User's Manual

may be overridden at any time.

Press the [UP] key to tune the receiver upward in whichever step size is selected, use the [DOWN] key

to tune the receiver downward in frequency.

3-6 RECEIVE MODE

Due to the necessities of signal bandwidth, channel occupancy and transmission efficiency, different

receive modes are used by various services. The tuning step and receive mode are allocated by

departments of Governments following international discussions so they are not consistent throughout the

world. For this reason, it is necessary to change receive mode in order to monitor various transmissions.

For your convenience, receive mode and tuning step size have been pre-programmed into the AR5001D

auto mode band plan data at the factory to simplify the operations of the receiver, especially while you

familiarize yourself with the functions. If needed, the defaults may be manually overridden at anytime

so that you may select an alternative receive mode and tuning step on any frequency.

AM – Amplitude Modulation

Used by broadcast services throughout the world on long wave, medium wave and shortwave.

AM is also used by VHF airband, UHF military airband.

SAM – Synchronous AM

Helps to listen to SW (Shortwave) AM broadcast stations with fading signals.

FM – There are two common types of FM (Frequency Modulation):

NFM – Narrow Band Frequency Modulation

Provides high quality communication for relatively short distance operation.

FM uses a greater frequency bandwidth than other modes.

NFM is the most common mode used above 30 MHz with the exception of the airbands. NFM is

widely used on the VHF bands: VHF marine band, 2m amateur band, 70 cm amateur band, PMR

(Private Mobile Radio) and utilities.

In the absence of a signal, the background white noise may appear quite loud. For easier listening,

the squelch control should be rotated clockwise until the background noise disappears; this should

be carried out while no signal is present. The point at which the background noise is cancelled is

known as the threshold point. Do not advance the squelch control more than necessary or the

receiver will appear to be desensitized and weaker signals will be missed.