You may not even need to use the relay in the Omni VI to key the
amplifier. The TX OUT line on the Omni VI which is used with Ten Tec
amplifiers is connected to the open collector of Q11 (on the Control
Board) a MPS-6514. When connected to a Titan 425 amplifier there is 28
VDC from the 425 connected here. That transistor pulls this line low
with 10 k ohms to the +28 VDC supply. That works out to 2.8 mA if Q11
pulled it all the way to ground. This does not prove that the MPS-6514
can handle 80 mA, but it can certainly handle 28 VDC so 12 VDC should
not be a problem. I suggest looking up the specs on a MPS- 6514 ( check
out the fairchild spec sheet I found) to see if it can handle 80 mA. If
it can, then you need not activate the relay in the Omni VI, and you can
just use the open collector TX OUT line of the Omni to key the HF-2500.
I found a spec sheet which says the maximum collector to emitter voltage
is is 25 Volts, which is kind of strange since the Titan 425 puts 28
volts on it. It also says the the maximum continuous collector current
is 200 mA. That indicates to me that you could safely switch 12 VDC at
80 mA directly with the open collector TX OUT of the Omni VI and not use
either an intermediate relay or even the Omni VI internal relay.
If the QRO HF-2500DX is not QSK capable, and you need a "hang time" on
the keying, you will probably want to opt for relay control.
Here is what I found on the MPS-6514:
> whether I will require an
>intermediate keying relay between my "new" Omni VI+ and a QRO HF-2500DX amp.
>Amp manual states that the t/r relay should be capable of switching 12v@
>80 ma. The OMNI op's manual indicates its to be used to switch low
>voltage DC only but does not provide a current rating.
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