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new fm? - Printable Version

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new fm? - fixinmyphilco - 03-11-2012

Found this on a web site not sure if it means its converted the old fm to new?
Philco 42-350 uses the old FM band that goes from 42 MHz to 50 MHz. It is relatively easy to receive, more or less satisfactory, some of the stations in the modern 88 MHz to 108 MHz by simply detuning the local oscillator so that its second harmonic together with an incomming signal of the modern FM band produce an IF frequency of 4.3 MHz which is the IF frequency of the FM IF (Intermediate Frequency) transformers in this radio.

Can anyone explain if it does and how to do it? Thanks Doug

RE: new fm? - Ron Ramirez - 03-11-2012

Can you give us the link to the site where you found this? More info would be helpful.

RE: new fm? - fixinmyphilco - 03-11-2012

Here it is

http://antiqradio.com/post_philco-radio-model-42-350-1942.html

RE: new fm? - Ron Ramirez - 03-11-2012

Okay, 4.3 mc is the FM IF in the 42-350. The point the writer was trying to make is, some strong local FM stations can often be tuned in on these older FM receivers - not on their normal frequency, but by the local oscillator of the 42-350 beating with the second harmonic of the modern FM broadcast signal.

No adjustments need be made to the 42-350 to do this (other than a normal alignment of the entire radio after it is serviced, that is). These sets will pick up a few signals from the modern FM band - but only if you have very strong FM signals in your area. It will not pick up weak signals of the modern FM band because of this.

Oh, and I had a good laugh from that site's description of the 42-350's "peptode audio output." Icon_lol Is that something related to Pepto-Bismol?

RE: new fm? - fixinmyphilco - 03-11-2012

Ah ok now I see thanks Ron!

RE: new fm? - Radioroslyn - 03-11-2012

(03-11-2012, 12:05 PM)fixinmyphilco Wrote:  Ah ok now I see thanks Ron!
If you are serious about trying to get this thing a pass a modern FM signal what you would have to do is replace or modify #7 ant coil to tune the FMBC band and then replace or modify the osc coil so it will tune the lo 4.3mc above the incoming fm signal. Like 92.3 to 112.3 then you'll be in business.
Terry



RE: new fm? - LASJayhawk - 03-14-2012

check out the converters section of this website. Has sone info about how they did it after WWII

http://www.somerset.net/arm/fm_only.html

RE: new fm? - fixinmyphilco - 03-14-2012

(03-14-2012, 08:16 PM)LASJayhawk Wrote:  check out the converters section of this website. Has sone info about how they did it after WWII

http://www.somerset.net/arm/fm_only.html

Very cool thank you!