parallel elements on the Agie antenna is
to create this directional effect. Yes, where a signal is
detected if you are pointing right at it, but it
is killed if you are pointing perpendicular to it right right.
Speaker 1 (16:53):
So the idea being that if you turn to your
right and the signal suddenly drops out, you know that
the the direction to the right is not the way
to go. You start turning to the left and you
find where the signal drops out, you can eliminate that.
It narrows down the range where the transmission can actually originate.
And since transmitter hunting is all about finding that transmitter,
(17:17):
that's important. And we're going to talk more about transmitter
hunting and really dive into the hobby and the sport
in just a moment, But first let's take another quick
break to thank our sponsor. All Right, we're back, and Joe,
(17:41):
I want you to tell me more about this sport
of transmitter hunting, a sport I did not know existed
until you brought this topic to my attention.
Speaker 2 (17:53):
Yeah, so I at some point want to try this.
I've never done it myself, but I've been reading about
it over the past couple months, and I've watched a
few videos of people trying it out on YouTube and
it looks very interesting. So the sport is known as
transmitter hunting, also t hunting or fox hunting, and a
(18:15):
standard game goes like this. You got one participant who
is the hider. This is sort of the dungeon master
of the fox hunt. Gotcha, and the hider puts together
a radio transmitter appropriate for the scale of the hunt.
So you might use a small handheld transmitter stashed inside
an old ammunition can for a small scale hunt on
(18:37):
foot or in a small several mile area with cars.
And in this scenario, you would set the transmitter to
repeat a signal at steady intervals, so it might be like.
Speaker 1 (18:49):
Bpity beep beep beep, bpit beep, beep beep, gotcha.
Speaker 2 (18:54):
And then you'd hide it somewhere, maybe in a public
park or another a reasonably small search area. For large
scale hunts, you could actually build a powerful antenna capable
of transmitting miles and miles across state lines. There are
people who do this in you know, these long all
day car hunts. Where they're going a really long way
to try to find a transmitter somewhere out in the
(19:14):
desert or something. It looks like a lot of fun
and you use it. You hunt it using cars or
maybe fan boats. Wow, you know, so.
Speaker 1 (19:22):
You can you can do this in the Everglades. I
would That's just the way I would like to do it. Yeah,
I just all I can imagine is now we talked
earlier about possibly making a movie. This movie would now
have to star Burt Reynolds.
Speaker 2 (19:36):
But if you are hiding a transmitter, there are some
social and safety concerns you probably want to keep in mind.
Speaker 1 (19:42):
Makes sense.
Speaker 2 (19:43):
Imagine, for example, you are out at a public park
with your children and you see some creepy loaner with
an antenna attached to their van pull up beside the
park and then put a bunch of electronics inside an
ammunition can and hide it in the bushes next to
the sandbox.
Speaker 1 (19:59):
I would say that that would raise at least one,
possibly two red flags.
Speaker 2 (20:03):
Right, So you probably first of all, need to be
careful where you hide your transmitters. You need to if
it's you know, in a place where you would need permission,
get permission first. In any case, if you're doing transmitter hunting,
I've heard that it is a good idea to notify
the police ahead of time that there are going to
be people running around with antenna's and that you're going
to be hiding a thing and let the police know
(20:26):
where you're hiding it so that it doesn't get mistaken
for a bomb or some other nefarious device. Yeah, it
also looks like it's a good idea to put some
writing on the device warning people that it's not dangerous.
Speaker 1 (20:39):
Right, although honestly you wouldn't believe it. Yeah, I mean,
I like if I were if I were the type
to make a device that was intended to be harmful
to people, I can't imagine that I would have the
ethics to avoid writing this totally will not harm you.
Speaker 2 (20:58):
It's like, I'm pretty sure a box of hot pocket
says this is not.
