[ICOM] Pro II vs. Pro III RX-ANT input circuit (was "Smoked ProII")

[Adam Farson]

Larry, Gus,

Many thanks for the comments. The RX-ANT protection circuit in the Pro3 is
actually independent of the T/R state. When it detects excessive RF power
input from any source, it will switch the receiver input line from ANT1 or
ANT2 to RX-ANT. This is useful in such applications as a multi-transmitter
contest station, a shipboard environment or a comm. centre where several HF
transmitters are co-sited.

I have suggested to Icom via my contacts that the RX-ANT jack be marked with
a maximum safe input level. In the meantime, by doing a rough calculation
based on the component values in the RF detector, I arrived at approx. +27
dBm input to RX-ANT for switchover.

Cheers for now, 73,
Adam VA7OJ/AB4OJ



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