Agc Selection; Squelch; General Coverage Reception - Yaesu FT-920 Operating Manual

tions are the JFET preamp on the 1.8 ~ 21 MHz
bands, and the MOSFET preamp on the 24 ~ 50 MHz
bands. We recommend that you use these settings
initially, and only change them later if you have a par-
ticular need to do so.
Although the MOSFET preamplifier provides
higher gain, the JFET preamplifier yields higher
dynamic range with respect to out-of-band signals.
Switching to the MOSFET preamp on 40 meters
will, undoubtedly, provide a higher S-meter read-
ing. However, the useful sensitivity will probably
not change. On the other hand, when using a
Beverage or small loop antenna for receiving on
the low bands, the MOSFET preamp may be the
better choice.
Remember: if you can hear background "band
noise" appear when you connect your antenna,
you already have adequate sensitivity. Any in-
crease in front end gain beyond this point will not
improve the signal-to-noise ratio on the incoming
signal.
The preamplifier chosen will always be on, unless
the [IPO] key is pushed. See the discussion of IPO
operation below in the section regarding " Tools for
Strong-Signal and Low-Frequency Operation ."
AGC (Automatic Gain Control) Selection
The AGC system of the FT-920's receiver prevents
potential ear damage and/or overload of receiver
components by establishing an "AGC Threshold" of
signal input. Once the AGC Threshold is reached,
further increase in signal strength does not result in
an increase in audio output.
The recovery time of the AGC system (the time re-
quired for the receiver to recover to full sensitivity) is
variable, and you may select the AGC recovery time
which provides the most operator comfort.
To select the AGC recovery time, press the front
panel's [AGC] switch repeatedly. You will observe the
display icons cycling through the available selections:
Þ AGC S
AGC F
AST
The AGC F position is usually preferable for CW
AST
and SSB contest work, while you may prefer AGC
S for more casual voice work. AGC O
LOW
often used for precise measurement of signals (when
evaluating antenna patterns, etc.), but strong signals
42
Þ AGC O Þ AGC F
LOW FF AST
is most
FF
will sound very distorted with the AGC turned off.
Rotating the RF G
help reduce the distortion.

Squelch

If you wish to mute the FT-920's receiver during no-
signal conditions, rotate the SQL (Squelch) control
clockwise until the background noise just disappears.
This threshold point is the setting which produces the
best sensitivity of the squelch to weak incoming sig-
nals.
When a signal is received which exceeds the thresh-
old set by the SQL control the muting function will be
disabled and normal receiver audio will flow. When
the signal disappears, the receiver will again be
muted.
The Squelch circuitry is most often used during FM
operation, but the FT-920's Squelch system is op-
erational in all modes. It may be particularly useful
while monitoring a 6-meter calling frequency (such
as 50.125 MHz), or when waiting for a Mode-A (29
MHz downlink) satellite to come within range.
To disable the Squelch system's muting capability,
rotate the SQL control fully counter-clockwise.

General Coverage Reception

You may have noticed that, if you tune outside of one
of the 500 kHz segments which contains an Amateur
band, the [G ] icon on the display becomes illumi-
EN
nated. This indicates that the transceiver is now re-
ceiving in the "General Coverage" mode. On such
frequencies, the transmitter is disabled. If you try to
transmit, "E
RROR
Since the FT-920 is chiefly an Amateur transceiver,
the one-touch band keys do not recognize non-Ama-
teur bands. However, you may use direct frequency
entry to establish a starting point in, for example, a
shortwave broadcast band; you may then use the
tuning dial(s) and/or the U
around the band. You may also program a "favorite
frequency" in each broadcast band into memory, then
Þ . . .
recall it quickly as a starting point for memory tuning.
See the section on Memory operation, beginning on
page 59, for details.
Otherwise, the FT-920's receiver facilities completely
support General Coverage reception, and you will
control counter-clockwise will
AIN
" will appear on the display.
/D switches to move
P WN
FT-920 Operating Manual