M3SR Series 4100 Switching the Rx Preamplifier On and Off
3.142 Operating Manual 6175.4760.02 – 01
3.7.2.7 Switching the Rx Preamplifier On and Off
Softkey Softkey Type Description
Toggle 1. Press softkey 'Preamp' to toggle preampli-
fier on/off.
Possible values:
•ON
•OFF
Default value:
ON
It is recommended to keep the preamplifier on
when the radio is operated on short, low-gain
antennas or at frequencies above 10 MHz,
where it can increase the signal-to-noise ratio
of the received signal.
In other cases, operation with Rx preamplifier
switched off can deliver even better reception
results.
Superimposed over these manual settings is
an automatic process (in case AGC function is
switched on) which controls the preamplifier
gain depending on received signal strength to
prevent saturation of subsequent stages. The
manual settings are limits up to which the au-
tomatic process controls, i.e. for low signals
the attenuation /gain values apply; if the signal
is above a threshold it is further attenuated.
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