What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Home brewed ADS-B receiver

hobby_rv6

Member
As an amateur radio operator, I occasionally use my 2 meter and 70cm hand held radios as the transceiver portion of a packet setup. I wire the audio output from my radio to a dedicated TNC (terminal node controller) which is then interfaced to the PC, but others feed the radio audio output into the audio input on a PC audio card and use software on the PC to handle the modem function and eliminate the TNC.

There are a couple of threads on the internet describing how to use a surplus satellite receiver as the starting point for an ADS-B receiver, tapping into the IF portion of the circuit to capture a usable signal, but it looks like way too much work and technical knowledge required for me if I already have a radio capable of receiving these frequencies.

I was wondering - I have an Icom scanner capable of receiving the 978Mhz and the 1080Mhz frequencies. If this scanner could receive the correct modulation, it seems like one might be able to construct a similar setup to packet described above. I know that software would need to be written, but the data sequence is a public specifation. If you could use a relatively low cost scanner and your existing PC with a graphical depiction on your PC screen to monitor ADS-B traffic in your area, it might be fun and useful.

Has anyone tried to constuct such a critter? Is it even feasible?

Hobby
RV-6 flying
270 hours
 
Most of the FAA's plan for ADS-B stuff is based on having ADS-B transmit capability in the aircraft. Meaning your airframe is sending information to the FAA and they are the consumers of your info.

A political hot point is their lack of a requirement to "re-broadcast" that information so the folks in aircraft have access to the same weather, traffic, and other information that the FAA is working with on the ground. That's all up for debate because the FAA doesn't want to pay for ADS-B to have an uplink.

Within their (possible) uplink architecture, there is (supposedly) a mechanism to prevent the mooching of ADS-B information. This means the FAA would not broadcast ADS-B information unless there is an ADS-B transmitter in range and transmitting to them.

So I think this shoots a hole in your plan. I do like the idea though of using something software based like a West Mountain Radio device and using software to decode the audio. I just think that model wouldn't work in the real ADS-B environment.

Phil - N5QCN
 
What I am talking about is something for the home, hangar, or FBO situation - not for an airborn application. Currently I have a radio in the hangar tuned to the local tower frequency to listen to who's departing and arriving while I am at the airport. A ground based ADS-B setup would allow me to "see" where the traffic was.
I have read about the debate and potential for the FAA to "cripple" receive only devices, in an effort to encourage everyone to have a transmitting unit in their aircraft. The Next Gen plan is based on all traffic participating by having working ADS-B transmitters. They don't really care if you have an ADS-B receiver as long as you have an ADS-B transmitter.
As I said earlier, this is just a thought about cobbling together some inexpensive components to allow me to "see" who's out flying while I'm at home or at the hangar.
 
First off I am a ADS-B Out mandate opponent.

However, I have not heard, and do not believe, that the FAA does not want to transmit ADS-B info from their ground systems. Maybe they do not want to transmit weather but to not transmit traffic info for folks with ADS-B In capability seems really odd.

If true (provide a source please) then it is ammunition to kill the ADS-B Out mandate on GA aircraft.
 
Phil, the FAA ADS-B Out mandate does not require ADS-B In capability which is where a pilot should get traffic, weather, etc. That does not mean that the information will not be transmitted or that pilots cannot equip with ADS-B In capability.
 
That means the FAA has a requirement for the pilot to send information only. There is no requirement for them to send a single packet of data back to the pilot. If you're okay with "hope" being a commitment on their part, that's fine. I'm not.

The FAA needs to mandate that they will be sending information for the aircraft to utilize. That is something the FAA has been unwilling to do because they don't want to be on the hook to pay for the infrastructure.

This means every one of us will be paying for and installing ADS-B out (on our nickle) so we can send the FAA the information they require from us. They don't want to step up to their half of the equation.

Can they send it? Absolutely.

Are they willing to step up to the plate and write it into their mandate? Absolutely not.

That's the problem. They want to keep the backdoor open so they can slip out of it and leave us with nothing more than an expensive and glorified transponder in the aircraft.

Don't get your hopes up on having access to any data until they get it mandated.

When was the last time you've seen the FAA spend any money to make like easier on the pilots? Historically they demand that we spend our money to make their lives easier on them. That's the same path ADS-B is heading down right now.

I hope it changes...
 
Last edited:
Ok Phil, I think I understand your reasoning. I honestly do not know if that is what will happen. Many of your points are exactly why I am against this mandate and will probably soon go Congressional to try to stop its applicability to GA aircraft. May not work but I have to try.

There was a FAA response to one concern about benefits and it was suggested that this mandate not apply to GA. The FAA stated that unless it applies at listed in the mandate, full benefits (or some such language) would not be achievable. I read that to mean full cost reduction for the FAA...on our nickle to use your words (and you are right). We pay a lot so the FAA can save money...and we get nada for it.

The essence of your concern is not one I had imagined but may be a possible scenario.
 
Yeah, I'm kinda black and white on ADS-B. Either all-in or folding.

If it's fully implemented, I think it's great. Especially for those who are flying in really congested areas. But if they aren't going to implement it fully, then I really don't want any part of it.

As it stands right now, I fall in the opposed camp like you. If they will step up and commit to fully implementing the system, then I'd easily swap camps and support it.

The good news is that we have 10 more years for them to change their mind. :)
 
To the OP:

The ADS-B data on both the 978MHz and 1090MHz frequencies has about 1MHz of bandwidth. This means you need a receiver that can take in a 1+ MHz wide channel and pass it on.

Most scanners are audio devices so they don't support more than 20KHz of bandwith. This is why they use the satellite receivers, since those do support wide bandwidths. Your sound card can only digitize about 20KHz of bandwith also.
 
A mate of mine and myself built a homebrewed ADS-B receiver, however its a very complex and detailed effort.

We used the Ettus USRP1 running at 8MHz bandwidth. The minimum sample rate you need is 2MHz, as Dynon have said this means 1 Mhz minimum bandwidth (Nyquist/Shannon theorem)

Put it this way, my mate is a PHD student in software engineering, and it took about 2 grand worth of hardware and 18 months to get the project to this stage:-

Fast forward to 11:38 mins its a great presentation --> http://www.youtube.com/watch?v=Vn-dpUegUDQ
 
I know this is kind of off-topic by now, but I keep reading comments here on VAF like Ron's or Phil's about how bad it is if planes need to transmit their position, but nobody on the ground relays it, and how useless this is and all that.

Living in a country with no ADS-B traffic information coming from ATC, I nevertheless have an ADS-B receiver in my plane, and I see all the traffic with ADS-B-out withing 30nm around me. I definitely wish that more (all!) planes had ADS-B-out. Independently of ATC relaying it or not. Because, lets face it, the little traffic monitor in your panel doesn't care whether the information it displays comes from the ground or directly from the other airplane. And yes, I do enjoy to see that low-level jet traffic before it blasts by when I'm on the ridge with my glider, and I do like to see that helicopter that is about to come out of the cloud right next to me.

I surely wouldn't like to miss it, and I can't understand how anybody doesn't like to be visible to the aircraft around him and doesn't want to see the other traffic.
 
Thanks Hendrik you answered my question before I asked. So we can get traffic by listening to the broadcasts of other aircraft. This doesn't fix all of the short comings of ADS-B out only but its something.

Brian
 
Back
Top