Motorola 100 Automotive Radio Schematic
June 1935 Radio-Craft

June 1935 Radio-Craft

[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.

Motorola 100: An 8-tube set of outstanding design. Of foremost importance is the use of a balancing-out circuit for counterbalancing car ignition-system interference. (When balancing out interference by the method used in this receiver, it is advisable to clamp the car hood down tight with the hood hasps, and to sit in the driver's seat; otherwise, in extreme cases, if the noise is balanced out without anyone in the driver's seat it may reappear when the driver is seated.) The reproducer (except for header types) is equipped with a universal mounting which permits swivel adjustment to take full advantage of car acoustic conditions. A novel push-pull output circuit is utilized in which one (treble) tube, V6, is capacity-inductance coupled from the plate of V5. The other (bass) tube, V7, is conductive-inductance coupled from the grid of V5, thus producing the desired 180 degree phase shift. Tone control is then accomplished by varying the degree of amplification by tube V6.

Motorola 100

Remarkable improvements in car sets are indicated these diagrams of the new automotive radio receivers shown on the preceding page.

Motorola 100 Automotive Radio Description, June 1935 Radio-Craft - RF Cafe Website

Posted June 1, 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 255 Radio Service Data Sheets as of April 30, 2025.

Werbel Microwave power dividers, couplers - RF Cafe Website

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 tying up your telephone line, and a lady's voice announced "You've Got Mail" when a new message arrived...