I’m probably already on a list of people who shouldn’t visit China.
Author Archives: clem.law@usa.net
1950 Two-Tube Two-Band “Progressive” Receiver
This duo are putting the finishing touches on a two-band, two-tube receiver, as shown 70 years ago this month in the January 1950 issue of Popular Mechanics. The set tuned the broadcast band and 1.5-15 MHz shortwave with plug-in coils. The set as shown here used a 6SG7 as RF amplifier, with a 6SN7GT detector and AF amplifier.
The chassis looks a little bit empty because this is a “progressive” set. The version shown in this magazine would start pulling in the stations, using headphones. Later issues of the magazine would show improvements. An external power supply is used, but at this point, only the filament winding of the power transformer is used. The article cautions to carefully tape the high voltage leads, as they wouldn’t be used until a later version. In the meantime, the filaments are run from the power supply, with batteries supplying the B+ voltage.
The article noted that hand-wound coils were requested by builders of earlier versions of the set, and they were obliged with complete coil winding instructions.
Are Engineers People? 1930.
We have many engineers in our readership, and they will undoubtedly be interested in the answer to this question, namely, “are engineers people?”
The question is posed in an ad by Sylvania tubes from the January 1930 issue of Radio Broadcast magazine.
Unfortunately, they ad doesn’t give a straightforward answer to the question. We agree, however, that one ought to be a suspecting person, a doubter. The company provided a coupon to write for more information, but you first had to affirm that yours was an open mind.
1960 Homemade Computer
Sixty years ago, the gentleman shown here was undoubtedly the first one on his block to own a personal computer, since he built this one, as shown in the January 1960 issue of Electronics Illustrated.
The device was essentially a binary counter. The pulses from the telephone dial went to a series of six flip-flop circuits, and the total was shown in binary with the top row of lights. So to add, you just dial in the numbers you want to add, and then read the sum (in binary) on the lights.
Subtraction was also possible, since subtraction of a number was the equivalent of addition of the number’s complement. In this case, since the computer handles 6 digit binary numbers, it can display 0-63. Thus, the complement of a number is 64 minus that number. The bottom row of lights showed the complement of the number shown in the top row. (For example, the complement of 110000 is 001111.)
Multiplication was possible by repeatedly adding, and division amounted to repeatedly adding and seeing how many times the addition was necessary.
The author does conclude by noting that the computer was intended as a demonstration model. Accordingly, it had little practical use “unless the builder takes the time to study some of the readily available literature on computer techniques and mathematics. I do not recommend that anyone not familiar with high school mathematics attempt to construct it, as it will merely become a toy of limited value.”
Belmont BRC-571 “Clockette” Radio Clock, 1940
This handsome device from 80 years ago wasn’t a clock radio. Instead, it was merely a radio clock, namely, a clock and a radio in the same enclosure, both of which operated independently. It is the Belmont Model BRC-571, also known as the Clockette, and it’s shown here in the January 1940 issue of Radio Today.
The set tuned 540-1720 kHz, meaning that it would pull in police calls in addition to standard broadcast stations. The clock was described as self-starting, and the radio was a standard 5-tube superhet, both of which were housed in a walnut cabinet.
You can see a nicely preserved example of the set at the Radio Attic Archives.
Postwar VHF Allocations
As you can see, there were still a few tweaks to be made, such as the elimination of TV channel 1, and the exact limits of the FM broadcast band. But by January 1945, the postwar allocations for the VHF and UHF spectrum were pretty much in place. This chart appeared in the January 1945 issue of Radio Service Dealer.
Avoiding Telephone Annoyance, 1920
For those who are annoyed by noise while talking on the phone, then this device from a century ago would prove helpful. As shown, the earpiece covers both ears, ensuring that your call won’t be interrupted.
The picture appeared in the Philadelphia Evening Public Ledger a hundred years ago today, January 19, 1920.
