KX99 static

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larry e
Posts: 1
Joined: Sun Aug 05, 2012 8:22 am

KX99 static

Post by larry e » Sun Aug 05, 2012 8:51 am

I have a KX99 that has been connected to a PS1200 intercom. The intercom operation is fine and radio reception is fine; but when the PTT is activated (by either the KX99 PTT or an external PTT that is connected to the PS1200) there is an undesireable static added to the sidetone when engine RPM exceeds 900. This seems to be magneto-generated noise and is non-existant at engine RPMs less than 900. It does seem to affect the transmitted signal but not so much as to make the transmission unreadable by ATC.

Both units are portable, are powered by a small 12v battery, and the only contact with the airframe is via the antenna ground. Diconnecting the aircraft antenna from the KX99 and re-attaching the small flexible antenna that came with the unit does not fix the problem.

If the radio's mic circuit is disconnected from the intercom and an independant headset mic connected to the radio through the mic input jack (leaving the radio's audio output connected to the intercom) the noise goes away.

Does this seem to be a shielding issue? The cable connecting the 2 units is a 3 wire twist plus shielding. The sheild is only connected to the mic ground at the radio end of the cable.

I'm new to the site and sure hope someone may be able to help!

Thanks

larry

User avatar
ka7wnf
Posts: 362
Joined: Mon Aug 30, 2004 1:37 pm
Location: Seattle, Washington

Re: KX99 static

Post by ka7wnf » Thu Aug 30, 2012 11:56 pm

Try looping your headset cord through a ferrite core.

http://www.icomamerica.com/en/support/k ... 64JA571413

Look here for a diagram.

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