Hey everyone, my name is Eric Escobar and today my presentation is going to be on talking
to satellites. And this is really a 101. You've never tried it before and you don't even know
where to begin. This is also going to be a one cut take like a normal DEF CON presentation
would be. So there's going to be a lot of flubs, a lot of hems, a lot of haws. That's
about it. Anyways, without further ado, let's get going. I can't even transition a slide
alright. So a little bit about me and my background. I started off my professional life as a civil
engineer. I went to college, got my bachelor's degree, master's degree in civil engineering,
became a professional engineer and realized it really wasn't for me. I didn't really like
it as much as I thought it was going to. I then got an opportunity to start a security
analyst position at Barracuda Networks. We started coming to DEF CON, DEF CON 22. So
I've been here for what, six years now, seven years now. And I love doing anything wireless.
I love wireless security. So I started playing in the wireless CTF and we won three years
in a row, I believe. And now I'm a village member. So now I get to help make the challenges.
And yeah, it's one of those things that the reason I started off with this is because
I forever feel like a noob. I forever feel like the imposter syndrome is a real thing.
And this talk is more of a, I'm not an expert in this, but it's something that I find really
interesting and it definitely encapsulates that hacker mentality. So if this is your
first DEF CON, you're going virtual, you're watching this talk, don't, don't hesitate
to get your feet wet to reach out to people. Because at the end of the day, I feel like
everybody feels like a noob. And if they don't, then they definitely are a noob. So that,
that I basically just want to give my background that I didn't have a, you know, computer science
degree. I didn't have a formal background in computer security or really anything at
all except for civil engineering. So don't, don't hesitate to get your, get yourself out
there. So this talk, talking to satellites, why? Personally, I think it's cool. The International
Space Station is specifically what we're going to be going to cover. But there's a lot of
satellites that are floating up above us or orbiting above us that, that are capable of,
you know, ham radio communication, or just communication from the ground, just by, by
normal citizens that don't require, you know, any special permission other than ham radio
license to transmit to. What's cool about the International Space Station, I mean, it's
orbiting 200 miles above us, which actually, when I, when I first started doing this, 200
miles didn't seem like a lot to me, it seemed like that, that should be orbiting higher
than that. But 200 miles up, it's going roughly 17,000 miles an hour. And that's 10 times
faster than a bullet, just kind of put it in like rough perspective. And it, it, it is
going, it's orbiting so quickly that it can go around the entire planet in about 90 minutes,
which I think is incredible. And it's also the most expensive object ever built, which
is kind of neat that just being a normal civilian, I can talk to the International Space
Station, even to astronauts on the International Space Station, with just, you know,
general equipment and just a ham radio license. And even if you don't have a ham radio
license, you can still listen to transmissions from the International Space Station, which
is also I think, pretty cool. So here's a quick overview. But basically, we're how to
talk to ISS on the cheap, the hows and the whys of, you know, why you'd want to do it
and how you do it, the gear that you're going to need, the software that you'll need, the
rough skills that you might need to have or, you know, brush up on timing when you're
going to talk to the International Space Station, because it's orbiting every 90 minutes.
And there's only very narrow windows that you can actually, you know, try and communicate
with it on. And then basically, just now that you have all this power, how not to be a jerk,
I feel like hacker mentality is the, you know, like, Oh, my gosh, we're gonna do all these
bad, terrible things. But at the end of the day, you know, should you, this is this is
something that's pretty cool. And you want to give others the opportunity to do it as
well. See, moving on. So the hows and whys. So there's AR-ISS, which is amateur radio
on the International Space Station. Basically, this is up there for educational purposes.
