[GreenKeys] RTTY receiver noise immunity?

[William Wuttke]

I’ve found that noise immunity is largely dependent on the TU. I have a number of HAL units,
an IRL FSK-1000, and a couple of Dovetron MPC-1000s. The best Automatic Mark Hold
circuit is best (in my estimation) in the Dovetron, followed by the HAL ST-8000. Both have front
panel AMH adjustments, but the Dovetron is easier to tune. Once you initially set the threshold,
it remains pretty much immune to the noise.

I don’t know anything about the old military units, but probably the best idea would be to turn
AGC off and use manual RF gain.

Bill
KE3BK