Defective Commant Belly-whip antenna?

[Pilottonny]

Hello guys,

I am wondering if my Commant Belly Whip Antenna is defective! My TruTrak AP plays up when I key the mike. Suggestions were made that it may be a defective antenna. Also see the following thread: http://www.vansairforce.com/community/showthread.php?t=20487

I am wondering if the whip of the antenna and the centre pin of the connecter need to be connected together. Checking with a continuity tester gives no result. But on the other hand when I check my ELT antenna, the centre pin is connected directly to the antenna rod (no resistance) and the ELT works fine.

I would like to know if I can just hook up the the ELT antenna to my radio to see if the problem with my Trutrak AP is due to the antenna, or is that going to hurt my SL30 comm?

Any advise welcome,

Kind regards, Tonny.

 

[mannanj]

Antenna

Hello guys,

I am wondering if my Commant Belly Whip Antenna is defective! My TruTrak AP plays up when I key the mike. Suggestions were made that it may be a defective antenna. Also see the following thread: http://www.vansairforce.com/community/showthread.php?t=20487

I am wondering if the whip of the antenna and the centre pin of the connecter need to be connected together. Checking with a continuity tester gives no result. But on the other hand when I check my ELT antenna, the centre pin is connected directly to the antenna rod (no resistance) and the ELT works fine.

I would like to know if I can just hook up the the ELT antenna to my radio to see if the problem with my Trutrak AP is due to the antenna, or is that going to hurt my SL30 comm?

Any advise welcome,

Kind regards, Tonny.

See post #6 about the disconnect switch on the above thread. This wire should be shielded too, I believe.

 

[PaigeHoffart]

Normally the whip and center pin will be connected for the simpler (read less expensive) antennas. Some antennas have internal matching networks which will show an open circuit (or sometimes a short circuit to ground) with an ohm meter. A SWR meter or antenna analyzer is necessary to check these antennas.

You can still use an ohm meter to check the coax, just disconnect both ends first.

Paige

 

[Pilottonny]

Disengage wire is not the problem.

Mannan,

As it is mentioned in the Trutrak manual as the most volnerable wire, I did check that, I disconnected the disengage wire at the Trutrak, but that did not change anything.

Thanks for replying.

Regards, Tonny.

 

[mannanj]

Antenna

Mannan,

As it is mentioned in the Trutrak manual as the most volnerable wire, I did check that, I disconnected the disengage wire at the Trutrak, but that did not change anything.

Thanks for replying.

Regards, Tonny.

Tonny:

My Tru Trak pitches down a little when I key the mic. at about 128.000 Mhz. and above. It increases in severity the higher I go in frequency. Below about 128.000 Mhz, nothing happens. Since it's only mildly annoying and I rarely use those freqencies since I fly VFR, I haven't looked into the problem much to try to eliminate it.

I believe that your problem is probably not caused by your antenna, but that it is Radio Frequency Interference getting into your autopilot wiring that causes the problem.

As others have suggested, seperate all autopilot wires from any antenna wires as much as possible, and where they must cross each other, do so at a 90 degree angle or as close to 90 degrees as possible.

Hope this helps.

 

[Doug Knab]

RF problem with AP

We had the same problem with the pitch servo activating when the mic was keyed. It turned out to be the location of the antenna. By moving the antenna location under the belly, we were able to find a place where it did not cause the AP pitch servo to activate. An easy way to find a good antenna location is to use a hand held radio. Key the transmit button and move it around until the pitch servo stays silent.
Good Luck