Icom IC-251A Instruction Manual page 27

TRANSMITTING
Insert the keyer plug into the KEY Jack on the rear panel of the unit, and set knobs and
switches the same as for CW reception.
By setting the T/R switch to Transmit, the transmit LED is lit and shows that you are ready
for CW transmission. When you key the keyer, the meter needle moves and your CW signal is
transmitted. ieee
CW MONITOR
When keying, the side tone oscillator circuit is activated and an 800Hz tone is heard from the
speaker. The loudness of this tone is adjusted by rotating the CW MONI Control, located
under the access cover. Rotating the control clockwise makes the tone louder. (In the
receive mode, this side tone is audible and can therefore be used for Morse Code Practice,
adjustment of the keyer, etc.) To receive again, place the T/R switch in the receive position.
SEMI-BREAK-IN OPERATION
The IC-251A/E has Semi-Break-In CW capability when using the VOX function. When keying,
the unit is automatically set in the transmit mode. After keying, it is returned to the receive
mode, also automatically, after a given transmit-release delay time constant. Leave the T/R
switch in the Receive position, and set the VOX switch in the ON (down) position.
The transmit release delay time constant is set by adjusting the CW DELAY Control located
under the access cover. Turning the CW DELAY Control clockwise will make the transmit
release time longer. Set for your keying speed.
FM OPERATION
1.
RECEIVING
Set knobs and switches as follows.
MODE SELECT SWITCH FM-s or FM-c
VFO SWITCH AorB
SQUELCH CONTROL Completely Counterclockwise
Other knobs and switches are set the same as for SSB reception.
Adjust the AF GAIN control to a comfortable listening level of noise, if no signal is present.
Carefully adjust the squelch control clockwise until the noise just disappears, and the RECEIVE
indicator goes out. This is the proper squelch threshold setting and must be done when no
signal is present. Your transceiver will now remain silent until an incoming signal is received
which opens the squelch and lights the RECEIVE indicator. If the squelch is unstable due to
the reception of weak or mobile stations, adjust the squelch control further until the proper
threshold is obtained.
When the MODE SELECT Switch is in the ""FM-s" position, the multi-function meter indicates
the signal strength of the incoming signals and is calibrated in S units and dB over S9. When
the MODE SELECT Switch is in the '""FM-c'' position, the meter indicates the off set of the
incoming signals.
The NOISE BLANKER and the AGC circuits do not actuate in this mode.
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