[Elecraft] K3 output power spikes

[dave]

I thought that one of the features of the K3/K3s was that it was able 
to run, and run well, off of batteries. These power spikes makes it 
sound like that is not the case? Or am I missing something?

Batteries start out at 12.6v and go down from there. The K3/K3s needs 
to run well down to something like 10.5 to 11v. But if they need at 
least 13v to prevent power spikes . . . .

73 de dave
ab9ca/4



On 3/1/16 9:30 AM, Don Wilhelm wrote:
> 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.
>>
>
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