[Elecraft] KPA1500 questions...

[dick at elecraft.com]

Hi, Jay!

The KPA1500 bypasses the power amplifier during ATU TUNE.

Your K3S can communicate its current VFO frequency to the KPA1500 via the
ACC cable.  The KPA1500 will then change the ATU based on frequency, without
transmission.

If you have several antennas, as I do, I've done the tuning on each antenna
about every 20 kHz across the band in what we've called an ATU "training
session".

The KPA1500 retains ATU settings for each of these antennas for each "band
segment".  Then when you QSY to that frequency and transmit, the ATU
evaluates SWR, if it's above an SWR threshold (that you set), then the ATU
switches the PA to bypass, runs through the available ATU settings, and
picks the best one, then restores the PA to full power.  Depending on how
many antennas you've tuned for, this takes small tens of milliseconds, about
15 msec per ATU setting that needs to be evaluated.    This behavior is
turned on with a configuration choice, "ATU HiSWR RETUNE".

After the training session, I tune across the band and change antennas as I
wish, and the pre-tuned ATU settings are determined in a few tens of
milliseconds.  I don't press any buttons to cause ATU tuning, once I've
asked the KPA1500 to memorize the ATU settings for my set of antennas.  The
KPA1500's amplifier is bypassed when it needs to be for ATU tuning.  We
can't hot-switch the ATU relays at full amplifier power. ATU tuning is done
at exciter power, usually around 20-50 watts, although 100W isn't too much
for the relays.

If I get to a new frequency that I've never tuned for, I have to press the
KPA1500 ATU TUNE button.  

I have a keying cable connected between the KPA1500 and K3 "straight key"
input that allows the KPA1500 to key the K3S when it needs carrier to tune
the ATU.  We're working on a signal between KPA1500 and K3S on the ACC
connector that will hopefully remove the need for that extra keying cable.

If this is as clear as mud, send me another note...

73 de Dick, K6KR


-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
Behalf Of Jason Pecora
Sent: Monday, March 26, 2018 14:55
To: elecraft at mailman.qth.net
Subject: [Elecraft] KPA1500 questions...

Group good evening. I have a certain style of operation and a question about
the KPA1500 I would like to ask in the group. My normal operation is the K3S
into a Palstar HF Auto that tunes several antennas on my property.
I have had a lot of amplifiers in the past, from solid state to tube amps.
Currently I'm running a OMpower 2000+ amplifier. My normal process is that I
have 2 memories set on the K-pod, one is that it puts the radio into tune
mode at 8 watts out. This 8w output tunes the HF auto with low power until
it gets a good match which is very quick. During this 8w tune I have the
amplifier in stand-by mode, and all set to tune it next. After the 8w tune,
I have the same button set up to "HOLD" the button for a 30w tune in which
then I tune the amplifier which is pretty much ready to go off of a list
that I compiled, just basically a touch up is all that is needed. The radio
stays at 30w after that tune and I'm ready to go... My question is this. Is
there an option with the KPA1500 that I don't have to reach over and keep
hitting stand-by on the amplifier every time I need to touch up the HF-Auto,
can I set up a K-pod button to do this, or a button on the K3S? So basically
does the K3S talk to the buttons on the KPA1500 so that I could create a
stand-by button on the K-pod...I'm right on the fence on a purchase and this
feature would really be of importance to me...

Jay KB8O
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