[Elecraft] Tranmit Audio Distortion after installing KPA3 100W amplifier

[Rick Low]

Just installed the Power Amplifier two days ago and I've got severe noise on
the transmit audio. As far as I could tell, transmit audio sounded clean
before the PA install (talked across town to a fellow ham). I'm using a Heil
dynamic element (HC-4) microphone with transmit audio going to pin 1, and
using pin 7 for microphone ground. Mic and Comp gain at 20-30,Some buzz may
be due to slight RFI but what I'm hearing seems much more than that. The
radio is bonded to a good station ground.

 

Current Symptoms:

I have a rumble/buzz superimposed on the microphone audio. This extra signal
varies from light to severe as power is increased, and distorts the transmit
audio. As an added bonus, it sounds like there is a buzz superimposed on my
CW signal at 18 MHz and above. All this as observed while transmitting to
50-ohm dummy load, with monitoring on a nearby, separate receiver
(IC756ProII). If I use the K3 as an exciter to an outboard amplifier
(Ameritron AL-80B) I can actually transmit at 100W PEP with only a little
bit of hum in the background, which you really have to strain to hear.

 

I'll take the transceiver off-line after the weekend testing (giving out
QSOs for CQP) but would appreciate any unofficial help inputs from this
experience pool and official K3 support J

 

73 Rick N6CY

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/elecraft/attachments/20081005/9785d4bc/attachment.htm