[Elecraft] K2 noise on receiver when switching from transmit

[Don Wilhelm]

Mike,

I am curious to hear just how long ago that "some time ago" really is.

The first thing to check is the setting of 8R - it should be set to HOLD 
with the KPA100 installed.  To check, go in the menu to T-R, edit the 
parameter and then tap DISPLAY.  If 8R was already set to HOLD, you will 
see 'nor' and you will have to tap DISPLAY again to set it back to 
HOLD.  OTOH, if you see HOLD when you tap DISPLAY the first time, it had 
been set to 'nor' - when you see HOLD, tap the menu button twice to exit.

There was a time when such pops could occur on some K2s that were 
equipped with both the KDSP2 and the KPA100.
The real source was never discovered other than it was caused by some 
transition in the KPA100 T/R switch and related to the unmute timing in 
the KDSP2.

That has not occurred in K2s that have the upgraded KPA100.  So check 
your KPA100 - remove the right side panel and look between the shield 
and the board.
If you see two toroids with blue cores, it has been upgraded, but if you 
see toroids with red cores, order the KPA100UPKT and do the upgrade.

73,
Don W3FPR

On 6/9/2015 11:13 PM, Mike Fanning wrote:
> Hi all,
> I have a K2 that I built some time ago that I added the KPA100 to at a later time.  I don’t have more than 10 minutes worth of run time on the KPA100 and I’m putting a dress rehearsal together for Field Day in a couple of weeks.  I noticed tonight that when I am running more than about 10 Watts (enough to kick the KPA100 on) that I get a nasty pop on the receiver whenever I come from transmit to receive mode.  Changing the tx-rx delay doesn’t affect the noise, and whenever I back the power down so that the KPA100 is not engaged, the problem goes away.  Any suggestions as to what might be going on?  It will be really tiring to listen to the receiver in this mode for 24 hours at FD…
>
>