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Comm Radio Tx Problem

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enhubbard(at)sbcglobal.ne
Guest

Posted: Thu Aug 17, 2006 11:42 pm Post subject: Comm Radio Tx Problem

I've just mounted a Microair 760 comm radio in my Pietenpol project.  

It's attached to a commercial solid-wire antenna that is mounted on a 

ground plane internal to the aft fuselage.  I'm using the built-in 

intercom.  It receives just fine, but when I try to transmit, I get a 

tone through the headset and the transmission is unintelligible.  The 

tone generally starts when I start to talk, not when I press the PTT, 

though that seems to happen occasionally too.  The tone goes away when I 

release the PTT.  Any Ideas?



Thanks,

Gene Hubbard

San Diego

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FLYaDIVE(at)aol.com
Guest

Posted: Fri Aug 18, 2006 1:43 am Post subject: Comm Radio Tx Problem

In a message dated 8/18/06 3:43:49 AM Eastern Daylight Time, 

enhubbard(at)sbcglobal.net writes:



 	  Quote: 	
		   I've just mounted a Microair 760 comm radio in my Pietenpol project.  

  It's attached to a commercial solid-wire antenna that is mounted on a 

  ground plane internal to the aft fuselage.  I'm using the built-in 

  intercom.  It receives just fine, but when I try to transmit, I get a 

  tone through the headset and the transmission is unintelligible.  The 

  tone generally starts when I start to talk, not when I press the PTT, 

  though that seems to happen occasionally too.  The tone goes away when I 

  release the PTT.  Any Ideas?

  

  Thanks,

  Gene Hubbard

  San Diego

====================
	


Gene:



It is very difficult to try to diagnose a problem when you cannot see or hear 

the symptoms.  BUT!  My first guess is you are getting FEEDBACK.  This is due 

to wrong wiring.  

Start with making sure you have ONLY one headset installed.

If you are trying to use two make sure it is on the head of someone.

Turn down the MIC GAIN on the TX.

Recheck all the wiring.



Have you checked to make sure that the jacks are insulated from the plane?



If you have two headset locations, try from each location.  BUT!  Disconnect 

one headset before you try the other.



Do you know what feedback sounds like?



These are the basics.  GOOD LUCK!



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

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klehman(at)albedo.net
Guest

Posted: Fri Aug 18, 2006 4:35 am Post subject: Comm Radio Tx Problem

FWIW the guys were spot on about too much mic gain causing lots of 

cockpit noise to be picked up by my icom A200 radio. After a couple of 

tries and turning the gain on the inside of the radio down at least a 

half turn, all is well. Turning down the gain at the mic helped a bit as 

well.

Ken



Gene Hubbard wrote:



 	  Quote: 	
		   

 <enhubbard(at)sbcglobal.net>



 I've just mounted a Microair 760 comm radio in my Pietenpol project.  

 It's attached to a commercial solid-wire antenna that is mounted on a 

 ground plane internal to the aft fuselage.  I'm using the built-in 

 intercom.  It receives just fine, but when I try to transmit, I get a 

 tone through the headset and the transmission is unintelligible.  The 

 tone generally starts when I start to talk, not when I press the PTT, 

 though that seems to happen occasionally too.  The tone goes away when 

 I release the PTT.  Any Ideas?



 Thanks,

 Gene Hubbard

 San Diego

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sat Aug 19, 2006 8:07 pm Post subject: Comm Radio Tx Problem

On Aug 18, 2006, at 12:41 AM, Gene Hubbard wrote:



 	  Quote: 	
		   

 <enhubbard(at)sbcglobal.net>



 I've just mounted a Microair 760 comm radio in my Pietenpol  

 project.  It's attached to a commercial solid-wire antenna that is  

 mounted on a ground plane internal to the aft fuselage.  I'm using  

 the built-in intercom.  It receives just fine, but when I try to  

 transmit, I get a tone through the headset and the transmission is  

 unintelligible.  The tone generally starts when I start to talk,  

 not when I press the PTT, though that seems to happen occasionally  

 too.  The tone goes away when I release the PTT.  Any Ideas?


	


Yes. You have RF feedback into your headset. Things to try:



1. Try a different headset.



2. Wrap the mic lead to the radio around a ferrite core. Several  

turns should do. Do this at the headset end and also at the radio end.



3. Move the antenna to a different place on the airframe more removed  

from the headsets.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

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