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View Full Version : Matching a panel mount V6 MGL with dipole antenna - P&M trike



Stevepattinson
21-04-13, 14:35 PM
Can anyone help. On the ground with engine not running, my comms are loud and clear, however in the air the tower says it sounds like I am talking into a long tube. Strength is good but this is affecting clarity. I was warned about the high output of a panel mount V6 and a dipole (V Rabbitt) on trike. It could cause RF feedback and/or over modulation. Could either cause this transmission problem and poor reception by the tower?? Reception is fine. Using Microavionics intercom and all settings on radio are correct. All input and feedback would be appreciated.

Tanarg derek
21-04-13, 15:28 PM
I have been running in my trike an V10 radio for many years now, without any problems. Have you fitted ferrite rings to the supply to the radio and on the output cables from the D15 plug, also, have you fitted screened the cables from the D15 plug, the screen goes to ground at the D15 plug end. your problem is RF feedback. Where is your antenna fitted?
May be worth a look at this forum http://www.mglavionicsusers.org/forum/index.php
I hope this helps

Stevepattinson
21-04-13, 17:18 PM
I will check the rf beads and the screening. The antenna is fitted at back of keel. thanks for your help. Are you able to confirm that the "talking into a tube" is RF feedback??

Tanarg derek
21-04-13, 18:12 PM
It might be worth having a look at page 21, third paragraph from the bottom of V6 manual, and V10 manual under title RF feedback- cause and elimination (page 32)

Never route your antenna cable inside a bundle with other wires in your aircraft. Keep your
antenna cable well separated from all other cables.

I hope this is of help

Stevepattinson
21-04-13, 18:22 PM
It might be worth having a look at page 21, third paragraph from the bottom of V6 manual, and V10 manual under title RF feedback- cause and elimination (page 32)

Never route your antenna cable inside a bundle with other wires in your aircraft. Keep your
antenna cable well separated from all other cables.

I hope this is of help
Thanks but coax nowhere near other cables. Appreciate the input.

Russ_H
21-04-13, 18:56 PM
Steve, are the dip-switches inside the interface set up correctly for your radio?, they affect microphone gain amongst other things.

Stevepattinson
21-04-13, 19:08 PM
Steve, are the dip-switches inside the interface set up correctly for your radio?, they affect microphone gain amongst other things.
Are you referring to the Microavionics intercom? Is so I will have to check with them to see. Never heard of them before. Thx for input though.

Frank Thorne
27-04-13, 08:15 AM
Hi Steve.. Very difficult to tell whats going on from a report of sounds like speaking through a long tube. If its working fine on the ground with no engine on then the system seems ok. Test again on the ground with engine running to see if any generator whine clicks whistles or any other nasties appear that change with engine revs. Is it a noise cancelling microphone? Position is all important it cannot touch the visor perspex as it will try to eliminate the high wind noise and vibration possibly clipping the frequency response of the microphone so it would sound muffled. Try it on the ground and in the air with engine on.

Check the VOGAD system on the V6 is not trying to auto adjust microphone gain on a noise cancelling mike it could be lowering the auto gain due to high background noise levels try turning it off if you can.

Stevepattinson
27-04-13, 10:52 AM
Hi Steve.. Very difficult to tell whats going on from a report of sounds like speaking through a long tube. If its working fine on the ground with no engine on then the system seems ok. Test again on the ground with engine running to see if any generator whine clicks whistles or any other nasties appear that change with engine revs. Is it a noise cancelling microphone? Position is all important it cannot touch the visor perspex as it will try to eliminate the high wind noise and vibration possibly clipping the frequency response of the microphone so it would sound muffled. Try it on the ground and in the air with engine on.

Check the VOGAD system on the V6 is not trying to auto adjust microphone gain on a noise cancelling mike it could be lowering the auto gain due to high background noise levels try turning it off if you can.
Thanks for input. I have ascertained that I am getting rf feedback and hopefully the placement of some rf chokes will help.