[BC] RF absorption by foliage

[Alan Alsobrook]

I have an AM Combo here in Florida that had allowed pine trees to grow 
in the near field of the tower. Our plan was to remove the trees and 
replace the ground system. Money being tight this plan has stretched 
out.  In the mean time I was building a new FM site (with a new tower) 
nearby .8 miles. I asked the owner of the AM to hold up on any work 
until I had completed the FM, which required before and after 
measurements of the AM's. Despite my asking, the AM owner got a "great 
trade" on the land clearing shortly after I had made the before 
measurements. When I made the after measurements both of the AM's showed 
a 20% increase in field in all directions. That was with NO ground 
system left and we didn't even get 1/4 wave cleared. So I have no doubt 
that pine trees suck up signal like a sponge.  The money still isn't 
available to put in the new ground system and I know for sure after the 
root rake went through there's nothing left of the old one which was 
known to be in poor shape.

Barry Mishkind wrote:
> There was a station in Denver that the consultant swore was affected by 
> a line of trees less than a mile away. When the trees were in full 
> bloom, the pattern went "out" ... and when they dried up, the pattern 
> "settled."
> 
> I personally was not able to measure the array, although I did discover 
> some other issues ... including a tower that was not in line with the 
> others (it was supposed to be in line!).
> 
> However, if it were merely conductivity, it would seem that the pattern 
> would have "grown" or shrunk proportionally....
> 
> At 06:57 PM 10/29/2005, Robert Meuser wrote
>> I have seen similar reports but based on season changes in ground 
>> conductivity. There was an extensive paper in BME back in the late 
>> 60s. I still discount trees.

>> Jerry Mathis wrote:
>>> I've heard much to the contrary over the years. It started with a 
>>> consultant who did field strength measurements based on the seasons 
>>> and what results were desired (low or high readings). Seems like I've 
>>> read, although I can't quote it at this time, that trees, especially 
>>> close in, absorbed a significant amount of an AM signal.

-- 
Alan Alsobrook CSRE AMD CBNT
St. Augustine Fl. 32086 904-829-8885
aalso at Bellsouth.net