Solutions to better Omni Six keying, including establishing the proper
timing to external, non-Ten-Tec amplifiers can be found in the Ten-Tec
Reflector archives. Most notably, you will find extensive information from
late 1997 and throughout 1998.
For external amplifiers, I have found the best timing source is derived from
the Omni's "T" voltage on the Control Board...NOT the "TD" voltage, and NOT
the TX-OUT signal as many are using. The only way to get away with using
TX-OUT, by itself, with an amplifier that cannot accommodate a full
handshake is with an amplifier that protects itself against hot-switching
(e.g., Alpha 87A). Otherwise, using the TX-OUT signal available at the
Omni's rear panel is a guaranteed invitation to hot-switching (the trailing
or "break" RF envelope) with a non-Ten-Tec amplifier. Since the trailing
edge becomes truncated, keying the amplifier ahead with a contact closure or
open-collector from your keyer does not help...this only helps on the "make"
RF envelope closure. Using the "T" voltage results in proper timing for
even the most sluggish amps, although the QSK listening "window" may be
shorter, depending on the speed of the amp in question.
----- Original Message -----
From: "Tom Rauch" <email@example.com>
To: <firstname.lastname@example.org>; <email@example.com>
Sent: Sunday, February 17, 2002 11:33 AM
Subject: Re: [TenTec] OMNI VI "click/chirp"
> Sounds like exactly the same problem ICOM has in some radios.
> > Probably easier than modifying internal circuits, one might introduce
> > a make delay between KEY OUT and KEY IN. The simplest delay would be a
> > relay. A reed relay should proved a few milliseconds delay and an
> > armature relay should introduce about 10 milliseconds delay. A relay
> > will introduce audible keying noise in the shack and the delay on
> > break may keep the signal up when the processor is starting to shift
> > the oscillators back to their receive frequencies. That's just moving
> > the chirp from start to end of each code element, not necessarily
> > progress. It would be preferable to use something like a TLC555 timer
> > and a bit of logic to delay the MAKE without adding delay to BREAK.
> > Likely a millisecond of delay will be very sufficient. I've not
> > detected the microchirp so I can't be sure it will have been cured.
> > I'd prove the microchirp was cured using the simple relay, then create
> > the necessary quiet circuitry to accomplish the make only delay.
> If you do a make-only delay, you also will have to stretch the signal
> from the key input to restore the weight. That shouldn't be difficult.
> The receive window on QSK will shorten, but anything is better
> than clicks or transmitting while the VCO is moving!!
> 73, Tom W8JI
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