Naked Science Forum
Non Life Sciences => Technology => Topic started by: Mazurka on 04/02/2011 08:37:09
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What factors influence the quality of FM radio?
& with a recevier in a fixed position and an aerial with limited movement; why does the aerial work better with a particular orientation one day and beterr with a different orientation on another day?
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The factors that influence FM radio quality are:
(1) The signal strength or, more precisely, the signal to noise ratio
(2) Multi-path interference - this is where the signal may be arriving via multiple routes from the transmitter and the waves destructively interfering. If any of the paths are reflections from moving objects this can cause variable reception.
(3) Poor quality in the studio so the initial audio is poor
(4) A poor quality receiver - any number of poor design techniques
(5) Interference from other radio transmissions or even poorly suppressed domestic electrical equipment
(6) Atmospheric effects. These can cause weak signals to be variable, but more often it can be that conditions allow reception of interfering signals on close-by frequencies that interfere with the wanted signal.
There maybe some I've forgotten.
Some of these may be responsible for your obsevation that the quality varies even if the radio and aerial are in the same position. You may just move some other items in your house about though, or maybe your neighbour has moved his car which has changed the multipath reception. A typical FM wavelength is around 3 metres so movements of objects one or two metres can make a difference.
It would be best to get an aerial feed via coaxial cable from an aerial as high up as possible and, preferably, in direct line-of-sight to the transmitter.
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I think the only thing Graham might have left out is that the valves (tubes) are worn out, although that would only be likely if your receiver is more than fifty years old [:D]