I am the lucky (?) owner of a used 444 that the previous owner used
with an Omni C. Yes, I know the output devices are long unavailable,
that it could be unstable, and that Ten Tec wishes they had never made
it. All that aside, I want to use it with my Omni V and my TS850.
What I've learned so far by studying the 444 manual, the Omni V
operating manual (sad, compared to my Omni A manual), the TS850 manual,
and the keying traces in QST product reviews:
1) All of these radios accomplish QSK by delaying transmit by 5-15 ms
after the key has been pressed. The keydown signal is called the
T-line, and is used to run the antenna relay. The transmitter is
actually keyed by a delayed version of the keying signal. In the Omni
A, it's about 5 ms, in the Omni V and TS850, it's more like 10-15ms.
2) The Omni A and the TS850 bring the T-line out to the amplifier
interface connector. On the Omni A, it's pin 2 of the 9-pin Molex that
also runs the amplifier's bandswitch. It's pin 7 on the TS850 amplifier
connector.
3) The Omni V does NOT bring the T-line outside the radio, so I've got
to drill a hole, add a connector (RCA, BNC, or whatever).
4) TheHercules II use a different keying system -- the amplifier keys
the radio and does the delaying -- and the Omni V (and later) are
designed to work that way.
5) The 444 is designed to work with the Omni A, so 5 ms is enough
delay. I interpret that to mean that the additional delay provided by
the TS850 and Omni V will work fine with the 444 Hercules.
6) The keying signal (T-line) is buffered by the 444 (a 2N5087), thus
the 444 doesn't load the T-line, so I I don't need to do anything
special to isolate the T-line.
7) The TS850 lacks a receive antenna input, so I need to add one. That
also involves drilling a hole.
8) With the Omni V and TS850, I key the radio and it keys the 444
amplifier.
Questions:
Can anyone find anything wrong with what I've outlined?
Any problems I haven't thought of?
I see two sets of T-R relays in the 444 -- one seems to be essentially
a PTT relay that switches the amplifier to transmit and would be held
in by the VOX delay. This one seems to be driven by grounding the relay
jack. The others are a pair of QSK reed relays keyed by the T-line that
short the receiver input and connect the ampfier to the antenna. Can I
run non-QSK by not using the receive antenna input of the transceiver
and keying onlly the PTT relay?
Jim Brown K9YC
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