Radio Survivor

This interview with Lieutenant Colonel R G Wells who constructed a radio receiver and transmitter in a Japanese POW camp during World War II has been making the blog rounds recently (via free103point via BoingBoing via MAKE). Though somewhat technical, the account is a fascinating example of what a simple technology radio is given that the prisoners in the camp had access to very little material except what could be scrounged, nicked or smuggled in.

In this digital era it’s important to remember that one can still build an analog crystal radio receiver that requires no external power, deriving all the juice it needs from the electromagnetic waves. That’s not what Wells and his fellow prisoners did–probably because they were working with more distant signals than a crystal set can receive–but so-called “foxhole receivers” based on crystal sets were used throughout World War II by both citizens and soldiers in order to stay in touch where powered radios were banned or impractical.

I remember building crystal sets both from scratch and from kits as a kid in the early 80s, amazed at the ability to listen to local AM stations without batteries or AC power. I wonder if this is something kids still do these days.

However a crystal set only works with analog, amplitude modulated signals; FM won’t work and neither will any digital signal. Well, you can pick up a digital signal, but it will just be a bunch of hash noise.

I think it’s important for analog radio to continue to exist exactly because of its technological simplicity and ability to transmit over long distances. That doesn’t mean digital or internet-based radio shouldn’t continue to be developed. Rather, keeping simpler, proven analog technologies in service provides a sort of insurance, even if most of our daily existence is highly electrified and digital.

Following up on last week’s post about LPTV stations on channel 6 effectively turning into radio broadcasters I’ve been researching the topic a bit more. Turns out that full-power TV stations had the option to stay on channel 6 in their transition to digital, as I learned from this April article in TV Technology. Although their channel space still bumps up against the low end of the FM dial, the don’t retain their analog audio, and so are no longer heard on the radio.

Interestingly, Fred Lass, the director of engineering for Schenectady, NY’s WRGB-TV, tells TV Technology that he’s considering methods for continuing to have an analog FM audio broadcast alongside the station’s digital signal:

“We have a plan to continue operating on 87.7 after we go digital,” he said. “We think that it’s possible to operate with a vertically polarized analog FM audio carrier when we go back to ch. 6 for DTV. That signal will be horizontally polarized, of course, and there should be enough cross pol isolation to make it work.”

Lass admits that he really hasn’t tried this yet, but thinks it should work.

It never occurred to me that DTV stations would be permitted to continue broadcasting an analog FM audio signal, and I wonder if this is something that would require permission from the FCC.
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A couple of weeks ago I was scanning the FM band as I made my short commute from my far-north Chicago neighborhood to WNUR in Evanston for a station meeting. At the bottom end of the dial I encountered a fading station playing a steady stream of smooth jazz with no DJ. I’d never heard the station before and I pretty much know every noncommercial station on the north side of Chicago and north shore ‘burbs. My first assumption was that it was a pirate station, perhaps run by a disaffected smooth jazz fan in protest of the recent loss of format stalwart WNUA.

WLFM 87.7FM & Channel 6

Still listening to the station on the way home I heard commercials, but still no station ID, leaving me more confused. Listening a bit longer at home gave no more clues, so the internet I did search. I quickly learned that the station at 87.7 FM is not a radio station, but actually TV channel 6, WLFM-LP. And I was right that the broadcast was a direct reaction to the shuttering of WNUA.

You see, analog TV channel 6 bumps right up against the bottom of the FM radio dial. TV sound is also frequency modulated, just like radio, so the sound for channel 6 can be heard at the very bottom of the dial. But, you might be thinking, “didn’t analog TV go away on June 12? Wouldn’t that kill WLFM?” Well, if you’re talking about a full-power station on channel 6, you’d be right. But WLFM is a low-power TV station (LPTV) and the digital changeover didn’t happen for LPTV.

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