Transponder interference

[Fireflier]

Hi

Having installed my dynon 262 transponder, an got it all connected and working I have now noticed I have a clicking sound coming through my headsets.

If I disconnect the transponder from the system the clicking noise stops, therefore I presume my intercom is picking up interference from the transponder.

Any advice on how to remove this interference would be much appreciated.

Look forward to your replies.

Kind regards
Donald

 

[Dynon]

How often are you hearing the click? Does it coincide with the reply icon on the transponder status area?

 

[dynonsupport]

What kind of cabling did you use to connect the transponder to the antenna? If you use something like a single shield RG-58, it will leak a lot of RF into the plane and this can interfere with the audio system. We have had customers with this issue replace the RG-58 with the RG-400 the install manual recommends and it fixed this issue.

 

[Fireflier]

Hi

Thanks for your reply.

I wiuld need to check to see if it coincides with the reply icon, i presume i can find this in the transponder set up menu?

I can confirm that the cable used is rg400.

Its certainly like a coded clicking sound and has a regular pattern to it.

Kind regards
Donald

 

[dynonsupport]

The reply light is right on the top of the SkyView screen next to the transponder mode-C code.

However, as this is a ADS-B out transponder, it broadcasts once a second even when not "replying" and thus the light will not be on. Your best test is really to put it in Standby mode via the SkyView buttons and see if this stops the issue.

 

[Fireflier]

Hi

Thanks for your reply. As im located in the Uk the ads-b output isnt connected.

Does this make a difference?

If it is ok on standby mode, is there anythig i can do to remove the interference when it is broadcasting?

Kind regards
Donald

 

[dynonsupport]

Donald,
You can't turn ADS-B out off with our transponder. If it's hooked to SkyView, you are transmitting ADS-B OUT once a second.

What kind of aircraft is this in? Does the transponder coax run in the same bundle as the intercom/headset wires anywhere?

 

[Fireflier]

Hi

Sorry my confusion over the ads-b.

This is loactaed within a europa xs (composite aircraft). The coax does not run anywhere near the headset/intercom bundle. The only cablesthat run close to these is the rx and tx out of transponder to the input for the skyview. These cables are screened from the back of the transponder to the where they are connected to the d37 harness behind my panel.

It sounds like it could be the ads-b as the clicking is happening ever second.

The only thing that i could think off that may be the issue is the transponder mounting plate is not ground. Couldthis be the problem?

Kind regards
Donald

 

[jakej]

Donald
What size is the Transponder groundplane ?

Jake J

 

[Fireflier]

Hi jake

The ground plane is a 6 inch square.

Kind regards
Donald

 

[randylsnarr]

Rg58. I am changing it for RG400.
Thx!
Randy Snarr
Lancair 235/320

 

[jakej]

Hi jake

The ground plane is a 6 inch square.

Kind regards
Donald

Also, what is the position of the antenna relative to the headset jacks & rest of the avionics ?

Did you use shielded cables for the ph/mic jacks ? Is the shield grounded at the radio or intercom end only ?

Jake J

 

[Fireflier]

Hi

The antenna is located in the rear section of the fuselage bolted through from the bottom. Rg400 cae runs from the antwnna through central tunnel to transponder which is mounted within the tunnel.

Headset cabeling was a harness made up by my avionics supplier, it is sheilded cable and is grounded at both the radio and intercom.

Cable route to the headset jackes is along the side of the fuselage well away from my transponder and com antenna cables.

Kind regards
Donald

 

[jakej]

Donald
You have a PM

Jake J

 

[Terke]

We have the same kind of clicking in the headset now.

We recently upgraded from a SV-XPNDR-262 to a SV-XPNDR-261. When the -261 is installed there is an audible rhythmic clicking in the headsets. When we swap back to the -262 the noise goes away. If I leave the power to the transponder turned on but stop the transponder's transmissions by selecting standby on the Skyview the noise goes away as well. The cable run from the transponder to the antenna is about 24" long. The transponder and antenna are in the tail of the aircraft. It is RG-58. It is a wooden aircraft, so the antenna ground-plane is a 6" square sheet of aluminum with the corners bent up (opposite to the antenna). There are no other antennae nearby nor does any of the intercom cabling run nearby. The only wire bundle near the transponder is the one running to the transponder from the SkyView. Any thoughts?

Thank you.

 

[dynonsupport]

In our experience, the issue is the RG-58. This cable leaks a lot more RF energy than RG-400, and this can get into the audio system. We've had customers with this issue before and a swap to RG-400 fixed it. This is why our install manual doesn't specify RG-58 as acceptable even though it theoretically is for very short runs.

 

[Terke]

Thank you. I have ordered RG-400. For the moment we added an additional sheath of shielding and grounded it on the transmitter end. That quieted the noise down 95%.

Cheers

 

[Pilotlight11]

RG 400 MAKES NO DIFFERENCE. I have the exact same problem with the 261. I am incredibly disappointed with the Dynon transponder. I replace all my avionics with a Dynon set-up. D1000T, 261, 470, radio and comm panel. I had a perfectly noise free system before, now I'm tracking down interference after interference. The popping noise is definitely caused by the 261. You do not even have to have the headset plugged into its jacks to get the interference just stand near the plane and you'll get the popping. Proof is indeed that if you go to stand-by the popping stops. We call that direct evidence. THE ONLY FIX I've come up with that worked was to move the antenna as far away from YOUR HEADSET as possible. Below your headset level is better. I have an amphibian - that prevents me having an antenna under the hull. I bought an antenna that does not require a ground plane and glued it to the inside of the hull (fiberglass) as far back as I could reach. This greatly attenuated the popping, but did not completely eliminate it. I know Dynon thinks the answer is RG 400, but that ain't it - I already had RG 400 for all my cables. If you really want to hear the popping hold any antenna on any cable next to the 470. The latest issue I'm trying to track down is any time I key the mic the red LED on my ELT remote panel lights up. There isn't even an electrical connection to the remote. The only wires to the ELT remote display is the phone cable to the actual ELT. So, I don't think "put shielded cable in" is a viable answer. I love the Skyview display, but so far having gone to the remotely located radio and transponder is proving to have been a mistake. :-[

 

[Raymo]

Bob,

Your problem is obviously different than the others. To say RG-400 is not THE solution is, in your case alone, true. It did, however, solve the problem for a number of others.

I would start with the antenna you selected. Since it is a dipole type, it may be the faulty component in your situation.

Another thing to check is that the RG-400 cable is not internally shorted. Disconnect both ends and check with a meter between the center conductor to the BNC shell.

Here is a FAQ that might help with the specifics for that antenna placement.

https://www.aircraftspruce.com/catalog/avpages/antennasystems1.php

 

[dynonsupport]

Bob,
Have you had an transponder test done on the new installation? This would tell us if there's any cabling issues leading to large power loss.

What transponder were you using before? Was it mounted in the same location, using the same RF cables? What's the new antenna you are using?

What ELT do you have? Some ELT's do have issues with receiving energy from radio transmissions and acting up.