Funke TRT800H and PilotAware

[Steevo25]

Hi Everyone,

It seems there are quite a few people on here connecting the PAW GPS out to the Funke TRT800H transponder. I have done this many times on the Trig TT21 but did it for the first time on a Funke over the weekend.

Everything connected up fine and the Funke was showing a valid GPS position. But using a 2nd PilotAware unit, it is not showing up on the traffic screen. Then moving the aircraft around, I noticed it briefly displayed on the PAW. Now on the Trig, it will show on the traffic screen permanently with the ADS-B parameters regardless of whether you are flying or on the ground in the hangar.

Does anyone know if the Funke only transmits ADS-B when it is being interrogated.

I have confirmed that the coax, antenna etc is all working by temporarily installing a Trig but whatever I do, I cannot get the Funke to display except briefly when the aircraft is being moved around the airfield. This has lead me to believe that it only transmits when it is being interrogated. I was under the impression that ADS-B should transmit at regular intervals regardless of whether it is being interrogated. Certainly, the Trig TT21 displays on the traffic screen as soon as it is turned to alt and this can be inside the hangar.

Regards
Steve

[Robski]

Does anyone know if the Funke only transmits ADS-B when it is being interrogated.

Good question. I have wondered about this for all S/ADS-B transponders.

Will an ADS-B signal get transmitted in the absence of an SSR interrogation?
If so how long after the final interrogation does an 'ADS-B only' transmission get made?

[PaulSS]

The extended squitter is the major difference between a Mode C transponder and a Mode S. A 'squit' is a package of information that is routinely sent from the Mode S transponder and it does this all the time i.e. without being interrogated. An extended squitter just adds more information to that package once it has the extra parameters which it receives from a GPS input.

So, to answer the question, NO a Mode S transponder does not need to be interrogated, since it squits all the time and adding a GPS input only means it adds a few more bits of info to the same squit.

Now, that is the theory and it obviously works with the Trig unit. The same SHOULD be true of the Funke but I think the only way of finding out is to talk to them directly.

[exfirepro]

Paul / Steve,

You are correct re the Short Squitter Paul, the only problem is that short squitter (AIUI) only contains the ID i.e. Hex of the transmitting aircraft, which isn't enough to generate an entry on the PAW Traffic Screen.

My experience is with Trigs, which definitely transmit the Mode S - Extended Squitter without the need for interrogation as Paul has said, hence why the Trigs show up in the Table. I'm afraid I can't say if the Funke is the same.

Regards

Peter

Edit: Just did a Forum Search - have you seen this document. Doesn't give the answer directly but tells where to look in the Funke Documentation and gives Funke contact info.

http://docs.fasvig.info/ADS-B/Funke_TRT800A-H_Connection_uncertified_GPS.pdf

[Steevo25]

Thanks everyone for your comments.

I have fired an email off to Funke but after further testing, it does seem that the Funke only sends the info when it is being interrogated. I had another play today and whilst on the apron, I was getting nothing on the PAW even though the indicator on the Funke was flashing on odd occasions to say it was sending. Whilst moving the aircraft, I noticed that it would appear on the PAW traffic screen briefly and then disappear.

Then I flew the aircraft and took my laptop and 2nd PAW unit with me. During the flight, the Funke was appearing on the traffic screen as full ADS-B even with the correct value for SIL and SDA (set to zero as the LAA require).

When I landed and stopped, the Funke disappeared from the traffic screen and again whilst taxying, it would appear briefly and then disappear.

This is definitely not how I anticipated it would work. With the Trigs, as soon as your turn them to alt, they appear on the PAW traffic page all the time whether flying or not and whether being interrogated or not. Surely this is a mistake by Funke, I have now found another couple of people who say their TRT800H work the same way. According to any documentation I have read, a transponder with ES should broadcast at a regular intervals regardless of being interrogated by ATC.

[exfirepro]

Disappointing 

It will be interesting to hear what you get back from Funke. In practice this shouldn't be a major problem, but would certainly seriously reduce the effectiveness of ADSB if you regularly fly in areas with no Radar / TCAS coverage ! 

Please let us know what they say.

Regards

Peter

[Steevo25]

Just an update for anyone that is interested.

During my search across the internet for this issue, I came across a few other people with the same issue. I also found a couple of posts on here where the OP had asked a similar question although they did have a much earlier version of the firmware (4.. I also discovered another pilot had reported the issue to Funke as well.

I had a reply from Funke this morning and there first suggestion was moving the PilotAware unit a greater distance away from the transponder. They said that due to the Funke being a class 1 transponder and putting out double the power of a class 2 (i.e. Trig TT21), it is possible to overload the DVB-T antennas. I have had no difference at 2m or 30m and I have never had an issue with a Trig TT22 which is also a class 1. They also said they were obtaining a PilotAware unit over the next week or two to test the issue.

[Keithvinning]

Ah so thats why they bought one. Nice

[exfirepro]

Next thing we know, they'll be on here asking how to work it 

[AlanK]

So no point in rushing out to get the cable to "test" on my 4.8 version?  

Its 300 euro to upgrade the FW so even if they fix this how many people are going to stump up that!?

[Steevo25]

Just some further update. I believe this to be a coax issue and not a Funke issue so you may not need a firmware update.

It seems the Trigs are a bit more tolerable of bad coax than the Funke is.  Unfortunately for me, I have only just bought the aircraft and installed the Funke on the original wire and cabling to upgrade the original Filser transponder (non ADSB). I didn't check what was there. I ripped it all apart over the weekend only to find that the coax was RG58 and well beyond the length recommended for RG58 for a transponder (around 7ft). The Trig works on this but the Funke doesn't. Replacing the coax with RG400 (which is what I usually only ever use) and the Funke has sprung in to life. I guess this is the reason I was getting it shown on PAW on an adhoc basis and I guess when flying and away from all objects, the coax was just about coping. RG58 is not recommended for transponders at all and RG400 up to about 8ft.

I also guess that it works perfectly on Mode A and Mode C as this is just interrogations and you probably wouldn't notice a few dropped ones on a ramp tester whereas ADSB is a constant broadcast. Waiting to try this fix with another person who has the issue that I suspect also has RG58 coax.

[Wadoadi]

I can confirm the Funke with firmware 5.2 does emit the full squitter message while on the ground.

We had ours up dated at our cost, due to it "dropping out" on some ATCs, Norwich being a case in point. We were told by NATs that it was a know compatibility issue. We also found a service notice from Funke confirming this, once upgraded we connected a mouse GPS and all has been rock solid since.

 

[AlanK]

Sounds like you may have upgraded to mod10 plus a more recent fw alongside as from what I understand the drop out on mode S was the mod thing causing issues with certain ATCs but not seen the FW being an issue alone.

That said I would love to know what he issues with PAW on earlier FUNKE FW version might be so know what to look out for.  I am up in Scotland so limited time in areas where the transponder operation might be so critical but want the conspicuousancy PAW affords.

[Wadoadi]

below is the info on the mode

http://www.funkeavionics.de/fileadmin/user_upload/Dateien/Service/Service/en/SB_TRT800-A-H-1_Rev1.04.pdf

[AlanK]

Sorry. Meant to say we have mod10 after a previous issue with transponder on purchase, just not the FW version needed for PAW (only 4.

Thanks though as took me ages working it out first time around so no doubt help someone reading this in future