Radio Waves: Digital Audio via Vintage Radio, “10-Minute-ish” Transmitter, Why No Channel 37, and Inventor of the Audio Cassette Dies at Age 94

Image by Jon Tyson

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Ron, Valdo Karamitrov, Ronald Kenyon, and the Southgate ARC for the following tips:

‘I play digital music through my 1949 radio’ (BBC News)

When we think of technology our imagination usually takes us to images of the future. But for some, technology links us to the past – whether for nostalgia or for personal reasons

Following our recent feature on vintage technology, we asked you to share some of your collections with us – and people from around the world responded..

Rob Seaward, North Yorkshire, UK: 1949 Murphy A146 radio

I have a collection of older technology which I have collected throughout my life – including old cameras, calculators, hi-fis and radios. I had been interested in music from an early age, but it was really when my father purchased a Bang and Olufsen music centre that my interest in not only music, but style and function really took off.

To me, a lower middle-class grammar school kid living in Bradford, I suddenly had access to a world of real style and glamour.

My favourite piece must be the Murphy A146 console radio designed by Gordon Russell in 1949.

Its nickname is the “Batwing” because of the shape of the back panel. The sound is rich, slightly warm and typical of valve equipment. In its day, the radio cost the equivalent of an average monthly wage, it was built to last and the original valves are still working today.

However, as it pre-dates FM it is a little limited. I’ve had it restored and as part of the process we had a Bluetooth adapter installed which means I can now play my favourite digital music through this wonder from the 1940s – which really amazes people.[]

Getting on the Air With a 10-minute-ish Ham Transmitter (Hackaday)

Artificially constrained designs can be among the most challenging projects to build, and the most interesting to consider. The amateur radio world is no stranger to this, with homebrew radio designs that set some sort of line in the sand. Such designs usually end up being delightfully minimalist and deeply instructive of first principles, which is one reason we like them so much.

For a perfect example of this design philosophy, take a look at [VK3YE]’s twist on the classic “10-Minute Transmitter”. (Video, embedded below.)

The design dates back to at least the 1980s, when [G4RAW] laid down the challenge to whip up a working transmitter from junk bin parts and make a contact within 15 minutes — ten for the build and five for working the bands. [VK3YE] used the “oner” — one-transistor — design for his 10-minute transmitter, but invested some additional time into adding a low-pass filter to keep his signal clean, and a power amplifier to boost the output a bit.[]

Why Channel 37 Doesn’t Exist (And What It Has to Do With Aliens) (Vice)

Since the advent of analog TVs, channel 37 has always been static. Here’s why.

A version of this post originally appeared on Tedium, a twice-weekly newsletter that hunts for the end of the long tail.

I’m endlessly fascinated by stories of the quirks that were built into the TV system where the well-laid plans of the system simply fell apart because it was asked to do too many things.

Nearly five years ago, I wrote about one of them, the tale of how radio broadcasters were able to shoehorn an additional FM station into the radio because of the proximity of TV’s channel 6 to the rest of the radio feed.

So when I was informed that there was another oddity kinda like this involving the TV lineups, I decided I had to take a dive in.

It’s a tale that centers around channel 37, which was a giant block of static in most parts of the world during the 20th century.

The reason for that was simple: it couldn’t fend off its scientific competition.


The year that the U.S. Federal Communications Commission opened up the television system to use UHF, or ultra high frequency signals. The practical effect of this addition of bandwidth was that the total number of potential TV stations increased dramatically, from 108 to 2,051, overnight. The first UHF applications were granted on July 11, 1952, according to The History of UHF Television, a site dedicated to the higher-frequency television offerings.

The radio telescope that became a headache for the television industry

Within a 600-mile radius of the city of Danville, Illinois, population 31,246, are numerous major cities—among them Chicago, Detroit, Milwaukee, Atlanta, Minneapolis, Pittsburgh, St. Louis, Toronto, and Washington, DC.

Nearly the entire length of the Mississippi River fits into that radius. If Danville was located just a little farther to the east, the radius would also include Philadelphia and New York City. For all intents and purposes, a 600-mile radius from Eastern Illinois covers basically the entire East Coast except the state of Florida and the Northeast.[]

Dutch inventor of the audio cassette tape dies aged 94 (Southgate ARC)

Lou Ottens, inventor of the cassette tape and a CD pioneer died aged 94 at his home in Duizel in Brabant on Saturday, Dutch media report.

Ottens, who studied to be an engineer, started working for Philips in 1952. Eight years later he became head of the firm’s recently introduced product development department. Within a year he and his team had developed the first portable tape recorder of which over a million were sold. Two years later he revolutionised the old reel-to-reel tape system by inventing the cassette tape.

