I have lost all previous contributions to this thread.
But Jimmie gave the description of his radial system -
12 12f t wires, Center ground stake 10 ft long, far end of each wire has
a
stake about 3 ft long. These are used more to just hold the wires in
place.
plus a brief description of type of soil and moisture content. I guessed at
wire diameters.
From which I deduce the following input impedances -
AT 1.9 MHz AT 7.0 MHz
---------------- ----------------
10 + j0 13 + j11 ohms.
Uncertainty = +/- 3 ohms which is adequate for the intended purpose.
The above figures have been obtained using programs ENDFEED and RADIALS2
(two different modelling methods) and averaging the results at soil
resistivities of 100 and 300 ohm metres. Programs can be downloaded in a
few seconds from website below. Calculating time no longer than needed to
enter the simple data.
In practice, only the resistances matter because the reactances are tuned
out simultaneously with the antenna, equivalent to minor readjustments of
the tuner. The resistance values, in conjunction with calculated radiation
resistance can be used to calculate radiating efficiency.
If Jimmie should ever measure input resistance with similar uncertainty (not
too difficult) then I should be pleased to hear his results.
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Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
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