Sterba Curtain

Recently I had a nice contact with Al, W0ERE down in The Ozarks, near Highlandville, Missouri and in the longstanding tradition, the customary exchange of QSL cards.

W0ERE

Al was running his Collins S- Line with 500W into his Sterba curtain for 40m. I was using my TS-590SG with 500W from my SB-200 into my Hustler 4BTV. W0ERE may well be one of the first stations I’ve worked that was using a Sterba curtain.

Sterba Curtain. A name that begs for a little Jean Shepherd echo chamber:

Imagine Jean Shepherd’s Echo Chamber

We had a nice chat about his antenna farm in general and the Sterba curtain in particular. The Sterba curtain has been around for a very long time. It was invented by Ernest Sterba, who received US Patent US1885151A Directive Antenna System for his work. The patent was filed in February 1929 and was granted in November 1932.

US1885151A – Fig. 4

Figure 4 of the patent illustrates the Sterba curtain. The primary purpose of the antenna was to provide a very directed, low angle of radiation for the “transmission of Hertzian waves of relatively high frequency.”

Obviously, Sterba curtains were very large antennas. There are some very nice pictures of VOA Sterba curtains that were located in Dixon, California here and some others here.

Sterba was a reasonably prolific inventor. Prior to the patent for the Sterba curtain, Sterba received US1792662A Antenna System for another large antenna system. He also invented an Antenna Sleet Melting Apparatus for which he received US2008266A, “This-invention relates to aerial systems and more particularly to such systems as are equipped with means for removing sleet therefrom.” From the patent specification:

In the operation and maintenance of both transmitting and receiving antenna systems located in sections of the country which are subject to sleet storms, considerable trouble is at present experienced because of the formation and the presence of sleet and ice on the radiating members of the system. The added weight of the ice tends to detune aerial systems as a result of the change in the dielectric constant of the medium surrounding the wires, the ice having a constant of 80. It also frequently causes an actual severance of the radiating elements which usually results in a complete interruption of the operation of the system.

US2008266 Antenna Sleet Melting Apparatus, Fig. 3

With all that wire in the air I’ll bet a lot of “severance of the radiating elements” occurred. His invention was to simultaneously energize the radiating system with direct or low frequency current for heating and high frequency current for radiation.

One last interesting patent was US2119607A Radio Communicating System which dynamically modified the characteristics of an antenna system. This patent was granted in June 1938.

US2119607A Radio communicating system, Fig. 3

I love reading old patents and I especially love the drawings. In those days there wasn’t any CAD, the drawings were done by a draftsmen sitting at a drawing table. Also, at the time of these filings the inventor or his agent\attorney were required to sign the drawings as part of the filed application. With most everything done electronically today we don’t sign drawings anymore and there aren’t any draftsmen with their power erasers. (Though I still have mine.)

Just for fun, and as an illustration of the fact that art lives on forever, I checked the last time that any of Sterba’s patents were cited in prosecution. The above patent,  US2119607A Radio Communicating System  was last cited by an examiner in the prosecution of US7286092B2 Radiocommunications antenna with misalignment of radiation lobe by variable phase shifter which was granted in October 2007.

Art is art forever. This was (and still is) the bargain described in the U.S. Constitution, Article I Section 8 Clause 8 – [The Congress shall have power] “To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.” You disclose your invention for the advancement of science and the useful arts and we’ll give you some rights for a period of time. Radio being part science and useful art has benefited from this bargain over many many years.

And no, there won’t be any Sterba curtains sprouting up at my antenna farm (garden?) any time soon.

 

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