HOW TO FIX YOUR FM RADIO by jkl84411

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									NOVA 93.7FM




   HOW TO FIX
   YOUR FM RADIO
   RECEPTION DIFFICULTIES
RECTIFYING FM RADIO
RECEPTION DIFFICULTIES
Good radio reception is dependent on the type of radio receiver, the type of
antenna and the signal strength at the listener’s location. Signal strength can
vary greatly with the distance from the radio transmitter and physical location
of the listening environment being key factors. Geographic locations such
as built up, wooded or hilly areas have great influence over received signal
strength.

Reception quality changes significantly between small cheap portable radios
and the more expensive hifi systems. Car radios generally offer good reception
as well.

The FM antenna is the most important factor in achieving good reception. Many
radio reception difficulties are caused by deficiencies in the radio or antenna
installation. Interference or obstruction of a radio signal to the antenna should
be kept to a minimum. The antenna should always be placed away from electrical
devices such as computers, refrigerators, power tools or in house wiring. If an
external antenna used, then the antenna should point in the direction of the
transmitter and be positioned to minimise the effect of obstructions such as
trees and buildings.


COMMON FM RADIO
RECEPTION PROBLEMS
Hissing
If your radio hisses it could be because it is receiving a weak signal.
This happens because radio receivers need reasonably strong signals to decode
the stereo component of an FM signal. A weak signal can be caused if you are
too far from a transmitter as well as large buildings or hills blocking the signal
path.

A good quality VHF Band 2 outdoor antenna correctly positioned to pick up the
best signal will usually always improve FM reception. If necessary, a VHF Band
2 amplifier can be fitted to the antenna to boost a weak signal as well.
If the radio is portable with no provision for plugging in an external aerial,
listeners should try adjusting the position of the radio’s own antenna to improve
the reception. Alternatively, moving the receiver to somewhere else in the



NOVA 93.7FM: HOW TO FIX YOUR FM RADIO RECEPTION DIFFICULTIES
room may help particularly as FM reception can vary a great deal over short
distances. Radio reception is often better near windows or upstairs rather than
downstairs.

Distorted “S” Sounds on FM Radio
This phenomenon is known as “Multi-path Distortion.” Multi-path distortion is
characterised by sibilance which is the distortion of ’s’ and ‘z’ sounds used in
speech to ‘shhhhh’ sounds. It is caused by the transmitted signal traveling to
the listener’s radio receiver by more than one path. This is usually caused by
the signal being reflected off hills or tall buildings. The reflected signal arrives
at the receiving antenna a moment later than the direct signal because it has
traveled further. The reflected and direct signals then interfere with each other
causing the distortion.

The best way to minimise multi-path distortion is to use a directional rooftop
FM antenna which will only pick up signals coming directly from the transmitter
and reject signals that arrive at the back or side of the antenna. It is also
sometimes possible to mount the antenna so that a building screens it from the
reflections but not from the wanted signal. If multi-path distortion is affecting
a portable FM radio, try moving it to a different position in the room.

Adjacent FM Channels
Adjacent channel interference is caused by an FM station which is close in
frequency to the station being listened to. It can sound like a twittering noise
in the background. This problem is usually only apparent on FM stereo but if
the interfering station is very close in frequency, ie. only 50 or 100 kHz away,
the effect may also be heard in mono.


GETTING THE BEST FM RADIO RECEPTION
AT HOME OR WORK
  • Make sure the antenna is suitable for receiving FM radio and is pointing in
    the direction of the radio transmitter at Carmel in Perth.
  • Check that the antenna cable and connections are in good condition.
  • If possible swap another radio for the affected one. If the radio reception
    improves, there is likely to be an equipment problem with the first radio
    - check the antenna.
  • Sometimes the TV antenna is used for both the TV and FM radio. If this is
    the case, remove the TV connection leaving only the direct cable between


NOVA 93.7FM: HOW TO FIX YOUR FM RADIO RECEPTION DIFFICULTIES
    the antenna and radio.
Listeners should also note that FM radio signals travel in almost straight lines
and are unable to travel over or penetrate large obstructions. This usually
means that parts of a coverage area may have a weak signal particularly in hilly
terrain or highly built up urban areas.

FM Dipole Antenna
The FM dipole antenna is economical and relatively simple to install, whilst
offering a considerable increase in reception quality. An FM dipole antenna is
built from TV ribbon cable, which is often supplied with hi-fi tuners or can be
purchased from an electronics store.

The length of the dipole antenna should be approximately 1.5m long and is
constructed by connecting the ribbon cable to the radio receiver. The dipole
antenna can be erected by attaching the cable to a wall with the 1.5m section
of the cable positioned horizontally where the best signal is found. This antenna
can be rotated to find the best position to further optimise reception.

External FM Antenna
The best quality FM radio receiver system consists of an FM antenna, permanently
erected externally. As FM radio signals occupy the same frequency band as
some VHF television signals an FM antenna is very much like a VHF television
antenna. A VHF television antenna designed to receive Band 2 TV channels
may be used to improve FM radio reception.

A professional antenna installer can split the cable from the TV antenna and
then run separate cables to the TV and FM receivers. If a splitter device is
used, the signal strength is reduced. In some cases, particularly in low signal
strength areas, an amplifier may also be needed. An amplifier boosts the signal
and ensures that adequate signal strengths are supplied to both the radio and
the television set.


GETTING THE BEST
FROM YOUR CAR RADIO
The metal bodywork of a vehicle prevents signals reaching the radio, so a
quality external antenna is needed for good reception.
FM radio reception can be difficult when traveling in built-up areas or in
undulating terrain. Multi-path distortion or a weak signals may be experienced.



NOVA 93.7FM: HOW TO FIX YOUR FM RADIO RECEPTION DIFFICULTIES
However, FM radio generally gives good results with quality sound and the
option for stereo reception.
Interference
Car radios should be relatively immune to ignition and other electrical interference
from the vehicle, but failure of the vehicle’s electronic suppression equipment
can cause crackles and interference or:

  • Rhythmic ticking varying with engine speed
  • Whining varying in pitch with engine speed
  • Regular crackling associated with a car heater or the windscreen wipers/
    washers

In most cases, a reputable auto electrician can fix this sort of interference.

Car Antennas
Car radio antennas are always located externally and are usually a telescopic rod,
although there are a number of cars fitted with heated rear window antennas
or stubby helical wound antennas. To get the best from a car radio:

  • The antennas should be as high as possible, preferably on the roof and
    away from the engine
  • Telescopic antennas should be fully extended
  • The antenna should not be folded back onto the roof and kept well clear
    of the bodywork
  • Antennas should be of the correct length - around 80 cm is ideal. Antennas
    much shorter or longer than this may provide inferior results




NOVA 93.7FM: HOW TO FIX YOUR FM RADIO RECEPTION DIFFICULTIES

								
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