[Elecraft] K3 output power spikes

[Don Wilhelm]

Bill,

Is there any way that you can increase the power supply voltage to 13.0 
volts or more during transmit?  If so, that should help.
Most of my experience with power control is with the K2 which starts out 
at lower than the requested power after a band change or a change in 
power level, but quickly builds up to the requested power.  The result 
is a lack of power spikes.
I figured that the K3 power control is similar, and if so, I would not 
expect power spikes at all.  Perhaps the power control loop should be 
investigated for critical damping.  If power spikes occur, that is an 
indication that the control loop is underdamped.

If the control loop damping is the problem, it is possible that this is 
not a problem for all K3s - the loop gain will may vary depending on the 
gain of the transmit RF stages, and while one K3 may have this problem, 
another may not (that is the case with the K2).  The RF Gain also varies 
from band to band, so there may be a difference in that behavior 
depending on what band is used.

73,
Don W3FPR

On 3/1/2016 10:12 AM, Bill Hammond via Elecraft wrote:
> Hi John,
> My power dances all over the place (my serial number is 00069).  Just had a quick QSO with the KPA500 indicating 560 watts at the beginning and then going down to 480 at the end.  That is typical.  My 12 volt supply drops to 12.2 on transmit, 13.3 on receive.  I have a long 12 volt  cable from the supply so  “I" squared losses are understandable in the cable. Driving power from the K3 is variable per band but typically set to 25 watts or so.  The QSO described above was on 17 Meters and the drive is 25 watts there for ~500 watts out or just below after stabilization.
>