[Elecraft] K3 TX power foldback with SWR

[jimk8mr at aol.com]

 I have found that power foldback for bad VSWR on SSB does not return to full power after retuning the ATU. It takes a dot or two of CW to convince the radio to return to full SSB power. (I have CW in SSB mode enabled, so it is not difficult to do). 
73  -  Jim  K8MR


    On Thursday, March 6, 2025 at 10:18:04 AM EST, Dave New, N8SBE <n8sbe at densbe.com> wrote:   

 Mike,

Maybe it was changing 'mode' or 'band' that did it?

On 2025-03-06 10:09, Dave New, N8SBE wrote:
> Mike,
> 
> I've encountered this on my K3 and K3s in the past, and one thing is 
> that the output power will recover after several seconds of 
> transmission.  I complained about this, and someone on the list pointed 
> out that temporarily doing 'something' (sorry I don't remember what 
> now, since I haven't touched my K3s since I upgraded to a K4D) would 
> immediately clear the issue.
> 
> Seems I remember that rebooting the K3 would do it, but that's a rather 
> drastic measure to take in the middle of a contest, especially because 
> some logging programs will complain quickly if the radio port is 
> missing for even a couple of seconds.
> 
> Not sure what search terms to use to find that conversation.  Sorry I 
> can't be more helpful.  I feel your pain.  I have archives of this 
> maillist going back to 2009 on another computer, here.  If I can 
> remember, I'll see if I can find the conversation.
> 
> 73,
> 
> -- Dave, N8SBE, Hamshack Hotline 550-0971, HamsOverIP 101018, 
> AmateurWire 1348
> 
> 
> On 2025-03-03 09:10, Michael Carter via Elecraft wrote:
>> For the first time that I can recall, I experienced my K3/100 reducing 
>> its TX output power abruptly (from 95 watts down to maybe 5 watts) on 
>> first transmission on a new frequency close to the one where the 
>> internal KAT3 ATU was tuned.  This occurred on multiple bands in this 
>> past weekend's ARRL DX SSB contest.  Since I rarely operate on SSB, 
>> and have never experienced this behavior on CW in years of contesting, 
>> I was perplexed.
>> 
>> This morning,  I explored the archive on both the original Elecraft 
>> reflector and the Elecraft-K3 at groups.io forum, and I found several 
>> mentions of the power foldback behavior.  VE3KI in one old post 
>> pointed out that the SWR change due to tuning away from the ATU tuning 
>> frequency may be modest, but the change in PA current or voltage may 
>> trigger the output power foldback.  I understand the basis for that 
>> protection.
>> 
>> My question:  how does one reset the TX power to full output after 
>> such a foldback event?  I tried an ATU retune on the same frequency on 
>> which the foldback had just occurred, but that didn't seem to restore 
>> full power.  I tried rotating the POWER control knob up and down 
>> around the desired output level, and that did seem to reset the TX 
>> output power to its original setpoint.  I was just tinkering during 
>> the contest and feeling like I didn't fully understand a methodical 
>> way to restore full power output.  Guidance from those who have dealt 
>> with this issue long ago is most welcome!
>> 
>> Thanks, and 73,
>> Mike, K8CN
>> ______________________________________________________________
>>