The Antenna I Can’t Part With

The rumor was, the guy who designed the antenna, an MIT grad student whose name I won’t mention, was really working for the CIA. Having the ability to monitor local radio stations from afar… let’s say Albania from Turkey, for instance, was a valuable tool in the Cold War.

altazimuth_loop.jpgI was just up in the attic a few minutes ago. I was looking for something that was actually right next to me!

While there, I caught sight of the ‘thing’ in the photo to the left. As any fool can plainly see, it’s an NRC DIGFET Altazimuth loop&#185.

OK – what’s that? You’re entitled to know.

When I was growing up… in fact, until the early 70s, I was a BCB DXer. That’s a person who listens to distant stations on a plain AM radio.

I heard the easy ones easily. It was those stations between the stations, the really long hauls with weak signals, that interested me.

There was (actually there still is) a club for these dweeby shut-ins desperately trying to identify what they were hearing: the National Radio Club. Its DX News, published by volunteers pounding on manual typewriters, was my source of knowledge… albeit months old by the time it got to me.

The loop antenna made it possible to eliminate local stations, allowing the distant ones to come right in. I know it sounds impossible, but by turning the antenna to just the right angle, vector math nulled the strong signal.

The rumor was, the guy who designed the antenna, an MIT grad student whose name I won’t mention, was really working for the CIA. Having the ability to monitor local radio stations from afar… let’s say Albania from Turkey, for instance, was a valuable tool in the Cold War.

While working in Charlotte, NC at 50,000 watt WBT, I could turn the antenna to hear KFAB in Omaha. They were both on the same frequency, with KFAB purposely sending very little signal in my direction!

I used that antenna to listen to the Radio Dakar in Senegal on 764 kHz and the BBC on 1214 kHz from my dorm room at Emerson. The signals weren’t great and I didn’t really mind.

In Cleveland in the early 70s, I caught a station ID from KORL 650 kHz in Honolulu while WSM in Nashville was off-the-air for weekly transmitter maintenance. I only heard a few seconds, but they included a jingle for “People Power,” their talk format slogan at the time.

Since I wanted to be in radio, having this amazing antenna allowed me to listen to disk jockeys and radio stations not normally available.

The antenna still works. Until Major League Baseball began streaming games on the Internet, we used it to hear the Phillies on 1210 kHz, even though there’s a station here in Hamden on 1220 kHz!

I really have no use for my ugly antenna anymore. I do nearly no AM listening, and haven’t BCB DX’ed in years.

There’s not a chance I’ll throw it away. You might not understand why. I’m the only one who has to.

&#185 – NRC is National Radio Club. DIGFET is short for “dual inverted gate, field effect transistor.” It’s a low noise amplifier to increase the signal strength. Two were used in a push-pull configuration. Altazimuth referred to the antenna’s ability to turn and tilt in order to find the perfect spot to null out a station.

9 thoughts on “The Antenna I Can’t Part With”

  1. How can you remember the call letters and frequencies of the stations you listened to in the 70’s and I can’t remember what I had for dinner last night?

    Cool antenna, and of course those of us with an interest in radio stuff can understand your reluctance to toss it out!


  2. As a SWL my high point was the QSL from a station on Guam, my low point a station in Australia taking the time to write that I could not have heard what I said I heard at the time I said I heard it!

  3. Tom brings up an interesting point. I often walk upstairs to get something, and forget what it is by the time I get there. Somehow, short term and long term memory are very different.

    As an example, I remember my first ham radio contact, made at my friend Ralph’s house. It was with WN2RNG. I still remember the rhythmic sound of his callsign suffix in Morse Code.

    Didahdit dahdit dahdahdit.

    Woody – I never got a QSL from KORL, though it was one of many Honolulu stations which shared the same chief engineer, Allan Roycroft. Allegedly, he was a good QSLer.

  4. Geoff, do they still make kits for these? How would one find them? If I’m going to search for one for sale, what’s the best short-hand search term?

  5. I recently built a loop like this but without the altitude adjustment. Its just azimuth. I live in an apartment with some unknown noise source. Unfortunately, since it travels through all the electrical wires in the building, cable TV, and telephone- there is a maximum radiation direction, but he radiation intensity is not narrow enough in degrees for for anything to null it out very well.

    But if I can find a single signal from farther way, its easy to get rid of since the radiation is confined over a very small slice in degrees.

    I got my idea from Tesla. I just remembered him making high voltage generators from such flat spiral coils, and thought it might work for receiver ham usage.

    One note on “capture area.” In the professional literature there is no such thing. Some ham just made up the term a long time ago. The correct term is effective aperture , which directly relates to Radar Cross Sectoin. Just try to find a formula somewhere that gives “capture area” as an output in sq meters and you will see what I mean.

    The key to understanding what I am saying is that an antenna with higher aperture can be much smaller than a larger antenna. The aperture of an antenna is directly proportional to gain. If your smaller antenna has more max gain than your largerer antenna do to ohmic or other factors, then the smaller antenna has a larger affective aperture.

    Rob 73

  6. I just ran across your remembrance of KORL in Honolulu. I worked there for several years starting in 1971 during the time of “People Power” Radio. I produced the morning show for Tom “Dynamite” Dancer. If he didn’t like what you were saying he would “blow you up” with his dynamite sounder. Those were the good old days. Allan Roycroft was an amazing man with radio antennas. He configured our antenna so that 5 radio stations could broadcast from the same tower. He was the first person in the world to do this. Most of the Honolulu radio stations would be off the air from midnight Sunday to 5 AM Monday mornings for maintenance. When I would drive in to work on Monday mornings I would listen to WBAP in Dallas at 820 on the dial. When I moved to Texas I met Hal Jay and Dick Siegal from the morning show. Thay were shocked when they found out I could receive the broadcast in Honolulu.

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