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Philco 42-350 FM - Printable Version

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Philco 42-350 FM - shaler78 - 01-03-2015

I'm looking to purchase a 42-350 with old FM. Are the upper frequencies of this FM band (76-99) the same as the lower frequencies of the modern FM band? The reason I ask, is because the FM transmitter I use can be set down to 76 mHz for use in Japan.

RE: Philco 42-350 FM - klondike98 - 01-04-2015

I believe the pre-war FM band was 42 - 50 MHz.  The old FM numbers on the 42-350 dial face range from 21 to 99 which correspond to 42.1MHz through 49.9 MHz.  So...there's no overlap with the modern 88 - 108MHz band and 76MHz would be above the old FM band.

RE: Philco 42-350 FM - Ron Ramirez - 01-04-2015

Bob is correct.

In ye olden days when FM first came on the scene just prior to America's entry into World War II, most FM radio dials were calibrated in "channel numbers" rather than frequencies. These channel numbers were arrived at by removing the leading 4 from the frequency and eliminating the decimal point. Thus, 42.1 mc became channel number 21 on the dial. 99 on the dial was the "channel number" for 49.9 mc.

RE: Philco 42-350 FM - shaler78 - 01-04-2015

Thank you gentlemen for your replies. I thought this might have been the case. I do remember reading somewhere in this phorum on how to redo the circuit on an old FM to receive the modern FM, or by building some sort of converter to do the same thing.

RE: Philco 42-350 FM - Raleigh - 02-14-2015

There are a number of designs for FM down-converters that you can build. They take the modern FM signal and convert it to the old FM frequency. You connect the antenna to the converter and plug the converter into the antenna connection on the radio. I don't know of any that you can buy ready made.

One problem is that the old band was only 8 MHz wide instead of the 20MHz today, so the converters have to be wired to pull in only a portion of the modern band.

Try Googling "Pre-war FM band converter" or similar. I found quite a few hits when I did this. Somewhere I once found a small design that would be easy to built on a piece of perfboard, but I couldn't find it with the short amount of searching I did just now.

My 42-350 will actually pick up a few strong FM stations nearby, but not very well, probably because of oscillator harmonics.

I plug an FM tuner into my SSTRAN low power AM transmitter to rebroadcast on an AM frequency. Once I did that I gave up the idea of using the old FM band on any of my radios that have it.

Edited to add: Here is a page with links to several ways to build a down-converter for the pre-war FM band.

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

Some of these are post-war designs from when radio shops were figuring out ways to help their customers adapt, and some are modern designs by old-radio enthusiasts. Near the bottom of the page is a "Simplified Modern Design" that I thought at one time of trying.