It's community driven. It's one of these things that kind of inspire the, you know, the heart
of people of, hey, what are we going to do with space? Why is space important? So I think
it's kind of cool that they have a couple, you know, amateur radio stations on board
in or not stations, but I guess transceivers on the International Space Station that are
that are meant for amateur radio operators to interact with. Specifically, what we're
going to be talking about is the two meter packet radio that's unattended on the International
Space Station. There are definitely some attempts that you can have where crew members might
be staffing the International Space Station and actually on the ham radio that you can
talk to via voice. However, to try and get that to work is is, you know, it's a far more
limited and you have to plan far more, you know, up in advance, whereas the unattended
packet radio basically is going to act as like a repeater for you. And it's always up
and always operational. And it's just one of those things that it's far easier to get
a communication, you know, repeated from the International Space Station because it's done
automatically. And there's a bunch of other operating modes that the International Space
Station has. And, you know, you can go online at any point in time and check that. But really
what we're going to be focusing on is the two meter packet radio. And it's also I also
had no idea that, you know, a lot of ISS crew members are also ham radio operators, which
I thought was kind of cool. Um, yeah, so we'll just, you know, break down the basics of it
to transmit and talk to the International Space Station, you're going to need a ham
license. And that's just a transmit. And that's really because you're going to be operating
on frequencies and with hardware that could, you know, cause issues for other people. So
it's not just like a cell phone where, you know, your phone is going to take responsibility
for talking back and forth to a cell tower. This is something that, you know, you're going
to have transmit power, and you want to be judicious with how you use it. However, that
being said, if there's something that's interesting to you, you can listen without a ham
license, no problem at all. You know, you don't need anything just to listen. It's really
just transmitting because that could affect other people. And if you want your ham radio
license, the ham radio village is offering a bleep $5 exams, which is, I mean, pretty
cheap, normally, I think $20. But everything's gonna be virtual, obviously, because it's
DEF CON and for $5 to, you know, make an attempt at your technician license. It's one of
those things, I think you have to renew it every 10 years. I definitely recommend checking
it out. You know, it's definitely a great opportunity. All right, so there's a lot of
things that I never quite understood when I was getting into all this. And I'm, again,
by all by no means an expert. So there's probably a ton of, you know, things in these slides
that a seasoned, you know, extra ham operator is going to know that I'm going to completely
flub up on. But I basically just this is something that, you know, I whenever I looked at this,
I would always kind of say, Oh, my gosh, I don't even know what all of this garbage
means. So when people always said two meter band, I had no idea what the heck is a two
meter band, you know, FM 1200 BPS packet radio, all that stuff just sounded like gibberish
to me, initially. And I really wish that somebody would have explained it to me in layman's
terms, you know, just so I could at least get the basics and then kind of dig down from
there at least, at least kind of get my feet wet. So if you look at that small little equation
on the right hand side of your screen, you're going to see it's C equals I think that's
lambda and then whatever the new I don't even know the Greek symbols, right. But at the
end of the day, what happens to C is the speed of light. So if you divide that by your frequency,
which is a megahertz, a megahertz is a million hertz, so million cycles per second. So, you
know, you can think of Wi Fi as 2.4 gigahertz, you know, or 5.8 gigahertz, just kind of put
that in perspective. So if you divide the speed of light by the megahertz of the frequency
you're transmitting on, you divide those two and you get two meters. That's, you know, kind of how
the math works out. And so when people say like, oh, it's only two meter band, well, you know,
that's the same thing as saying it's about, you know, 144 megahertz ish. And I think the two meter
bands anywhere from 144 to 148 megahertz. But but that's what people are talking about. So 70
centimeters, you can do the same, you know, the same math and figure out that it's, you know,
about 460 megahertz, I think of off the top of my head. And that's also considered VHF. So you'll
hear VHF, two meter and 144 megahertz. Those are all kind of in the same ballpark. You know, and
that's just one of those things to hear those terms thrown around a lot. And I had no idea what
they meant. So I figured it would be helpful to kind of throw out a slide and explain that briefly
when somebody says I'm operating on the two meter band. Oh, okay, that means 144 megahertz ish. You
know, and that's also considered VHF, very high frequency. So the next part of that, what is FM?
You probably have heard of AM FM radio on in your car. AM is amplitude modulation. So you can see
the little graphic on the bottom right of the screen. That's where the wave is actually
modulated up and down. So you can kind of think of this waves in a pond. You know, if you throw a
rock in and there's big splash, those waves are going to be bigger. And that's going to be
amplitude, you know, there's a varying amplitude there. Whereas FM is how close those waves are,
you know, in a ring and a circle. So I'm using my hands a lot. I don't probably look like a
you're stretching like a slinky. You know, FM waves, you're modulating the frequency how fast
it goes. So you know, there's AM FM. So we're looking at two meter band FM. So it's frequency
modulated. And this is typically not something that you're gonna have to worry about. It's lower
level stuff that the radio is going to take care of. But it's just good to know because I didn't
know it when I started out. Um, gosh, 1200 BPS. So it's BOD not BITS. If you mess this up, you know,
internet's gonna murder you because you're, you know, technically wrong. I always thought that
BOD and BITS were exactly the same. It wasn't until I dug into it that I actually realized,
oh, gosh, they're, you know, they can be different. So you can think of a BOD as like a signal
interval or like a pulse. And in the early days, I guess, I don't know, I wasn't around during the
early days. But early modems would do one BIT per BOD. So basically just be one BOD and one BIT
were the same. So 1200 BITS and 1200 BOD were the same exact thing. However, now there's craftiness
in there that allows you to transmit at a higher BIT rate with the same level of BOD rate. So if
you can transmit eight BITS in a single BOD pulse, that should come out to 9600 BITS per second,
even though your BOD rate is only 1200. I don't really know. Again, it's one of these things that
that's just what APRS or the packet radio service uses. The software takes care of it all for you.
You don't have to worry about it, but it is helpful to know so that the internet doesn't
murder you. And then the technique that is used for like, you know, packing things, you're
packing eight BITS per single BOD is called quadrature amplitude modulation. Say that at a
party and no one will want to talk to you. So it's one of those things, again, super nerdy stuff, but
it kind of helps to know. For me, you can look at that and at least kind of digest it and understand
maybe not why it's that way, but at least that that's what all of these things mean.
Somebody says, oh, two meter band FM at 1200 BOD, you kind of know what's going on there.
