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
www.n4py.com
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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