NEC-LIST: Four Elevated Radials with NEC-3

Merv:

I believe that Al Christman, then of Ohio University, and Jim Breakall
of Penn State University, used NEC-3 to address the case you asked
about. I believe they published something on this in the IEEE Trans.
Broadcasting a few years ago. At least they were planning to do so.
As I recall, their conclusion was that 4 elevated radials, properly
done, were equivalent to the 120 radials required by the FCC for all
MW (AM band) broadcast stations. NEC-3 has been used by Mel Weiner,
when at MITRE (Bedford) to show that 120 radials are the equivalent to
perfect ground as far as impedance is concerned. This confirmed with
NEC-3 the result from the 1920s or 30s (Brown or Carter?) that led to
the current FCC requirement. Dick Adler, if on the net while TDY, may
recall more on this. Also, he may have Breakall and Christman's
current email addresses. I assume they are on nec-list and may be able
to respond to you directly.

George H. Hagn

P.S. I tried the 4 elevated radials in Alaska at HF, in 1989, and
didnt get the total improvement. That led me to conclude that you have
to take care in how the elevated radials are implemented (e.g., for
ham use at HF). The taper up from the ground, and the height above
ground and the radial length (for a given ham band) all need to be
considered. My measured check was for the 4 radials on the tundra and
then the same 4 radials elevated about 6 ft. The monopole was a 30-ft
monopole of 1-inch copper tubing, except the top part was 3/4-inch. I
had intended to model it myself when I got home from that TDY , but I
got spinal meningitis (which almost cost me my life!) and never got
back to it. So let me know what you find out. Thanks. Geo.
Received on Thu Jun 25 1998 - 10:05:46 EDT