[Elecraft] K3S - Alpha 87a combo - loss of keying amp

[E.H. Russell]

Kimo,

In order to keep my 87a from tripping into fault on band change, I sometimes
need to lower the drive power. About 10w seems ideal.

On my 6700 and 890s I am able to configure a low drive power for the TUNE
function. I'm not sure but think the K3 has a similar function. Of course
make sure the antenna is matched before TUNE is activated.

TKS,
73 ED W2RF





-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
Behalf Of Kimo Chun
Sent: Tuesday, October 20, 2020 7:22 AM
To: elecraft at mailman.qth.net
Subject: [Elecraft] K3S - Alpha 87a combo - loss of keying amp

In a K3S tested with two Alpha 87a amps using RF sensing to change band and
tuning the K3S appears to easily trip the amp into Fault mode. When amp is
cycled between Operate and Standby to clear the Fault, K3s can no longer key
the amp unless you cycle power to the radio. Then it works properly again.

1. Manually change bands on the radio, with amp still sitting on prior band
and with the drive turned down to 5 to 8 W to try to ensure we won't trip
the amp while possibly transmitting into a momentarily high SWR of the wrong
band input circuitry? When keyed on the new band to have the amp auto-tune
it trips into Fault.
2. After cycling the amp from Standby back to Operate the K3S can no longer
key the amp. It is transmitting in apparent bypass mode as indicated by the
low RF level still indicating on the built in Watt meter of the amp.
3. This was tested with two 87a amps. Same issue.
4. Pulling the key line and shorting RCA plug at radio end does successfully
key the amp.
5. Another K3 radio with updated syn) doesn't do this.
6. I believe the pertinent default settings of the two radios were set to be
the same, though perhaps the band by band default drive setting or limit may
not have been mapped (If I understand correctly).

I am the new owner of the K3S and I have zero experience with the radio or
type. I've not set up my station yet (working on rebuilding tower and
antennas) since buying the radio.  It is about 3 years old but only used for
6 months by the prior owner and once by my group at last year's Field Day.
The radio and P3 are being loaned to a friend to use in an SO2R entry in a
contest.

Has anyone experienced this? Any ideas on what may be wrong?
Can my K3S be sending a spike of power, anyway, to cause the trip? We
haven't gotten further into verifying this or other things as we only
started this today.Thank you for any help you may provide.

Kimo Chun, KH7U
kimo at lava.net
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html Message
delivered to ehr at qrv.com