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Kirt Blattenberger (KB3UON)

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National Company Advertisement: AC Power Strip
April 1939 QST

April 1939 QST

April 1939 QST Cover - RF CafeTable of Contents

Wax nostalgic about and learn from the history of early electronics. See articles from QST, published December 1915 - present (visit ARRL for info). All copyrights hereby acknowledged.

Could this be the world's first publically documented rack-mounted AC power strip? The National Company of Cambridge, Massachusetts, which began life as the National Toy Company, ran a long series of advertisements in QST and other electronics magazines that were heavy on text and light on pictures - definitely not the norm in advertising. This one, number 62, from a 1939 issue describes, along with a reference frequency oscillator, how their engineering team fabricated what we now call an AC power strip for use in an equipment rack. According to the sketch provided, there does not appear to be an On/Off switch and almost certainly not any form of surge protection as is common (maybe even required by UL) for modern power strips. Someone at National should have patented the idea; their heirs would be rich today.

National Advertisement

Number sixty-two of a series

World's first AC power strip? - RF CafeWe have just completed a 100 kc. crystal oscillator for our own use that we think is pretty nifty. It is designed for relay rack mounting, is completely self-contained and has a front-of-panel control for the crystal holder air-gap, so that the frequency can be checked and adjusted against WWV or any of the "even 100 kc." broadcast stations by adjusting the proper harmonic for zero beat. The oscillator tube is an 1851, and the rectifier a 6X5. Useful harmonics for receiver calibration can be had as high as the 14 mc band. Thus when used in connection with a good ham receiver the frequency measuring requirements of the new FCC regulations can be complied with on the 160, 80, 40 and 20 meter bands. Of course our "National" parts were used throughout except for the crystal, which is one of Herb Hollister's. As this space is much too small to give further details here, we have prepared a small descriptive pamphlet (with the hope, of course of selling a few of our parts) which can be had from any of our regular franchised dealers, or free by mail.

National Advertisement - AC Power Strip, April 1939 QST - RF CafeTalking about making things brings to mind another handy gadget we recently made for our own home lab and shop. It is a multiple AC outlet unit. In fact, we found the first one so handy that we soon made several more, one for the back of the relay rack, one for the work table on which we do most of our circuit experimenting, and one for the photographic darkroom. The illustration above gives the general idea. The chassis is the standard National unit made for the fixed-tuned high fidelity band tuners. The socket holes were enlarged to the right size for the standard flush-type AC outlets by means of a Greenlee punch, although a plumbers reamer could, if necessary, have been used for the same purpose. Additional holes were added between the former socket holes so that in the 17 x 3 x 1 1/4" chassis eight outlets could be mounted. The AC cord was brought in through the rubber-grommet lined hole originally intended for the power supply cord.

In the past, we have strongly recommended the HRO's equipped with 2.5 volt tubes over those equipped with 6.3 volt tubes where operation was to be from an AC power pack rather than batteries. This recommendation was based largely upon the difficulty experienced with modulation hum encountered in the vicinity of 15 mc. when AC was used on the 6.3 volt tube heaters. For some months now, the 6.3 volt tubes we have been receiving from both of our suppliers have been so completely free of this former trouble that we are now able to offer a 6.3 volt tube HRO for AC operation that in every way equals the 2.5 volt tube model. A new power unit, the No. 697 (same rating as the No. 5897 but with 6.3 volt, rather than 2.5 volt, heater supply) is also now available. This new power unit should not be used with the 6.3 volt HRO's heretofore supplied for battery operation, as the plate voltage will be much too high. Incidentally, all National power packs are now furnished complete with rectifier tubes, at no additional charge.

James Millen



Posted June 3, 2022
(updated from original post on 5/9/2016)

Here are all the National Company advertisements I have:

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

1996 - 2024


Kirt Blattenberger,


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 nice lady's voice announced "You've Got Mail" when a new message arrived...

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