Yes indeed, the problem back then was AM tended to get into analogue tvs and radios with poor screening or overload protection. The amplitude of the
signal varies, and this is directly detected somewhere in the circuit.
Because FM does not vary in amplitude, only frequency, there is far less likelihood of interference.
The 27Mhz band is used by many countries, but in an attempt to segregate
ours from others in Europe, we made ours start around 27.6Mhz, a bit above
the most used AM channels. Sadly, it was not policed very well and people
still used AM by buying multimode transceivers that could additionally do
SSB, which arguably was worse than AM as it was distorted by normal
detection circuits. You needed something called a product detector, which combined a low frequency oscillator with the sideband signal to get
recognised audio out.
Then everyone bought 'burners' or amplifiers that made the legal 4 watts
into as much as you wanted or could afford, and aerials were being sold that could be modified to work on that band instead of the little whip aerials.
So gov said, why not use UHF and lots of people bought expensive UHF transceivers, only to find that a few years later the band was flogged off
for mobile phones and the buyers were left with expensive door stops.
Brian
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"NY" <
me@privacy.invalid> wrote in message
news:u9384j$14nhq$
1@dont-email.me...
I was searching through some old paperwork the other day and I found a >collection of newspaper cuttings and articles I'd kept from many years ago. >And I came across this gem.
It appeared in the Glasgow Daily Record on 27 February 1981 and described
the Government's recent concessions to CB users.
"All illegal equipment at present in use works on a frequency of 27 MHz
AM - that's the medium wave. The Government will let them [CB users] keep
the same frequency but on a *different* wavelength, FM (VHF), which means that to be legal they must buy new sets."
The conclusions may be correct, but no marks for the technical knowledge
of the reporter who dared to write such drivel.
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