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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!


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  • (Score: 2) by ilPapa on Tuesday August 23 2016, @04:46AM

    by ilPapa (2366) on Tuesday August 23 2016, @04:46AM (#391996) Journal

    I like to imagine that if you powered up one of those old Cold War era spy radios the first thing you'd hear would be the Ink Spots.

    https://youtu.be/6l6vqPUM_FE [youtu.be]

    --
    You are still welcome on my lawn.
  • (Score: 2, Interesting) by anubi on Tuesday August 23 2016, @05:17AM

    by anubi (2828) on Tuesday August 23 2016, @05:17AM (#392004) 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 last link in interesting... about the construction of a radio in a Japanese POW camp. I wonder what tube he built around as a receiver. Sure reminded me of my high-school days where I used to take apart television receivers then re-assemble them into damn near anything. It took two TV receivers to make a pretty good guitar amplifier, as I liked to run the horizontal output tubes ( like 6CD6 or so ) push-pull, and the TV had ample other tubes of various power ratings that made excellent pre-amps, drivers, and specialized tubes I could make some really weird sound effects with...like the 6BN6 gated-beam tube.

    I used to love those tuner and IF tubes for preamps.... high gain and low noise.

    I would think for a war receiver, getting one's hands on something like a 1N5 would have been a goldmine. Throw in a 3Q5 or 1A5 and you are really in hog-heaven.

    --
    "Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
    • (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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      Travel the galaxy! Meet fascinating life forms... And kill them [schlockmercenary.com]
  • (Score: 2) by Spook brat on Tuesday August 23 2016, @06:50PM

    by Spook brat (775) on Tuesday August 23 2016, @06:50PM (#392241) Journal

    It's amazing what motivated people will do to communicate!

    There were a lot of passive setups rigged together with junk you'd find laying around; this sort of receiver got the nickname "foxhole radio". [bizarrelabs.com] Anything is better than nothing, and these would at least let you listen in on an AM radio broadcast.

    --
    Travel the galaxy! Meet fascinating life forms... And kill them [schlockmercenary.com]