[TenTec] Omni Vl Plus Amplifier Switching

Rick at dj0ip.de Rick at dj0ip.de
Fri Mar 27 11:55:48 EDT 2020

I used my OM6 with Ameritron amps, no problem; because I used an external keyer with built in time-sequence keying.

Originally I used my own home-brew keyer; ugly but effective.  I built it with a fixed 25mS TXD and variable Hang.
Later I bought an MFJ Millennium MFJ-495 keyer.
It has front-panel adjustments for the front-end TX Delay (TXD) as well as back-end hang-delay. 


This is cheaper than buying a new amplifier.

Rick, DJ0IP
(Nr. Frankfurt, Germany)
May the Sunspots be with us!

-----Original Message-----
From: TenTec <tentec-bounces+rick=dj0ip.de at contesting.com> On Behalf Of Bob McGraw K4TAX
Sent: 27 March 2020 16:41
To: tentec at contesting.com
Subject: Re: [TenTec] Omni Vl Plus Amplifier Switching

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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> TenTec at contesting.com
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