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

[Geoffrey Mackenzie-Kennedy]

Hi Bruce,

During my "Kill Birdie" project with my K2/100 #3255, I found that all of 
the "birdies" which disappear if the KPA100 is *not* in use were caused by 
the fundamental or a harmonic of the KPA100's HV Bias oscillator mixing with 
the fundamental or harmonic of one or more of the other oscillators in the 
K2. Any product of this mixing will be heard as a "birdie" if (1) the 
frequency of the product is "in band" and the receiver is tuned to the same 
frequency, or (2) the frequency of the product is the same as that of a 
spurious response of the receiver when tuned to the frequency at which the 
"birdie" is heard. Of course the product must be strong enough to be heard 
above the noise floor.

Unfortunately I do not have my notes here, but because your "birdie" steps I 
suspect that the PLL Reference oscillator could be part of the mix.

In my K2/100 the HV Bias oscillator signal was getting into the K2's RF 
board via the KPA100's diode TR switch and the ribbon cable.

Because this rural QTH is very quiet I could hear this type of "birdie" on 
different bands, which forced me into repackaging the HV Bias oscillator 
into its own shielded enclosure, which solved my problem.

73,

Geoff
GM4ESD



 "K1FFX" <bruce.rosen at rcn.com> wrote on Saturday, January 29, 2011 at 3:02 
PM:

> Additional info:
>
> The "birdie" also goes away when the power setting is clicked below
> 11 watts.
>
> - Bruce
>
>
> -----
> Bruce Rosen
> K1FFX