[GreenKeys] Tempest "Big Bird" Dovetrons

Fri, 18 Jul 2003 18:08:41 -0700

WHO'S DALE?
----- Original Message -----
From: "Jack" <[email protected]>
To: <[email protected]>
Sent: Friday, July 18, 2003 5:26 PM
Subject: [GreenKeys] Tempest "Big Bird" Dovetrons


> 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
>
> NNNN
>
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