Charles

Inspired by FLIR Systems scientist Austin Richards' recent book, "Alien Vision," I decided to see if I could put together my own imaging-based tour of the electromagnetic spectrum using web-based resources. This post is the result. Here are 17 striking images from across the spectrum at wavelengths ranging from one meter down to one-trillionth of a meter, from radio waves to gamma rays, arranged in order of increasing frequency / energy. Each is accompanied by a caption identifying the instrument used to record the image, the approximate wavelength at which it was recorded, the subject, and a link for those seeking more information.

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I read through this article about the ongoing restoration work of an RCA SSB T-3 transmitter and found it interesting.  The RCA T-3 transmitter is a 20 KW SSB/ISB HF (2-28 MHz) unit designed for point to point telephony service.  Because SSB requires class A or AB low distortion amplifiers, this is a large unit, even for its age and power levels.

From the looks of the before pictures, this transmitter was in sorry shape.

Here is a brief video of transmitter start up:

These units were designed to be switched on and run at 100% duty cycle from most of their operating lives. That is some heavy iron there.  This particular unit was made in 1959. More here and video part 2:

Anyway, before geosynchronous satellites, HF point to point transmitters were used to make long distance phone call connections and send data and pictures back and forth over long distances. Out in Hicksville, Long Island, Press Wireless ran a data and fax system that used HF for long haul data transmission.  Much of the WWII reporting from Europe and the Pacific Theaters was carried over this system.

Text would be printed out on a mechanical teletype machine at something like 60 words per minute, which was considered fast for the time:

Tuning across the band, one can often hear Radio Teletype (RTTY or RATT) which uses a 5 bit baudot code, 170 Hz shift with 2125 HZ representing a Mark or 1 bit and 2295 Hz representing a Space or 0 bit, which is bit different from the Bell 103 modem specifications. This is what it sounds like at 75 Baud:

So slow you can almost copy that by hand.

The RCA H (SSB T-3) unit above was independent side band (ISB), which means that either side band or both could be modulated independently of the other, thus two channels of information could be transmitted.  SSB bandwidth is about 2.7 KHz, which is good for telephone grade audio or low speed data.

I sort of wish I was living in California again, I’d lend a hand.

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The folks at Beagleboard.org are teasing us with a sneak peek of the newest version the of the BeagleBone, their embedded Linux development board. According to the post on their site, the new board comes at a lower price, touts more processing power, and has an on-board HDMI port so [...]

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