Eighty years ago, if you needed room filling volume from your Harmonica, there was no need for additional lung power. Instead, you could move up to the next level with electronic amplification, courtesy of this microphone shown in the April 1941 issue of Popular Mechanics. As shown here, your kids will be delighted at the prospect of this musical entertainment.

The microphone was designed to plug into the phono jack of a radio, and up to five could be wired in parallel for your next harmonica quintet performance.  The microphone was also suitable for guitar, violin, piano, and many wind instruments.  It was manufactured by the Amperite Company, then of 561 Broadway, New York.

Eighty years ago, the radio repairman was a heroic figure, as shown by this illustration on the cover of the April-May 1941 issue of National Radio News.  While the lady of the house and faithful canine companion look on, he is getting this set back into operating condition.

Perhaps he had to replace a tube, or perhaps he was resetting the set’s pushbuttons.  This was necessary since the FCC had just changed the frequencies of most U.S. radio stations on March 29, 1941.  An article in the magazine included a timely feature going into detail on the circuits involved.

A hundred years ago this month, the April 1921 issue of Radio News showed how to build this simple receiver, said to have a cost of only 25 cents. Tuning was accomplished with a variable capacitor consisting of aluminum plates separated by waxed paper. By compressing the plates, the capacitance was changed.

The magazine lamented that there were probably thousands of lads who looked wistfully at the catalogs, only to be discouraged by the high prices. The thought was that if they got a chance to listen in with this inexpensive set, they would be sold on the idea of radio and would soon figure out a way to put together a more impressive station.

Accroding to the magazine, almost every town had a good amateur station holding court on 200 meters, and receiving them even with this simple crystal set would be a simple matter.

I have no doubt that the parts shown here could be had for a quarter. The problem, however, is that the prospective radio ham would still need a headphone with which to connect the set. Looking through the magazine, the least expensive was $4.50, or about $66 in today’s money, according to this inflation calculator.

Those headphones, of course, would still be good when the listener was bit by the radio bug and upgraded to a better set. But the cost of entry to the hobby was $4.75, and not the 25 cents promised by the magazine.

Eighty years ago today, the April 21, 1941, issue of Life magazine carried this ad from General Electric reminding readers such as this businessman and his efficient secretary that his desk would be an excellent spot for a radio, for keeping up with news and stock reports affecting his business.

Their suggestion was the model L-500, which sold for only $9.95 (according to this inflation calculator, $162.17 in 2021 dollars).  The  “All American Five” set had the then-standard tube lineup of  12SA7, 12B7, 12SQ7, 50L6GT, and 35Z5GT.  According to the ad, the set had excellent tone. We previously featured the L-500 at this link.

The ad also featured the portable model LB-502, a five tube ( 1R5 1T4 1S5 3S4 35Z3) camera-style portable that would run from either batteries (1.5 and 67.5 volts) or household current.  It carried a list price of $21.95, or almost $400 in today’s money.

The September 1951 issue of Popular Mechanics showed how to put together this simple two-tube receiver. It was earmarked especially for the new ham, since it covered the 80 meter ham band. But it would also pull in a wider range of frequencies, including police calls and the 49 meter international broadcast band.

The timing of the article wasn’t a coincidence, since the circuit was specifically targeted at those interested in the Novice class amateur radio license. That new license, which required only a 5 word per minute code test, had just been announced by the FCC, which started issuing them on July 1, 1951. Armed with this receiver, and a key and buzzer, the prospective Novice would be able to pass the test with ease. The magazine promised that the October issue would include an accompanying transmitter.

Construction was simple, as it used two pieces of hardwood mounted on wooden cleats. There was a gap between the two boards, allowing for easy mounting of the sockets for the two tubes and one plug-in coil. Power came from a 45 volt battery, but to prevent having to replace A batteries, a 6.3 volt transformer was used to light the filaments. No power switch was provided, and the magazine noted that a switch could be mounted somewhere on the operating table in line with the transformer.

The magazine recommended a 10-15 foot indoor antenna and ground for the two-tube regenerative set. One variable capacitor was used to control regeneration, with another one serving as the main tuning dial. The procedure for using the set was to advance the regeneration until the set came to life, and then tune the main tuning dial until 80 meter stations were heard. At that point, the larger bandspread dial would be used for tuning.

Eighty years ago this month, the April 1941 issue of Popular Science showed this novel little one-tube receiver. Even though it’s basically a crystal set, it qualifies as a one-tube radio since it uses a rectifier tube, a 25Z5, in place of the crystal.

The article points out two things that might not be obvious. First of all, even though the set is running on AC power, there is no hint of 60 cycle hum. The electric power does nothing but heat the filament, and the heated cathode and plate serve as the detector, with no electrical connection to the power. The magazine also notes that it’s safe to use a ground connection, since there’s no direct connection.

Even though the filament normally runs on 25 volts, it should be under 6 volts in this circuit. An 80 watt resistor is used to drop the voltage, although I bet an incandescent light bulb could be used.

Fifty years ago this month, the April 1971 issue of 73 Magazine was a special issue devoted to FM repeaters. The cover shows Murry Sessions, the daughter of Managing Editor Ken Sessions, K6MVH, at the mike of a Drake TR-22, a one-watt portable 2 meter FM rig with six crystal-controlled channels. According to a review in the magazine, the set retailed for $199.95.

Of particular interest is the nationwide repeater directory, which took up seven pages in the magazine. The 30 kHz channel spacing had been widely adopted, with some channels designated for wideband and others for narrowband. However, there was no uniformity as to repeater inputs and outputs. 146.34 MHz was a very common repeater input, and 146.94 was a common output, but they weren’t necessarily paired. For example, many repeaters were 146.34 input and 146.76 or 146.88 output. In many cases, frequencies were shared in the same area, with different audible burst tones at the start of the transmission.

This makes sense, since crystals were expensive, and using the same frequency for two repeaters would have allowed users to save having to buy an additional crystal. When I got on 2 meters in the mid-1970s, the most common repeater pair was 146.34/146.94 (although this was not used in the Minneapolis-St. Paul area). However, 146.94 was the most widely used simplex channel. My first two meter rig had crystals for .34/.94, but also had a transmit crystal for .94.

In the 1971 listing, Minneapolis had a repeater with an output of 146.46. The “priority input” was 146.34, with a “courtesy input” of 146.94. The magazine noted that this system was in operation 24 hours. Many systems had limited operational hours. The Minneapolis system also had an input on 6 meters, 53.64 MHz.

Two meter FM saw great growth in the following years, fueled partly by the availability of autopatches to allow phone calls to be made from a mobile or portable radio.  This continued through the 1970s and 1980s, but waned considerably with the rise of the cell phone.  My first two meter radio was a semi-homebrew portable unit with four channels.  Around 1976 or so, I bought a Drake TR-22C, the twelve-channel updated version of the one shown above.  It was loaded with crystals for popular repeater pairs, which had by then been standardized.  Therefore, almost anywhere I travelled with the radio, I was probably within range of a repeater, and it was almost always possible to raise a fellow ham.

Fifty years ago this month, this young comrade was able to help feed his family by locating a school of fish. He managed this by seeking out the perfect water temperature, thanks to an electronic thermometer he constructed himself.

The plans for the project were contained in the April 1971 issue of Юный техник (Young Technician) magazine, which also contained the plans for making the raft, shown at left. It included a number of other circuits, including the one transistor regenerative radio receiver shown below.