Electronic Design

Bob's Mailbox

Is anybody interested in joining us on our next TREK in Nepal? We had such good hiking on our LAST trek that we're planning to go back for 31 days this October (to the Everest/Kala Pattar/Gokyo region). Inquire by snail- or e-mail to the usual address. And start saving up your VACATION TIME... (and a little money). /rap

Dear Bob:
Since you like the strange and bizarre with a funny side to it, I thought you'd like to hear what happened to me on Jan. 1, 2000. All my computers are running the Linux operating system. Well, all except one, which has DOS on it because I have a few old DOS programs and they're so good that I never felt any urge to replace them. Because of this, there was not going to be any trouble or unexpected crashes due to the Y2K Bug. And all the computers have a BIOS that will recognize year 2000. So I had no problem there, as I knew I would not.

However, I have an electromechanical clock—not sure if it can be described as analog or digital. It operates like this: It has a storage of steel balls that are lifted every minute on the top by a mechanical arm. The ball then rolls down an inclined guide rail on a seesaw arrangement. Once there are more balls on the right side, it tips over, sends one ball to the next lower seesaw, and the rest roll down to the storage bin. There are three of those seesaws. The first one indicates minutes (0-4), the second has increments of 5 minutes (5 to 55), and the last has hours (1-12; the 1 has the ball permanently fixed there). It is driven by a synchronous motor and, as I said, one ball rolls every minute. I had this clock for quite a while and it always worked well with an unprecedented accuracy, because our mains here in Australia are kept precisely at 50 Hz. They actually count the cycles and make corrections every day at the power stations, so there are 4,320,000 cycles every 24 hours. (Yeah, these clocks are fun. I've seen them. /rap)

I was rather astonished when, on New Year's Day, I found the clock stopped at 1:03 a.m. and all the balls scattered at the bottom. The reason? Well, it's now summer in Australia. At this time of year, we have a "plague" of small beetles called, appropriately, the "Christmas Beetle." One of those crawled inside the clock, up the inclined ramp, and there it got rolled over by the ball and jammed it. Naturally, all the other balls that followed just fell down from the ramp. So it can truly be said that I actually caught the real Y2K bug and killed it!
via e-mail

Now that is FUNNY! That's what happens when an analog problem gets into a DIGITAL clock.—RAP

Dear Bob:
In the Jan. 10 issue of Electronic Design, you mention that in the good old days, high-frequency alternators were field-modulated to produce AM. Actually, that was not the case. The high-power machines (200 kW) were modulated by a magnetic amplifier reactively shunting the output. A very complete description of the New Brunswick Maine transmitter, circa 1920, is given in a book titled Magnetic Amplifiers by H.F. Storm. The chapter on "Magnetic Amplifiers for Radiotelephony" was actually written by E.F.W. Alexanderson, the well-known designer of alternators who worked for General Electric.

Papers published by Alexanderson in the Proceedings of the IRE Vol. 8, 1920, and Vol. 9, 1921, give detailed descriptions of the transatlantic communication facility and even oscillographs of the actual modulated RF waveforms. At 30 kHz, this was possible in 1920.

The Alexanderson alternators were quite famous in their day and provided reliable and vital military transatlantic communication during the WWI conflict. In fact, Woodrow Wilson's famous 14 Points leading to the armistice was broadcast using CW to all of Europe from the New Brunswick station.

Predating all of this, in 1906, the irascible but talented R.A. Fessenden used a 2-kW alternator (it was designed by Alexanderson and Steinmetz of GE) for radio-telephone experiments. In this case, he modulated the alternator output with a carbon-button microphone in series with the antenna. His rather glowing account of this is described in Vol. 27, 1908, Proceedings of the AIEE.
via e-mail

Hello, Bill. Since I am such an EXPERT on RF and transmitters—i.e., I am NOT an expert—I apologize. Now, you are saying that substantially NONE of these transmitters worked by modulation of the field? Maybe you are quite right. I may have misremembered or misunderstood what I read. Or, maybe somebody else mis-stated it before I read it—unlikely. Thanks for setting me straight. I'll look into this a bit more. Up to now, nobody else has corrected me on this.—RAP

All for now. / Comments invited!
RAP / Robert A. Pease / Engineer
[email protected]—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

TAGS: Components
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