rf everywhere

Apparently...

Why not?

Tim

No one home.

Oops, nix the trailing backslash.

Tim

-- Deep Friar: a very philosophical monk. Website:

The WWII, British, CH radar (circa 50MHz), used open wire feeders to the transmitting antennas. The transmitters were a Marconi-EMI television design, of a few hundred kW, modified for pulse modulation, one of the reasons for killing the early British TV service.

The guy I knew who'd worked on it described how the routing at one site, around the edge of the field, with several corners, to conceal the feeders from the air, couldn't be made to work, and they had to go direct, making a beautiful sighting line to the camouflaged transmitter.

Good grief, I didn't say open-wire was never used, just that it is more difficult.

Perhaps Coax wasn't available? Seems like a perfect opportunity for a ruse. ;-)

This was 1942 Britain.

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

Duh, really?

That station is long gone, and the site it sat on is now a golf course. I got the nickel tour of that station in '70. SOme of the switching was done in underground vaults at that time. They were in the process of a total upgrade of that plant at the time. 10 new 50 KW custom National .5 to 30 MHz transmitters. A complete new control room, and they were replacing the wood poles with small towers. The only thing that wasn't replaced was the Curtain antenna that was aimed at Europe & Russia.

Well, a lot of it is. THAT antenna array Is still there, however.

No, it isn't. it isn't even a Frisbee golf course.

That particular array is one of the only remaining historical elements of the site. It is now a learning center for radio broadcasting.

And your alzheimer's set in in the mid '90s.

And some was done by hand on that array in the picture.

Original footprint.

Never happened.

VOA BBC still exists.

The BBC used motorized balanced feeder switches that were about two stories tall. They actually convey a lost sense of whimsy that once made pre-CAD technology interesting.

The original transmitters at that site were made by Crosley. Green metalflake paint and big glass doors in front of the finals. Beautiful examples of '30s industrial design, but built before Television. They tried numerous methods to eliminate the TVI, and were replacing them with custom designed National radio transmitters. When you changed frequency, the transmitter reduced power and self tuned every stage. All 10, or any combination could be fed from one MFO for power levels from 50 to 500 KW. The self tuning was done with detectors to measure the signal and large servos to drive the variable capacitors & roller inductors.

The new control room had two layers of corrugated concrete precast panels stacked at an angle to allow them to run cabling between any two racks or consoles by drilling holes in the panel(s). It was being converted to the secondary control point for the VOA network, and a private microwave link to Washington D.C. was under construction to the earth terminal to uplink the various feeds. If that failed, other VOA stations were to tune in to the Bethany plant and retransmit. That curtain antenna was a sight not to be missed. Three huge towers, with the network of antennas strung between them. We had to get special permission to tour the site, and had armed MPs follow us through the building & grounds.

Once upon a time i had a USC-30, 2 to 30 MHz 1kW transceiver, in my care. It auto-tuned in the same way. I got to watch it once (with the covers off) and it was a thing of beauty to behold. It had its own low power (50 W) dummy load and tuned up into that. Then it commanded the auto-tuner of the selected antenna to tune up. Just beautiful, but 30 seconds for any frequency change from 100 Hz to 28 Mhz. You used a different receiver and antenna to find an empty spot in an authorized band to transmit.

?-)

You could see all of the hand crank tuning knobs on the front of the transmitter turning at the same time. :)