"Richard Harrison" wrote
Mark wrote:
"Is this practical?"

Trees near an antenna cause some loss. It`s hard to quantify in advance,
but in ww-2, the signal corps estimated that hf loss is usually
negligible if horizontal polarization is used (page 241 of 'electrical
communications engineering').

I`ve found that horizontal HF dipoles, directly fed by coax in various
Bolivian Chaco Jungle sites, below the the tree canopy, but not too
close to the trees, communicated well with Cochabamba and La Paz,
Bolivia. So, the dipoles didn`t suffer too much from the trees. The
Signal Corps was right.

Best regards, Richard Harrison, KB5WZI


Hi Richard, it's not easy to compare your rainforest canopy to loblolly
pines, but at approximately 50' my dipole is well below the pine canopy, and
well surrounded by them. If there is an impact from the pine trees it would
be hard to quantify since the dipole exceeds everyone's expectations for
short and long range performance. We have heard comments that pine-fron
clusters when wet, affect a near field, but that has not been our
experience. Neither does snow, ice or winds. Overall, there appears to be no
effect on the antenna being in fairly close proximity to many tall trees,
and suspended from them.

Best regards,

Jack

Jack Painter wrote:
"Overall, there appears to be no effect on the antenna being in fairly
close proximity to many tall trees, and suspended from them."

That was the Signal Corps conclusion for horizontal polarization at HF.
For vertical polarization, surrounding trees are better energy
absorbers. At VHF and UHF, absorption gets worse and worse as frequency
goes up. Too much foliage is impenetrable at VHF and UHF, regardless of
polarization, humidity, ice, snow and wind.

The Signal Corps advises trying horizontal HF antennas among the trees
to avoid detection by the enemy.

Best regards, Richard Harrison, KB5WZI