The attached plot shows errors of 2.0 and 3.5 degrees on either side of the resonance of the antenna. Errors elsewhere (110 to 250 MHz) are 1.5 degrees or less. Display Bearing error vs frequency plot. Down load plot as a GIF Image. Its name is BearingE.GIF.
The test was done in the Santa Anita race track parking lot on July 23, 1982. All equipment needed to conduct the test was supplied by the FCC except for the SuperDF Antenna and Control Unit. Test method was established by the FCC, and conducted by Dan Bosque and Jim La Fontaine, both experienced field engineers. Russ Andrews, owner of BMG Engineering observed and made suggestions. The SuperDF antenna was mounted 3 to 4 feet above the center of an FCC van on a PVC pipe. The signal source was in a second FCC vehicle about 200 feet away, at 91.5° to the side of the van, with the front of the source-vehicle facing the van. The source antenna was mounted at the front of the vehicle's hood on the vehicle center line.
The peak in error occurring at resonance is explained as follows. For a system with a resonance, the plot of phase vs. frequency changes most rapidly at resonance. Because of this, a very slight difference in resonant frequency of the two dipoles will result in the maximum phase tracking error between the two dipoles at resonance.
George R. Andrews (Russ, K6BMG) BMG Engineering, Inc. 9935 Garibaldi Avenue Temple City, CA 91780, USA Voice 1(626)285-6963
Fax 1(626)285-1684 (24 hour automatic)
grandrews@aol.com
Web: http://members.aol.com/bmgenginc (1 Jun 1997)
Send E-mail to grandrews@aol.com.
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