Antenna Mistakes...

[Robb]

I sometimes read that some guys will mount their antennas in trees - along side of the trunk. Like a Antron A 99 - for example. Sure, you can mount an antenna at the top of the tree - but not so close to any object. The antenna needs to be clear of the tree - and above it. Th radials can be touching. The best way to do this is to put the antenna on a 10 ft steel mast and mount the mast to the trunk. The entire antenna needs to clear of anything close by as well! I'm not saying that it won't work the other way - but performance has been greatly diminished. Since the antenna is the most important part of the radio system - maximize it's capability all you can.

Another one is too keep in mind that nearby objects within one full wavelength will also affect antenna performance.
Give it a free space - 36 ft in all directions if possible.
The more free space - the better the performance.
Does it have a chance to make its first ground bounce without being absorbed?

I'm sure others know of antenna compromising installation problems.
What have YOU learned lately?

 

[neubauej]

When building a dipole, both radials need to not only be the same length, but the same diamater and material. Not doing so makes for an awfuly ugly match...

Found this one out the hard way.

I forgot to think.

 

[hookedon6]

When building a dipole, both radials need to not only be the same length, but the same diamater and material. Not doing so makes for an awfuly ugly match...

Found this one out the hard way.

I forgot to think.

my OCF antenna works very well

btw: it has been my experience that anything green (trees, anything that is growing) really doesn't have much (if any) effect @ hf.

 

[wavrider]

In theory trees are invisible to RF, but take into account that there is water with minerals in the water that feeds the tree, moisture in the leaves and wood.

Reflection, Refraction, and Filtration, will effect a signal, antennas mounted in trees will do all of the above mentioned. Just like Rob mentioned. You may not see an impact on VSWR but performance will lack.

Get it out the top, in the clear and it will have an omni direction pattern.

 

[Captain Kilowatt]

my OCF antenna works very well

btw: it has been my experience that anything green (trees, anything that is growing) really doesn't have much (if any) effect @ hf.

True on both accounts.OFC's, or Off Center Fed antennas work quite well despite not being of equal length either side of the feedpoint. Vegetation,or foliage, has very little affect on HF and only the high end of HF at that. It is barely noticeable on 6m but does become quite noticeable on VHF and on UHF it can be quite dramatic.

 

[towerdog]

I hang antennas every day off the side of STEEL towers, the wost it does is block and reflect the signal a bit in the direction of the tower, and I had a tree dipole for 11m when I was a kid and know the advantages of having your antenna 60 feet up in a tree outweigh the disadvantages. unless you have a tower in your back yard or live atop a mountain, you cant tell me a tree is a bad place to have an antenna. A tree is not much of a conductor anyway, thou it can (especially pine tree) a capacitor, but thats not a problem till you get into microwave frequencies like sattelite or commercial wireless internet service (WISP) but then that from a tree being in the way between your antenna and theirs.

I sometimes read that some guys will mount their antennas in trees - along side of the trunk. Like a Antron A 99 - for example. Sure, you can mount an antenna at the top of the tree - but not so close to any object. The antenna needs to be clear of the tree - and above it. Th radials can be touching. The best way to do this is to put the antenna on a 10 ft steel mast and mount the mast to the trunk. The entire antenna needs to clear of anything close by as well! I'm not saying that it won't work the other way - but performance has been greatly diminished. Since the antenna is the most important part of the radio system - maximize it's capability all you can.

Another one is too keep in mind that nearby objects within one full wavelength will also affect antenna performance.
Give it a free space - 36 ft in all directions if possible.
The more free space - the better the performance.
Does it have a chance to make its first ground bounce without being absorbed?

I'm sure others know of antenna compromising installation problems.
What have YOU learned lately?

 

[towerdog]

I got a project I am working on, an array of antennas to put up a tree, I want to have a dual 5/8 colinear for 2m on top and under it and I am thinking a j-pole for my CB setup, and I have a nice tree hanging off the side of the hill with the bottom of it 60 feet above the house making the top branches 140 feet up. I made a neat little line launcher out a crossbow pistol for the job and use fishing line to pull up 550lb "para-cord" with antennas attached. That solves what I always thought the problem of a tree install was, getting it up there.

 

[Robb]

I think you missed my point. My point is that it is best to maximize the antenna - not allow for compromises. Give it some free space if you can. If you can't; then expect some compromise in performance. Sure put it up in a tree; but do so in a way the is BEST. Since the antenna is the most important part of any system - do it in a way that you won't have to do a second time. My mistake for not making myself clear...

 

[towerdog]

do it in a way that you won't have to do a second time

you got that right, especially in my line of work.

 

[HiDef]

I got a project I am working on, an array of antennas to put up a tree, I want to have a dual 5/8 colinear for 2m on top and under it and I am thinking a j-pole for my CB setup, and I have a nice tree hanging off the side of the hill with the bottom of it 60 feet above the house making the top branches 140 feet up. I made a neat little line launcher out a crossbow pistol for the job and use fishing line to pull up 550lb "para-cord" with antennas attached. That solves what I always thought the problem of a tree install was, getting it up there.

Good stuff but a J pole is a waste of material on CB. The first 1/4 wave of metal is just a match which doesn't radiate much. OK on 2 meters though.

 

[towerdog]

i'll read up more, i might just go with a dipole or one of the variations of, or a 5/8 wave but the ground plane would be kinda a vunerability in a tree, maybe i put the plane inside something that flex back but i am too tired to think of something that flex, I seen a couple of neat designs on the net and in my ARRL antenna book but they involve mess drooping from strings and it not be long before a branch falls or a squirell jumps on it and it break.

 

[CDX-007]

i'll read up more, i might just go with a dipole or one of the variations of, or a 5/8 wave but the ground plane would be kinda a vunerability in a tree, maybe i put the plane inside something that flex back but i am too tired to think of something that flex, I seen a couple of neat designs on the net and in my ARRL antenna book but they involve mess drooping from strings and it not be long before a branch falls or a squirell jumps on it and it break.

A 5/8 would be one of the best, IMO, to have in a tree if you can't quite get the bottom above the tree since it's current maximum is ~13.5' above the radials.