Speaker 1 (21:01):
Dangerous on it. Yeah, I mean it, but it was
trust them, but definitely go to that extra effort. Yeah,
we were talking offline about this before we came in
here to record the episode, and the world is a
very different place than what it was when. Uh. Transmitter
hunting was really one of those hobbies that that people
(21:23):
could essentially go anywhere and play. No one really noticed
because they didn't even It was just be beneath the
public consciousness. Joe found a book and lent it to
me that I got to read, and in it they
describe a situation where one person who was hiding a
transmitter didn't have the time to actually do it himself,
(21:44):
and so entrusted the transmitter to two other people who said, oh, yeah,
we'll totally hide it where you told us, and instead
they went and hit it under an overpass. And I
thought those days are over. You would get into so
much trouble now because you.
Speaker 2 (21:59):
Rememberary prank back then now freaks people out.
Speaker 1 (22:02):
Yeah, you remember the Moononites. Those are characters from Aquitine
Hunger Force, where they Cartoon Network had done this promotional
stunt where they put very simple led displays of the
Moononites over certain bridges and it freaked people out. They
thought perhaps it was like a weird warning about an
(22:22):
explosive that had been attached to said overpasses. Turned out,
of course, no, it was just a promotional stunt, but
no one knew that at the time, and in the
world that we live in today, it's probably better to
take those extra precautions and to let whatever authority oversees
the area that you're planting the transmitter in to know
about it ahead of time, get approval, that kind of thing,
(22:45):
and take these extra steps to make sure you don't
inside a panic.
Speaker 2 (22:49):
By the way, you mentioned this book, and I just
wanted to throw out the name of it, sure, because
I was looking at this too.
Speaker 1 (22:55):
It's a book I order.
Speaker 2 (22:56):
Called Transmitter Hunting Radio Direction find being simplified. It's from
the late nineteen eighties and it is a radio hobbyist
manual by Joseph Moell and Thomas in Curly.
Speaker 1 (23:09):
An exhaustive hobbyist manual.
Speaker 2 (23:11):
Well, they've got a lot of projects and stuff back
then for building different antenna types, but also just sort
of an overview of what the sport looks like, you know,
when people practice it. Sure, so when you get into
a transmitter hunt, you've got the transmitter hidden somewhere, yeah,
and you've got some boundaries established, and then the players.
Speaker 1 (23:30):
Are set loose.
Speaker 2 (23:32):
They're like the dogs on a fox hunt, which I
assume is where the name comes from and not some
other counterintuitive naming scheme. But they know what to listen for,
so they've got the frequency established, they know what the
signal is, but they've got to somehow find the physical
location of the transmitter.
Speaker 1 (23:49):
Yep.
Speaker 2 (23:49):
Now, once you think you have isolated the direction from
which a signal is coming, and in just a second,
we'll talk about ways you could do that, some different
equipment you could have. Typically you'll have some kind of
antenna or device that gets you a bearing, so you've
got a line to where you think the signal is
coming from, and then from there there are a couple
(24:10):
of primary ways you can hunt. One is the simple way,
which is just chasing the bearing. Even this is not
as simple as it sounds.
Speaker 1 (24:18):
Idea is that you found you've found a direction, and
you're like, okay, well the transmission is coming from the southeast,
so let's just get in the car and travel as
close to southeast as we possibly can for a while,
and then we'll jump out and check again.
Speaker 2 (24:34):
Yeah, so you just follow it and then keep checking
the signal. The other way would be what's known as triangulation.
And so there imagine you would need a map.
Speaker 1 (24:45):
For this, Yes, an actual physical paper map would probably.
Speaker 2 (24:48):
You're going to make marks on as accurate distances and measurements.
So you get a bearing from one known location. You
know where you are, You mark your location on the
map and then you get a bearing. So you draw
a line on the map, saying, okay, it's coming from
this direction. Then you go to another place on the
map and you mark your location there and you get
a bearing again. You say, okay, it's coming from this direction.
(25:11):
Draw another line. Then you go to a third place,
get a bearing again, and maybe do that another time. So,
if everything is working correctly, those three or more lines
should begin to intersect right the location of the transmitter.
Speaker 1 (25:24):
There should be a convergence around the general area. Now,
it may be because of geography and buildings and such
that the signal you're picking up is a reflected signal
and not really indicative of the actual source of transmission.
