[Elecraft] K2/100 birdie at 28.020 MHz

[Geoffrey Mackenzie-Kennedy]

Jeff,

I see that Bruce K1FFX has made you aware of Don's (W3FPR) and my comment on 
the "birdie" that Bruce found on 21029 kHz, which also disappears when the 
KPA100 is not active. However may I add a little more.

Don speculated that some of the oscillator energy (HV Bias oscillator) could 
be picked up by the T/R switch when the KPA100 is in-line, and I can confirm 
that this is fact. The fundamental and harmonics generated by this 
oscillator and the assocated voltage multipliers are also found in many 
other places in the KPA100.

It might be worthwhile to remove the audio leads from the KPA100 board, i.e. 
those which connect to the K2 and to the speaker, to see if in your case 
this affects this particular "birdie". The bundle of pcb traces in this area 
(and other areas) of my KPA100 was quite hot with RF from the HV bias 
oscillator/ voltage multiplier.

73,

Geoff
GM4ESD


Jeff Martin N7KRT wrote on Wednesday, February 02, 2011, at 12:26 AM:


>I have a loud birdie at 28.020 MHz on my K2/100. The KPA100 is integral to 
>the K2. I thought it might be from the 4.0MHz oscillator on the KPA100, but 
>the birdie does not respond to changes of C27. The birdie stops when the 
>power is reduced to low power mode. The birdie is loud...can be heard when 
>the 2nd antenna is selected with no antenna connected.
>
> This may have been covered before, but I seem to recall that there was no 
> firm resolution? I never reaaly worried about it for the past few years, 
> but with the solar cycle waxing, I might miss some DX!
>
> Thanks all for any insight.
>
> Jeff Martin
> N7KRT
> K2/100 #5471