[TenTec] Omni Vl Plus Amplifier Switching

Bob McGraw K4TAX rmcgraw at blomand.net
Fri Mar 27 11:41:27 EDT 2020

Barry et al:

To the best of my knowledge, having owned 2 of the Tentec Omni VI Plus 
transceivers, there is no RF delay upon key closure.   Thus the radio is 
designed to work in QSK mode with the Tentec series of amplifiers.  Thus 
the delay is effectively incorporated in the amplifier.  This then 
places the delay in the TX EN line.

As to using the KPA500, and I have one of those on the desk, some form 
of keying and timing will be required such that the amp is keyed first 
and then the Omni VII Plus is keyed.    This of course will cause a 
delay of some small amount in your keying.  That may be operational 
problematic depending on the amount of delay and would not likely be 
satisfactory in operating QSK.

There is a short delay of about 10 milliseconds which does occur on the 
Control Board.  See page 4-16, paragraph 3, in the manual. This delay is 
available on the keying loop.  Personally, I would carefully measure the 
timing from key closure to RF generation to make sure the 10 ms is 
indeed present.  If so that is most likely adequate to switch the 
KPA500.  Even so, some interface switching arrangement is needed.

A friend of mine is using an external keyer which does provide keying 
output for the amplifier and adjustable delayed output to key the 
radio.  I think it is an old MFJ product.    Even then, he removed the 
internal relay and converted the circuit to a open collector circuit.

I suggest buying a Tentec amp, Centurion or Titian, and be done with it.


Bob, K4TAX

On 3/26/2020 9:54 PM, Barry Simpson wrote:
> After a two year search, I have finally acquired a very nice Omni Vl Plus.
> I would like to know if anyone has designed/undertaken a modification to
> eliminate the slow noisy amplifier relay to allow solid state QSK switching
> of an external amplifier.
> I know that the Omni has the keying in/out function that fulfils the keying
> role with Ten Tec and other amplifiers with the same keying in/out
> circuitry. However, I want to control an Elecraft KPA500 which does not
> have the in/out function.
> I look forward to any responses.
> Regards and 73 to all at this difficult time.
> Barry Simpson  VK2BJ
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