And then packet radio, you know, I guess to me this wasn't any news, but it's packetized data,
right? And so that's one of those things where instead of it just being a continuous flood of
data, all the data comes in packets. And especially for, you know, for APRS, it uses the AX25,
which includes your call sign. And I believe for FCC requirements, you need to transmit your call
sign anytime that you're going to transmit, you know, power out into the atmosphere. And so this
basically satisfies that. But yeah, data comes in in packets. And what happens is say you have
like a small walkie talkie, or not walkie talkie, but a small handheld radio. If you were to
transmit on that small radio, what's going to happen there is it is going to get sent out,
you know, and not a very far distance. And so the goal of the packet radio service,
packet reporting system, I can read my slides, is basically to repeat that information out
farther. So your handheld, you know, radio is going to only make a certain distance, hopefully
gets far enough away that, you know, that it can reach a larger repeater that's then going to take
your message and repeat it. And the way that APRS works, I think I have this in my next slide,
but the way that essentially works is you can select how far out you want that message to be
repeated. So if you're say, you know, out in the sticks, and there's not a whole lot of,
you know, there's not a whole lot of repeaters out there, you might want to set a wider setting,
or, you know, like a time to live, if you're familiar with, you know, internet lingo,
that basically says, hey, you know, repeat this out this many hops. And the whole goal of this
is essentially to reach what's called an IGate. And an IGate will take your packet radio, your
take, take your transmission, and put it on the public internet. So that way, you know,
anybody in the world then can now look at it or, you know, any other, if you have a program written
or something like that, you can digest that information and see where it's coming from,
from anywhere in the world. So APRS was created by somebody, his name is Bob Brun... I don't know
his last name. Bob created it, I believe, in 1973-ish. And if you look at this, this image
of the world, every, every continent-ish or every, you know, region of the world has a different,
slightly different frequency that it transmits APRS on. And those are all in megahertz. So you
can see anywhere in the United States, if you're, you know, which is where I am, at least, it's
going to be transmitted on 144.390 megahertz is the frequency that everything's going to share.
The kind of bummer part about that is that because we're all using, you know, and say we
ham operators, if we're all transmitting 144.390 megahertz, well, your transmission will interrupt
somebody else's transmission. So there's a lot of room for collision, especially when you figure
that every time you transmit a message, what's going to happen is that's going to be repeated
by any number of other larger repeaters. So there's a lot of, you know, potential congestion
in there. So it's one of those things that you don't always want to transmit your message as far
as it will possibly go. You just want to get it as far as you need to go to kind of be respectful
of the space. And again, I'm breaking all this down because you'll see why it's important when
it comes to the ISS later on. So automatic packet reporting system, that's what APRS stands for.
A lot of times what people will do is ham operators will have, you know, little tracking
beacon devices that have a GPS unit on there and they will beacon out, you know, a location at a
set interval, you know, it could be 10 minutes, could be one minute, whatever their specified
interval is. And they will beacon from the small transmitter to, you know, larger repeaters with
the intent of getting online. And this is useful if, you know, you're somewhere where there's not
cell coverage or, you know, this was invented before cell phones ever existed, like, I guess,
like as ubiquitous as they are now. And so it was a great way to track things, you know,
you can put them in your car, put them in a boat, put them in a plane, you know, people have used
them for hot air balloons, you know, and just all sorts of things where maybe cell coverage isn't
going to fit. This is a great way to track assets really. So you can see from this little image
there, you know, this is kind of like the traditional what people think of when they hear
APRS or, you know, packet radio. They think of a radio that actually transmits the signal.
They think of, there's a little device, I think it's called a terminal node controller. Yeah,
TNC, which basically takes your GPS data and any message data or any other additional data.
And it basically makes that into an audio format. You know, it encodes into an audio format that
then is transmitted out by your radio. So that's kind of the traditional way that this looks.
However, things have changed now since everybody has cell phones. So you can do a couple things
here. So instead of having, you know, a device that has to have onboard GPS, and you already
have to have an additional piece of GPS information and additional computer and additional
encoder and all this different stuff. Instead of what you're going to have here is you can have a
Raspberry Pi that does it. Or you could just have a phone that, you know, automatically has GPS on
board, automatically has the audio cable on board. And basically you hook up an audio cable or sound
card if you're using a Raspberry Pi to a radio. I chose Baofeng. People love and hate these types
of radios, but I like mine personally. And basically what you do is you use then these
devices to encode your message, you know, as an audio file that is then transmitted out your radio.
And the whole purpose of that is essentially, you know, you could take what used to be a giant
apparatus that would fill, you know, like an entire desk, and now it's something that can
easily go in your pocket and the batteries last for a pretty decent amount of time.
And so that's kind of how this, how like the hardware-wise, at least what you need or what
that looks like. The next part, at least what I, when I was starting out looking at this,
I thought that, man, I must need a ton of power in order to transmit to the International Space
Station. Like it must just be crazy amounts of power. I'm probably going to dim the lights in
my house trying to get the signal that far away. But really it's incredibly low. I've heard that
people have done it on as low as a single watt, but five watts that comes on your standard
Baofeng radio is more than enough to transmit to International Space Station.
