Tree Signal Attenuation

[BOOTY MONSTER]

Tree Signal Attenuation

f a vertical 28 MHz antenna is surrounded by moderately thick trees that are higher than the top of the antenna signals will be attenuated 2 to 3 dB on average. Tree attenuation with horizontal polarization under the same conditions usually will be negligible. At 144 MHz the same trees will attenuate signals 6 to 12 dB on average with vertical polarization and 3 to 4 dB with horizontal polarization. However, with vertical polarization at both frequencies and with either polarization at 144 MHz there will be large strength variations with small changes in antenna position due to standing waves caused by tree reflections. ©2004 Tigertek, Inc. All rights reserved.

 

[hookedon6]

i don't think i agree with all of that.
the uhf/vhf part i tend to agree with.

the HF part is pure fabricationop:

add on: all my hf antennas are horizontal.
i just reread it and noticed this statement: " Tree attenuation with horizontal polarization under the same conditions usually will be negligible"

ok,.... i'll buy that

 

[kd-5-bgt]

I used to have a Moonraker 4 at about 40 feet,and had the thickest part of the trees at that level as well ...good old pine trees... they were sitting to the west of the antenna.... It seemed to me personally that I could not talk or hear as well to the west as I could in any other direction...Now it just could have been the terrain...I just dont really know....

All I know is that when the band (the freeband just above CB ) was open to the west,people that were close to me(with a compairable station/antenna/power) could work stations west alot better than I could....

I do know for sure that VHF/UHF is effected big time by trees,leaves.....

It makes sence to me that a HF signal would be effected as well,to what point I cant say

This should be a good debate ....

Chime in guys !! What do you all think ?

 

[W5LZ]

I guess you could say it's a sort of 'sappy' answer? Or maybe, a 'sappy' statement?
Much more literally than just what I might think about it . The amount of attenuation that trees/flora may produce is directly related to how much fluids/sap they have in them, which changes with the season mostly. How much attenuation depends on the mineral content and the frequency of use, so it's frequency dependent too. The higher the frequency the more attenuation possible/probable. Oh mercy, and it depends on where that fluid is located! As in leaves, or trunks.
There are probably a lot more thingys that affect all that attenuation, but you'll have to excuse me. I need to go get more coffee and to quit hyperventilating now. Just think of the possibilities with all that! 'Tree-hugger' antennas! Naw... just too sappy.
- 'Doc


(Geeze! And I get accused of starting 'sh**'! Booty', you are bad... )

 

[BOOTY MONSTER]

just trying to stir up conversation

 

[Lazybones1222]

Well we operate our radios despite things we can't control. Like my neighbors big a$$ oak tree. There it is. Can't cut it down. Life goes on.

 

[Wire Weasel]

There is truth in Booty's OP. Would be interesting to see the science data on this but none was provides. "Somebody saying something" doesn't equal facts or proof.

A scientific study would be very difficult and not very much repeatable as every station's yard and tree quantity and configuration ect.... would be different.

I have seen a similar situation at one of my past stations. Had a heavily wooded yard with oak trees and neighbors with trees. Had 10 element CushCraft 2 meter Cross Yagi. In winter seemed to definitely TX/RX better-further with all of the leaves down.

 

[Highlander_821]

I am surrounded by timber on 3 sides, and I definitely notice a difference on 27-28 MHZ when the leaves are up. I can still punch out a good signal, but incoming signals seem to suffer. If I had to guess, I'd say there is maybe 20 percent less signal coming in with the leaves up. Lower HF bands don't seem to suffer as much.

 

[wavrider]

Doc hit the nail on the head, as he usually does (read as having a big hammer).

Reflection, refraction, and filtration.

The sappy subject has to do with density of the organic matter that is directly in the way of the tx or rx signal.

In theory HF signals is invisible to organic material, but, ah yes always that dreaded but, that does not take into account the water content, thus the reflection comes into play.

Good old water, H2O makes one heck of a ground plane but is real pain in the a@$ to penetrate with rf, even at SLF frequencies, (read as submariner communications with mega watts and miles of wire antennas from the stateside location).

Sap in any tree, they all have it, will bend, twist, and distort an rf signal of any frequency, higher freq more affected as previously stated, this the refraction comes into play now.

In full foliage trees have leaves, that have water, that will filter incoming or outgoing rf signal.

So does trees have any effect on HF signals? Not if they are laying on the ground after someone has cut them to get a clear path for their tx/rx hf signal.

How much does it effect the signal? No study that I know of exists, but anyone that has had to deal with a "tree" can tell from experience that those darn tree's do compromise a good signal.



Booty as DOC said you are stirring it up again.