Atwater Kent Model 20 "Big Box" - 1924

Ok, you got me. This isn't technically an amateur radio blog post but I would argue that radio in the early 1920's was the pursuit of the amateur, the enthusiast and the tinkerer. The amount of crossover between commercial broadcast radio and amateur radio in those days was much greater than it is now. Anyway, that's my excuse ... but why the Atwater Kent Model 20?

The model 20 or AK20

Well, to make along story short, I found an example of this Atwater Kent model sitting in a flea market stall in Hot Spings Arkansas. It looked like it had seen better days but was fully complete including the five '01A' vacuum tubes. The owner wanted $200 for the radio and explained the better part was the included horn type loud speaker which was worth $150. The horn speaker looked to be in fairly bad shape and lacking any way to test it I cheekily asked if he would take $50 for the radio ... "Sure", he said and my wallet was instantly $50 lighter.

Now I have a few vintage radios at home, perhaps a few too many depending on who you ask, and I consider them all to be interesting examples in their own right. More or less money, time and research was employed to create these radios and a great variety of circuits and designs was the result.

First impressions told me this was different, I had never owned anything like the Atwater Kent radio before. It was certainly older than my other radios but it was also constructed unlike any other radio I owned. Even under layers of grime, dust and mud dauber's nests this was obviously an article of quality. The finish on the wood cabinet and the metal front panel had seen some heat and were very badly checked in addition to the 90 or so years that had taken its toll. On the lip of the hinged top was a protected area which still showed how the finish looked originally, the dark mahogany and subtle gloss hinting that it had once looked very smart indeed.

The model 20 compact or AK20C

Once I had Internet access again I started to research the model 20 and try and learn something about it. It was at this stage, after some initial confusion, that I noticed that my model 20 was the older and perhaps slightly rarer "Big Box" version. There isn't much between them but some important differences crop up as far as restoration goes, for example:

Most references I found online suggested that the front panel of the model 20 was painted with a crinkle finish however this was only true of the later versions.

In an Atwater Kent advertising booklet, published at the time, they write, "The front of the cabinet is of metal with a deep brown mat surface which brings out the sparkling sheen of the lighter brown Bakelite dials, knobs, etc., and the nickel-plated trimmings."

I'll need to clean my Bakelite parts and possibly wax them to bring up the original "sparkling sheen" of the tuning, aerial tap and filament rheostat knobs.

A suggestion from the Antique Radio Forums that Rust-Oleum Earth Brown paint followed by black KIWI boot polish applied using 0000 steel wool sounds like it would come pretty close to producing the right finish and will probably be the path I choose when I refinish the front panel.

This AK20, from The Backwood Realm, appears
to have the original finish and looks similar to mine.

For the woodwork we're fortunate to find the description below and some more research indicates that nitro-cellulose lacquer was used at the time and is still available now.

"The cabinet of the Model 20 Receiver, pictured above, is of solid mahogany, stained a dark brown, then shellacked, triply lacquered, and rubbed to a dull, glossy, long-wearing finish."

Overall it seems very understated compared to modern electronics, even down to "The name plate, of dull bronze, is both distinctive and unobtrusive."

I hardly need to say, to most folks at least, that Ebay is a wonderful, and terrible, place to shop for antique radio parts. Wonderful because at any one time there are parts available for just about any radio you might have and terrible because you'll be jostling with tens, or hundred, or thousands of other collectors and re-sellers ... many of which have some very deep pockets indeed!

Unused Atwater Kent Radio Log card.

After vowing I would never pay Ebay prices I lasted approximately 3 minutes and then started looking on Ebay for some of the things I knew I was missing.

Before too long I had found an all-important unused "Atwater Kent Radio Log" card and envelope. I intend to scan these items in with a high resolution flat bed scanner and make copies to use and share.