Right Like, let's say that the source of the transmission
is off by a few degrees from where you get
(25:45):
your bearing because of this reflection. Well, as you do
your triangulation, you might notice that that this intersection is
a little weird, like, not all the it's not like
all the lines are converging on a single point. It
might be that they create a trapezoid of possible, and
then the idea is that, all right, well, now we're
going to need to get further closer to that trapezoid
(26:06):
because we know that the transmitter is most likely within
that area somewhere, but we have to narrow it down
from there.
Speaker 2 (26:12):
Either way you go, if you're just homing in on
a bearing or if you're trying to do triangulation, it's
not as easy as it sounds, because, as you alluded to,
the propagation of radio waves can be affected by all
kinds of stuff, many variables like terrain, presence of water,
reflective obstacles like fences, power lines, or even concrete buildings.
(26:34):
So a hill can block your line of sight to
a transmitter. Yeah, so the hill, a hill can be
in the way. You might jump out of.
Speaker 1 (26:42):
Your vehicle and you're trying to pick up the signal
and you can't pick up anything or whatever. You pay
so a week that you can't really get a reading
on where it's coming from, and instead of freaking out,
it just may mean that you have to travel a
little bit further to get the hill out of the way.
Speaker 2 (26:56):
Also, apparently, sometimes water and shorelines can change the apparent
direction from which a signal is coming. So if the
signals coming at you over water and then there's a shoreline,
it can sort of shear the direction of it. There
are some obviously, things like metal fences, power lines, buildings
can create these reflective surfaces that will bounce the signal around.
(27:20):
Some environments, like cities are absolutely jammed with radio reflective objects.
So if you're in a city, the very buildings around
you are just like bouncing the signal back and forth
like a pinball, and this can create what's known as
a multipath environment. So multipath is going to be one
of the biggest problems to overcome if you are looking
(27:42):
for a hidden transmitter, especially in a city or other
area crowded with reflective obstacles, and it just means that
you're getting the signal, you're tracking from multiple different directions,
and you've got to have some experience and knowledge of
how exactly to work around problems like that. Yeah, so
(28:08):
a good hunter needs to have experience and skill, but
they also are going to need, not necessarily need, but
it really helps to have some specialized equipment, including special
antennas and receivers.
Speaker 1 (28:21):
Now, as the authors of that book, Joe mentioned point
out multiple times, and experienced and skillful hunter can use
seemingly inferior equipment and still produce a better result than
someone who has lots of money and has dropped it
on a bunch of high tech equipment but has little
(28:42):
to no experience actually using set equipment. So there is
a lot of art to this. It's not just science.
There's a bit where you know, knowing kind of having
an intuition about how radio waves work and the geography
that you are in, and kind of getting an idea
of how that could be affecting what you are receiving.
(29:02):
It might be way more helpful than just a high
tech antenna that is the costs a lot of money.
Speaker 2 (29:09):
Yeah, I have read the authors of this book say,
and it does seem true to me based also on
other things I've read that one of the most important
pieces of equipment in a transmitter hunt is a map. Yes,
it's having a good map, especially like a topographical map
that includes surface features and buildings.
Speaker 1 (29:27):
And they also say that, you know, it can become
incredibly challenging because the game doesn't necessarily confine itself to
the area of any given map, so you might need
multiple maps and that also becomes a bit of a
challenge because unless the maps are both produced at the
same scale, you can't just overlay them, you know, and
(29:50):
tape them together or whatever it may be. That it
requires a lot of math on your part. Yeah, so
that's a strike against it for me. Well, let's do
a real brief overview of some of the main types
of antennas you might encounter absolutely transmit on. So we've
mentioned by name several times the yagi or yaggy antenna yep.
(30:12):
So this is a directional antenna. There are a couple
major kinds of directional antennas, but a directional antenna, as
we've said, it is designed to isolate the directionality of
the signals. So if you point it at a right
angle to the signal, you shouldn't be getting much of anything.
Right if you point it in the opposite direction, most
of them should say you know nothing or not much.
