[TenTec] Omni Vl Plus Amplifier Switching

Carl Moreschi n4py3 at earthlink.net
Fri Mar 27 12:17:30 EDT 2020

The scheme used in the Tentec radios that have TX EN and TX OUT goes 
like this.

When the radio wants to transmit, it sets TX OUT low.  The amplifier is 
supposed to receive this line and when the antenna relay in the 
amplifier is transferred, that sends ground out the TX EN line.  So when 
TX EN goes low, the radio actually sends out RF.

Tentec amplifiers have this.  Also Acom amplifiers have a key in and key 
out line that is compatible with this scheme.

Carl Moreschi N4PY
127 River Moss Way
Hertford, NC 27944

On 3/27/2020 11:41 AM, Bob McGraw K4TAX wrote:
> 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.
> 73
> 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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