Also I was able to get a set of three tuning knobs since one of the originals on my radio was shattered. Although someone had thoughtfully placed the remains inside the cabinet it was never going to piece back together well enough to look "right"

I had found the Atwater Kent Radio Instruction Book Vol. 2 online and printed out a copy but couldn't resist the temptation to pick up an original as well as another envelope along with some instruction sheets for various models of AK loud speakers.

I already own a modern ARBE-III battery eliminator so this really left only one thing to find ... a loud speaker.

Even the parts you don't see, are expensive.

I should have known that finding "the right loud speaker" for the model 20 would not be a simple task. While it will work with many different speakers including later cone style Atwater Kent units and those manufactured by other companies, the "right" speaker ... the type shown in all the period advertising literature ... is the Atwater Kent type M, L, H or R radio speaker.

All but one of those models allegedly used pot metal in their construction which eventually succumbs to the dreaded "pot metal disease" making it crack and expand. I have dealt with pot metal disease before and have no intention of doing battle with it again ... this left one model, the model M, as the one I was looking for.

Ok, so there was one model M listed on Ebay and it looked to be in good condition as well as "working" according to the seller. In fact the more I looked at it, the better it looked ... it seemed to be in very nearly new condition. After I finished drooling over the photographs I decided that I would limit myself to $100 not including the $50 shipping involved. The shipping was more than average and I hoped this would keep bids low and reduce the amount of interest. This seemed to work for a while ... the bids topped out at around $80 and I thought I might be on a winner, however this was short lived and the bids jumped to over $100 and kept on going. "Ah well", I thought, "such is life". I knew there would be an vintage and antique radio auction coming up in a month and I could probably find something there at a reasonable price.

The Atwater Kent Type M Loud Speaker.

At this point I took a shower, which is something I would recommend to anyone suffering some disappointment ... or a bath. Worst case you end up cleaner if still disappointed which is surely a small improvement.

At the same time my wife, who perpetually despairs of ever buying the right gift for a husband who is notoriously difficult to buy for, noticed my dejection and moved over to my computer which I had foolishly left logged into Ebay (I should know better, really).

A furious round of bidding started between my wife and a number of others who knew little of her determination to win this auction. I won't mention the final amount, I would like to say because, "One doesn't discuss money" but mainly because it still makes me a little woozy to think about.

If you were bidding on that same speaker then I apologize, but you never really stood a chance.

After further research I've learnt a bit more about the internals of the AK20 and uncovered the meaning behind its three tuning dials and various other controls. In order to provide more amplification, not to mention more selectivity, the AK20 uses three largely identical tuned circuits. Each tuned circuit is controlled by a separate knob on the front panel and all three must be "in agreement" before you will hear anything from the loudspeaker. Next comes the detector circuit which converts the amplitude modulated radio frequencies into audio frequencies and finally two further stages of audio amplification.

The other controls on the front panel are the aerial tuning switch which selects different taps on the first set of coils and the filament rheostats. The filament rheostats, in addition to correcting the voltage supplied by the batteries to the vacuum tube filaments, also act as the volume control by lowering the filament voltage which in turn lowers the volume from its maximum to a comfortable listening level.

Next steps will involve re-finishing the front panel and cabinet, checking tubes along with the few capacitors and resistors, then a careful power-up with high impedance headphones ... the AK loud speaker can wait until I am absolutely sure that it is working as intended!

I hope to update the blog as I progress, as well as uploading pictures and more detailed data such as circuit diagrams and service information HERE.

Virtual Tour of W1AW, the Hiram Percy Maxim Memorial Station

Virtual W1AW Tour on Sunday, February 12 at 5 PM EST (2200 UTC)

Join W1AW Station Manager Joe Carcia, NJ1Q, on a virtual tour of W1AW, the Hiram Percy Maxim Memorial Station, the Amateur Radio station at ARRL Headquarters in Newington, Connecticut. Carcia will lead this tour via a live webcast on . Anyone with an Internet connection will be able to watch the tour here.