(30:35):
But if you finally find the direction of the signal,
the strength of the signal that comes through the antenna
two year receiver should spike yes, and so a yaggi
antenna is made of a series of metal elements arranged
in parallel. So if you're trying to picture this, think
of one long pole could be like a broom handle
or PBC pipe or whatever. And then there are metal
(30:58):
rods or wires of very lengths, and the lengths are
very specific and very important, yes, and they are determined
by the frequency of the signal that you're looking for.
The relationship of the links of the various elements are
very important, depending upon what their job is. Yeah.
Speaker 2 (31:17):
So there is the most important elements. The main one
is the driven element, and this is the electrically active part.
This is the one that connects to the wires that
go down to your receiver handheld radio receiver. This is
what is resonating with that frequency. But then there are
these other elements that are known as the parasitic elements,
(31:37):
and they're not connected to the receiver, but they're there
to manipulate the types of waves that the driven element receives.
Speaker 1 (31:45):
Yeah, this is what gives these directional antenna their directionality. Yeah.
Speaker 2 (31:50):
So there's a reflector element that goes behind the driven element.
So if you're pointing at the signal source, the reflector
element should be closer to you and behind the driven one,
and it reflects the signal back and focuses the reception
field to the direction that the antenna's pointing. And then
there may be multiple director elements, which are more elements
(32:13):
in parallel ahead of the active element to help manipulate
the shape of the wave forms and enforce directionality.
Speaker 1 (32:21):
So if you're looking at these different elements, first of all,
if you're trying to envision this in your head, imagine
that broomstick, all right, the broomstick you are holding out
from yourself. These elements are perpendicular to the broomstat stick,
but parallel with each other, right, So at the closest
end to you, you have this reflector element. It's going
(32:44):
to be the largest of those elements. Then you have
the just slightly not just slightly and not by a
whole lot, and it sort of is acting kind of
like the dish in a satellite dish antenna sort of
in that same style. So it's it's slightly larger than
the driven element. That's the one that you were you know,
is actually hooked up to the sensor so that it's
(33:06):
pulling in the signal. And then at the far end
you have the director elements. These are the shortest of
the elements. And again it's not dramatically shorter, it's just
a little shorter. All of the size sizes of these
depend upon the frequency you're searching for. I mean, if
you want to build a yagi for a very specific purpose,
(33:29):
you would look at the frequency you're looking for, and
there's a mathematical formula you use that gives you the
ideal driven element size, reflector elements size, and director element sizes,
And it's essentially you take a number and you divide.
Also also their distance from each other. That is also Yeah,
(33:50):
the spacing is also important. The spacing between these elements
is very important. You can't just put them anywhere along
that broomstick. You need to have them spaced out properly.
So both of the those things are very important in
order for you to get an antenna that is going
to resonate properly with the frequency you want and therefore
help you narrow down its direction. Yeah.
Speaker 2 (34:11):
So then there's another very popular form of directional antenna
that is accomplishes the same goal but with a different
type of construction, and that's the quad antenna.
Speaker 1 (34:20):
Yeah. They're also typically used to detect frequencies in the
high frequency or very high frequency ranges. So they consist
of the driven element and the direction and a reflective
element or directive elements, I should say, just like the
yagi is, but they're arranged in a slightly different way.
(34:42):
They use loops of wire, these loops that are not
necessarily in a circle, They just need to be closed off.
So the example I saw was a cubicle two element
quad antenna, and actually it's technically a three element, but
because you've got the driven you've got the reflector, and
the the direction one the directive element. I liked it
(35:04):
because it kind of looks like a tie fighter.
Speaker 2 (35:06):
Oh yeah, they look like tie fighter wings the loops do.
Speaker 1 (35:09):
Yeah. Now that's just the cubicle version. There are other
variants of the quad antenna. These are these are slightly
different look, I mean, a very different look from the yagis.
They have a very sensitive directionality to them, and they
also tend to have a slightly higher gain than Yaggi's
(35:30):
by about two decibels. Decibel is a sliding scale, by
the way, it's a logarithmic scale, right, not so two
decibels on its own means nothing. You need to have
another point of reference for you to understand what.
Speaker 2 (35:41):
To decibles, but if you've got a weak signal and
you need to amplify it, that could be important.