And really, when you think about it, that's less power than what your,
what your, you know, your phone charger puts out, which I thought was pretty, pretty interesting
that you could transmit up to something orbiting up, up in, you know, upper atmosphere, you know,
low Earth orbit for just five watts. It just seems kind of crazy that, that there, you know,
that it can get that far, I guess. So this kind of is a better way to, to show what I was trying
to explain is that there's a little tracker. You can see that. I think that I've, I forget what
the name of that tracker is, but basically it's super small tracker. I think it's about a hundred
dollars that, you know, we'll, we'll beacon out, I believe one watt at a pre-described interval
with GPS and everything on board. And the whole goal of it is that that little transmitter may
not be able to get very far, but the whole point of it is that you're trying to reach a single
digipeter and these digipeters are set up by their ham radio operators. And if there's not one in your
area, you know, it's one of those things that'd be kind of cool to set one up just to spread the net
of APRS far and wide. But essentially the whole goal is for that little tracking device or, you
know, any other, any other end node that you maybe have in your pocket or whatever to transmit to a
higher power digipeter, you know, repeater that digitally repeats it with the express purpose
of really trying to get it to a larger gateway. And the gateway, you know, in this case is an
iGate and an iGate can then connect it to the internet. A nice part about that is once it's
connected to the internet, there are websites like APRS.fi, which will aggregate all of this data
globally. So you can look around and see all the devices that are transmitting out and about in
the world. And, you know, you can look at the other side of the world and just see all the devices
that are out there. And there's weather stations, there's, you know, hot air balloons, a lot of cars, boats,
planes, you name it. There's a lot of devices that are tracked, you know, on APRS. And it's kind of
neat to be able to see where all these devices are out on the internet. So that was a full big
explanation of APRS. And why it matters is that the ISS has one of these DigiPeters on board,
which at the end of the day is kind of neat because you figure normally you would try and, you know,
reach a DigiPeter that is going to be, say, on a mountaintop nearby. But really, if you can transmit
to the International Space Station and have it repeat your signal, so DigiPete your message,
well now you can be received on a huge far and wide area down below because the International
Space Station has a great vantage point on the rest of the planet. So what's kind of neat is I
think I've gotten up to 800 or 1,000 miles from how far I've heard somebody else transmit from.
And likewise, normally to, you know, transmit a message that far to, you know, 1,000 miles,
you would need a decent amount of power, a great vantage point, and, you know, everything would need
to be kind of go right to transmit on, you know, especially VHF or the two meter band that far.
Whereas now with the International Space Station, because of its vantage point in space and clear
line of sight, you know, down to the earth, you can transmit your message really far, which I,
again, I just think is really cool that, you know, the most expensive object that any, you know,
that's ever been built that we have the capability as, you know, as amateurs to be able to transmit
and relay a message off of it. I just think it's kind of neat. Yeah, so this is a website. If you
go to ariss.net, you know, it looks like what a website would look like if I made it. You know,
the graphics aren't crazy, but at the end of the day, it's really cool in that it aggregates all of
the stations that heard the ISS and have transmitted to the International Space Station. So again,
you don't need any hardware at all. If you have a phone, you can pull up ariss.net
and basically just see, oh, what stations around me have heard the International Space Station?
Where is the International Space Station? What messages are coming off the International Space
Station? Again, because the whole point of it, or maybe not the whole point of APRS, but, you know,
at least, at least a, I don't know, a takeaway of APRS is that if that information all gets
aggregated online, you know, you can see it from anywhere in the world, which I think, again, is
kind of neat. So let's talk about the hardware. I have made the horrific mistake in the past of
trying to post links to hardware on, you know, my slides and then, you know, I find a better price
somewhere or I find, oh, it's not there anymore. So what I'm going to try and do this time is,
if you want to look at the hardware, I'm going to try and keep an up-to-date list at github.com.
Again, you can see the link right there. And the whole purpose of that is so that I can update this
list and find better prices or whatever, because things change and, you know, there are better
spots, you know, to potentially get some stuff at. So again, this is kind of my like go-to hardware,
which again, if you look at it, it's pretty darn cheap. You're looking at $35, $20, $10, $8. You're
looking at under $100 to be able to transmit a signal to the international space station, which
again, for that price and the skill requirement and just being an amateur and a civilian,
I think is pretty cool. Baofeng Radio, this is a cheap Chinese radio. I personally really like
them. I know a lot of people on the internet have hate for them, but it works well for me.
And I find that it, you know, for $35, it's a great way to just, you know, not break the bank,
but really figure out if ham radio just in general is going to be a good hobby for you.
It has a lot of other capabilities. You can listen to normal FM radio, you know, can be a police
scanner. There's just a lot of other stuff that it can do. And so I really like it for $35 on Amazon.
You can't really beat it. So let's see. So it comes with what's, you know, a little stick antenna,
like what you'd see on a walkie talkie. That's what if you were to buy this Baofeng Radio,
it would come with, but you can build a directional antenna, which is what you're going to want
if you're going to talk to satellites or the International Space Station, because
a traditional stick antenna is going to radiate its signal out kind of like a donut. So if you're
to hold it like thumbs up, you know, so the radios, so the antenna sticking up, it's going to
radiate out like a donut. And I should probably have a slide in there that has, you know, these
radiation patterns. But really what we want is a directional antenna that kind of focuses that
beam more like a flashlight, you know, into the general spot in the sky where you're trying to
focus all of your energy. And so for $10, $20, you can really build your own antenna, which I
think is even cooler. And then you need an audio cable, an audio card, if you're going to use the
Raspberry Pi, or if you're, if you don't use Raspberry Pi at all, and you're just going to
use your cell phone, you know, typically most people have cell phones. And so just an audio
cord for that, you know, under $100, you can no problem transmit the International Space Station.
