[Elecraft] K2/100 High Refl shutdown driving amp

[Vic Rosenthal]

Floyd Sense wrote:

> The K2 is sn#1987 with Rev B changes, latest firmware.  I recently built the
> KPA100 and have been testing the setup while chasing DX with the AL-800H
> amplifier.  The 8R Hold feature is being used, and I can drive the amp to
> full legal output with 50-60 watts from the K2.  Over 6-8 hours of
> operation, I've had one situation occur three times now.  If I pause just a
> bit too long between characters on CW, the amplifier relay drops out and the
> problem occurs when the next character is sent.  The problem is a High
> Reflected power message, and complete loss of output power from the K2.  I
> suspect that the problem originates when the K2 output rises during the
> amplifier relay drop and reactivation, presenting the K2 with a momentary
> high SWR situation.

The AL800H uses an open-frame t/r relay whose pull-in time is just too 
slow.  You can replace the relay with a reed relay for input and a 
vaccuum relay for output (see <http://www.somis.org/QSK922.html>) and 
the amp will be fast enough for full QSK if you wish.  Ameritron also 
makes an (expensive) PIN-diode QSK unit, but the vaccuum relay system is 
effective and cheap.  The 8r hold function will keep the relay closed 
during characters and prevent hot-switching when it opens, but obviously 
can't anticipate your sending!

I realize that this doesn't answer your question about reseting the K2 
after the Hi Refl message, but you should realize that in any event the 
amplifier is hot-switching when you start to send which causes a loud 
click on the first keyed element.

73
Vic K2VCO
Fresno CA