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Author Topic: Beams and trees  (Read 1046 times)
VE4BLB
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Posts: 31




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« on: July 03, 2011, 09:24:54 AM »

I am doing research on local restrictions for a tower in my yard and have the following facts and a question.
 Facts are,  I am limited to 48 feet of tower but have trees 75 feet high on the East side of my lot and 3 story appartments on the North side. Am I going to benefit over my Cushcraft R8 vertical or am I just asking for trouble?
73 de me BLB
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73 de me BLB
N1UK
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Posts: 1436




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« Reply #1 on: July 03, 2011, 01:15:37 PM »

What type of trees are they? I think pine trees are pretty invisible to RF. Deciduous trees may have some effect in the summer. If it was me, I would go ahead and put up your tower. I am sure that it will work very well for you.

Mark N1UK
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KI4SDY
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Posts: 1452




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« Reply #2 on: July 03, 2011, 03:07:50 PM »

The effect of the trees at low frequency are going to be minimal, the apartments are different, but it sounds like the 48 feet will get you over them. A crank up tower that will get you to 60 feet (when no one is looking) would be ideal!  Wink
« Last Edit: July 03, 2011, 07:41:08 PM by KI4SDY » Logged
MM0KTC
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Posts: 5




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« Reply #3 on: July 04, 2011, 04:36:32 AM »

i have a similar situation in Scotland. the trees around me are approx 19m high. planning permission only allows me to go the 17m, when in use, i have to retracxt the antenna when not.
the solution, after dark, raise the tower t the full 22.25m it will go to, and i am over the problem. as we live in the country side, somehow, i do not think people would mind or notice.
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W4VR
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« Reply #4 on: July 04, 2011, 01:26:48 PM »

Trees would have minimal effect on your radiated signal at HF.  The building, however, is a different matter....depends how far away the 3 story building is from your tower and whether the construction is wood or steel.  Metal objects such as steel beams can act as antennas by inductively receiving and then "re-radiating" some of the energy in the radiative near field (Fresnel region), forming a new radiating surface.  At best, if the building is in the far field (2 or more wavelength from your tower...140 feet on 20 meters) then you should be OK.
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VE3FMC
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Posts: 987


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« Reply #5 on: July 04, 2011, 03:39:49 PM »

I am doing research on local restrictions for a tower in my yard and have the following facts and a question.
 Facts are,  I am limited to 48 feet of tower but have trees 75 feet high on the East side of my lot and 3 story appartments on the North side. Am I going to benefit over my Cushcraft R8 vertical or am I just asking for trouble?
73 de me BLB

My 80 and 40 meter dipoles run right through a red maple tree at the present time. Have for years. Insulated wire, and at one point it touches a branch or two.

Put the tower up and mount that yagi up there!
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KB4MB
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Posts: 295




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« Reply #6 on: July 04, 2011, 03:41:29 PM »

My tower is nestled right in between two trees.  30ft tower, 60ft trees.  I don't think the pattern is skewed much, if at all, and it certainly is worth the time over a vertical. 

Don't worry about it, it will work Smiley
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W8JX
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Posts: 5765




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« Reply #7 on: July 04, 2011, 06:15:11 PM »

A 20 meter beam at 30 or 40 feet it going to be radiating well above horizon/zero angle so it will likely not even really see trees anyway unless they are right next to it. Angle of radiation on average gets lower the higher the beam is located above ground.
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