VHFcontesting
[Top] [All Lists]

Re: [VHFcontesting] Trees, et al

To: vhfcontesting@contesting.com
Subject: Re: [VHFcontesting] Trees, et al
From: Roger Rehr W3SZ <w3sz73@gmail.com>
Date: Fri, 22 Jul 2016 14:32:07 -0400
List-post: <vhfcontesting@contesting.com">mailto:vhfcontesting@contesting.com>
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
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting

_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting

<Prev in Thread] Current Thread [Next in Thread>