"Reg Edwards" wrote in message
...
Radials Continued.

Perhaps some kind person who has been able to afford the latest issue
of NEC4 could calculate the radiating efficiency of a typical vertical
antenna of height 9 metres (29.5 feet) and diameter 50mm (2 inches) -

- when fed against a ground system of 50 uniformly distributed radial
wires, each 1.64mm in diameter (14 AWG) buried to a depth of 25mm (1
inch), of length 10 metres -

- in soil of typical resistivity = 150 ohm-metres and permittivity =
16.

But first I should like to ask, can NEC4 complete such a calculation
without human intervention or assistance? If yes then please
continue, perhaps keeping a record of the time involved.

Using program RADIAL_3 the answer is - Radiating Efficiency = 86.0
percent.

If several of you participate, perhaps using different tools, it would
be interesting to compare results. By all means, join in!

Thank you for your assistance.
----
Reg, G4FGQ.

Reg, I made some changes to the antenna, but should not effect
the result too much. The maximum number of junctions without
a workaround is 36, so I reduced the number of radials to 36.
Ok, I know that give 37 junctions, but doubt it will effect the
result. I changed the vertical diameter to #14, since I
had a warning with the 25 mm diameter. Again there are
workarounds, but I did not want to spend all day figuring
out segmentation and length tapering.

You did not specify the frequency, but assume from the
dimensions it is 7 MHz. I used 7.000 MHz. The input impedance is
27.33 - j 109 ohms. Since I am only learning how to use the program
I don't know if NEC can provide the total radiated power. I
computed the total radiated power by summing power density over a
hemispherical region. For 100 W input I get a total radiated power
of 30.5 W. It took me 90 minutes.

Regards,

Frank