Speaker 1 (35:46):
Yeah, So quad antennas are a popular way of trying
to track down a signal, especially if you need a
little bit more sensitivity than you would with a yagi.
So both of these are popular. They also come in
different sizes. I mean, obviously it depends upon what frequencies
you're looking for. The quad antenna is interesting because the
(36:06):
length of the loop is dependent upon the frequency you're
you're searching for. So the squares in the tie fighter,
like the wing size of the tie fighter, are dependent
upon that frequency. And the reflector is actually going to
be slightly larger than the other ones. So I was
watching a video on how to make this, and that's
(36:27):
when I said, I kind of want to make one
of these. And you know, the mobile ones are slightly
smaller than the ones you might mount at your house
if you happen to live out in the country and
you can have a forty meter tall antenna in your backyard.
But they are and it definitely doesn't look like something
that's easy to carry around. I mean, they're not, they're
(36:49):
not small. A lot of people who are serious about
this hobby they have.
Speaker 2 (36:55):
They have mounts attached to their cars.
Speaker 1 (36:57):
Yeah, yeah, so you'll see vans with the things attached
or jeeps that kind of thing, with these things attached
to the vehicles themselves mounted on them, and they're not
meant to be taken off. So that's another popular one.
Another one is the Doppler direction finder.
Speaker 2 (37:14):
Now this is going to be somewhat different than the
directional antennas. It still ultimately establishes directionality, but it makes
use of the eponymous Doppler effect.
Speaker 1 (37:24):
Yes, named after a Christian Doppler who was known for
running down the hallways going e I got Dylan laughing
on that one. Who's just so absurd that Dylan Stern laughing.
It's rare that I get our producer to laugh at something,
but that was one of them. No. So, Doppler was
a nineteenth century physicist, apparently in my world, a slightly
(37:49):
absurd one, and he came up with the equations to
describe the apparent frequency shifts we perceive that happened from
the relative motion of us center of a signal and
the receiver of a signal or a wave. Now you've
heard me talk about this before you probably experienced it.
The easiest way to give an example is with sound waves.
(38:12):
So if you've ever noticed a siren on an approaching
emergency vehicle being much higher pitched than it is when
it passes you, So it's coming at you, it's a
higher pitch noise, it passes you, it's a lower pitch noise.
Or if you happen to be next to it and
the two of you are either motionless or you're moving
at the same speed in the same direction, it may
sound like a pitch that's somewhere in between. That's because
(38:36):
of the Doppler shift. When the vehicles moving towards you,
it is effectively compressing those sound waves. So it's increasing
the frequency, which we perceive as an increase in making
the pitch go up. When it's moving away from you,
it's elongating those sound waves, and so our perception of
that is that it's a lower frequency and the pitch
(38:57):
goes down. Same sort of thing is true with electro
magnetic radiation. Actually it's also true with light I mean,
which technically is part of electromagnetic radiation, but it's not
radio waves. The same thing is true for all of
these things. Yeah, so you shift exactly. Yeah, it's how
we measure how fast we're moving away from or toward
other galaxies, for example. So using a very special type
(39:21):
of antenna you can take advantage of this property of physics.
So Toppler direction finders typically have several rotating elements and
it's usually between three and eight vertically oriented antenna. The
antenna pick up these signals that then are sent to
a processor that determines where is the signal really coming from?
(39:44):
The incoming signal, where is that coming from? And typically
there's like a circular display that it's just a circle
of led lights is the simplest version, and whatever direction
the signal appears to be coming from with respect to
the the front of your vehicle, a light will pop up.
So it's not telling you that, oh, you need to
(40:07):
go northeast. It'll tell you, oh, the signals coming this
many degrees to your right, or this many degrees to
your left, or it's actually coming from behind you. That
kind of thing. So if you were driving due west
and the signal at the three o'clock position or the
light at the three o'clock position on your little circular
display lights up, that would tell you that the signal
(40:27):
is actually coming from the north. Yeah, because to your
right would be true north if you're going due west.
So you look at this signal the circle of lights,
and whichever one is lit up, that's telling you, all right, well,
we need to start changing our bearing toward that direction
if we want to head in the direction of the
transmission itself.
