I remember reading, somewhere on the net, a US Army contractor paper on
the subject of using trees as radiators, by using such a solenoid to
couple RF to the trunk. IIRC this was for special ops in the triple
canopy forests of Indochina. The paper might have some measured data on
absorption.
73, Pete N4ZR
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On 11/3/2009 11:36 AM, Ward Silver wrote:
> I suggest the following tests to be done by someone else than me...any of
> which could give us some anecdotal evidence about trees and RF, at least.
>
> Wind a several-turn solenoidal coil with a diameter large enough for a
> section of tree to be inserted. Measure the inductance and the Q with and
> without the branch inserted. Significant changes in the L or Q (at RF) would
> indicate interaction between tree and field.
>
> Make a vertical dipole and suspend the top from a pulley that can move along
> a non-conductive catenary (i.e. - a rope) between two trees at least one-half
> wavelength apart. Measure the resonant frequency and SWR bandwidth of the
> dipole when suspended in the middle of the catenary. Move the dipole closer
> to the tree in steps of about 0.1 wavelength, repeating the resonant
> frequency and SWR bandwidth measurements at each step. Significant shifts in
> either resonant frequency or increases in the SWR bandwidth indicate
> interaction between tree and field.
>
> Have at it - that would make a nice QST or QEX article!
>
> 73, Ward N0AX
> _______________________________________________
> 160 meters is a serious band, it should be treated with respect. - TF4M
>
>
_______________________________________________
160 meters is a serious band, it should be treated with respect. - TF4M
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