W1AW - The Hiram Percy Maxim Memorial Station

"We want viewers of this live Internet tour to feel as if they are actually at W1AW," Carcia explained. "If you came to W1AW in person, you would see the same things that we are going to show on the virtual tour: The three operating stations, the W1AW workshop, the transmitter racks that we use to send out our bulletins and use for the code practice transmission, the control console and Old Betsy, Hiram Percy Maxim's personal spark gap transmitter."

Al Petrunti, KA1TCH, of the New Day Group, will follow Carcia as he leads viewers through the station. ARRL Staff members, including Media and Public Relations Manager Allen Pitts, W1AGP, and Chief Operating Officer Harold Kramer, WJ1B, as well as local television weatherman Geoff Fox, K1GF, will also be on hand at W1AW during the tour.

"Hams around the world know of W1AW, and thousands have made contacts with this impressive station -- but most hams never get to see it," Pitts said. "Thanks to Al Petrunti's group, we hope that folks enjoy seeing what's at the other end of the signals. As in all live broadcasts, you never know just what might happen. We invite you to join us." Pitts is producing the live web tour.


From the ARRL Letter, available at http://www.arrl.org/arrlletter?issue=2012-02-09

Homebrew Hero - Homemade NBTV video recording system in 1974

What do you do in 1974 if you are 20 years old and want to send video to other Amateur Radio operators?

An off-the-shelf home-video camera was the equivalent of $8000 USD (if you could find one) and the circuitry required to transform the high bandwidth signal into one that could be transmitted on AM would have been prohibitively complex.

Believe it or not the only solution was to build your own narrow band video camera! These creations followed on from narrow band television work done in the 1930's and took advantage of advances in materials and solid state technology.

The camera used by VK3AML (Chris Long) in the video below was a Flying Spot Scanner camera which required a completely darkened room and used a spot of light that scanned the scene. The reflected light was picked up by a photomultiplier tube and recorded as a frequency modulated audio tone on tape or broadcast via radio.

We're fortunate to have some of the original video preserved from 1974 since the audio and video signals had been recorded onto open-reel tape.

The 30 line television system developed by John Logie Baird in the 1930s allowed home experimenters to build their own equipment, a practice which still exists today through the Narrow-bandwidth Television Association. Relatively few narrow-band TV signals are transmitted nowadays so most amateur radio operators are unaware of this special interest group.

The video below shows some of the actives and projects that members of the Narrow Band Television Association have been involved in and gives some historical background on this interesting field.

Chas (WA1JFD) from the Antique Radio forums mentions that at approximately the same time other amateur radio operators such as Donald Mara (WA1PLT) were experimenting with Slow Scan Television (SSTV). SSTV sent higher resolution pictures at a slower frame rate, typically taking 8 seconds to send a complete image. Below is a picture of some of the first commercial SSTV equipment that was made available to US hams.

Robot 70 (monitor) & 80 (camera) SSTV system introduced in 1970

I wasn't able to find exact prices for SSTV equipment like the ROBOT 70 & 80 but period articles seem to indicate you wouldn't get much change from $1000 in 1970 for a complete SSTV station. This is equal to around $5000 USD today.

A gentlemen hacker, circa 1903

From New Scientist:

A century ago, one of the world’s first hackers used Morse code insults to disrupt a public demo of Marconi's wireless telegraph

LATE one June afternoon in 1903 a hush fell across an expectant audience in the Royal Institution's celebrated lecture theatre in London. Before the crowd, the physicist John Ambrose Fleming was adjusting arcane apparatus as he prepared to demonstrate an emerging technological wonder: a long-range wireless communication system developed by his boss, the Italian radio pioneer Guglielmo Marconi. The aim was to showcase publicly for the first time that Morse code messages could be sent wirelessly over long distances. Around 300 miles away, Marconi was preparing to send a signal to London from a clifftop station in Poldhu, Cornwall, UK.

