Topband: Antennas in trees

Tom Boucher tom at telemetry.demon.co.uk
Wed Nov 14 13:50:23 EST 2007




Andreas

Trees are not ideal antenna supports because it is not easy keeping the wire
away from branches. This autumn my inverted 'L' gradually moved it's
resonant frequency up the band by about 20 KHz as the leaves dropped off the
deciduous tree supporting it! I spent today moving the antenna away from the
tree - I've lost a little in height but see an immediate improvement in feed
impedance which has dropped significantly. I've re-adjusted the matching
network so we'll see how it performs on the long path to ZL tomorrow
morning!

 Eddy VE3CUI suggested that a lossy tree is better than a mast - not true
Eddy because the tree is resistive and any RF current induced in it will be
dissipated as I squared R heat. A metal mast on the other hand will not be
so lossy.

 73
 Tom G3OLB



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