Ramsey Electronics AR2 Manual de Instruções descarregar pdf (Página 20)

ABM1 • 20

ABM1 ALIGNMENT AND ADJUSTMENT

TUNING THE ABM1

The ABM1 does not require any frequency tuning. It will receive the entire

Aircraft Band at one time with the audio volume level being greatest for the

strongest signals. The ABM1 is a total band monitor so you will hear any

signal generated in that band. Since this is a total band receiver the band-

pass filters have been specially designed to be wideband. The aircraft band is

located between the FM broadcast band and one of the Pager bands. At

times and in certain locations low level signals from these bands may be

detected and heard in the ABM1. To reduce this align the band-pass filters.

Weaker signals may also be eliminated by adjusting the squelch control.

BAND-PASS FILTER ALIGNMENT

Your unit will probably work great without any alignment. Some users may

find that the FM Broadcast band is easily picked up by the ABM1. To reduce

FM band reception the band-pass filters can be tuned. Alignment of the

ABM1 band-pass filters consists of stretching or compressing coils L3 and L4.

Start off with the coils as they were when received (fully compressed). Start

spreading the coils apart simultaneously a little at a time keeping both coils

about the same. If you start to hear paging signals (152 to 159 MHz) then you

have spread the coils too far. In a heavy RF environment you may have to

balance the coils between a little FM and a little paging.

SQUELCH ADJUSTMENTS

The ABM1 uses your headphones as an antenna. Since each brand and

model of headphones is different the reception for each will be different.

Some headphones will provide better reception than others. Different areas of

the country have different RF environments. Some areas will have more RF

or higher noise than others. The squelch circuit will react a bit differently

depending on the antenna and RF noise in the area of use. Building the kit

with the parts supplied, it should work well for all different conditions, however,

the user may want to optimize their squelch circuit for the area they are in and

the headphones they wish to use. To get the squelch to open closer to the

low end of the potentiometer’s (R4) range decrease R5. To get the squelch to

close nearer to the upper end of the potentiometer’s (R4) range decrease R3.

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Ramsey Electronics AR2 Manual de Instruções Página 20