[Elecraft] K2 noise on receiver when switching from transmit

[Mike Fanning]

Thanks for the quick reply Don!  I checked the 8R setting and it was indeed set to hold (and is set there again after toggling it to make sure).  I do have the KDSP2 option with the KPA100, but after peeling off the right side panel I see two baby blue toroids.  The K2 is serial number is 5882 and it was purchased in December 2006.  The KPA100 was bought at Dayton in 2009.  I think it took me another year to get around to building it, so it was probably buttoned up about 5 years ago and has been the backup/receive only rig since doing all the alignment checks.  This will be the first time I have really done any transmitting with it since adding the KPA100 (I’ll make sure to revisit the PA screws as instructed).  You have given me something else to check though - I need to pull the KDSP2 and see if that affects the problem.  I’m wondering if there were other upgrades to either the K2 or KDSP2 that might affect this as well?

Anyway, thanks for the lead and please let me know if you have any other ideas.

73,
Mike, K4GU


On Jun 9, 2015, at 10:52 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:

> 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…
>> 
>> 
> 
>