Furuno FAX-410 manual Operation with external receiver

２.５ Operation with external receiver

(1) External receiver

When an external receiver is used, it should have a local oscillator with very good frequency stability. The A1 detected beat, a low-frequency output, can be monitored with the unit when the signal is supplied through receiver jack of the external receiver. If the signal is supplied from the speaker terminal, it is suggested to use a dummy resistor and supply signal from both ends of the dummy resistor. The signal enters the input terminal (EXT-IN) on the back of the unit and should be 50mV or larger at the input terminal. When an external receiver is of ordinary type, there will be no problem of excessive input since there is a protection circuit inside the unit. However, if direct current is superposed, be sure to input it through a non-polarized capacitor of about 1μF.

(2)Operation

a)Beat adjustment

When using an external receiver whose beat frequency is adjustable within a range of ±2kHz or more by means of the beat knob, set the frequency dial so as to maximize the deflection of the receiver’s “S” meter, and adjust the beat knob so that the center LED of the tuning indicator of the unit is lit. When a signal from station with ISB communication from a U.S. Navy station, e.g., Guam, Pearl Harbor or San Francisco, is received, sometimes an adjustment of the frequency is necessary with a variable condenser or spread variable condenser, because the frequency may shift within a range of ±2kHz from the specified frequency of the station.

b)Band width

When noise is low, a wide bandwidth is advantageous to have good picture quality. However, a narrow bandwidth down to 1kHz is preferable in a noisy condition.

c)Selection of external receiver

Refer to 1.4.1 to use an external receiver and also to return to the internal receiver.

d)Recording

Refer to 1.3.3 for recording operations and for reverse reception. In reverse reception, set the external receiver to the FBO, LSB or USB mode similarly.

NOTE
BFO	: Beat frequency oscillator	LSB	:	Lower side band
USB	: Upper side band	ISB	:	Independent side band
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