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   Home   Help Search  
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Author Topic: Trees and HF  (Read 4649 times)
M5AEO
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Posts: 339




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« on: August 28, 2010, 02:59:59 AM »

I am planning a mini-DXpediton to my sister's house in the countryside.  She has an acre of land (this is BIG in England!), but most of it is covered in trees.  My question is: is there any chance of me getting out a signal on the HF bands at all?  I was planning on using my 7mHz 1/4 wave vertical.  Will the trees have much effect at high frequencies?

Jonathan, M5AEO, London.
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AC5UP
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Posts: 4546




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« Reply #1 on: August 28, 2010, 03:48:30 AM »

Will the trees have much effect at high frequencies?

Virtually nil.
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N8CMQ
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« Reply #2 on: August 28, 2010, 05:55:47 AM »

Will the trees have much effect at high frequencies?

Virtually nil.


I agree, trees and aluminum sided houses didn't hurt my signal, and I used a ground mounted trap vertical in my back yard. I had a very large ground plane of radials under it.
My present location has trees around it as well,and I am still running the ground mounted trap vertical. Again, lots (125) radials 30 to 36 feet long. They fit in a 60 foot square quite nicely!
It is the best antenna I have tried, other than my 3 element beam on 10 meters!
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N8CMQ   Jeff Retired...
W5LZ
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Posts: 477




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« Reply #3 on: August 28, 2010, 06:45:37 AM »

Can trees have an affect on an antenna?  Sure.  In most cases that won't be much of an affect, but there will be some.  It'll probably show up primarily in that antenna's tuning.  It won't be the same as it is when at home, probably.  I doubt if it would be enough 'difference' to rule out using that antenna.  Or one hanging from a couple/few of those trees.
Having hung antennas in trees for a very long time, I've noticed that the season of the year can make a difference.  How much sap is in those trees?  A 'sappy' tree tends to be more conductive than a 'dry' one, summer/winter sort of thingy.  It hasn't been enough to not use those antennas, but it was a difference.
Do it anyway!
Paul
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K9BAY
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Posts: 144




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« Reply #4 on: August 28, 2010, 06:53:06 AM »

I have one side of my 20M dipole running almost through a pine tree.  I have been able to tune and use it on 17M, 20M and 40M.  My goal is to get it above the pine tree.  But I don't think it makes a big difference on these bands.

73, K9BAY

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W4VR
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« Reply #5 on: August 28, 2010, 10:51:29 AM »

I've been surrounded by forest for decades and never had a problem getting good reports.
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G0GQK
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« Reply #6 on: August 28, 2010, 02:03:33 PM »

A quarter wave vertical on 40 metres will work well, if you are able to use 30 metres with a tuner that will work OK as well.

G0GQK
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KO7I
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Posts: 134




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« Reply #7 on: September 06, 2010, 06:31:04 PM »

If you have a radio has an auto tuner (or you have a manual external tuner) try a little longer wire 3/8th wave to raise the input impedance of antenna and reduce the ground losses that adversely effect antenna efficency.
You will be amazed at the lower noise floor of the rural setting, very nice operating conditions.

Have Fun! 73, Don KO7i
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K2OWK
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« Reply #8 on: September 06, 2010, 09:13:06 PM »

You will have very little problem with the trees, till it rains. Then all bets are off.

73S
Barry
K2OWK
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K3YD
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Posts: 55




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« Reply #9 on: September 07, 2010, 07:56:38 AM »

Will the trees have any effect on HF?  Probably.

Will it be significant?  Probably not . . . unless the tree and antenna are in parallel contact or closely coupled, within a couple of feet.  You might notice a change in SWR on wet days in this case. 

Rather than a setting up a vertical, you might utilize the trees for supports for a dipole or loop.

Remember, any antenna is better than no antenna.   So, try it and have fun!
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VE3KKU
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Posts: 16




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« Reply #10 on: September 08, 2010, 11:11:43 AM »

Definitely! But you might get better results with a wire antenna in the trees. I have done a lot of portable operations with antennas in and around trees and have always been able to get on the air and work lots of stations. Use insulated antenna wire to reduce the effects of capacitive coupling to the trees (do you best not to let the antenna touch the trees).

Try putting up a dipole or OCF (off center fed) dipole from one tree to another - use trees on the outer bounds of the property. I use an old fishing spool, with 20 pound test, mounted on an old pitchfork with a couple of screws. This allows me to put the pitch fork in the ground at an angle I need, freeing my hands to use my slingshot (with a 1 once weight on the line). I then fire the line up and over some high branches, and wait 15-30 minutes (good time to read QST Wink) while the weight and line descend to the ground. Then attach and pull a rope back over, then attach the end of the antenna to the rope. Then repeat all of this for the other side. Takes me 30 minutes to 2 hours for each setup, but well worth it when you get on the air!

You can also buy a commercial slingshot/fishing spool combo - such as EZ Hang, but I found making my own out of spare parts just as efficient.

Good luck!
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W7ETA
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Posts: 2527




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« Reply #11 on: September 08, 2010, 02:11:25 PM »

My first 40 meter vert was a gp puled up into a pine tree.  I used an SO239, 4 radial and vert to center conductor.  I had to re-inforce the connection for the vert portion at the SO239 with duct tape coated with twin epoxy glue--it make a type of fiberglass.  There were enough trees surrounding the pine tree so that I could run the radials to small trees.  I used a step ladder to get all of the radials about 7 feet off the ground.
73
Bob
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KG6MZS
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Posts: 476




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« Reply #12 on: September 08, 2010, 02:26:17 PM »

You will have very little problem with the trees, till it rains. Then all bets are off.

Boy, did I ever find this to be true.  Now I use insulated wire and try and place my doublets in free air as much as possible.

73 de Eric, KG6MZS

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