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Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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Fairbanks-Morse Model 81 2-Band 8-Tube 2 V. "Farm" Set

Radio Service Data Sheet
March 1936 Radio-Craft

March 1936 Radio-Craft

March 1936 Radio-Craft Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

Page 843, Gasoline- and wind-powered electricity generators - RF Cafe

Page 843 - Gasoline- and wind-powered electricity generators, storage batteries.

Prior to the Rural Electrification Act of 1936, the year this Radio Service Data Sheet appeared in Radio-Craft magazine, commercial electric service was limited primarily to urban and suburban areas. Vast expanses of rural farmland were without electric service and had to rely on individual wind and, where possible, hydro power generators for DC power. The output voltage was of course direct current since it could be stored for later use. Even through the early 1940s many farms and rural households had only the convenience of DC power by virtue of banks of lead-acid batteries. Sears, Roebuck &Co. sold wind-driven electricity generators for farm use to charge batteries in place rather than having to load them onto a wagon and truck them into town for charging. Many farms already had windmills erected to mechanically drive grist mills, saws, water pumps, and other machinery, so often they would add an output shaft to a generator. Alternating current output would be too unreliable and unstable. This Fairbanks-Morse Model 81 2-band, 8-tube 2 volt, "Farm" radio set targeted the AC-less households as being designed specifically for their needs.

Fairbanks-Morse Model 81 2-Band 8-Tube 2 V. "Farm" Set Radio Service Data Sheet

Fairbanks-Morse Model 81 2-Band 8-Tube 2 V. "Farm" Set Radio Service Data Sheet, March 1936 Radio-Craft - RF Cafe(Ranges - 540 to 1,740 kc., 5.5 to 16 mc.; full A.V.C.; class B output; R.F. stage; new type speaker.

This set has provision for use on either dry cells, storage cell, or air cell. An Amperite 6-1 ballast tube is needed for 3 V. operation. For air-cell use, a resistance link is inserted in the socket provided for it in the set. A jumper link is plugged into the same socket when a storage cell is employed.

When a doublet antenna is used on this set one lead connects to the blue wire, and the other to the blue and black wire.

I.F. alignment is made with the band switch in the broadcast or left-hand position. Supply a 465 kc. signal to the cap of the 1C6 tube and adjust trimmers on first I.F. transformer and then on the second.

R.F. alignment on the broadcast band is made first on 1,400 kc. with the signal fed in through the antenna post. The oscillator trimmer is adjusted first, then the antenna trimmer. Then a 600 kc. signal is used and the oscillator padding condenser adjusted.

Feed a 15 mc. signal to the antenna circuit and, with the dial set at 15 mc., adjust oscillator for highest output. Then set the shortwave R.F. trimmer for best signal with least input from the service oscillator. It is advisable to rock the condenser back and forth across the signal while making this adjustment to make sure the peak of greatest intensity is obtained.

*Anode grid-165 V. All voltages measured from ground with 1,000 ohms-per-volt meter, 300 V. scale.

After re-aligning, it will often be necessary to reset the dial. This is done with the chassis bolted in place. The set-screw in the travelite dial hub is loosened and the dial turned to the correct location.

The speaker may be adjusted by means of the 3 screws on the rear.



Posted January 13, 2020(original 7/13/2015)

Radio Service Data Sheets

These schematics, tuning instructions, and other data are reproduced from my collection of vintage radio and electronics magazines. As back in the era, similar schematic and service info was available for purchase from sources such as SAMS Photofacts, but these printings were a no-cost bonus for readers. There are 227 Radio Service Data Sheets as of December 28, 2020.

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