[TenTec] QRP-ifying an IC-745 and TT 1208 Transverter

[Dr. Gerald N. Johnson, electrical engineer]

I don't know the circuit details of the TT1208 but I presume the IF port
is quite similar to that of the TT1209 with the same IF port ratings.

I've driven my TT1209 with a HP608F signal generator at +5 dbm by
shorting the series resistor of the input PI attenuator. I had to hard
key it because the RF sense wasn't sensitive enough. A simple grounding
of a transistor collector was easy to accomplish. Hard keying is better
than RF sensing anyway. I found the RF sensing tended to operate the
transmitter stages with lower than designed bias leading to greater
distortion. 30 mv is quite a bit less than +5 dbm. The transmit mixer
probably needs between -10 and 0 dBm drive. 70 to 700 mv at the mixer.

73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.