RF Cafe Software
About RF Cafe
1996 - 2022
BSEE - KB3UON
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 Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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January 1939 Radio-Craft[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.
I have been scanning and posting Radio Service Data Sheets like this one featuring the Stewart-Warner (R-127 Chassis) Models 1271 to 1279, all-wave superheterodyne radio receiver for many years now. There are still many people who restore and service these vintage radios, and often it can be difficult or impossible to find schematics and/or tuning information. The thumbnail image of a real-life Stewart-Warner Model 1271 was found on the radiomuseum.org website.
(1) Connect a 400 to 500 ohm, 1 W. carbon resistor in series with the service oscillator output and the receiver antenna lead. This resistor must remain connected for all broad. cast and -short-wave adjustments in order to secure proper alignment of the antenna· stage. Ground the receiver chassis and connect the oscillator ground lead to the chassis.
(2) (a) Tune in a 1,400 kc. service oscillator signal. (b) Adjust trimmers No. 6 and 7 (range No. 1 broadcast detector shunt trimmer, and range No.1 broadcast pre-selector shunt trimmer, respectively) for maximum output. (c) Retune and check trimmers Nos. 6 and touch trimmer No.5 since this will change the calibration.)
(3) (a) Tune in a 600 kc. service oscillator signal. (b) Adjust trimmer No. S (range No. 1 broadcast oscillator padding trimmer) for max imum output. (c) Retune, and readjust the trimmer. (d) Continue this procedure for maximum output meter reading. This procedure must be followed or the receiver will not be properly aligned.
(4) Repeat 2a, 2b, and 2c.
Posted February 2, 2017
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 185 Radio Service Data Sheets as of April 12, 2017.