[Elecraft] KPA500: Bonehead Input Overload

[Luis V. Romero]

ALC would not have helped, as it is too slow to respond to a momentary
overload of this magnitude.

My station is set up exactly as described by Andy below.  Also, the K3 is
set to remember output power by band. KAT500 hancles disabling the amp on
SWR faults and when tuning (rarely done as Ive taught it my antennas), it
will inhibit the KPA500 until the SWR issue is corrected. 

The KPA500 also communicates with the radio.  When it trips or turns off for
any reason, it will talk to the K3 and tells it it went offline. It also
screams at me to call attention to the issue and the K3 beeps in my headset
and flashes a crawl message on its screen to tell me the amp is offline.

I have fewer communications between the amp and the tuner with my TS590.  On
an SWR fault or tuning, the KAT500 keeps the amp in standby until it is
happy with the SWR (in my case, below 2:1). Sometimes when changing bands
with the '590, it takes a microsecond more to have the KAT500 figure out
where the rig QSY'd to, so it keeps the amp offline until it figures things
out.  In this case, I need to manually re-enable the KPA500 for any reason.

Ive also boneheadely transmitted the TS590 at 100w with the amp enabled. The
amp IMMEDIATELY goes to standby and screeches loudly at me.

 Lu W4LT

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Date: Fri, 15 May 2020 23:43:55 +0000
From: Andy Durbin <a.durbin at msn.com>
To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] KPA500: Bonehead Input Overload
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"That is a very good argument for having ALC active between the amp and
radio. "

ALC is just another reactive protection.   In my station the KAT500 is
commanded to inhibit the KPA500 key line by default.  Only when all required
conditions are met is the key line enabled.  Enabling conditions include
Hi_SWR false and TS-590 power set and verified.  Set drive power is not
allowed to exceed 120% of band max drive power.  (That overhead allows the
psychological boost of turning the wick up when chasing needed DX but
prevents doing anything too stupid.)

73,
Andy, k3wyc