Heathkit Changes (November 19, 1979) from SB-104-84
Obtaining A more Logarithmic S-Meter Response
The S-meter in most units is largely insensitive to plainly audible
signals, while allowing slightly louder signals to peg the meter [with
R-534 set for an S9 meter reading at 50 microvolt signal at the antenna
connector]. To provide a more logarithmic response, perform the following:
Replace ZD-502 with a 1N191 signal diode [PN 56-26]. Install this diode
opposite that shown on the circuit board, so that it is forward-biased
[cathode towards R-534].
Set R-534 to S9 with a 30 microvolt signal.
The meter will register slightly more accurately from S9 to +30 but will
have little or no action above +40.
Perform this modification only if the customer specifically complains of
this problem.
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