‘I got annoyed with the clunky, user-unfriendly reel to reel system, it’s that simple’, Ottens said later. The new carrier had to be small enough to fit into his jacket pocket, Ottens decided, and he had a wooden model made to determine the ideal size. In 1963 the first plastic encased cassette tape was presented at an electronics fair carrying the slogan ‘smaller than a pack of cigarettes!’ The tapes were quickly copied by the Japanese but in different formats!

Ottens managed to make a deal with Sony to use the mechanism patented by Philips to introduce a standard cassette which was then rolled out globally. Over 100 billion were sold worldwide. Ottens went on to develop the CD, which again became a Sony-Philips standard and which sold over 200 billion.

In 1986 Ottens retired but he was often asked if he was proud of his inventions, which allowed millions to have access to music. ‘I have no ‘pride dial’’ Ottens said in an interview, stressing that both inventions were team efforts. His biggest regret was that that Sony, not Philips, invented what he considered to be the ideal application for the cassette tape, the Walkman. ‘That still hurts,’ he said. Dubious about the recent revival of the cassette tape Ottens said ‘nothing could beat the sound of a CD.’


Do you enjoy the SWLing Post?

Please consider supporting us via Patreon or our Coffee Fund!

Your support makes articles like this one possible. Thank you!

Spread the radio love

5 thoughts on “Radio Waves: Digital Audio via Vintage Radio, “10-Minute-ish” Transmitter, Why No Channel 37, and Inventor of the Audio Cassette Dies at Age 94

  1. Mangosman

    Pretty irrelevant really. They did not use crystal controlled servos to control motor speeds in players or recorders to get that accuracy. What is the effect is as tiny change in pitch. The momentary speed variations caused by rubber rollers and belts caused flutter in the sound reproduction.

    During this time broadcasters used carts not cassettes which used conventional audio tape as an endless loop. Who remembers the Nagra portable reel to reel tape machines carried by reporters and interviewers? They could record with the same quality as in the studios, which the cassette was nowhere near this quality. For broadcasters, cassettes where a dictating machine!

    1. Ron F

      Apparently the NAB had a different opinion to you about relevance and accuracy.

      “NAB Audio Recording and Reproducing Standards for Audio Cassette Tape Systems”

      “The Standards contained herein were adopted by the Board on June 16, 1972.”

      ” 2.10 Tape Speeds
      It shall be standard that the tape speeds be 1 7/8 and 3 3/4 ips +- 0.3% (4.76 cm/s & 9.53 cm/s
      +- 0.3%).”

  2. Frans

    Beste mede lezers van SWLING , zelf heb ik er veel , en nu nog , gebruik van gemaakt de Compact Cassette .
    Diverse bandjes met kortegolf radiostations uit de hele wereld waar nog regelmatig naar wordt geluisterd.
    Een prachtige uitvinding. Mijn cassettes zijn nog steeds van goede kwaliteit.
    73 de Frans pa3fek , Dutch swl number 110, member of the VERON.

  3. Mangosman

    Whilst the development of the audio cassette enabled music to become convenient and portable particularly with the Sony Walkman it was a big step backwards in sound quality compared to both reel to reel tape machines and records.
    The cassette tape is 3.175 mm wide which was a half the width of the commonly available reel to reel audio tape. The cassettes were available in stereo and you could turn them over dividing the tape width by 4 per audio track. A gap was required between tracks and a wider one in the centre to stop obvious cross talk between the forward and the reverse direction tracks.
    Reel to reel tape machines had the following tape speeds; 19, 9.5 and 4.8 cm/s. The lower the speed the poorer the high frequency response, with 4.8 cm/s regarded as speech quality. 4.8 cm/s is the only speed cassettes machines would operate at.
    With the narrow tracks and the slow speed, the voltage from the record/playback head was very low making hiss a big problem. As a result many cassettes produced by the record companies had Dolby B noise reduction. When recording their cassettes, if the level of high frequency audio was low it would be boosted prior to recording and the player would reduce the level of high frequencies below a certain level. The result is that the hiss was reduced.

    1. Ron F

      > “4.8 cm/s”

      Fun fact: Philips’ original spec stated 4.75 cm/s, & I believe that was adopted as the original IEC standard. Somewhere along the line that got translated to imperial 1 7/8 inches/s (4.7625 cm/s) +/- 0.3% as the US NAB standard, and I believe the IEC later adopted that.

      4.7625cm/s often gets incorrectly rounded up to 4.8cm/s, but 4.8cm/s is actually out of spec (+ ~0.8%). The original Philips 4.75cm/s is, however, still just within spec (- ~0.27%).


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.