26-08-2015, 08:32 AM
(This post was last modified: 26-08-2015, 08:33 AM by Ian - g4jqt.)
Hi Terry,
OK, wrong when I said "globally standardised", since as far as I know, no international agreement came to this decision. But for the past 30 years or so, any new MW radio I ever bought, or saw someone buy, came from the Far East, with fixed ceramic filters at 455 kHz. Even those without ceramic filters had an IF of 455 kHz, so we got it by default.
Nevertheless I may be wrong if there are still moderately-priced MW radios assembled in Europe, or especially for Europe with a non 455 kHz IF.
I wonder what the IF is in modern analogue Roberts Radios - assuming they're still using some sort of superhet circuit?
In old service sheets I've seen reference to some British manufactures changing the IF when new stations appeared at or near twice the IF, so indeed, this problem was known about.
I believe planning FM use had to take into account 10.7 MHz IF and local oscillator radiation, but expect that's now a thing of the distant past!
Ian
OK, wrong when I said "globally standardised", since as far as I know, no international agreement came to this decision. But for the past 30 years or so, any new MW radio I ever bought, or saw someone buy, came from the Far East, with fixed ceramic filters at 455 kHz. Even those without ceramic filters had an IF of 455 kHz, so we got it by default.
Nevertheless I may be wrong if there are still moderately-priced MW radios assembled in Europe, or especially for Europe with a non 455 kHz IF.
I wonder what the IF is in modern analogue Roberts Radios - assuming they're still using some sort of superhet circuit?
In old service sheets I've seen reference to some British manufactures changing the IF when new stations appeared at or near twice the IF, so indeed, this problem was known about.
I believe planning FM use had to take into account 10.7 MHz IF and local oscillator radiation, but expect that's now a thing of the distant past!
Ian
