The MININEC and NEC cores provide gain figures relative to isotropic for
any specified azimuth and zenith angle set. In NEC, the desired pattern
request is set via an RP input line or "card." The core does not know
where maximums are, but calculates avccording to input instructions.
For many type of antennas, the user knows which azimuth angle will yield
maximum gain--for example along the boom of a Yagi. so we can start with
an azimuth angle and request an elevation pattern. The software output
interface will often--depending on which program is in use--identify the
elevation angle of maximum radiation. Then we can use that data to select
that "take-off" angle and request an azimuth pattern at that elevation
angle. Or, we can choose an elevation angle of special interest to the
band and path we are most interested in and use it for the azimuth
pattern. Or, of course, both.
In some cases of using low-band wire antennas on upper HF bands, we may
not be able to predict accirately either the azimuth or the elevation
angles of maximum radiation. In these cases, we must move back and forth
between azimuth and elevation plots, refining each angle as we go until no
further increase in gain is shown for the pattern maximums. How
convenient this process is depends on the program in use.
Note that the cores use zenith angles--counting from overhead downward to
the ground--while most ham and many engineering uses call for elevation
angles--counting from the ground up. Almost all software automatically
translates zenith angles into elevation angles, but some uses zenith
angles. AO does the translation for you.
Hope this helps orient you to how the software provides its reports from
the core's calculations.
L. B. Cebik, W4RNL /\ /\ * / / / (Off)(423) 974-7215
1434 High Mesa Drive / \/ \/\ ----/\--- (Hm) (423) 938-6335
Knoxville, Tennessee /\ \ \ \ / / || / (FAX)(423) 974-3509
37938-4443 USA / \ \ \ \ || firstname.lastname@example.org
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