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FM-to-AM Converter for Vintage Radios
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The inventions and products featured on these pages were chosen either for their uniqueness in the RF engineering realm, or are simply awesome (or ridiculous) enough to warrant an appearance.

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FM-to-AM Converter for Vintage Radios - RF Cafe

FM Converter for Vintage Radios

Specifications:

  • FM 87.5-108 MHz using radio's dial for tuning. Choose where FM starts/ends on dial.
  • US/Canada buyers will receive a module for 75 µs deemphasis. Others: 50 µs.
  • Mono audio output using radio's tube amplifier for listening.
  • No additional controls required, no external mods ! - Easy to install: three grounded holes + grounded bottom layer.
  • Powered directly by tube heaters circuit (schematics included in PDF) or a DC source (16 V max).
  • 2ft external antenna is enough in most cases (can be housed in radio cabinet).
  • Very compact: 3 cm x 3.5 cm

RF Cafe visitor Bob D. sent me information on this interesting device that allows owners of vintage AM radios to receive FM stations while using the original tuning dial to cover the entire 88-108 MHz band. Monsieur David Winter, of France, is the designer and seller of this FM-to-AM Converter for Vintage Radios. Installation and calibration is not for the faint of heart, since it involves tapping directly into the circuitry and disconnecting some of the sections where the device inserts the signal into the audio frequency (AF) section, totally bypassing the RF and IF sections. A direct connection to the tuning capacitor is used to tune the module throughout the FM band, which is a primary feature of scheme. However, it requires the capacitor to be disconnected from all other circuitry to prevent normal voltages and impedances from adjacent connected components from entering the integrated circuit (IC). Retaining the AM reception (and possibly shortwave reception) function requires the installer to devise a custom switching scheme. It uses the 6.3 VAC vacuum tube (valve) heater supply. In older radios you need to be sure to locate a "real" ground (common) point to assure the voltage is properly referenced. The price is €29.90 ($32.83), which is currently the cost of 7-8 gallons of gasoline in the U.S. 

Again, the intention is to allow the original tuning dial to be used for getting the FM band, so some people (M. Winter hopes many people) will consider the effort worthwhile in spite of needing to alter the circuitry. Another option might be to create a sort of "Mr. Microphone" type device that is completely separate from the vintage radio and converts the tuned FM station to a low power broadcast somewhere within the AM band. The listener would simply tune his radio to pick up the manufactured AM signal (there could be some FCC intentional radiation issues involved). In both cases the stereo component is lost and the radio would be subject to AM ambient external noise (QRM and QRN), but the integrity of the radio is preserved, and it's so easy a caveman can do it.There are (or have been) products available which do just that (Cuthbert FM to AM Converter MKII, FM2AM), but possibly due to the aforementioned FCC regulations might not be available anymore except maybe directly from the designers (don't tell anyone, though).

 

Contact Info

David Winter
16 Rue de Vaugirard, 75006
Paris, France Tel: 01 46 33 20 17 - 06 0318 0518
Phone: 01 46 33 20 17 - 06 0318 0518

Website:  www.paleophonies.com/FM-DW.htm

E-Mail:  email@paleophonies.com

 

 

Posted March 15, 2022

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