And again, I'm going to try and keep this updated. If there's something, you know,
missing from it, I'll shoot me a message and I can update it or see if there's
really anything else out there. And again, it's one of those things, you know, for the amount
of money, what you get out of it, especially because I'm sure a lot of you have kids that
are home from school, or maybe you're a kid that, you know, is learning remotely now.
What an awesome project for under $100 to learn about physics, space, orbits, math, you know,
all these things that are super nerdy, because I'm super nerd, but really, there's a lot of other
applicable lessons to other stuff out there. The other thing that you're going to want to do is
turn on Vox. Again, this is one of those things that I'm probably getting internet hate mail for.
Vox is voice operated switch. So basically, you can think of it as when you start talking,
radio is going to detect that you're that you're talking already, and it will then start
transmitting right away. That's nice, because that means if you plug an audio cable in from
your phone or from a Raspberry Pi, the second that it starts playing audio over that jack,
it's going to start transmitting. Why this isn't ideal is because there's always a little bit of
space of, you know, a little bit of transmit time after you're done talking where the radio is still
on and that can mess up some some communications. So it's not ideal, you really want push to talk.
But if you're just getting started, it doesn't hurt just to use Vox just to just to get your
feet wet. That's my personal opinion. Again, going to get hate mail, I'm sure. But whatever.
So I own an aero directional antenna from it's very similar to the one that's in that image
right there. It's like $150, which is more than the entire cost of the project. And if hand radio
is potentially something you're not going to get into, you know, you're going to want to buy some
giant antenna. I don't really know. Personally, I have one because it's something that I really
enjoy. However, it's $150 and it's pretty steep. Or you could build your own. And this is one of
those things that I was just, you know, checking stuff out online and I saw that somebody had built
a their own directional Yagi antenna for like $10 in like PVC parts and like a measuring tape,
which is like perfect because I build everything with Raspberry Pis in PVC anyway. So I had a lot
of that basically just lying around. And a measuring tape, which funnily enough, I didn't
even think about it, but I guess it's, you know, measuring tapes are steel. And so if you, as long
as you, you know, basically sand off the tips of your antenna to solder your cables to, it's one
of those things that, oh, wow, that's kind of neat. Like you can make an antenna out of a steel
measuring tape and it folds up nicely too, which is the added benefit. I'll have a link to this on
that GitHub page that I mentioned, but if you just want to Google it right now while you're
watching this, if you just do Legios, I don't know how you say it, that's how you say it, but that's
how I say it. And then Yagi, all the instructions, the build list, everything. I'm not going to go
over all the super details or my time-lapse of me building mine, because it's not really necessary
at all. Just go online, look at it. Plenty of other people have done a lot of work to make that
pretty nice. So it's one of those things too that like, I personally think this is a nerd merit badge
to build your own antenna. That's one of those things, if you're a student, if this is
interesting to you, it kind of gives you a little bit more stake in it, not just to like, oh, I
bought all this stuff off the internet, put it together, and I can talk to International Space
Station. There's a little bit of that like hacker spirit, hacker mentality, just to like, you know,
I built this antenna out of raw parts, you know, and kind of cobbled it together to get it to work.
To me personally, I think that's kind of neat, just to, you know, kind of have this project of
like, yeah, this is something I built with my hands, and you know, I'm talking to the most
expensive object, you know, that humanity's ever built, you know, arguably, right?