Yet before the demonstration could begin, the apparatus in the lecture theatre began to tap out a message. At first, it spelled out just one word repeated over and over. Then it changed into a facetious poem accusing Marconi of "diddling the public". Their demonstration had been hacked - and this was more than 100 years before the mischief playing out on the internet today. Who was the Royal Institution hacker? How did the cheeky messages get there? And why?

It had all started in 1887 when Heinrich Hertz proved the existence of the electromagnetic waves predicted by James Clerk Maxwell in 1865. Discharging a capacitor into two separated electrodes, Hertz ionised the air in the gap between them, creating a spark. Miraculously, another spark zipped between two electrodes a few metres away: an electromagnetic wave from the first spark had induced a current between the second electrode pair. It meant long and short bursts of energy - "Hertzian waves" - could be broadcast to represent the dots and dashes of Morse code. Wireless telegraphy was born, and Marconi and his company were at the vanguard. Marconi claimed that his wireless messages could be sent privately over great distances. "I can tune my instruments so that no other instrument that is not similarly tuned can tap my messages," Marconi boasted to London's St James Gazette in February 1903.

That things would not go smoothly for Marconi and Fleming at the Royal Institution that day in June was soon apparent. Minutes before Fleming was due to receive Marconi's Morse messages from Cornwall, the hush was broken by a rhythmic ticking noise sputtering from the theatre's brass projection lantern, used to display the lecturer's slides. To the untrained ear, it sounded like a projector on the blink. But Arthur Blok, Fleming's assistant, quickly recognised the tippity-tap of a human hand keying a message in Morse. Someone, Blok reasoned, was beaming powerful wireless pulses into the theatre and they were strong enough to interfere with the projector's electric arc discharge lamp.

Mentally decoding the missive, Blok realised it was spelling one facetious word, over and over: "Rats". A glance at the output of the nearby Morse printer confirmed this. The incoming Morse then got more personal, mocking Marconi: "There was a young fellow of Italy, who diddled the public quite prettily," it trilled. Further rude epithets - apposite lines from Shakespeare - followed.

The stream of invective ceased moments before Marconi's signals from Poldhu arrived. The demo continued, but the damage was done: if somebody could intrude on the wireless frequency in such a way, it was clearly nowhere near as secure as Marconi claimed. And it was likely that they could eavesdrop on supposedly private messages too.

Marconi would have been peeved, to say the least, but he did not respond directly to the insults in public. He had no truck with sceptics and naysayers: "I will not demonstrate to any man who throws doubt upon the system," he said at the time. Fleming, however, fired off a fuming letter to The Times of London. He dubbed the hack "scientific hooliganism", and "an outrage against the traditions of the Royal Institution". He asked the newspaper's readers to help him find the culprit.

He didn't have to wait long. Four days later a gleeful letter confessing to the hack was printed by The Times. The writer justified his actions on the grounds of the security holes it revealed for the public good. Its author was Nevil Maskelyne, a mustachioed 39-year-old British music hall magician. Maskelyne came from an inventive family - his father came up with the coin-activated "spend-a-penny" locks in pay toilets. Maskelyne, however, was more interested in wireless technology, so taught himself the principles. He would use Morse code in "mind-reading" magic tricks to secretly communicate with a stooge. He worked out how to use a spark-gap transmitter to remotely ignite gunpowder. And in 1900, Maskelyne sent wireless messages between a ground station and a balloon 10 miles away. But, as author Sungook Hong relates in the bookWireless, his ambitions were frustrated by Marconi's broad patents, leaving him embittered towards the Italian. Maskelyne would soon find a way to vent his spleen.

Nevil Maskelyne

One of the big losers from Marconi's technology looked likely to be the wired telegraphy industry. Telegraphy companies owned expensive land and sea cable networks, and operated flotillas of ships with expert crews to lay and service their submarine cables. Marconi presented a wireless threat to their wired hegemony, and they were in no mood to roll over.

