Remember way back when, perhaps in high school or college, you met this really cool person who seemed to be wonderful in every way? Yeah, then you got to know them a little better, and, well, those first impressions changed a little bit.
The Crossed Field Antenna (CFA) sort of reminds me of my first prom date. There was a lot of promise there, but plans fell through.
From a 1999 Radio World article:
Imagine an AM antenna one–fiftieth of a wavelength long, that needs no radial ground system, occupies a small parcel of land, produces little or no RFI (Radio Frequency Interference), has great bandwidth and performs better than a full–sized vertical radiator.
This potential new antenna was all the rage during the early 00s or whatever you call that decade. I remember thinking to myself; I will believe it when I see the test results. At one point, there was a battery of tests run in the installation in Egypt and China. The test results are spotty at best, however, none of these installations performed up to expectations. While it looks like a cool idea, and it would have been great to see it succeed, it seems that sheer willpower alone will not make a particular system work outside of the laws of physics. There are a few of these still in operation out in the wild, mostly in Egypt.
8 thoughts on “Whatever happened to the CFA?”
I recall it never met the minimum efficiency requirements. Basically an outdoor dummy load.
If something seems too good to be true…
There was actually one about 80 miles east of the New York state line in Webster, MA. WGFP tore down their tower and put up a long wire along with a CFA antenna. http://licensing.fcc.gov/cgi-bin/prod/cdbs/forms/prod/getimportletter_exh.cgi?import_letter_id=33076 , is the FCC STA for the long wire and CFA.
Are all pictures of the installation. I don’t really know what is there now, it’s been a couple of years since I drove by.
(Maybe time to drive by again). All I know is the 940 signal (Long Wire) was horrible. WX1CFA ran on 1640.
I can’t be the only one who wants to roll a bowling ball in there..
Mike; I had no idea there was one of these in Webster. I wonder if it is still there?
Bob; I don’t know, ugly is a subjective term.
Chuck; perhaps it could be re-purposed as a rube goldberg type mouse trap. Lure a mouse into the bottom and start the bowling ball around the top.
Saw something like it in a 1930s movie as the frame of a fancy southern ball dress
I guess people have a right to be cynical. However, we did build a working CFA in Webster. Here is part of the report submitted by Kurt Gorman, who did a great job and supervised the construction:
Testing the CFA at a frequency of 1630 kHz has yielded a radiation efficiency of approximately 80 mV/m for 100 W input power. This corresponds to 253.0 mV/m/kW. The 253.0 mV/m/kW would be approximately equaled to a conventional monopole that was 69 feet (41.1o) tall at 1630 kHz. The CFA stands approximately 24 feet tall. The input resistance of the monopole would be less than 5 ohms as compared to the 40 – 60 ohm phased input for the CFA.
The CFA as presently adjusted is within 10% of the FCC required minimum efficiency of 282 mV/m/kW. This, in conjunction with the superior input impedance, will allow this antenna to perform well at this time for many transmitting applications. Further adjustments, which are in process, will only improve this.”
Unfortunately, we were not able to conclude the final testing. The CFA structure still stands in Webster, but all electronics have been removed. We have plans to build a new CFA at a site in southern NJ, supervised by Ted Schober, PE.
With the FCC’s emphasis on improvements in AM, we have received great support by some really supportive folks at the Commission.
Mike Fitzpatrick’s photos (above links) are terrific.