Transponder

[mholton63]

I'm looking for a good working transponder with tray unless you have a Narco AT150 TSO.

 

[Old3pacer]

Saw a couple on ebay

 

[mholton63]

So I purchased a good used (and tested) Garmin 320A transponder and installed it with the new tray. This was due to my old Narco AT150 only transmitting 0000. After I installed my new used transponder and turned it on, all I get is 0000. Obviously it wasn’t the transponder. Anyone have any ideas? I disconnected my antenna and used a new short cable to connect it to my Garmin thinking it might have had a bad cable, but I still get 0000. This is according to my Uavionix ADSB out. Thought?

 

[Jspey]

What does ATC say you're squawking? I don't know which Uavionix you have, but I came across this: https://uavionix.com/skybeacon-software-upgrade-to-ads-b-1-5-1/

• Flight Plan ID (squawk code) is now reported as ‘0000’ instead of ‘Not Available’, prior to the skyBeacon Transponder Monitor detecting a squawk code. This situation can occur in non-radar environments, or prior to achieving radar contact. The change is in accordance with updated TSO deviations as approved for skyBeacon, to better integrate with the operational characteristics of FAA Air traffic control (A

 

[mholton63]

I’ve not flown it yet to find out. That was going to be my next step. I have both Skybeacon.

 

[Steve Pierce]

I would get with an avionics shop, they are going to have to test that new transponder anyway. I have not heard of a transponder only transmitting 0000, maybe a glitch with the uAvionix?

 

[Old3pacer]

I don’t think is a uAvionix glitch. I think it was a firmware update changing the value broadcast.
I do think there is an avionics shop visit in your near future. If you have a good relationship with class c atc, you could query what they see

 

[Gilbert Pierce]

Does the Garmin use a separate encoder? If so it’s an altitude encoder failure . I had the same problem a while back with my KT76A and old drum encoder. New encoder solved the problem.

 

[mholton63]

I thought the mode C encoder only transmitted altitude and the transponder transmitted the squawk code. Is that correct? Can’t the transponder work without a mode C encoder?

 

[Jspey]

If the transponder is working, it should transmit in mode "A" by turning it to "ON" instead of "ALT" (mode C). http://russellw.com/manuals/narco_at150/1product_description.htm#ProductDescription

 

[Gilbert Pierce]

You

I thought the mode C encoder only transmitted altitude and the transponder transmitted the squawk code. Is that correct? Can’t the transponder work without a mode C encoder?

You are correct. My mistake, I thought the transponder was reporting zero altitude.

 

[Stockdale]

Your Uavionix is not seeing your transponder replies.

This can be caused by a few things.
1. Your transponder is not being interrogated. If you are not near an ATC facility you will not be interrogated and those older transponders will not send out a reply. This could be perfectly normal but you would need to fly it or interogate it with a XPDR test set to verify.
2. Your Uavionix Monitor threshold is set too tight. You can adjust this on the Uavionix App. But again, for this to work your XPDR needs to be interrogated.
3. Your Transponder output frequency is off. The FAA wants your Output frequency to be 1090MHZ +/- 3MHZ. I have found that the Uavionix sky/tailbeacons need your transponder to operate within 1MHZ of 1090. This can be adjusted internally in the transponder, but your cabling and antenna can also pull this frequency up/down.

You are best off taking it to an avionics shop with a XPDR test box to figure out what is really going on.

 

[mholton63]

This is great information, thank you. My plan is to fly It and see if ATC recognize the squawk code and if they don’t, then I’ll take it to an Avionics shop.