Dear J,
On Wed, 12 Jan 2005, J. Allen wrote:
Since optimum Q in an inductor with solid wire requires an air space between
adjacent conductors equal to conductor diameter, would it make sense to wind
a coil with two varnished conductors in parallel and have the conductors in
tight contact? The idea of parallel conductors is to lower the Q, space the
conductors, and make winding the coil easier.
Though it is a good idea.
I need to know is simply how big the elevated counterpoise should be in
meters to be effective but I do not understand how to extrapolate the
diameter of and effective counterpois in meters (its size) from the graphs.
Please explain use of the graphs for me.
This figure us usefull to unerstend qualatively only dependance on
conterpoise high. Also it is posible QUALATIVELY see how losses is
chanded if conterpose is elevated or burred. This graph is
for T or L antenna 20 m high with all wires radius 1 mm when conterpoise
is equal to top load. Besides top load (and conterpoise length) should
be much more then vertical wire length. Only for such a simple antenna
geometry it is posible to derive analiticaly some formulas for ground loss
resistance. Ro is some resistance depending on conterpoise lenght an soil
conductivity. Formulas used to draw this figure was derived by me few
years ago. Unfortunely I have forgot where is my writings with this
formulas. Somewere they are but it is dificult to find them in my 'pile
up' of different papers:-) I'll try to find. Also this formulas may be
posible to find in archive of this list.
But any way You can estimate ground loss for REAL antenna geometry if
conterpoise is elevated. One should use a NEC-2 (EZNEC-2) with
Sommerfeld-Norton ground description. Unfortunely this can not be done for
burred conterpoise. Burred conterpoise require NEC-4. ELNEC (NEC-1) is not
usefull to estimate ground loss at all.
73 de RA9MB/Alex
http://www.qsl.net/ra9mb
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