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[VHFcontesting] DEMI Interface to TS-850S Keying Circuitry

To: "'vhfcontesting@contesting.com'" <vhfcontesting@contesting.com>
Subject: [VHFcontesting] DEMI Interface to TS-850S Keying Circuitry
From: "DUGAS, JASON A. (JSC-EP) (NASA)" <jason.a.dugas@nasa.gov>
Date: Tue, 21 Sep 2004 22:48:13 -0500
List-post: <mailto:vhfcontesting@contesting.com>
Hello all,
I wrote several weeks ago asking for advice on building a DEMI transverter,
well I ordered it and so far everything has gone GREAT!

Today I got down to the final steps of soldering some of the wires for the
keying circuitry in the transverter and the directions say "Depending on the
keying circuit required by the IF transceiver, connect the wire from either
the TTL or PTT point on the board to the wall mounted RCA jack labeled PTT -
H-L."

Well, I bought my TS-850S about 3 weeks ago (used of course) and it didn't
come with an owner's manual, so I really have no idea what the keying
circuitry looks like...  

Best I can tell, if I connect the TTL line to the jack, the transverter will
be looking for a 5V signal to bias ON a transistor which energizes the relay
K1 on the transverter.  If I connect the PTT up, the transverter will be
looking for a GND potential to sink current in order to energize K1.  If I
had to guess, I would think that the 850 uses PTT, but I'm not sure if it
has a TTL output and if so, where does it come from.

Thanks for any help you can provide!


Jason
KB5URQ
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