Hello Jim & group,
G3NYK (6m high, 30m long inv. L): Rloss = 4733/f^0.86 (for points
below 600kHz only)
M0BMU(8m high, 40m long inv. L): Rloss = 1550/f^0.75
ZL2CA(Don't know, but must be quite big!): Rloss = 142/f^0.50
While doing research for my LF antenna webpage I came across a formula the
gave the pentration depth of an Efield in the soil as :
D = 509/(S^0.5*F^0.5)
where D = depth in m, S = soil conductiviy in S/m and F = frequency in Hz
Assuming the the ground loss is proportional to the distance 'traveled'
through the soil the results of Bob (ZL2CA) seemed really a textbook case
compared to the measurements of Jim (MBMU) and Alan (G3NYK), so I wonder if
the 2 last do suffer more from additional losses (buildings and greenery
close to the antenna) compared to Bob ?
BTW : The emperical equations are a bit dependent on the frequency range
you take. For Jim's measurements I get R = 1555*F^0.75 for the whole range
but then I took only the points between 100 and 300 kHz (to have the same
range as Bob) and got R = 1830*F^0.79.
73, Rik ON7YD
