[GreenKeys] Tame Your Dovetron Tempest

[Jack]

I know there are a lot of Dovetron "Tempest" units out there,
and many are on the shelf, unused ,due to the lack of a HV loop
keyer.
I just (finally) put together a simple circuit which operates off
the +/- 12VDC EIA output and keys an external loop. There
was no rocket science involved; I just had to "get around to it".
The circuit uses a handful of junkbox parts with tthe only
specific part needed being the HV keying transistor ( I use the
good old MJE340). 
I built the circuit on an old piece of Radio Shack perfboard 
and mounted it inside the TU. I used an insulated two-circuit
1/4-inch jack for the loop and, while I was at it, replaced the
audio input BNC with an RCA phono jack. 
If anyone is interested in the circuit, I can FAX a copy to you.
Don't have any CAD for an online drawing...
The input keying for the AFSK requires either RS232 or the
MIL standard (+/- 5VDC). The real way to tame this beast is
to build Gil's complete board with the loop and transmit/receive
capability all there. 
By the way, if you really want to do it the cheap way, you can
drive a standard polar relay right out of the EIA connector.
Tried that too, and it works fine. It is important that you have
a well-adjusted polar relay or one of the WECO 314 types which are
sealed.

Jack WA2HWJ

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