And it's just kind of cool to me that you can talk to International Space Station with PVC
and a measuring tape and like a radio that you bought off Amazon. And it takes about an hour
to build. If you have kids and you want to at all get them interested in space and engineering and
STEM stuff, you know, or just to get their hands dirty. I think this is personally a really cool
project, and it's not going to break the bank to try it. And let's see, I don't know why I can't
change sides. Oh, there it goes. So this is my antenna up on top of my patio. It's on top of my
patio, obviously, so I can get a better line of sight. And I keep everything in my little ammo
box. And I use a tripod. But again, you can just hold your hand out there with an extra piece of
PVC and it works just as well. It's one of those things that it looks, it looks homemade. And
that's what it is. But you're talking to a satellite with a homemade antenna. I think
that's pretty cool. Um, so obviously, if you build your own antenna, you're gonna have to tune it a
little bit. Luckily, if you follow the instructions online of the, you know, of the antenna that at
least I made, when I went to tune it, and from what I've heard from others, when they go to tune
it, everything is pretty spot on it if you measure things carefully. But the way that you tune your
antenna is by looking at the standing wave ratio or SWR. And this really just measures the
performance. I like to think of it as say you have a, a like a tube of like, you know, gift wrap,
right? And you shout down that tube, how much of your sound that's from leaving your mouth going
through the tube is actually making its way out the tube. And that's kind of how you can think of
SWR working with your antenna of, hey, if I'm going to put five watts of power into my antenna,
how much of that power is actually going to be coming out my antenna, or how much of it's going
to be wasted, you know, kind of just banging around the, you know, just kind of radiating
off of it. So there's one of those things that that, you know, if you know, a ham radio operator,
I'm sure they have, you know, a SWR meter, you can buy a cheap one online for $20. I don't have
one of those. I don't know how well it works. I personally have a nano VNA. It was like 50 or
something dollars online and does a bunch more stuff other than just looking at SWR, but it's
really small, has a battery. I personally really like it. But again, if you're trying to not break
the bank, you know, maybe a $20 one online is worth it. Or you find a ham radio operator that
you just say, hey, can I plug this in real quick and test it? You know, there are plenty of older
ham radio operators that would love nothing more than the talk radio and talk shop. And it's a
great way to, you know, build a community, build a hobby, because ham radio operating is an aging
hobby. You know, just go to any ham radio operator meeting, you know, in your city, in your state,
in your wherever you're from. And it's definitely an older person's hobby. But I don't think it has
to be that way at all. The next thing is, it's really just one of those things that if you follow
the instructions, you can probably have a pretty good SWR. And again, I think mine when I did it
was 1.3 to 1, which I think perfect SWR is 1 to 1. To me, this is just magic. I don't really
understand how it works. I just know that you want your numbers to be as close to 1 to 1 as possible.
Again, if I'm wrong, shoot me a message and let me know and I'll update the slides.
So the next piece of this is the software. Again, I have lots of Raspberry Pis lying around
from a bunch of other projects. I personally like to use Raspberry Pi. I use the software called
Direwolf. It's just an apt-get install. Again, if you check out the GitHub page, I'll have the
instructions on how to set it up perfectly, as well as my configuration files to kind of mess
with so you can look at them and not have to recreate it from scratch. And then when you
install Direwolf, it'll also install Kissutil, which is what I use to be able to transmit messages
into Direwolf. And then the next thing is there's a tool called Zaster. I don't know how you actually
say that because it has an X and a str in it. So I don't know. I assume that's how you say it.
And this is more of a GUI tool that you can have on the Raspberry Pi, which is kind of neat
because you can see, you know, it'll automatically plot where radio transmissions are coming from
as they come in through APRS. So if you were to be receiving information and you had Zaster up and
running and you're receiving it with Direwolf, you could potentially see all of the beaconing devices
or all the other APRS, you know, transmitters that are out and about, which is kind of cool when
the ISS goes over and all of a sudden you have to zoom far out to see, wow, look, there's all these
people, you know, transmitting from all over the world. The last time that I did this, I got a
contact from Canada, which, you know, I'm in central California, right? So it's, you know,
crossing over at least two states just to get there and a good part of California as well. So
I thought that was kind of neat. And those are all applications that you want to look at if this
is something you're interested in. There's also a lot of APRS applications for phones. I personally,
like I said, I use the, you know, I use the Raspberry Pi. So that's not something that I'm,
you know, I've checked out a couple of them for iOS, but I haven't played with any of the Android
applications. So it's one of those things that I would just recommend checking out an app. You can
get trials, I'm sure, of all of these applications and just try it out. Hook up an audio jack to your
phone and, you know, just plug it in your Baofeng and you're off to the races. And it's one of those
things that your phone is kind of the perfect device. It has a battery, has a GPS, has a nice
touchscreen, and it can encode audio like nobody's business. So it's one of those things that before,
like I said, you'd have a desk full of equipment, and now it's a phone and a radio. And that's all
that's really required, as long as you have the audio cable in between. Let's see. So the next
part of this is planning your path of like when the ISS is going to be over. This is a screenshot
from my app when I was doing the slides. I use this application called GoSatWatch. It's for iOS.
It gives you a little bit of augmented reality, which I really like. So what you can see, at least
from this screen, is you can see that this is like currently where the International Space Station is
and you can see like, you know, what its orbit is. It's kind of cool. It gives you statistics of,
you know, how high, you know, how high it is. So you can see it's like 264 miles,
you know, orbiting like that's its altitude elevation. I don't know the technical satellite
terms for that. It's also going 17,000 miles an hour. And then you can kind of see how far it is
relative to where you are. And what's nice is that if you are trying to make, you know, some
communication, if you're trying to digipede off of the ISS, what this app allows you to do is if
you hit the sky button down below, you can actually hold up your phone. And since it has the compass
and everything in there, it'll kind of like orient as to like where do you want to point your
antenna up in the sky to be able to get your, you know, best transmission or, you know, your best,
you know, point of contact. And it gives you live stats. It'll notify you on good passes. And then
you can, you know, based upon where you are, you can see all the different times of day or night
when the ISS is going to come. And it also does a ton of other satellites. And that's another thing
that I probably neglected to mention is that this is just talking to, or this talk is just going
over talking to the ISS. But there are tons of other satellites out there that also perform
basically the same operations. All right, let's see. Sorry, I had to resume it. But yeah, so this
application is great. I think it was like $7 in the App Store. But there are plenty of other
applications that probably do similar things to just check out. It's worthwhile, at least.
