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smills(at)e2psi.com
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 Posted: Mon Aug 18, 2008 7:36 am Post subject: AT 165 Noise in headset |
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Bob, et all
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 is related to the reply function of the transponder. Anytime the LCD is blinking “RCV” I hear the noise. Here are some of the specifics.
<![if !supportLists]>1. <![endif]>If I turn the new transponder (Narco AT165) to standby 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. The A200 sits on top of the AT165 in the radio stack. (These are the only two radios I have) 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? Could it be the multiplexing LCD display causing the interference? 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.
Is there a simple fix for this? Where do I start troubleshooting? All help is greatly appreciated.
Regards,
Scott Mills
N339A
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berkut13(at)berkut13.com
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| Posted: Mon Aug 18, 2008 3:40 pm Post subject: AT 165 Noise in headset |
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How are your headset/mic jacks mounted? Are they insulated from airframe? Could you be picking up a ground loop during transmit?
James Redmon
Berkut #013/Race 13
www.berkut13.com
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