Re: KX1: new build & transmit problem on 20m ...

Posted by Stan Gibbs, KR7C on Jun 05, 2012; 11:34pm
URL: http://elecraft.85.s1.nabble.com/KX1-new-build-transmit-problem-on-20m-tp7557147p7557182.html

VK7JB wrote

But I've noticed that when listening to the KX1's transmitted signal (using my K3 as receiver) on 20m only is very raspy.

John,

I had a similar experience to you (though without the 30/80 module).  My P3 showed strong 60Hz modulation of the output signal on 20m and a much smaller modulation on 40m (not audible).  The audio on 20m was definitely "raspy".

The KX1 was connected to a dummy load via 25 ft. of RadioShack RG58 and I had no antenna on the K3.  I thought the modulation was an oscillation at first, but after monitoring the KX1 output signal on my scope, I realized that the modulation had to be due to some other cause, and I suspected RFI in the power supply or cables because of the 60Hz sideband spacing.

I changed my coax to a 3 ft piece of RG213.  The 20m signal immediately became clean on my K3.  The longer the coax, the more apparent modulation of the received signal.

All signal reports that I received from QSOs gave me a clean tone report and I asked several ops whether there was any hum or buzz on my 20m signal.  Nobody reported any modulation.

Do you have a scope to look at the KX1 output?  If not, you might want to get some on-air reports to determine if there is a real problem in the transmitted signal.