Speaker 2 (40:46):
Now, another type of direction finder that you could use
would be something that's known as a time difference of
arrival antennas. Yeah, and this is another interesting thing. So
it has multiple receips elements arranged in a pattern that
passed the signal along to an electronic or computational core
(41:07):
that compares the time delay between when the different elements
received the same signal pattern.
Speaker 1 (41:14):
Now this is crazy because remember these signals travel at
the speed of light, so the differences are not detectable
by humans, right, Like, there's no way that we humans
would be able to tell the difference.
Speaker 2 (41:26):
And this is obviously easier if you have, you know,
something where there are multiple elements that are very.
Speaker 1 (41:32):
Far away from each other.
Speaker 2 (41:33):
Absolutely installations, sure, sure, but yeah, so you can use
time difference of arrival. Since we know the speed of
radio transmission is constant. We know exactly what the speed is,
and we know the difference between the different elements. We
can use the time delay between when they receive the
signal to calculate the direction the signals coming from.
Speaker 1 (41:55):
All right, So we've talked a lot about antennas and
we've we've mentioned receiver quite a few times. Now. Some
people listening maybe thinking that what you're doing is you
got a pair of cans on your ears and you're
listening really carefully for the beaty beeps. But as it
turns out, most of the time, we're actually talking about
(42:15):
a piece of equipment that indicates when it's receiving a
signal and giving you an idea of how strong that
signal is. Let's talk about that for a second.
Speaker 2 (42:22):
Well, so it is going to be a receiver, radio receiver,
a radio receiver you might be familiar with, but the
most useful ones obviously are going to be ones that
are equipped with what's known as an S meter. So
you've got your antenna and you've got a wire running
from your antenna to the receiver or wires running from
the antenna to the receiver, and the receiver should be
(42:45):
able to translate the signal into something you can make
sense of. That might be sounds, or that might be
a number, and in the case of an S meter,
it would be a number. It's a gauge that gives
you a direct reading in a numerical value of the
strength of the signal. So you're not just relying on
you know, subjective impressions from listening or some other method, right,
(43:08):
so you just find the direction where the number on
the S meter is the highest.
Speaker 1 (43:12):
This makes it a lot easier, and the signal strength
is going to increase the closer you get to the transmitter.
There's actually a very specific amount where you can sit
there and say, like, all right, I look to see
when the strength of the signal has doubled. That gives
me an idea of how much closer I am to
(43:33):
the transmitter. But using you know, describing that requires lots
of calculations and variables that I don't really have the
time to go into right now, But just general rule
of thumb, you know, you look at that signal strength,
and that gives you an idea of how much closer
you are to the transmitter without actually giving you any
sort of units, Like it doesn't tell you, oh, it's
(43:56):
a mile away, or it's a thousand yards away or
anything like that. It just tells you, oh, you have
halved the distance between you and the transmitter. Whether that
distance was ten miles or one mile, who's to say.
It all depends upon the strength of the transmitter.
Speaker 2 (44:12):
So yeah, so you mentioned when you get close. Another
important factor is going to be that most of your
equipment is going to be attuned to weak signals. Yeah,
you want to be able to detect a signal coming
from a long distance.
Speaker 1 (44:29):
Right, But when you get close to something that is,
you know you is no longer a weak signal, it
can overpower your equipment.
Speaker 2 (44:36):
Right, So you might suddenly you've got your receiver and
you've got your directional antenna and you can point it
around in a circle, and no matter what direction you
pointed in, your s meter is maxed out, right.
Speaker 1 (44:47):
Because you're just you're just too close. It's it's it's like,
you know, the water is completely around you. So detecting
where the water is coming from is not easy to do, right.
Speaker 2 (44:57):
So in this case, another piece of equipment that some
people might have that would make a big difference would
be known as an attenuator and so yeah, in this case,
an attenuators and electronic element that can help you knock
down the power of the signals, sort of the opposite
of an amplifier yeap, and so that your equipment can
tell which direction the signals strongest and not just be
(45:19):
maxing out at the top of the s meter.
Speaker 1 (45:21):
Right. This is also when the harmonics can come into play.
