World War II can be thought of as the first electronic war. Radio technology was firmly established commercially by the late 1930s and poised to make huge contributions to the prosecution of the war on all sides. Radio was rapidly adopted into the battlefield, which led to advancements in miniaturization and ruggedization of previously bulky and fragile vacuum tube gear. Radios were soon being used for everything from coordinating battlefield units to detonating anti-aircraft artillery shells.

But it was not just the battlefields of WWII that benefitted from radio technology. From apartments in Berlin to farmhouses in France, covert agents toiled away over sophisticated transceivers, keying in coded messages and listening for instructions. Spy radios were key clandestine assets, both during the war and later during the Cold War.

The Limping Lady

Virginia Hall had all the makings of a diplomat. Impeccably educated, fluent in multiple languages, and worldly from her years spent abroad from her native Baltimore, Virginia’s dream of a life in the foreign service was shattered when a hunting accident led to the amputation of her left leg. Attitudes toward disabilities were different in the 1930s, and even fitted with a prosthetic leg (which she named “Cuthbert”) Virginia was deemed unfit for the life of a diplomat.

The outbreak of WWII changed that attitude. Virginia, by then living in France, was well-placed to act as a forward agent for the Allies. Volunteering first for the British Special Operations Executive (SOE), Virginia worked agents, ran safehouses, and reported intelligence from Vichy France. Later, she volunteered with the US Office of Strategic Services (OSS), forerunner to the CIA. Her efforts earned her a place on the Gestapo’s “Most Wanted” list as “The Limping Lady”. She and Cuthbert continued to work against the Nazis right up through the Normandy invasion and liberation and earned a Distinguished Service Cross for her efforts – a rare honor for a civilian, and rarer still for a woman.

Behind Enemy Lines

While Virgina was adept in all aspects of tradecraft, one of the most powerful tools at her disposal was the suitcase radio, a catch-all term used to describe any transceiver small enough to be transported into the field and operated covertly. A suitcase was often used to house the radio as it would be less likely to arouse suspicion if the spy’s lair was discovered. The suitcase was also a great form factor for a portable transceiver – just the right size for the miniaturized radios of the day, good operational ergonomics, and perfect for quick setup and teardown. You can even imagine a spy minimally obfuscating the suitcase’s real purpose with a thin layer of folded clothing packed over the radio.

Great care was given to ensure that the field agent would have every chance of using the radio successfully and that it would operate as long as possible under adverse conditions. With a power budget often limited to five watts or so, these radios were strictly QRP affairs. Almost every suitcase rig operated on the high-frequency bands between 3 MHz and 30 MHz, to take advantage of ionospheric skip and other forms of propagation. An antenna optimized for these bands would likely be a calling card to the enemy, especially in an urban setting, so controls were provided to tune almost any length of wire into a decent antenna.

While some radios were capable of AM voice transmission, continuous wave (CW) modulation and Morse code was used almost exclusively for their ability to punch a signal through any natural (QRN) or man-made (QRM) interference, the latter often being intentional jamming by the enemy. And to make sure the radio kept running, a full set of spares – fuses, tubes, crystals – was provided. Most radios even had a full schematic for troubleshooting. Operators were also meticulously trained:

While the suitcase ruse was perfect for urban and even rural operations, something a little sturdier was needed for true field operations. Resistance forces often found themselves deep in enemy territory and working outdoors in all weather conditions, so a waterproof radio was needed. The British B2 radio was a good example of this; one variant was housed in two metal housings with padding for the delicate electronics. The waterproof containers were designed to be dropped to covert agents on a parachute and lugged around like a backpack.

Bugs In Their Shoes

The end of WWII was by no means the end of electronic intelligence. Indeed, the advances in electronics spurred by the war gave the spies even more toys to prosecute the next phase of the twentieth century’s seemingly unending wars – the Cold War.

Foreign service officers have always enjoyed diplomatic immunity, which today in places like New York City also apparently extends to parking ticket immunity. But it also makes any diplomatic mission a thinly disguised nest of spies in the host country. To take advantage of this, countries go to great lengths to gather data. Sometimes it’s as simple as reading the local newspaper or watching activities at the docks or airport, and reporting information back to the home country in the inviolable diplomatic pouch. But some information is harder to get and requires a little electronic assistance. That’s when the bugs come into play.

Some Cold War bugs were hugely successful, like Theremin’s “Great Seal Bug” placed by Russian agents in the US Ambassador’s residence in the late 1940s. It operated for nearly seven years before being discovered; the secret to its longevity was its passive operation, depending upon a resonant cavity that could transmit voice when illuminated by high-power radio waves. In hindsight, a group of Soviet scouts presenting an ambassador with an enormous carved wooden plaque probably should have seemed suspicious.

Perhaps more subtle was the Romanian Securitate’s attempts to bug diplomats in the 1960s and 1970s. Fashion not being a strong suit of Iron Curtain countries back in the day, Western diplomats in Romania preferred to order their attire from the fashionable shops of London and New York. With operatives in the Romanian post office, it was easy for the Securitate to intercept packages destined for consular personnel. Men’s shoes were whisked away to the Securitate’s technical division, where the heels were removed so that a tiny transmitter could be installed. The shoe was reassembled, sent on to the diplomat, and it would transmit for several days before the batteries died. One imagines that the audio quality must have been poor; pity the poor Romanian signals analyst listening to hours of shoes clopping down hallways. Such bugs were used up until they were discovered during routine sweeps that revealed the presence of radio signals that disappeared when diplomats were out of the room.

I’ve always maintained that pretty much anything that you can imagine is possible with electronics; as long as it doesn’t violate the laws of physics, whatever you can imagine can probably be built. Few things spur the collective imagination and spirit of invention like war, and nothing focuses effort and resources better. It’s a pity we put so much effort into fighting each other, but you’ve got to admire the ingenuity it takes to create devices like these, and the bravery of the men and women who take them into harm’s way.