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FRONT PANEL CONTROLS
1.
MICROPHONE INPUT
A 6-pin, lock ring type, microphone connector is used.
Microphone wiring is as follows:
Pin 1 : Microphone Audio
Pin 2 : Receive
Pin 3 : Transmit
Pin 4 : Down (Up w/ 22K Ohm Resistor)
Pin 5 : Ground
Pin 6 : +13.8 VDC
2.
MICROPHONE GAIN CONTROL
Increases or decreases the energy developed in the
microphone amplifier circuit. The gain increases as the
control is rotated clockwise. For optimum setting, press
the push-to-talk (PTT) switch on the microphone, ad-
just the mic gain control until all segments of the S/RF
display are lit. Next, rotate the control counterclock-
wise until the last segment of the display starts to flicker.
The S/RF display is the bar graph located on the lower
edge of the LCD screen.
3.
RF GAIN CONTROL
Adjusts the receiver sensitivity to both signals and back-
ground noise. This affects the distance at which a sig-
nal can be detected. Turning the control counterclock-
wise reduces the receiver sensitivity. This is particu-
larly useful in areas where large volumes of traffic (sig-
nals) are present. The S/RF display indicates the re-
ceived signal’s strength. The S/RF display is the bar
graph located on the lower edge of the LCD screen.
IMPORTANT!
Operating some of the features in 4 through 9 re-
quire the use of the function control. To activate
the function control, momentarily push the FUNC
(10) control, the FUNC prompt will be displayed in
upper left-hand corner of LCD. Push the control
again to deactivate the function control.
2
3
4
10
1
5
6
7
8
9
11
16
17
12
13
15
14
4.
STEP \ NB \ 1
STEP: Tuning Step. The STEP control selects fre-
quency resolution in either 1 kHz, 10 kHz or 100 kHz
steps. Press the STEP button, one of the digits will
flash on and off. Press the STEP button again to change
stepping resolution.
To tune frequencies in either 10 kHz or 100 kHz incre-
ments, press the STEP button until the desired digit is
flashing. Rotate the FREQUENCY control in either di-
rection. The entire frequency range of the Magnum 257
can be stepped through in 10 or 100 kHz increments.
To tune in 1 kHz increments, press the STEP button
until the 1 kHz digit flashes on and off. Rotate the FRE-
QUENCY control. NOTE: When stepping in 1 kHz in-
crements, you are limited to tuning within a 10 kHz
frequency range.
NB: Noise Blanker. Noise blanker on and off control.
This circuit eliminates pulse type interference usually
associated with automotive ignition systems. To acti-
vate the noise blanker, press the FUNC control and
then press the NB button. NB will appear on the LCD
indicating the noise blanker is turned on. To turn off
the noise blanker, repeat the same process.
1: Memory Channel 1. After programming this button
is memory channel 1. See M.LOAD \ M.SAVE control
for programming instructions.
5.
LCR \ RPT \ 4
LCR: Last Channel Recall. Press the LCR button to
return to the last frequency that was transmitted on for
more than 3 seconds.