Exactly if you can switch to the third harmonic or
the fifth harmonic, then you're using weaker signals and it
is less likely to overwhelm your equipment.
Speaker 2 (45:35):
Now we've been talking about, you know, antenna types and
stuff like that. If you are a HAM hobbyist and
you want to build something or you want to spend
some money and order something on the internet, you can
have these interesting setups that will give you a big advantage.
But some of these hams will talk about how you
don't actually have to have something like that to do
(45:56):
ham hunting. No ham hunting, transmitter hunting.
Speaker 1 (45:59):
You are the hand I've hunted ham before.
Speaker 2 (46:02):
Ham The most dangerous game it was there was There
was this time where I spent with a bunch of
my school friends on an island hunted HAM.
Speaker 1 (46:10):
I don't like to talk about it, though it didn't
turn out well to serve Ham.
Speaker 2 (46:16):
But one example of an interesting hack for crude tea hunting.
If you don't have a directional antenna, but you just
got a standard receiver a handy talkie, you know, is
this thing that I read about called body blocking or
body fading, which doesn't involve tackling somebody. No, but this
is a really interesting idea. So let's say you've just
(46:37):
got a little handy talking The antenna on this thing
is omni directional, right, like a standard radio antenna, It directs,
it listens to all directions equally, right, So if you're.
Speaker 1 (46:47):
Picking up a signal, you can't tell where it's coming from. Hell,
just you just know that you are within range of
that signal.
Speaker 2 (46:53):
But here's what you can do. You take your regular
omni directional antenna and press it tied up again your chest,
hug it to your body. Now, stand in place and
rotate your body slowly. You should find, actually that your
reception will be fine in most directions, but that it
will deteriorate when your back is facing one direction. And
(47:17):
that's because you're suddenly that's the direction where you're putting
your body directly between the transmitter and your receiver.
Speaker 1 (47:25):
So it's called body blocking because you are physically blocking
the signal from getting to the radio effectively.
Speaker 2 (47:31):
Yeah, it's sort of the opposite of a directional antenna here,
because you instead of saying go to where the signal
is strongest, you find the direction where you are most
able to block the antenna from receiving the signal, and
then you know that your butt is facing the transmitter.
Speaker 1 (47:49):
Yeah, as is always the case with me. Yeah, I
like this idea. I like the idea of actually holding
a competition that only allows for that sort of tan.
It's been her hunting. I think it could be really interesting.
It would also be really interesting to see it from afar,
like be able to see at least three or four
Like you're just seeing these people turn around very slowly,
(48:11):
stop and then immediately do a one eighty and start
running in that.
Speaker 2 (48:14):
Direction, passionately embracing their little handy talkies.
Speaker 1 (48:19):
Yeah. When walking. Yeah, and again, like before you brought
this topic up to me, I had never I'm not
a ham radio operator. I've never gotten into amateur radio.
I think it's fascinating, but I've never it's just not
that's never been a world that I've explored, so I
didn't even know that this was a thing when you
brought this up, and learning about it, I'm like, you know,
(48:39):
this is it does appeal to me because just as
geo cashing and letter boxing and those other forms of
of kind of using technology to help hunt down something.
It's kind of cool because that, you know, it does
had that relationship between technology and skill, and that that
desire for us to uncover secrets. I mean, I think
(49:00):
that's something that's kind of innate in humans, right. Yeah,
this desire to the scavenger hunt is a very powerful
thing because it's just it's fun to go through that
experience and to uncover mysteries and stuff. That concludes the
two part episode series about Transmitter of Hunting. I hope
you enjoyed that conversation from twenty seventeen. This episode originally
(49:21):
published March fifteenth, twenty seventeen. And uh yeah, I gotta
get Joe back on the show sometime. It's been a
while since I've had a chat with him. Hope you
all are doing well and I'll talk to you again
really soon. Tech Stuff is an iHeartRadio production. For more
(49:42):
podcasts from iHeartRadio, visit the iHeartRadio app, Apple podcasts, or
wherever you listen to your favorite shows.
TechStuff News
Hosts And Creators
Oz Woloshyn
Karah Preiss
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