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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October 1930 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.
How did we ever accomplish research without the Internet? Sure, that is a rhetorical question, but I find myself asking that often when I find information on something I figured there was no way anything would be available. Such was the case when looking up this Kolster K20 radio. Its Radio Service Data Sheet appeared in the October 1930 edition of Radio-Craft magazine. Mr. Gordon Bell, WA2YQY, provided the photo of the one to the left, which I found on the RadioAtticArchives.com website.
Before proceeding with a detailed description of these Kolster receivers, of which the "K20" is the most popular representative, we will point out the major differences that differentiate the several models broadly referred to as the "six-tube" sets. The "K20" model is a table-type radio receiver incorporating the four-tube chassis and the two-tube audio amplifier, which is combined with the 60·cycle powersupply unit shown in the schematic circuit; the "K25" has the same general design for operation on 25 cycles. The "K22" is a console arrangement of the tuner chassis and power pack used in the K20; while the "K27" is a console adaptation of the 25-cycle equipment. Another model of the Kolster line was designed for use as a portable demonstrator; this number, the "K37," employs the circuit of the "K20."
Posted July 29, 2016
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.