8
nat 05 operation
connections
The FM aerial input socket must be connected via 75ohm low-loss coaxial cable to a suitable roof-
mounted directional aerial.
aerial requirements
The tuner aerial should be mounted on the roof, clear of obstructions and also as high as possible.
Horizontally polarised aerials will respond to all UK broadcasts whilst partially rejecting police and taxi
transmissions, and are therefore recommended. Use of an aerial preamplifier will disturb the muting
operation of the tuner and may cause cross-modulation problems. Such preamplifiers should only be
used as a last resort.
In the UK, BBC and commercial radio broadcasts are usually radiated from different sites even though
the target areas of the services may be similar. This means that unless the transmitters are in almost
the same direction looking from your house, an aerial aligned on one transmitter will give less than
optimum performance on the other. In these circumstances you should fit an aerial rotator, or a less
directional aerial if appropriate. The more sensitive and directional the aerial you use, the less good
will be the reception in directions other than the one towards which the aerial is pointing. If you are
particularly interested in receiving a wide range of VHF transmissions an aerial rotator is a necessity.
Your dealer will be familiar with local conditions and will be able to advise you on which stations are
capable of being received satisfactorily.
The tuner’s audio output is adjustable internally both for level and channel balance. It is set to 700mV
and should match almost any preamplifier without difficulty. Preamplifier input impedance should be
more than 10K .
buttons
mode:
Toggles the tuner through three operational modes -
frequency, scan and preset.
Use
of
preset
mode is covered overleaf in the
narcom 2
remote handset section.
down:
In
frequency
mode, adjusts tuning frequency downwards in 50kHz steps or
continuously if held. In
scan
mode, causes the tuner to “scan” down the FM band
searching for signals above a preset level. The tuner will stop searching at each tuned
station and, using the
narcom 2
remote handset, the option to store the station as a
preset will be available. If no satisfactory signals are found during the first scan, a
second scan at a lower preset signal level will automatically commence. In
preset
mode, causes the tuner to step sequentially down through previously stored stations.
up:
Controls the tuner in a similar manner to the
down
button.
mono:
Combines the left and right channels to produce a mono output signal. Switching to
mono can reduce background noise with weak stereo signals.
display
main:
Displays tuned frequency, selected preset number or
“--”
indicating that no preset
number is allocated to a specific tuned frequency. Allocation of tuned frequencies to
preset numbers is covered overleaf in the
narcom 2
remote handset section.
indicators
stereo:
Indicates when both a stereo signal is received and stereo operation is selected.
freq:
Indicates when the tuner is operating in
frequency
mode.
scan:
Indicates when the tuner is operating in
scan
mode.
preset:
Indicates when the tuner is operating in
preset
mode.
