[Elecraft] [K3] Power variations in K3 / 3.19

[myles landstein]

sorry your still having trouble

Can't say for sure   but could very well be  some  funky grounding.

check  it into a dummy load  to at least  eliminate  the antenna  System

If you can  also  try to   vary the length of the coax going from the  
rig to  amp (sometimes helps)

using a speech compressor?

measure  your  grounds  and  any external power supplies used  for   
ac  leaking  over  , maybe a long shot easy to check w/vom



goodluck
N2EHG

On Jul 18, 2009, at 11:28 AM, K2QI wrote:

> Björn's description of the KPA3 behavior sounds incredibly similar  
> to issues
> I've been experiencing when only operating in sideband.  My problem  
> however
> isn't so much of an initial low power transmit, but what appears to  
> be the
> complete opposite.  Some of you may recall the post I submitted to the
> reflector several days ago about strange RF activity and my K3.  In a
> nutshell, my SWR alarm on my wattmeter will trip upon initial  
> keydown when
> operating in sideband and the linear is on.  It functions fine on  
> the other
> hand if I key down with a continuous carrier.. even up to 1200W.  The
> exciter drive level doesn't seem to make too much of a difference  
> UNLESS I
> turn the power output to 12W or less.  The moment I switch back to  
> 13W or
> higher and the KPA3 is in line, the problems begin.  Looking at my  
> wattmeter
> in peak mode shows an initial burst of power when keying down.   
> After a few
> seconds, the power drops back to a normal level.  I have a theory that
> there's some sort of RF burst in sideband mode upon initial keydown;  
> perhaps
> the KPA3 oscillates for just a few seconds and transmits off- 
> frequency until
> it stabilizes.  This is just a theory though.
>
> I'm still playing with my RF grounding and isolation to fully hope in
> eliminating all other possibilities before pointing the finger at  
> the K3.
>
> 73 de James K2QI
>
>
> 2009/7/18 Björn Mohr bm at broadcast.se
>
>>
>> This problem has been around for some time with my K3. What happens
>> for me is that when I set the power to specific level and push TUNE
>> the radio stabilizes at that preset level. Then when keying and begin
>> talking the power level is a lot lower that verified with TUNE. After
>> a few seconds the power peaks are in the vicinity of the preset  
>> level,
>> but sometimes peaks are reaching above the preset level which makes  
>> me
>> reluctant to mess with TXG VCE. Another observation is that this
>> problem is only with the PA in line, taking power below 12 watts  
>> seems
>> to eliminate the issue.
>>
>> Earlier the problem was reversed as power overshot the set level in
>> SSB, now I am less worried but seeing the issue solved would provide
>> some comfort when using the amp.
>>
>> I am also using a factory calibrated LP-100A to verify my  
>> measurements.
>>
>>
>> 73 de Björn,
>> SM0MDG
>> SE0X
>>
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Myles Landstein
myles.landstein at gmail.com
please note my   new email address
dti will soon be eliminated , gmail is my new home  update your dir