[TowerTalk] Is "The Truth about Trees and Antenna Gain" the whole truth?

[Shawn Donley]

I believe the article certainly is accurate with respect to trends.  The NEC tree models track well with the infinite lossy cylinder closed form solution, which is a good double check.


But the real world, at least the one around my QTH, doesn't have a single tree to consider but a forest of trees.   One of my wire antennas is a full wave loop in a vertical plane fed from a lower corner with ladder line.   The top and bottom runs are 100 feet and the vertical sections are 40 ft.  The top is about at 65 feet.   Running EZNEC, I saw that I could get a lower takeoff angle on 40M if I fed the middle of one of the vertical sides.  But then the polarization is primarily vertical, and those trees (hardwoods) are about 15 ft away.   I may try it anyway just to see if I can notice any difference.


For the Yagi-in-the-trees, I have that situation too.   My Optibeam OB9-5 is at 70 ft but the trees are 80-100 ft high.  I have 20+ feet clearance to the nearest branch, but some of those branches approach a horizontal orientation coming off the trunk.  So like the vertical wire near the tree trunk, I suspect there may be some tree losses.


This is interesting stuff and not easy at all to model completely.   Another reference for measurements is at


http://nvlpubs.nist.gov/nistpubs/jres/68D/jresv68Dn8p903_A1b.pdf


But the measurements were in a jungle environment (most of this stuff was back in the Vietnam days).


And how about reversing the whole problem.   Here's one article on using a tree AS the antenna. 


http://dtic.mil/dtic/tr/fulltext/u2/742230.pdf


And even an old patent:


http://www.rexresearch.com/squier/squier.htm




There's even an old patent