1960 Squelch for Benton Harbor Lunchbox
Sixty years ago this month, the January 1960 issue of Electronics World carried a simple modification for the venerable Benton Harbor Lunchbox, in this case, the Model CB-1 CB transceiver.
James Green, the Chief Engineer of WELO, Tupelo, MS. The station had purchased two of the sets for communicating with one of the station’s engineers “living in a rural area devoid of telephone services.” For that reason, the set was going to be in operation for 18 hours a day, and the constant rushing noise of the superregenerative receiver “simply could not be tolerated.”
Green came up with a simple solution to the problem. Contrary to what one might think, the voice peaks of a received signal are louder than the rushing sound. Therefore, he simply used a sensitive relay from the rectified output of the audio output transformer. Then, the volume was turned to just to the point where the voltage was too low to energize the relay coil. At that point, the relay switched the speaker out of the circuit. When a call came in, the voice peaks generated a higher voltage, and the speaker kicked in. A capacitor kept the relay engaged for a short time so that the relay wouldn’t chatter between words.
A switch bypassed the squelch, so that the volume could be turned up or down.
The remarkable thing about this article is that a rig as simple as the CB-1 was actually put to a business use. For those who malign CB, I’ve noticed that 11 meters is so quiet these days that it can probably be used for useful communications, just like it was 60 years ago. As shown below, CB rigs are dirt cheap, and an antenna can be made for next to nothing. For short-distance communications, they can be useful for many applications.
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Official BSA Radio Kits: 1960
Sixty years ago, Scouts looking to put together their own radio receiver could head down to the local BSA authorized dealer and pick up one of these official BSA radio kits, as shown in the January 1960 issue of Boys’ Life magazine.
There were two sets for the standard broadcast band. A two-tube set for $11.95 had a built-in loudspeaker. For headphone use, the one-tube set sold for $7.25. Both reuquired batteries. The filaments on both sets ran off a 1.5 volt battery for 20 cents. The two-tube set’s 90 volt B battery sold for $3.95, and the one-tube set’s 22.5 volt battery sold for $1.50.
For Scouts who already had radio building experience, it was time to move up to the short waves. That set, which looks like a regenerative receiver with one or two tubes, sold for $15.95. It ran off standard household current, so no batteries were necessary. Headphones were an additional $2.95, and “3 extra coils,” presumably to tune the short waves, were $2 for a set.
There was also an official BSA crystal set sold complete for $2.95. We actually had one of these around the house when I was a kid, and the chassis for this set was the bottom of the cardboard box it came in.
Finally, for Scouts working on their code, the Official S-O-S Signal Set sold for $1.95 for a single unit, or $3.95 for two units. The mathematically astute will realize that you paid a nickel extra if you bought two, but that presumably included the wire to hook the two units together.
This issue of the magazine also contained a reminder of the upcoming February Boys’ Life radio contest, and in anticipation, contained some SWL’ing pointers by none other than Tom Kneitel. Kneitel’s article contained some tips for pulling in DX, and a listing of some of the loudest and most likely to be heard stations from 3.2 to 25 MHz.
1960 Kit Building Venue
The hottest night spot in Greenwhich Village 60 years ago was a loft at 732 Broadway. A wide cross section of New Yorkers gathered there–school kids, attorneys, mailmen, a concert violinist, and a lady psychologist. For a dollar an hour, they had access to a workbench, tools, soldering irons, and test equipment where they could assemble electronic kits.
The workshop was the brainchild of Dave Muirhead and Elliot Gorden, described by the magazine as experienced audio men. In addition to the physical facilities, there was plenty of expert advice available as the customers put the finishing touches on their Heathkits, Knight Kits, and Eicos.
That address is currently the home of Universal Musical Instrument Co. From their Yelp reviews, I wouldn’t be surprised if there were a few old Heathkits buried under the musical instruments. According to one review, it’s a great place for those building or inventing their own musical instruments in search of affordable parts. “The proprietor often will let you browse, chaperoned, once he understands what you are there for.”
The profile shown above appeared in the January 1960 issue of Electronics Illustrated.