[GreenKeys] ST-8000A Info

[Jack]

ZCZC

I've been playing with my HAL ST-8000A and have the following to
report:

- I removed the rear "mil" connectors and installed RCA phono jacks
for the audio in and out connections, and a DB9 for the RS232. The mil
connectors have internal jumpers that plug into the circuit board. If
you
remove the connectors and PC plugs, you can wire wrap to the pins on
the PC board. I used wire from a 25-pair telco cable (what else?) and
my
good old Bell System wire wrap tool. To mount the new connectors
I installed an aluminum plate across the inside of the
rear panel, covering the holes from the removed connectors. With
some careful measuring and hole cutting,
two RCA audio jacks can fit into the AUDIO hole and the DB9 fits into
the DATA hole (with a little work). If you want to bring out
the control relay that operates whenever the AFSK is keyed,
you can put another RCA jack in the DIVERSITY blank hole.
The aluminum plate is held to the rear panel using the original
mil-connector holes and hardware. 

- if the RS232 TX and RX data leads are tied together, the ST-8000A
can
be used as an audio in/audio out regenerative repeater feeding any
basic RTTY TU that has a HV loop. How about this...I tied the
HAL ST-8000A to a HAL ST-5 (kit built) to copy ITTY to test the
concept. (I have the ST-5 permanently mounted in the base of a
28RO that's dedicated to ITTY.) You can also make the output
tones any combination you want. This way you can key old
military TUs that have oddball tones, etc. I'm going to
dig out my old UPI TTY subset that requires FDMA types of
tones and key it with the ST-8000A. High tech to low
tech, for sure!

- anyone who purchased the Black Box RS232 to current loop converters
can easily interface one of them to the ST-8000A. For loop output, I
use
a junkbox 12VDC reed relay, with a "snubber" across the contacts, to
drive a HV loop. Option the BB to put out a 20 ma. active loop for
the relay. This works for receive-only. Option the Black Box
gadget for two-wire loop operation and it will take care of repeating
the
received audio to key the TX AFSK audio. If you want to transmit,
the easy way is to separate your keyboard or TD connections and put
them in
series with the LV loop that's keying the reed relay. Any time you
type or send from the TD, you'll key the HV loop to your printer and
also key the HAL through the RS232 connection.

- don't forget my "lazy man's" RS232-to-loop converter...a good old
WECO 255 polar relay hooked directly to the RS232 ground and RX-out
connections. I haven't tried it with the ST-8000A yet, but it will
probably work.

- if you want to use the ST-8000A on the air with the control relay
keying your transmitter, you'll have to option the BB's RS232 output
for four-wire (full duplex) operation. Otherwise, received signals
will
cause the relay to key the transmitter. Your keyboard/TD would then
connect to the TX loop input. Remember, the $5.00 BB units that were
on
Ebay can only key loops under 30VDC.

All of the ST-8000A mods can be easily "undone".

I'm going to document all of this and add some pictures. I'll ask
W7TTY
to put it on www.rtty.com when it's done.


73,
Jack K0TTY

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