Seventy years ago, the March 1956 issue of Radio Electronics showed this circuit for a sound-powered transmitter, which could be built into a telephone handset. Power was provided by rectifying the output of the microphone.
For some actual contacts made with a similar transmitter, see the writeup about the New England Code Talker QRP transmitter.
If you were in the market for a radio in East St. Louis a hundred years ago, then you would want to get yourself down to Barney’s, 10th and Washington, (on Saturday, where they were open until 9) and get a Crosley model 50 one-tube set, for only $3.98, about the same price as an extra pair of pants for your $9.90 suit.
The ad appeared in the East St. Louis (IL) Daily Journal, March 5, 1926.
If that wasn’t in the budget, you could take home a crystal set for less than the cost of a pair of shoes. In either case, headphones, unless you already had a pair, would be an additional $1.98
Sixty years ago this month, the cover of the March 1966 issue of Electronics Illustrated featured the “Mini-Mitter,” a compact and lightweight (28.5 oz.) 15 watt transmitter for 40 meters. The construction article, is written by Russ Alexander, W6IEL, whose work we have seen previously. He notes that the radio weighs less than the missing power transformer. No transformer was necessary for two reasons. First, the 50-volt tubes were wired in series (along with a 130 ohm 5 watt resistor) directly to the AC power. And the B+ was courtesy of two solid-state diodes wired as a voltage doubler to produce about 310 volts.
The first day on the air, the author, in California, worked both the East Coast of the U.S., but also a 579 report from Sakhalin Island, Russia.
As shown here, the transmitter was constructed with two chasses. The front contained the controls, meter, and tuning indicator. The rear panel was for mounting the tubes and crystal, and for the key and antenna connections.
The other piece of news heralded by the magazine cover was the appearance of a new column in the magazine, questions and answers by “Uncle” Tom Kneitel, then K2AES, whom we have previously featured.
Contest automation in Amateur Radio is nothing new, as shown by this illustration 70 years ago in the March 1956 issue of QST. “Jeeves” was, of course, a common character in the Gil cartoons that filled the pages of QST for many years. If you’re looking for more, you can find them in this collection, available at Amazon.
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Seventy-five years ago this month, the March 1951 issue of Popular Science showed how to put together a science fair project that was, for many years, quite popular. You can make your own cloud chamber, which allows you to watch cosmic rays and the decay of atomic particles. It’s rather easy to make. You make a supersaturated layer of alcohol vapor, which is done with the use of dry ice. The only other materials needed can be found around the house.
The alcohol can be ethyl, methyl, or isopropyl. If Junior is taking it to school, it’s probably best to avoid ethyl alcohol. In addition, that kind (in the form of “Everclear” most likely) is more expensive than isopropyl, which can be had at any drug store.
Dry Ice can be found at the better convenience stores in your area. Of course, use caution when handling it. Actually, you shouldn’t handle it at all. Bring an insulated container to the store and have them place it in there.
Fifty years ago this month, the CB column in the March 1976 issue of Popular Electronics carried some pointers for CB’ers to be prepared for emergencies. Included was this simple circuit to ensure that the radio could see uninterrupted service in the event of a power outage.
A trickle charger keeps the 12 volt battery ready to do at all times. And the 4PDT relay ensures that switchover is automatic. (If you can’t find the 4PDT, two DPDT relays would work just as well.)
Edit: I just noticed that the diagram is wrong. Can you spot the error? Post a comment below.