The portable radio Type A Mark III was the smallest and one of the most popular of all the spy and suitcase radios produced for S.O.E agents and members of the French Resistance to send and receive secret messages to London. They had to send and receive their messages using morse code. There was no voice circuit on these radio sets which could be plugged into any household A/C mains circuit, whether 110 or 220 volts.
Some of the radios were issued with an electric vibrator box which could take 6 volts DC power from a car battery and convert it to an A/C voltage to operate these radios just about anywhere, with or without power. These were the parachutists radios, which were dropped in two steel boxes marked “C” and “D”. The spy suitcase radios meant for use in the towns and cities did not include the DC to AC box. It took the power from a 6v car battery to power a chattering relay (the vibrator) which changed the DC current into AC. It then used a power transformer to multiply the 6 volts up to 110v or 220v to run the valves inside the radio set.
The transmitter was locked to its exact operating frequency by a large quartz crystal that had to be plugged into the spy radio set before every transmission. The radio operators were issued with 10 crystals, which were each tuned to for a different radio frequency, somewhere between 3 MHz and 9 MHz in the HF bands. The agents were instructed to use certain channels on different days, such as days of the month with odd or even numbers, and different frequencies for day time or night time use.
Then the wireless operator had to rig up an end-fed wire antenna that was about 60 feet long, and hope it wasn’t spotted by the enemy. Sometimes the antenna wire would be hidden indoors, zig-zagged back and forth across the floor, walls and ceiling of some room. The radio transmitter has a built-in antenna tuning unit which allows it to work with a wide range of impedences.
Because the enemy was always listening for these radio signals, the spies had to encrypt their messages by using a system of codes and cyphers, and they had to finish their transmissions in less than 30 minutes. At first they would use an obscure book the spy had to keep with him, while his controllers in England had a copy of exactly the same book (identical edition) to refer to. They would agree to use a certain word on a particular page of the book as a key to encoding and decoding each message. And the keys would be changed regularly. Later in the war the agent would just memorise a poem or a song, and use those words to do their coding. That way they did not carry any incriminating evidence if they were stopped and searched by the police or soldiers.
The Germans were very skilled at tracking down clandestine radio transmitters, so to make radio detection by the German military and the Gestapo more difficult, these British spy radios were usually designed with low-powered transmitters. The transmit power of a Type A Mark II tube radio (glass valves) was only 5 watts, which made it harder for the enemy to detect the direct ground-wave signal. Yet the spy radio’s little sky-wave signal would be faithfully reflected off the ionosphere, and would bounce down to earth again across the English channel where sensitive British radio receivers and dedicated radio operators, often women, would type or write down the apparently meaningless morse code letters and numbers they heard through their headsets.
The messages looked like gibberish because they were still in code. This jumbled-up text would then be sent to cypher clerks to be decoded, and then the “en clair” decoded information, now readable to anyone, would go to the intelligence specialist who handled that particular secret agent or partisan group.
The average life expectancy of a spy radio operator was perhaps one month. Sometimes it was less. So this important job was almost suicidal for those who volunteered to do it. But it was vital for the war effort. When they were tracked down and cornered, some agents would start a gunfight against hopeless odds so they could get themselves killed. Or they might chew down on a cyanide capsule or “L-pill” as the British called them so they could die quickly of oxygen starvation.
Any spy who was taken alive could expect to be tortured and broken to reveal their comrades identities. Then, if they were lucky, they would be used to send false information or to lure other spies and resistance members to their deaths. And in the end, they knew would probably be shot by a firing squad. Some, like the three British women spies who were sent to the Dachau concentration camp (just outside the city of Munich) were only executed days before the war in Europe ended. Presumably the SS did not want the women recounting their torture at the hands of the Gestapo secret police.
But what has this got to do with Amateur Radio, you are probably thinking. Well, I came across this spy radio completely by accident. I found it in its two steel boxes at a Trash and Treasure ham radio event here in Sydney. The radio had belonged to an Australian ham who was in the armed forces during World War II. He was now a Silent Key (ham speak for the “SK” morse signal). He was now dead and the spy radio was part of his deceased estate. I recognised the historic spy set immediately for what it was and bought the two boxes on the spot.
So what is my interest in spy radio sets? Well I only found out in 2004 that my mother worked at Bletchley Park in England. From the little she told me before she died, I think she was a cypher clerk of some kind. She did handle the actual messages from these agents in the field. But she never told me much more than that. Even as late as the 1970s, decades after the end of World War II, most of the people who had worked at that most-secret British military intelligence center were still maintaining their silence. They were all bound by the UK’s Official Secrets Act, which had no date of expiry.
So for me, this 1944 spy radio is a link to my dear departed mother. Will I ever use it? Well, if I can obtain a quartz crystal or two for the 80m or 40m Amateur radio bands, I could try and get it to work on 3.5 or 7 MHz. The wiring looks fine, but with vintage valve radios like this one (which is 70 years old now) the capacitors will probably need replacing, and there are about 40 or more of those to be dealt with. That would be a pretty major task, especially if it the authentic look and feel of the old valve transceiver is to be maintained.
It is amazing to think that this radio was absolute state-of-the-art in its day and was manufactured by the Marconi Radio Company.
The Secret Wireless War, The story of MI6 communications 1939 – 1945 by Geoffrey Pidgeon
Resistance, The clandestine radio operators, SOE, BCRA, OSS by Jean-Louis Perquin