Interesting!
I wish i would know my ERP during the 9 kHz test where i reached 2km. But the
grabber is still not calibrated :-(
Roger, when will you try 137 kHz?
73 es gl
Stefan/DK7FC
________________________________
Von: [email protected] im Auftrag von Rik Strobbe
Gesendet: Fr 18.06.2010 23:10
An: [email protected]
Betreff: LF: RE: Earth electrode loop area - I'm struggling
Hello Roger,
my pennyworth:
assuming
- 50uW ERP
- antenna is traded as a loop (gain = -0.4dBd)
Due to the negative gain (-0.4dB versus dipole) a loop antenna must "radiate"
55uW to get 50uW ERP.
Since the antenna feeding current is 0.15A the radiation resistance is 2.44
milliOhm (R= P/I^2)
The radiation resistance of a small loop is : Ra = 320xPi^4*A^2/L^4
where A = loop area (m^2) and L = wavelength (m)
For 500kHz Ra = 5*10^(-7)*A^2 or A = 1416*sqrt(Ra)
If Ra = 0.00244 Ohm then effective the loop area is 70m^2
73, Rik ON7YD - OR7T
________________________________
Van: [email protected] [[email protected]]
namens Roger Lapthorn [[email protected]]
Verzonden: vrijdag 18 juni 2010 22:29
Aan: [email protected]
Onderwerp: LF: Earth electrode loop area - I'm struggling
Please can someone help me with the maths? I've been trying to work out my
effective loop area and I cannot get sensible answers. These are the measured
or estimated numbers I have:
Voltage across "loop" = 24.48V rms - measured
Current flowing in "loop" = 0.15A - measured
ERP (from far field levels) = 50-100uW (may be less) based on -18dB S/N with
M0BMU
>From these figures I should be able to work out the loop area, but either my
>calculations are wrong or the figure is correct and the effective loop area is
>very very small.
Help!
73s
Roger G3XBM
--
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