[Elecraft] K3 - KPA500 Power control

[Art Nienhouse]

/*I had the same issue which appeared out of no were after a update in 
firmware I think it was because it was not happening when I first built 
the Amp.
When my radio was new it did 140 watts output a later firmware update 
cut this back to 110 watts when the over shoot of power to the amp on 
the first dit started to appear the Amp would do a soft fault and fold 
back to 250 or 300 watt output if I kept sending it would build back to 
full power out put 500 watts.

What I was seeing happening was the K3 would on the first dit of the day 
(cold start for the fist operating session ) would spike to 140 watts 
then fold back to 110 watts this is without the amp in operate I would 
see the K3 power spike 140 watt on the meter display on the Amp and the 
K3  if the Amp was in operate the 140 spike would cause an instant  soft 
fault ((high drive pwr ) or some such message on the KPA500 display 
causing the pwr output to fold back to 250 watts or so then build back 
up to normal 500 watt output.

I think there might be a software code error which is allowing the K3 to 
over shoot power out at the initial touch of the key.

The strange thing is it only happen when I first started up operation I 
could run the amp for a hour rag chew and it never happened again.... 
but shut down the radio and amp come back latter this issue would be 
there again.
I have peak hold setting selected on both the Amp and K3 this spike is 
very fast but shows up if peak hold is selected.

Another poster stated he played with the ALC THR menu setting on the 
KPA500 setting the number to 150 and this fixed the issue.
I did the same thing to my setup For most bands the ALC THR is set 150 
but on 1.8 mhz my setting is 210
on 3.5 my setting is 129 on 54. mhz is also 129.

This hides the over shoot on power from my K3 on the first dit of the 
day even if I have the power set to 100 watts not full right the over 
shoot still is there in the radio..... and yes the drive power was set 
correctly for the Amp.
I have not called service on this issue as the work around is working 
the issue is with the K3 power control which is not there on the first 
dit, after start up.

Regards
Art
ka9zap
*/
On 6/7/2013 10:09 AM, Arie Kleingeld PA3A wrote:
> Hi all,
>
> My K3 and KPA500 combo seems to overshoot the powersetting at the 
> beginning of a morse dot or dash. It happens with all morse code, not 
> only the first dot or dots.
>
> Pwr at start of dot: abt 570 W, steady state pwr 520 W. It does show 
> on my peak reading measurerents and the 550W led on the KPA lights 
> with every dot/dash. Holding the key 440W led is off, so that confirms 
> my other measurements.
>
> Checking the manuals does not help me at this time.
>
> Here's the setup:
> K3 #1255 with all HW mods and FW 4.60 / 2.80, running 33W on 12m
> TX ALC On (normal)
> EXT ALC Off
>
> KPA500 #1497, brandnew, FW 1.23
> ALC THR 210 (default)
>
> KAT500: BYP
>
> K-line is connected via the elecraft aux cables.
>
>
>
>
> So.....What did I miss, or is this normal?
>
>
> 73
> Arie PA3A
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