To All from PA0SE
Rik, ON7YD wrote:
The radiation resistance of a multiturn loop is :
Rs = 31200 x (n x F / L^2)^2
where Rs = radiation resistance, n = number of turns, F = loop area, L =
wavelength.
For my loadingcoil n = 120 and F = 0.04m^2, so at a wavelength of 2200m
the
radiation resistance will be about 30 nano-Ohm. Estimated radiation
resistance of my inverted-L antenna is about 40 milli-Ohm.
Shielding the coil (done properly - avoiding short circuit turns) would
make my signal 0.000003dB weaker.
I am not shure whether this calculation is applicable to a loading coil. The
coil in a mobile antenna for the HF bands is considered to radiate as a
linear conductor with a length equal to the length of the coil. I think this
could also be the case for a loading coil at LF. So if the coil is 1 metre
long (high) with its axis vertical it acts as a 1 m long vertical antenna
and when at the bottom of a vertical antenna it makes the radiator 1 m
longer.
73, Dick, PA0SE
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