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posted by martyb on Tuesday August 23 2016, @02:22AM   Printer-friendly
from the getting-the-word-in-and-out dept.

Submitted via IRC for butthurt with a story from hackaday that became:

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.

What follows is an interesting presentation on some of the advances that made their way out to the field. The epitome of miniaturization was the "suitcase radio" which provided a simple means of transporting and somewhat concealing a working radio receiver and transmitter. The included pictures and video provide a glimpse back to a time that seems so quaint — so many people today think nothing of the advances which permits a cell phone to fit in a pocket.

Even more fascinating, one of the comments to that story referred to this amazing act of clandestine creativity: Construction of Radio Equipment in a Japanese POW Camp. POWs were able to construct a radio receiver with a lot of trial and error, best guesses and approximations, and a smuggled-in valve (tube) and headphones. Fascinating read!


Original Submission

 
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  • (Score: 3, Informative) by Spook brat on Tuesday August 23 2016, @06:38PM

    by Spook brat (775) on Tuesday August 23 2016, @06:38PM (#392235) Journal

    With today's spread-spectrum technologies, good luck finding the transmitter. The old spectrum analysis techniques don't work, as you have no idea where the carrier is at any given time.

    That's not a problem anymore, modern sigint gear can analyze the entire spectrum at once. The equipment you need isn't even restricted to military; if you've got the cash you can buy it off the shelf. Back before computer power was cheap you could only tune in to one frequency at a time; it was like being blind to every color but one all the time. These days the same sort of gear looks at the field and sees a frequency-hopping radio as a rainbow-colored strobe; as long as it's strong enough to see against the background it's easy to locate.

    Same sort of advancement in computer power makes it possible to listen in on the broadcast, too. It's kinda trippy listening to a broadcast that's hopping frequencies multiple times per second and seeing realtime what frequencies it's using.

    TL;DR version: frequency hopping doesn't let you hide, and doesn't make you hard to hear. If you're broadcasting, they know where you are. Encrypt your transmission or assume you're being listened to.

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