[Elecraft] [K2] KPA100 "birdie" at 21029

[Don Wilhelm]

  Bruce,

That is a bit of a mystery.  I just checked a newly built K2/100 and 
could find no instance of any response at all with no antenna connected.

There are no oscillators switched in and out when the KPA100 is active - 
both oscillators in the KPA100 run whether the KPA100 is in-line or 
not.  Have you grounded the crystal cases?  Try varying the 4 MHz 
oscillator capacitor and see if the frequency shifts.  If so, ground the 
crystal case near the bottom to see if that takes care of it - I am 
speculating that some of the oscillator energy could be picked up by the 
T/R switch when the KPA100 is in-line.

The only thing that changes between PA on and off (or with power 
above/below 11 watts) is that the receive signal path flows through the 
T/R switch instead of through the straight-thru path from relay K1 to 
K2.  You might want to check all the components in the T/R switch for 
proper value, diode orientation, and good soldering.  The components 
associated with the T/R switch are shown in the schematic at the top of 
sheet 2.

73,
Don W3FPR

On 1/29/2011 10:02 AM, K1FFX wrote:
> Additional info:
>
> The "birdie" also goes away when the power setting is clicked below
> 11 watts.
>
> - Bruce
>