Download (1) AR8600 Index Section 1

Section 3-7-2
With regard to receive mode, generally speaking the following modes will apply:
AUTO
Receive mode and tuning step will be selected automatically using the pre-programmed auto
bandplan data.
WFM
Wide band Frequency Modulation - used by VHF and UHF broadcast stations as excellent audio quality
is available due to the relatively wide frequency bandwidth employed. Used only for local services such
as VHF Band-II stereo (received as mono on the AR8600) and UHF TV sound channels.
When listening in VERY strong signal locations especially when using an external aerial, adjacent
channel interference may be observed due to the wide nature of the IF filters. Should interference
be encountered, use the attenuator to reduce signal strength or swap to the standard telescopic whip
aerial.
NFM
Narrow band Frequency Modulation - this provides high quality communication for relatively short
distance operation. NFM uses a greater frequency bandwidth than other point-to-point modes such as
SSB so is less efficient.
NFM is the most common mode used above 30 MHz with the exception of the airbands (which use AM).
NFM is widely used on the VHF bands: VHF Marine band, 2m amateur Band (145MHz), 70cm amateur
band (433 MHz), PMR (Private Mobile Radio) and utilities.
In the absence of a signal, the background white noise may appear quite loud. For ease of listening the
squelch control should be rotated clockwise until the background noise just disappears, this should be
carried out when no signal is present. The point where the background noise is cancelled is known as
‘threshold point’. Do not advance the squelch control more than necessary or the receiver will appear to
be desensitised and weaker signals will be missed.
SFM
Super Narrow band Frequency Modulation - this mode is specific to the AR8600. Essentially this is the
same mode as NFM but uses a narrower IF filter for added selectivity when monitoring crowded bands
such as PMR utilities.
WAM
Wide Amplitude Modulation - this mode is specific to the AR8600. It is essentially the same as AM but
uses a wider IF filter, particularly useful for monitoring parasitic airband transmissions when ‘repeater
transmissions’ are employed. Provides good broadcast quality for MW (medium wave band) listening to
strong local signals when adjacent channel transmissions are not encountered.
AM
Amplitude Modulation - Used by broadcast services throughout the world on medium wave and short
wave. AM is also used by VHF civil airband, UHF military airband and some PMR (Private Mobile
Radio) and utility services.
NAM
Narrow Amplitude Modulation - this mode is specific to the AR8600. It is essentially the same as AM
but uses a narrower IF filter for added selectivity when monitoring crowded bands such as short wave.
Due to the narrower bandwidth employed, the audio quality will be compromised.
USB
Upper Side Band - is a form of Single Side Band (SSB). USB is used commercially and by radio
amateurs on frequencies above 10 MHz (below 10 MHz radio amateurs tend to use LSB to assist the
separation of commercial and amateur users on traditionally shared bands, this prevents them from
attempting to communicate with each other… which is prohibited).
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