You paid for it, so you might as well get to read it:
http://www.dtic.mil/dtic/tr/fulltext/u2/a118343.pdf
73,
Roger Rehr W3SZ
On 7/22/16 1:35 PM, STEVE NOTEBOOK wrote:
Tree attenuation has been studied quite a bit. I am on vaca but I do
have an old 2way radio paper on this from Motorola which is great with
simple answers and examples.
The main factor is the type of vegetation and how much water they will
hold. At high frequencies the leaves can become quarter or half way
reflectors.
Pine trees probably are the worse offender for absorbing RF as Steve
mentioned. Google tree attenuation to see some engineering studies
that are hard to make sense of
unless you are and Engineer.
Steve, you are correct about Cellular RF seasonal adjustments.
Cellular has come a long way since I retired in 2001 as a Cell Engineer.
They not only adjust power but the antennas have electrical beam tilt.
I happen to own a cell site and a couple of weeks ago AT&T changed out
the 3 band panel antennas to 4 band both fed with fiber optics and
powered by top mounted amps. The new panel antennas can weigh as much
as 180lbs.
The frequencies AT&T are using range from 700mhz to over 2ghz. The
cell tower is 150' away from my ham towers and you can imagine the
amount of filtering
I have. Cell technology is difficult to keep up with AT&T going from
Analog, TDMA, GSM and now LTE. It is so great we got to keep a portion
of the 47ghz band with the Cell companies
attempting to take OUR UHF frequencies, so lets use them to save our
bands.
Thanks for listening.
Steve K1IIG
Yes, trees make a difference. Especially at higher freqs. I have pine
trees on a couple of sides of my QTH that are over 100'. Getting through
them on 902 is tough, nearly impossible on 1.2 and 2.3. I'm sure they
will affect the rest of the bands too although it might not be as
severe. Regarding a tower, you got good advice regarding Rohn 45 vs.
25. Sturdier and MUCH easier to climb I am told. :))) Cellular
engineers typically adjust power and coverage from winter to summer as
leaves come and go so this validates the issue with trees soaking up
RF. I understand pine trees are especially bad for some reason.
Steve, N4JQQ, EM55bd
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