[GreenKeys] Tempest "Big Bird" Dovetrons

[Jack]

ZCZC

Greenkeyers,

I received my Tempest Dovetron today!!! The one I got
definitely one of the stranger configurations. There is absolutely
no regen board at all. Instead, there's a three-tone-set AFSK board
(allows three different tone groups to be selected) and another
board for reversing the tones (?). The tones are set for
compatibility to other military RTTY units. You get 85,
200 and 850 HZ shifted tones out of the unit. They are
all adjustable with trimpots inside the unit. Finally, there's a "KOX"
board which is the "keyboard operated transmit" feature. It
allows you to key the transmitter when you hit the keyboard.
There's a few small boards which I didn't have time to
figure out yet. But, I can attest to the fact that these
beauties cannot provide regeneration or speed conversion
as they are now setup. I have already sent a note to
Gil and I believe he will be looking into an external
"digital widget" solution.

The output is either RS232 or MIL188 voltages. A very simple
adaptor can be made with three parts to be able to key
a high-voltage TTY loop from the MIL188 BNC. You'll need a 1k Ohm 1/4
resistor, a 1N914 diode and an NPN high voltage keying transistor.
I'll get a schematic (ready tomorrow) to George for him
to put onto RTTY.COM. The only hard part to find will be the
keying transistor. You'll need a Motorola MJE340 or a "TIP"
equivalent. I'll let you know what else might be substitiuted.
Maybe there's a Radio Shack replacement? If any of you have
Gil's interface converter board, it can be plugged right into the
RS232 BNC, and away you go.

The Dovetron Tempest manual that just I received from WW8S is not
the manual for this particular unit. The manual does match a few
of the older Tempest units I have seen. Those units did have the
regen board. Some of them have been on Ebay lately. Look for
the 3-speed switch on the front panel.

The parts inside seem to point to this unit as being late 80's
vintage (datecodes). My guess is that these might have been
used as "modems" in the simplest sense...maybe on VHF
frequencies or even wirelines? The lack of the regenerator seems to indicate
the use wasn't for critical HF radio use. There is no
military nomenclature label on my unit. I would also
point out that there might be variations amongst the
units that are being sent to everyone. So, the above is a
guideline based upon the unit I received.

My thanks to George and Dale for the hard work in getting
these units for us. The Dovetrons are beautiful pieces of
engineering and we should all have a great time with them.

73,
Jack WA2HWJ

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