Hi Mal and Group.
On Fri, 15 Nov 2002, hamilton mal wrote:
and have found the vertical a lot better and easier to tame, easy to match
using a series inductor and tuned against an insulated ground radial
system to match 50 ohms, and manageable RF current to get up to 1W erp
radiated power. To try doing the same with a vertical loop at the same
height would require 50 + amps RF and I would not even consider this
approach at this power level.
I do not see any unsolvable problem with 50 or 100 amps in a loop. It is
usial RF curent in transistor TX of power of few kW. But surely one should
put some attention to conections and use large diameter wires at this
curent level.
Besides one can use ferrite transformer to convert large
curent input to less curent input and THEN compensate iductance. It will
requre not so large C of variabale capacitor to tune. My recieving small
loop is done in such a way :-) Certanly in transmiting loop one should
use large ferrite core to build such a transformer.
If Rac of a transmiting loop is about 0.5 Ohm (Bill's example) then
one should use 1:10 transformer to get 50 Ohm. Curent will change from
50 A to 5 A only. Or use 10 turns loop - it give the same.
Sure in free field vertical is better and more easy to build. But it may
be some special case when loop is better.
73 de RA9MB/Alex
http://www.qsl.net/ra9mb
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