There was some recent discussion about chicken wire ground screens
vs conventional radials. What I would like to know is: how do
you measure any proposed ground screen to determine its ground losses?
You can measure the driving point impedance of a vertical antenna
and subtract 36.5 ohms to get "ground resistance". HOWEVER, it isn't
necessarily true that the impedance of your particular vertical is
36.5 ohms (that number is for a zero radius wire). Should the vertical
be a physical 1/4 wave long, or shortened to resonance? Should the
test vertical be a piece of thin magnet wire held up by a string?
Remember: if you can't measure it, you can't optimize it, as the
saying goes.
Rick Karlquist N6RK
rick@area.com
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|