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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April 1934 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 Emerson Model 678 "Auto-Dynamic" 5-tube superheterodyne tabletop 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.
Use a high-resistance voltmeter. The figures given are average values taken with a fully-charged storage battery and with no signal being received, The field coil has a resistance of 6 ohms; the potential across the coil is 6 volts.
If the positive terminal of the storage battery is grounded no changes are necessary in the receiver when making the initial installation. If the negative terminal of the battery is grounded a slight change in the receiver connections is necessary. Remove the top screw and loosen the bottom screw holding the serial number plate to the right side of the receiver cabinet. Tip the plate down and reverse the red-and-black-marked spade lugs so that the black-marked lug will be on the top, and the red-marked lug will become the lower one. Test for battery polarity by using a low-reading D.C. voltmeter. When connecting the twin-conductor, shielded cable to the battery the black wire always connects to the grounded terminal of the battery, and the yellow wire to the "hot" terminal, regardless of battery
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.