"tony sayer" wrote in message
...
In article , David Looser
scribeth thus
"tony sayer" wrote in message
...

Its only in recent times that they have had an opportunity to
downgrade
it owing to the bitrates they can set it at.. You'd never hear
someone
from the pre digital times saying that they could -downgrade- the
transmission system in use.


Rubbish!. AM radio was downgraded by reducing it's bandwidth from 9kHz
to
4.5kHz betwen the 1930s and the 1960s.


Could you qualify that please?
AM radio, AFAIK, has always has an audio frequency response limit of
4KHz which means it needs an RF bandwidth of 8KHz. The station spacing
is thus set at 9KHz to (theoretically) leave a guard band between
stations. In practice for most domestic radios this is of little
consequence as it would be nigh impossible to hear two stations on
adjacent frequencies - something that would be possible on a
commercial/professional receiver with a much more closely controlled
passband.


--
Woody

harrogate three at ntlworld dot com