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Author Topic: Trees & 6 and 2 Meter Antennas  (Read 535 times)
K1CJS
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Posts: 6055




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« on: July 06, 2004, 11:50:13 AM »

Just my .02, I have an antenna mounted as high as I can right now, and its surrounded by trees and buildings.  The buildings are older construction to boot.  (Metal lathe covered by plaster)

The antenna is a simple 1/4 wave ground plane.  I routinely talk to stations 25-35 miles away using about 10 watts of power with no problem.  

How often do you have a marginal signal, move the antenna a couple of feet, and find you now have that same signal as a S-9+!

As it was said earlier, get the antenna in what you think is the highest, clearest place you can with the resources you have and go at it.  You won't be dissapointed.  
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WB2WIK
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« Reply #1 on: July 06, 2004, 11:39:34 AM »

It depends a lot upon:

-How close the trees are to your antennas, and...

-What kind of trees they are.

If the trees lose their foliage in winter and the weather is dry, their impact on VHF signals can nearly disappear.  On the other hand, when they're fully foliated and the weather is wet, foliage can be an excellent attenuator to VHF signals.

But, it still depends a lot upon "how close."  If the trees are a couple of hundred feet away from your antennas, I wouldn't worry much about it.  If they're very close, however, your system performance is almost guaranteed to be negatively impacted, and possibly very badly impacted.

The only real-life experience I can relate, where I could "change" things and notice the difference, was when I lived at the Jersey shore and had a crank-up tower loaded with VHF-UHF beams, as well as a yard full of 50-60 foot tall trees, pretty close by.

When I brought the tower down so that my two meter beams were below tree level, I couldn't even hear a beacon in Rochester, NY (325 miles away) at all, ever.  With the same beams "up" at the tower's fully telescoped level and above the tree tops, that same beacon was S9, nearly always -- and I could make this change occur in about three minutes, by cranking the tower up or down.  The most abrupt change occurred the moment the beams cleared the trees -- and this difference, which was several "S" units, occurred with less than five feet change in antenna elevation.

Once you've seen such a dramatic change first-hand, you'll strive from that point forward to get your VHF antennas above the trees!  Or, at least I certainly have.

WB2WIK/6


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AA4PB
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Posts: 12989




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« Reply #2 on: July 06, 2004, 09:34:56 AM »

Yes, the trees will attenuate the signals quite a bit. That doesn't necessarily mean that you won't hear anything at all however. It depends on the strength of the signal.
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W3ULS
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Posts: 69




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« Reply #3 on: July 06, 2004, 09:20:00 AM »

I have two Carolina Windom antennas strung from trees around the periphery of my lot. They work well enough on 80-10 meters even though their maximum height is about 50' and the surrounding trees are at least another 25' or so in height.

Question: if I want to hear anything on 6 and 2 meters do I need to have antennas mounted on a tower that reaches above the tree height? (I'm assuming horizontal polarization.) Put another way, if I were to use a 12' mast attached to the back deck, will the trees that surround my house block/absorb most of the VHF signals?

73,
John, W3ULS
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AB0UK
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Posts: 74




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« Reply #4 on: July 06, 2004, 10:29:34 AM »

Hi,

There most likely is some attenuation.  However, I have a 2m/70cm j-pole between a jack pine and the house (~4 feet apart) and it does well.  I run a 2m simplex net once a week.  I also have a GAP Titan in a grove of aspen trees on the back of the lot and it performs about as a vertical would.

Try it you will probably not notice the difference.  Microwave frequencies are another story.

Jim,  AB0UK
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W7DJM
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Posts: 1




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« Reply #5 on: July 06, 2004, 10:33:14 AM »

Well, trees or no trees, some sort of 2m antenna, fed with high quality coax, up high "in the trees" is better than some rubber duck/ magmount lashup in the basement/attic, etc.

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AA4PB
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Posts: 12989




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« Reply #6 on: July 06, 2004, 10:47:31 AM »

In addition to the trees, 12-foot off the typical house deck is not going to be a killer antenna for 6M and 2M SSB work unless you are located on the top of a mountain somewhere. The higher you can get the antenna, the better and a tower is definately worth while if you can manage it. I'd definately say you will notice the difference.

On the other hand, you have to work with what you have available so the antenna on the deck is better than nothing if nothing is the only other option :-)

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W3ULS
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Posts: 69




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« Reply #7 on: July 07, 2004, 08:08:43 PM »

Thanks for the replies. My lot is surrounded by locust, poplar, sweet gum and pines, so there is a lot of open space in the winter.

It also appears the lot is not large enough to accomodate a tall tower, given the proximity of a power line (which is VERY quiet, I might add). So unless I move, it would appear that 6 and 2 meters will be adjuncts to HF at best.

Thanks again and 73,
John, W3ULS
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