[Collins] Query about 6m transverters and S-line

[Dr. Gerald N. Johnson, electrical engineer]

There are some limitation using the Tentec transverter with the S-line.

First the Tentec expects a transceiver, because its IF out and IF in are
on the same connector. That could be remedied with some circuit changes
adding a connector and disconnecting some of the switching.

Then the transmitting converter output of the 32S comes from a high
impedance (10 pf) capacitor off the PA grid or RF driver plate. There's
not a lot of power on 10m and 1/4th that on 20m when driving a low
impedance load.

I suppose one could install a variable resistor in place of the screen
disconnect and use the HF TR relay of the S-line to run the transverter
as designed. Just give the PA screens something like 50 volts to cut the
power down. Might need a good solid audio bypass capacitor at the PA
tube end of the series resistor or a solid state regulator to keep the
changing screen current from causing a great deal of distortion.

It would be practical to build a power attenuator to accept 100 watts
and put out 10. Just 10 dB loss. Perhaps a couple hundred feet of RG-58
coax would do it though the Tentec needs 14 MHz and the coax loss is
less there. Maybe RG-174 or a gaggle of resistors.

It should be possible to drive the Tentec with lower power. I know my 2m
to 6m Tentec transverter runs full output with just 5 milliwatts drive
if I short the series resistor in the IF power attenuator. But I have to
hard key it because there's not enough RF voltage to run the RF
detector. But then I also find that the RF detector circuit doesn't
saturate and makes the transverter PA bias dependent on the drive level
and that causes transmitted distortion, so the next time I use it, it
will have hard keying installed.

73, Jerry, K0CQ, Technical Advisor to the CRA.


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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
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