And the other thing too, that again, I really like about this is that it'll notify you and you can
point this app up and you can see like where in the sky it is. And that matters for a couple of
reasons, which we'll go over here in a second. So when you're planning your pass, you also have to
take into effect the Doppler effect. I really like the, I'm not sure if anybody's seen Big Bang
Theory. I'm sure plenty of you have Sheldon's costume of the Doppler effect. I just had to
throw it in there. But you've all heard the Doppler effect before. It's, you know, if an
ambulance or police car is going by, as you can see the little graphic down below, you know, if
it's going away from you, the sound will appear, you know, slower because it's a lower, you know,
longer wavelength. And as the car's approaching you, it'll be higher pitch because it's a smaller
wavelength relative to, you know, the object that's traveling. And because the International
Space Station is traveling at 17,000 miles an hour relative to where you are on the planet,
it's actually having the frequency, you know, its frequency that that's on board is Doppler
shifting. So when it's coming by you, it's going to be at a higher frequency, you know, so it's
going to be 145.825 megahertz plus 3.5 kilohertz. And then as it's leaving, you know, so as it's
going away from you, it's going to be a longer wavelength. I hope I did that right. If not, again,
whatever you understand, that depending on where you are situated on the planet and where
the International Space Station is either approaching or leaving you, it's going to change
slightly the frequency that you're going to tune your radio to. Personally, what I do for this is
I try and find a pass when the International Space Station is as far overhead as possible,
or as close to overhead as possible, because then there will be no Doppler shift that I really have
to take into account. And again, a single pass is about five minutes, so you don't have a lot of time
to really fiddle with your radio and try and readjust or do anything like that. So this is
one of those things to take into account to try and find a pass where the International Space
Station is coming as close to overhead as possible. And you can go Google this online, you don't even
need an app for it. But I personally found that having the app makes it easier to make more longer
distance communications, because if the International Space Station is directly above you, and you're
sending a signal to it, well, it's going to radiate that, or it's going to digitally beat that signal
right below you. So you're not going to get a contact that's going to be far away necessarily,
or at least as far as you can possibly get it. The optimal kind of thing, if you're looking to try
and transmit your signal as far as possible, would be to kind of hit the edge of the International
Space Station and then have it transmit at a farther area away from you. Again, it's one of
those things, you know, you can see, I'll go back a couple slides, you can see the size of the area
that International Space Station covers. So at any given point, you can hit, you know, that's a large
portion, you know, of whatever that land mass is, Asia and Europe. And then if that were to fly over
the United States, you know, it covers a good portion. And when it flies over California,
you can hit Idaho, Colorado, you know, again, depending on whatever its orbit is.
Okay, so this was the hardest part for me, is finding out how to actually send a message. I
didn't think it would be as difficult as it was. But again, I was using Raspberry Pi, and I was
trying to do everything on command line. And maybe I was making it more difficult for myself
than I really needed to. But again, I could use my phone had it been easier. But again,
with some of the plans that I have going forward, I'd rather do this kind of more in an automated
fashion. So I use screen, you can use tmux, you can use multiple putty sessions, or you know,
whatever you want to connect to your Raspberry Pi. But essentially, I had three separate screens
for my Raspberry Pi. I had direwolf that ran my direwolf configuration. That's what dash c is,
dash t is to not do any color on the output of when direwolf runs. I have the kissutil,
which is installed when you install direwolf. And basically, I have the folder rx and the folder tx
that you know, if anything I receive will go into the rx folder, anything that I transmit will go
into the tx folder. And so that's kind of nice, because I can just drop text files in there.
And then the kissutil and direwolf will take care of converting that to audio and then transmitting
it out, which is which is awesome, because then at that point, you can script up whatever you
want, you can do things on in an automated manner or manually. But again, you only have five minutes
or so that you're trying to, you know, communicate with International Space Station. And then even
more of a narrow window when it's directly above your when it's kind of primetime. And you don't
want to necessarily, you know, you want to have everything set up in such a way to where you can
send out a single message per pass, you know, or maybe just a handful of messages per pass,
because there are other people also trying to communicate with it. And if you remember,
the International Space Station is operating on a single frequency, you know, it's operating on
145.825 megahertz, which again, I don't know if I put that in notes, but again, it'll be,
you Google it, right? Like it's out there. But, but only one person can talk to International
Space Station at a time. So you don't want to be constantly transmitting, because then you'll
prevent other people from also communicating with it. So basically, what I had is on a I believe
every minute interval, I would have it, you know, copy my message.txt into the transmit folder,
and they would shoot that message off, or you know, transmit that message off, I guess I should
say. And so what's kind of neat about this is that you can script it up in such a way that you know,
if you have a program that you want to have automatically begin something out, you can,
or anything like that. Personally, I like that. But if this is just you're just trying to make
a contact, or you know, you're trying to, you know, begin some or did you be digipeded off of
the International Space Station? Oh my gosh, I can't talk. If you want to be digipeded off the
International Space Station, that's your only goal. You know, just with your phone, you can
just send the message out that way manually, you don't have to go through all this direwolf
craziness. Most most phone applications should be able to do it pretty darn easily.
