REFLECTOR: Trig TT-31 ADS-B transponder

[John Dibble]

I'm using the same cable as before with the Collins 950 transponder.  
Never had a problem with that.  Is my new transponder different 
(stronger transmission)?  I'll check if the cable is close to something.

Thanks,

John

On 1/15/2014 11:12 AM, sbjknox at earthlink.net wrote:
> Well, as I suggested before, it appears to be that the transmitted rf 
> from the transponder is getting (radiating) into circuits where it 
> should not be. This can be caused by having the coax from your 
> transponder too close to some other wiring.  There are various 
> "qualities" of coax.  All coax will leak some rf but lesser quality 
> coax can be unsuitable for rf transmission. Double-shielded (and more 
> expensive) coax is probably best for transponder application.
> With our plastic airplanes we will experience a higher lever of 
> radiated rf inside the plane from comm and transponder transmitters 
> than will those flying in spam-cans.
> Or there may be a problem with the coax and/or the transponder antenna 
> installatoin.  If the antenna (and the coax feeding it) has a problem 
> then some of the rf that should be radiated will be reflected back to 
> the transponder (excessive VSWR).  Also, the antenna needs to have a 
> "ground plane" to operate correctly... ie., needs to be mounted on a 
> metallic surface  (plate or screen) which is electrically bonded to 
> the coax shield at the base of the antenna.  Mr Google can tell you 
> all about it.
> Even with your plane sitting on the ground your transponder will be 
> interrogated by nearby ATC radar or by other aircraft.
>
> Sid
>
> ----- Original Message ----- From: "John Dibble" <aminetech at bluefrog.com>
>
>> Also, the noise goes away if I turn off the transponder.  In case I 
>> wasn't clear this series of pops continues all the time the 
>> transponder is on.
>
>
>> Looks like the noise is not random. It's 3 pops, each a second apart 
>> and then a group of 3 which is what made it seem random.  I tried it 
>> inside the hangar with the gps, encoder, intercom, radio, and noise 
>> cancelling headset off.
>>
>> John
>>
>> On 12/30/2013 10:35 AM, sbjknox at earthlink.net wrote:
>>> If the "...slight popping noise in my headset." is somewhat random 
>>> in occurrence, it is probably the transponder's high-power rf 
>>> response being picked-up by some portion of your audio system (com 
>>> radio, intercom, headset...).  Watch the activity light on your 
>>> transponder... if the radiated rf is causing the noise, it will be 
>>> coincident with the light.
>>> If the noise is not random but rather regular like once-per-second, 
>>> then it is probably related to the serial data stream out of the GPS 
>>> or some other serial data device that sends a data stream 
>>> periodically.  If this, perhaps improper grounding of a shielded 
>>> cable is the cause.
>>>
>>> $0.02
>>> Sid Knox
>>> Oklahoma
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