[Elecraft] worse carrier rejection when KPA100 active?

[Don Wilhelm]

Oleg,

It does not look like the pattern is related to the 2 tone test, but is 
at a much lower frequency - perhaps related to your AC line frequency.
Are you powering the base K2 from a power supply different from that 
used on the KPA100, then check that supply for ripple.  Even if you are 
using the same supply, check it for DC purity at the current draw at 10 
watts and again at the current draw at 11 watts (or greater).

To eliminate the power supply from question, try running the KPA100 on a 
sizable 12 volt battery (like an automotive battery) and see if there is 
any improvement.

You might also see what happens if you change the tones.  The Elecraft 
2Tgen uses tones of 700 and 1900 Hz which have greater spacing than the 
tones you are using (do not use harmonically related tones).

73,
Don W3FPR

Amateurfunkstation TUHH wrote:
> I've built KPA100 for my K2. When doing two-tone test, I was
> satisfied with results at 10 watts power (KPA100 in bypass), they
> are shown on photo (1).
>
> Then I increased the power to 11 watts, and what I saw wasn't just a
> two-tone signal any more, see photo (2). As if carrier rejection
> were not enough when running with KPA100.
>
> So I decided to do a single tone test. While looking good at 10
> watts (see photo 3), at 11 watt it looked like an AM signal with
> small modulation depth (photo 4). I even played with carrier balance
> pot on KSB2, and I was able to make it worse, hi. (Then I re-balanced
>  it at 10 watts, with mic disconnected, using oscilloscope.)
>
> Any ideas of possible reason?
>   
>