This is a simple message. So if you have a, you know, a client on here, this is this is one of
those things that like this is what I use. Basically, I transmit this text in that message
dot txt. Again, that's my call sign. When you see my call sign, or so then you see AR ISS,
essentially, all that means is that you want to be digipeded by the International Space Station,
that's its call sign. And when you do that, you basically are just saying, Hey, I want you to
digipede this message to the International Space Station. And then what you have is you have my
call sign again, followed by dash seven, that's because it's my mobile unit. Again, not getting
too deep into APRS, having that designation there, that dash seven is just showing that you're
mobile. And then the next, you know, digits and numbers right there, it's kind of a weirdly
encoded way that I had to like Google how to do of what your current GPS coordinates are. And then
after that, you can see, you know, your message. So digipeding, you know, DEFCON 28, Aerospace
Village out to the International Space Station, which then gets relayed, you know, down to
ground stations that receive that message and then off to the greater internet. This is the folder
structure. So when I run direwolf, I run it from my home directory, direwolf config is right there.
And then I have a tx and an rx folder for the messages that I'm going to send go into the tx
folder and messages that I'm going to receive come from or, you know, get placed in the rx folder.
Um, let's see, let's see if I can get this. All right, so some of the things going forward,
I think that are important to cover, you know, so my goal of this is I want to automate it,
I want to make some rotors and rotors, if you're not familiar, are basically what it would allow,
you know, rotors would allow me to change the elevation, you know, up and down. So like,
if you're looking like a tripod is a great example, right? I could, you know, change the
orientation 360 degrees, like a compass, and then the elevation up and down. Because it'd be really
cool if on the Raspberry Pi you had some software that basically tracked where the International
Space Station was, and anytime it was up overhead to transmit a message automatically. So that's
kind of my idea of what I think would be kind of neat. So we'll see how that goes. And then I would
also like to see, you know, how far away can I hear from, you know, or how far could I be
digipeded by the International Space Station? And if you kind of think about it, you know,
out onto the horizon. So if you were, if you were out, you know, basically to the horizon,
that would be zero degrees. But obviously there are trees, there are houses, there are all those
things in the way. And so there's a point at which, you know, you can hit the International
Space Station, you know, with a signal, maybe is that 20 degrees? Is it 30 degrees? Is it 40 degrees?
The higher the elevation is, relative to where you are on the ground,
the easier it will be to communicate with it. So it's one of those things that automating it,
I think would be kind of neat. And then I also like to, you know, investigate looking at other
satellites. Yeah, and basically just just seeing what else is out there. A huge thank you to AMSAT
and ARISS.net just because checking out that website inspired me to, you know, try and get
on the board. It's in the AMSAT. There's tons of great information there on how other people have,
you know, had successful communications. And really at the end of the day, I think this is
just something that's kind of cool. You know, the hacker mindset here of just kind of scraping and
cobbling together all these things to really do something that's kind of neat to be able to
transmit to the International Space Station. Not to mention too, that this is how you can transmit
to a lot of other satellites. And it's really kind of covers the basics in terms of what's
required to talk to a satellite, right? There's a whole bunch of different satellite orbits, a whole
bunch of different satellite communication protocols, frequencies, modulations, and this is
just dipping your toe in the water of what's available and what's out there. And it's for
honestly a pretty small budget, right? For $100, $200 you could get a really solid setup to, you
know, to communicate with the International Space Station with other satellites with just a HAM
license, you know, just be an amateur radio operator. And if you just want to hear, if you
just want to listen to what gets transmitted, you know, you can do that without a license. And
really, you can just get a Baofeng radio, your phone, and, you know, it doesn't even have to be a
directional antenna at that point. You know, if you just want to listen, you can have an omni-directional
antenna, which is basically just, you know, a longer version of the normal stick antenna that would
come with the Baofeng. Again, I'll post links to everything on that GitHub page. But yeah, at the
end of the day, this is a great way just to get started if it's something that you're
interested in. And then from there, who knows how much farther you can level up and, you know, what
other satellite communications you can do. You can spend thousands and thousands of dollars and,
you know, sink a full-time work week into all of this stuff, especially as an amateur. So it
definitely helps to have a good starting point and to have a good point in time of, like, this is
something that I can measurably check off a list and do. And especially, again, I know that I've
said it a bunch of times, but if you have kids at home, if, you know, you're a kid at home, this is a
great project to really get your feet wet and you learn a ton of different principles from physics
to, you know, radio to computers to, you know, protocols to just... there's so many small
lessons intertwined that I just think it's kind of one of those perfect projects to, you know,
to basically figure out if it's for you, if ham radio operating is for you, to find out if chasing
satellites across the sky is for you. So again, I encourage you to take a look at it. Feel free
to check out the GitHub page. I'll post some of my contact information on there along with the
links to all the hardware and all the apps and all the things that I've mentioned. And yeah,
hope you enjoyed the talk. Let's see, how do I pause this thing?