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AT165 Headset noise

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smills(at)e2psi.com
Guest

Posted: Mon Aug 18, 2008 6:23 am Post subject: AT165 Headset noise

Alas my AT50 gave up the ghost and had to be replaced. Well of course, we all know where this is headed. I now have a new annoying sound in my headset. While it is more noticeable when on the ground as opposed to flying it is always there. It’s related to the reply function of the transponder. I have read the other posts regarding this issue and, while mine is similar I‘d like to give some of the specifics.  

<![if !supportLists]>1.      <![endif]>If I turn the new transponder (Narco AT165) to standby, the noise goes away.  

<![if !supportLists]>2.      <![endif]>Turn transponder back on and turn comm radio off (ICOM A200) noise goes away. In all cases the intercom is still working (Flightcom 403)  

<![if !supportLists]>3.      <![endif]>Adjusting volume knob on the A200 makes the noise louder/softer.  

   

So it would appear that the problem is related to interference between the AT165 and the ICOM A200. This is where I’m stumped. The AT50 never gave this problem. The encoder was not changed (Trans-Cal).  

Is the issue with inductive coupling in the wiring or is the power output of the AT165 a problem for the ICOM? Although these weren’t problems with the AT50.  

The Antennas are bottom mounted on an RV9A. The transponder is up by the right fuel tank vent and the com is centered under the pilot’s seat, they’re about 30 inches apart. Nowhere do the cables ever cross or run together except at the radio stack where they come in from opposite sides anyhow. I used RG 400 for this installation.  

What’s the fix for this? Where do I start troubleshooting? All help is greatly appreciated.  

   

Regards,  

   

Scott Mills  

N339A  

       [quote][b]

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Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Mon Aug 18, 2008 6:58 am Post subject: AT165 Headset noise

I don't have a clue what in the AT165 might do with your Icom. However, 

one thought would be to bypass your intercom or just turn the intercom 

off. Intercoms are well known for picking up stray RF in the cockpit and 

amplifying for your listening annoyance. I also suspect Icom might be 

more responsive than Narco on inquiry. Narco does have toll free number, 

so it can't hurt to call.



Scott Mills wrote:

 	  Quote: 	
		  

 Alas my AT50 gave up the ghost and had to be replaced. Well of course, 

 we all know where this is headed. I now have a new annoying sound in 

 my headset. While it is more noticeable when on the ground as opposed 

 to flying it is always there. It’s related to the reply function of 

 the transponder. I have read the other posts regarding this issue and, 

 while mine is similar I‘d like to give some of the specifics.



 1. If I turn the new transponder (Narco AT165) to standby, the noise 

 goes away.



 2. Turn transponder back on and turn comm radio off (ICOM A200) noise 

 goes away. In all cases the intercom is still working (Flightcom 403)



 3. Adjusting volume knob on the A200 makes the noise louder/softer.



 So it would appear that the problem is related to interference between 

 the AT165 and the ICOM A200. This is where I’m stumped. The AT50 never 

 gave this problem. The encoder was not changed (Trans-Cal).



 Is the issue with inductive coupling in the wiring or is the power 

 output of the AT165 a problem for the ICOM? Although these weren’t 

 problems with the AT50.



 The Antennas are bottom mounted on an RV9A. The transponder is up by 

 the right fuel tank vent and the com is centered under the pilot’s 

 seat, they’re about 30 inches apart. Nowhere do the cables ever cross 

 or run together except at the radio stack where they come in from 

 opposite sides anyhow. I used RG 400 for this installation.



 What’s the fix for this? Where do I start troubleshooting? All help is 

 greatly appreciated.



 Regards,



 Scott Mills



 N339A



 *

 *

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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

smills(at)e2psi.com
Guest

Posted: Mon Aug 18, 2008 8:25 am Post subject: AT165 Headset noise

I tried that. The noise does not appear to be coming through the intercom. What is interesting is that whenever the “RCV” blinks on the AT 165 I get this static noise. It seems as though the LCD on the transponder is causing the interference in the ICOM. Could this be a multiplexer in the AT 165 wreaking havoc with ICOM? Not sure. Would and RF filter help? If so where should I connect it?  

   

Scott  

   

I don't have a clue what in the AT165 might do with your Icom. However,   

one thought would be to bypass your intercom or just turn the intercom   

off. Intercoms are well known for picking up stray RF in the cockpit and   

amplifying for your listening annoyance  

       [quote][b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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