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Yes Rik, theoretically the efficiency should be
independent of soil resistivity:
Loss resistance ~ resistivity,
radiation resistance ~ area ^2 ~ skin depth ^2 ~
resistivity.
In practice the situation may be different, because the
loss resistance occurs predominantly in the immediate vicinity of the
earth contacts. The return current depth depends more on the
large-scale ground properties, including deeper layers along the whole
length of the antenna. In the ELF facilities, deep well grounding was used
to minimize local current densities and potential gradients near the
ends.
Best 73,
Markus (DF6NM)
Sent: Tuesday, December 14, 2010 9:11 PM
Subject: RE: LF: BODGE ANTENNAS
In my view it does work as a loop antenna on
136 and 500kHz with the loop area being determined by the soil conductivity
(lower conductivity, bigger loop area). The very fact that it is low-Q
does suggest loss.
Hello Roger,
if
low conductivity = large loop
area (A) but small antenna current (I)
high conductivity = small loop area (A)
but large antenna current (I)
Would this result in A*I = constant
?
The radiation resistance of a loop is
proportional to the square or the loop area (A). And the ERP is proportional to
the square of the antenna current (I).
If A*I is a constant (independent or soil
conductivity) this would mean that the ERP would no depend on soil conductivity
?
73, Rik ON7YD -
OR7T
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