The Eastern Telegraph Company ran the communications hub of the British Empire from the seaside hamlet of Porthcurno, west Cornwall, where its submarine cables led to Indonesia, India, Africa, South America and Australia. Following Marconi's feat of transatlantic wireless messaging on 12 December 1901, ETC hired Maskelyne to undertake extended spying operations.

Maskelyne built a 50-metre radio mast (the remnants of which still exist) on the cliffs west of Porthcurno to see if he could eavesdrop on messages the Marconi Company was beaming to vessels as part of its highly successful ship-to-shore messaging business. Writing in the journal The Electrician on 7 November 1902, Maskelyne gleefully revealed the lack of security. "I received Marconi messages with a 25-foot collecting circuit [aerial] raised on a scaffold pole. When eventually the mast was erected the problem was not interception but how to deal with the enormous excess of energy."

It wasn't supposed to be this easy. Marconi had patented a technology for tuning a wireless transmitter to broadcast on a precise wavelength. This tuning, Marconi claimed, meant confidential channels could be set up. Anyone who tunes in to a radio station will know that's not true, but it wasn't nearly so obvious back then. Maskelyne showed that by using an untuned broadband receiver he could listen in.

Having established interception was possible, Maskelyne wanted to draw more attention to the technology's flaws, as well as showing interference could happen. So he staged his Royal Institution hack by setting up a simple transmitter and Morse key at his father's nearby West End music hall.

The facetious messages he sent could easily have been jumbled with those Marconi himself sent from Cornwall, ruining both had they arrived simultaneously. Instead, they drew attention to a legitimate flaw in the technology - and the only damage done was to the egos of Marconi and Fleming.

Fleming continued to bluster for weeks in the newspapers about Maskelyne's assault being an insult to science. Maskelyne countered that Fleming should focus on the facts. "I would remind Professor Fleming that abuse is no argument," he replied.

In the present day, many hackers end up highlighting flawed technologies and security lapses just like Maskelyne. A little mischief has always had its virtues.

Paul Marks is senior technology correspondent for New Scientist

Preserving the past - Australian built broadcast transmitters

Arguably some of the best looking radio equipment was produced in the 50's and 60's when art-deco motifs, streamlining and other elements of design made their way onto consumer and even industrial electronics.
Unlike modern times, when cost is the only consideration, designers and engineers took the time to ensure that their creations looked good as well as being functional and long lasting. It was worth taking time over the placement of meters, switches & panels, even if it did mean that the final product cost a few dollars more to manufacture.
Amalgamated Wireless (Australasia) or AWA produced an extensive range of home and commercial equipment in the 60s and many vintage radio collectors have examples of AWA radio receivers in their collections. The larger equipment like broadcast transmitters takes an extra special effort to preserve as their large size, demanding power requirements and the specialized knowledge required to maintain them presents a barrier for all but the most dedicated enthusiasts.
We are fortunate then that Don Bainbridge has taken up the challenge and preserved a remarkable collection of Australian built broadcasting equipment and maintains much of this equipment in operational order. The YouTube video below and his website linked here offer a rare glimpse into the world of vintage high powered broadcast equipment before plastic took over and economical design stripped away the chrome and pinstripes.

Old Time Radio (OTR) at Archive.org

When tuning across the AM broadcast band I'm often reminded that there is little left but sports radio and talk shows. I'm not particularly against either but I remember that in the past there was a lot more to pick from. With this in mind I have been looking around the Internet for a source of old time radio and found an excellent storehouse at archive.org.

I noticed while talking with friends that not too many people know about archive.org or assume its only used to hold podcasts. Nothing is further from the truth.

Take a look at  for an excellent collection of old time radio shows and once you've had your fill there, take a look at http://www.archive.org/details/movies and the video archives.

For a quick taste click the play button below and listen to Strange Tales.

Tales of the strange and bizarre, the weird and the wicked. Stories not necessarily of the supernatural, but of the unnatural

(If the player doesn't appear you may need to go to http://www.archive.org/details/oldtimeradio and listen to the radio show there)