
01-27-2009, 06:29 AM
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| Senior Member | | Join Date: Jan 2009 Location: Coulterville Illinois about 40 miles southeast of St.Louis Mo.
Posts: 181
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Quote:
Originally Posted by Marconi Ron, all vertical antennas are adversly affected by the earth and it can really be significant if the voltage end of the antenna is close to just about anything. Much power to a vertical dipole only 2-3 feet above the earth will show heavy losses as heat in the soil. Horizontal polarization is much better in this regard, but it too likes to work high above the soil. The fact that the top of the dipole is above the tree top is of little importance, the bottom is the issue and it may show as much current flowing as does the top. The height and vertical polarization you mention are not serving you well. Your dipole will work, but you may not compare well with other stations nearby and other vertical antennas manufactured for CB that are mounted well in the clear.
You need the bottom to be maybe 10'-20' high for minimal results with a vertical dipole and that makes all the other requirements for location more difficult. A center fed dipole needs the feedline to exit the antenna perpendicular to the plane of the antenna for some considerable distance in order to avoid the worst kind of pattern distortions and that is straight up. Of course the tree and the shed are effecting you pattern in the worst way. If you have to work your vertical near the ground at your location, it is even more important that you be in the clear for at least a wavelength or more in all other directions.
It appears to me that you may be doing you antenna building and comparison work in the worst conditions possible. | I will have to move the antenna. I'm just right now testing the swr and trying to see if I have done a good job. I'm always trying to figure out where I can put this antenna. I've got a lot of trees and stuff around, my hope is that this tree I'm using is just a trunk that is approximatley 10 foot tall and want to attach antenna to the top which is higher than the shed. I'm just worried cause the wood dowel I use is a hardwood but it breaks easily. So I'm trying to get something I can use to connect the two sections that is strong enough to handle the weight |