AOR AR5000 User Manual download pdf (Page 9)

AR5000 OPERATING MANUAL PAGE 9

Note: A microprocessor

reset

switch is hidden behind

the upper section of the lever’s slot. Reset can be useful

if the receivers operation has been upset due to static

discharge or power supply transients. Details are given in

section 18 of this operating manual.

5-7 Removable feet

The front of the receiver is lifted up clear of the table top

to allow easy access to the front panel controls and clear

visibility of the LCD. The front feet may however be

removed (unscrewing by hand in an anti-clockwise

direction using the knurled disk) for mobile operation.

Additional height may be added by fitting the two spacers

provided with the receiver in the accessories bag.

5-8 Internal speaker

The AR5000 is fitted with a lower case mounted speaker.

In order to provide best projection of audio from the

receiver, a custom horn has been designed and fitted to

the receivers underside (visible from the front panel).

5-9 SQ - squelch control (plus RF control)

The squelch control is used to eliminate unwanted

background noise when monitoring a normally inactive

frequency and is also used by the AR5000 microprocessor

to determine when a channel is

active

(busy).

The

receiver cannot scan or search when the background

noise is present.

The squelch control requires careful setting to achieve

optimum operating performance. Rotate the control

clockwise until the background noise just disappears

(threshold), this is the most sensitive setting of the control.

In practice the control is usually rotated a little further

clockwise beyond the threshold point to prevent the

receiver from stopping on noise or very weak and

unreadable signals.

If the control is rotated too far clockwise then weaker

signals will be totally lost and only local strong signals will

be heard.

When the squelch control is rotated anticlockwise so that

background noise is audible, the squelch is referred to as

being

OPEN

. In a similar manner, when the squelch

control is rotated clockwise so that the background noise

is muted, the squelch is referred to as being

CLOSED

The squelch is not normally used when listening to short

wave transmissions due to the relatively high short wave

background noise, the usual setting for the control when

listening to short wave is fully anticlockwise (squelch open).

When the squelch is OPEN (busy), a “BUSY” legend is

displayed on the left of the LCD.

Note: Even when the squelch is fully CLOSED a very

low level background noise may still be audible. This is

because the receiver’s audio amplifier circuit is

permanently operational in order to provide fast search /

scan rates and an efficient squelch opening characteristic.

This phenomenon is common with other wide band

receivers on the market today.

When the squelch is set up for normal operation, the

legend “N-SQL” is displayed on the top line of the LCD

slightly centre-right, this stands for Noise SQueLch.

RF GAIN

It is possible to configure the squelch control to function

as RF GAIN by selecting

on the keypad, the

“N-SQL” legend is removed from the LCD to confirm

operation. The RF GAIN control reduces the level of

amplification applied to the receiver’s I.F. circuits. This

has the effect of reducing the sensitivity of the receiver in

much the same way as the attenuator but is more

controllable.

The usual position for the AR5000 RF GAIN control is

fully anti-clockwise when the set is at its most sensitive.

As the control is rotated clockwise the S-meter will

advance to indicate what strength signal is required to

produce solid and readable results.

The control is most useful on SSB where the RF GAIN

should be adjusted so that the

peaks

of SSB signals just

deflect the S-meter. This will greatly reduce the level of

background noise especially during pauses in speech or

inactivity.

When RF GAIN is used (squelch switched off), the word

“N-SQL” is removed from the top line of the LCD.

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AOR AR5000 User Manual Page 9

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