[Amps] QSK-5 in AL-80A

[Kim Elmore]

I decided to bite the bullet and replace my (nearly prototype) 
ancient PIN-5 QSK switch I'd had in my Ameritron AL-80A amp with the 
newer QSK-5 switch. As some of you might recall, my PIN-5 had 
developed a problem that is almost certainly a bad switching 
transistor, but the QSK-5 offers some nicer features along with a 
true QSK keying loop capability.  Installation was pretty easy, since 
I'd already installed the PIN-5 switch about 23 years ago...

One thing I was not prepared for is that when installed internally, 
the QSK-5 cuts off the tube when the keying line is high (not keyed). 
The old PIN-5 didn't do this, so sitting in rx mode the tube was 
dissipating about 200 W. In winter that makes for a nice, albeit 
expensive heater. In Summer, not so nice. That's a nice touch and 
will probably keep everything cooler.

I haven't used the keying loop yet, as my Orion II properly times the 
RF to avoid any hot switching of the T/R switch. But, that raises a 
question: if I enable the keying loop in the Orion II, transmit is 
inhibited until the loop is "complete," by which I mean that transmit 
is inhibited until the transceiver gets a signal out of the amp that 
indicates all internal switching is complete. That will work fine 
when the amp is on, but will it work when the amp is turned off? Is 
the switch in some bypass mode, wherein it always shows "keyed" on 
the output? I tend to doubt it, but I haven't yet tried it. Does anyone know?

73,

Kim Elmore N5OP