Choice of 455 kc and 10,7 mc as IF frequencies

Sun Mar 21 04:22:39 EST 1999

At 08:50 PM 3/19/99 -0700, you wrote:
>Just an idle thought I had, as I was browsing my radio books: why are so
>many, and at one time nearly all, radio receivers designed to use IF
>frequencies of 455 kc and/or 10.7 mc? There must be some fundamental
>electronic principle that applies to this choice, I can't imagine these
>IFs are only a matter of convention and interchangeability of parts. So,
>how were these frequencies chosen, and why have they remained the
>overwhelming favorites?

        455 is one khz away from one of the Marine band CW working
channels, 454  Khz.  Fortunately, this is no longer being used as of the
first of the Month.  The only big interference noted was if a ship in port
went to 454
to pass a piece of traffic, where the docks were close to downtown or a built
up area.
        10.7 mhz is a post war choice.  The pre-war FM band was in a
different place
and as I remember the IF of choice then was 4.3 Mhz.
        The exact "WHY" the frequencies were chosen I'm not privvy to.
Another "popular" IF was 1650 Khz.  Hallicrafters loved that number in their
dual conversion sets.  I'd imagine those set users will run into trouble
if they have a broadcast station on or near 1650 khz near them since they
extended the band to 1700 Khz.
Sandy WW5TVW

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