[Elecraft] K2 FM-ing on 80 Meters

[Don Ehrlich]

 My just completed #4438 with SSB, DSP, 160M, and 100Watt Modules 
seems to be working just fine .... except:

.. on the low end of 80 meters (3500-3700 approximatly) the signal 
sounds like there is a 'ringing' on it when listening to another 
receiver in the shack.  This happens only at power levels above about 
50 watts and only on the low end of 80 meters.

Here is what I have done:

Replaced my power supply with a large lead-acid car battery to 
eliminate any possibility of interaction with the power supply. 
Results the same with either power source.

Tried two different monitoring receivers ... same results with each.

I am using a 50 ohm dummy load (Heath Cantenna).


This is what I see:

A scope looking at the RF waveform shows NO am modulation.  The 
envelope is clean.

A scope looking at the RF waveform does show a slight blurriness in 
the horizontal axis indicating rapid but slight frequency shift.

A scope monitoring the 12 volt input shows a small sinusoid waveform 
on the 12 volt input (a hundred mV or so)  indicating that there is a 
significant AC component of current being drawn from the battery.  The 
frequency of this AC component of input current is about 30 hertz.

I suspect ALC instability of some kind.  I could sure use some help 
here.

Don  K7FJ