Volution of Power

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Part I : dvnamotors and vibrators

Hugh Wefts W6VVTU 1411 18th Street Manhattan Beach CA 90266-4025

II you vc been around ham radio ven long you've seen a number of power supply types, but are you aware of how they \ e changed over the years? What t^ referred to as a "power supply" is the interface between the ordinary wall plug and a radio, or between an automobile battery and a radio. I he evolution of the interface device has seen a great many changes out the past i>() years. Reviewing the various common types raises feelings of nostalgia for some hams, w hile for others it is an educational step through historical memorabilia.

Latecomers to ham radio are familiar with radios thai require a l2™\oft power supply, because most radios today are of a solid stale design that operates directly off an automobile battery; However, prior to semiconductors, almost all electronic equipment used vacuum tubes— which required a much higher voltage than most semiconductors. Throughout the hisiorv of nidio.

4B mf power supplies have been available that obtain power from commercial power mains, and we think of that power as being typically 120 VAC which must be stepped Lip or down in voltage level to meet the radio's requirements. The change in \tillage level has been pro vided by a power transformer d ig- 1 h of which there arc many variations in

the rectifier and filtering circuits, A DC voltage i^ obtained In rectifying

the AC output from the transformer and. for vacuum tubes, an AC voltage was also provided to the healers.

AC1 power supplies have gone ihrouiih a transition from heav\ iron bi F

transformers to powdered iron switching circuits, hui power supplies for mobile radio applications have had an even greater evolution. To show the various steps in the evolution, we will discuss some ol the more popular mobile supplies, starting here in Part I w ith the dvnamolor and vibrator \er-Mons. Part 2 will pick up with switching power supplies of the types used in mobile and home computer applications.

I)\ namotor

i lie dynamotor power supply was developed during the late 1920s and early 1930s for use in auiomchile car radios. An outline of one is shown in Fiji, 2, At the time, they were called rotary converters (also called rotary transformers), with many applications both inside ami outside of automobile radios. Dunns World War II. dvnamotors were produced in huge quantities for military applications, and following the war many dvnamotors became available to hams through the surplus market.

Perhaps one of the most famous dynamotors was called the PE-103. It was capable of being operated from either a six- or 12-volt car battery. The output voltage was 300 VDC (600 V output if 12 V was applied to the 6 Y input) which made it ideal for mobile ham transmitters. Another feature of the PE-103 was that it could be remote!) turned on and off. his made :t more convenient to use. particularly during sliort transmission periods after which it would be turned off. The armature inertia was a little troublesome during a push-to-talk situation bccausc

Continued on page 14

)20 VAC

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DIY Battery Repair

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