/*KPA500 fold back on power output with the first dit or dah then it
builds to what its set for.
Try changing the ALC THR settings in the menu of the AMP I changed some
per band settings which stopped this from happening.
Default is 210
Some of my bands i use 129
Check page 10 of the manual
My K3 (was / is) over shooting power on the first dit or dah I would see
power as high as 140 watts ...(it originally did this much but software
change has it limited to 120 w now), power over shoot is only for an
instant, this over shoot is causing the amp to shut down because of high
power on the input while in operate mode, even though my full power is
set at 100 watts and the drive power is set to 30w I would see for just
an instant on a watt meter set for pep 140 w.
If you are using full qsk or vox this keeps happening resetting the AGC
THR should help or fix the issue.
Could be a software code line needs to be tweaked in the K3 to stop this
over shoot of power on the first dit or dah
which was happening to my radio even though the power is set to 100 or
95 watts total, the over shoot still goes to full
power the finals are capable of.
Check the archives for the e-mails that talked to this issue, I'm not
sure how far back it was but adjusting per band in my KPA500 Menu did
the trick for my setup.
Regards
Art
ka9zap
*/
On 10/27/2013 10:35 AM, Mike Schultz KS0T wrote:
Hi Don and all,
Thanks for the ideas, but still having the problem. Don, I looked
at the K3 output on the analog meter on my old Waters dummy load and
saw no change from first dit onward (30 watts thru amp in standby).
Band changes don't seem to help although it sees on 40 it gets to
higher power a bit faster - maybe 1 second instead of 2. Also on 4o
the problem seems to go away if I start keying again within say 5 or
10 seconds. Also, the change form low to high output from the amp is
abrupt after a second or two of dits. It is also about a 3 dB
difference (attenuator?). A few hours ago I also tried taking the
KAT500 out of the mix and using new coax. I HAD K3 to KPA500 to dummy
with different coax jumpers and still had the delay. Also had PTT
direct rig to amp. I was testing in CW vox/qsk but the problem also
occurred if I asserted PTT via footswitch so that I saw the asterisk
on the amp display before I started keying.
I have everything wired up normally again and still observe the
original problem I had yesterday when I tried to enter the contest.
That is, I transmitted fine at 100 watts with the tuner in use (1:1
SWR) for my vertical on 40. When I turned on the amp I get a hi SWR
and the tuner starts hunting. That is what got me started
troubleshooting and observed this delay problem I've been describing.
Well, I going to go get some more qsos on low power now. I'll
check my email again in a bit to see if any more ideas come up.
Thanks, Mike KS0T
-----Original Message----- From: Don Wilhelm
Sent: Sunday, October 27, 2013 8:01 AM
To: Mike Schultz KS0T ; elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 delay in getting to full power
Mike,
Make certain it is the amp and not the K3.
Check the actual output from the K3 - disconnect the amp and drive the
dummy load through an external wattmeter. Don't change anything in
the K3.
Does the power out follow the same pattern?
Try a band change (up and then back down) and then test again.
What I am saying is that it may be the K3 behavior instead of the amp.
The K3 power control starts out at a low value and then builds up to the
requested power output. The power output control is reset on a band
change and at power on.
It should only take a couple dit times, it sounds like yours may be
responding more slowly.
Probably not as noticeable at lower power, but certainly noticeable at
the output of the amp.
73,
Don W3FPR
On 10/27/2013 7:58 AM, Mike Schultz KS0T wrote:
A problem just showed up with my 4 month old amp. If I send a
string of dashes at 30 Watts out of my K3, the KPA amp puts out
around 120 Watts for the first second or two then goes up to the
expected output of 480 Watts. This is on 20 meters to a Dummy load
through my KAT500 tuner in bypass. The ACCY plug was disconnected
and PTT was direct from K3 to KPA500. Amp firmware was beta 1.33 but
no change when I reverted to release V1.23.
Any ideas while I continue the CQWW SSB contest at a frustrating 100
Watts?
73, Mike KS0T
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