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"Bill Turner" wrote in message ... On Fri, 26 Nov 2004 10:14:46 -0500, James wrote: I'm trying to decide whether I need to improve my antenna ground by adding a dynaplate (costly and requies the boat to be taken from the water for installation) or whether the range I am getting is decent. __________________________________________________ _______ I'd say your system is working pretty well. 50 feet is too long for a 20 meter antenna, however. Your auto tuner is correcting for it, but a shorter length will actually work better, since the auto tuner won't have to introduce as much correction and therefore will have lower loss in the tuner itself. The vertical part of a ground plane antenna (which is what you have) can be determined by the formula Feet=234/Freq, or for 14.3 MHz, 16.4 feet (rounded off). The exact footage depends on variables in the immediate environment, but that should be close enough. If you have to have a 50 foot overall wire because of the height of the boat's mast, just put an egg insulator at the 16.4 foot length to break it up. For multiple bands, figure the length of each section and put egg insulators where needed, and then to change bands, just connect a jumper wire across various eggs to get the correct length. Neat, huh? :-) Exactly what I was going to suggest. This will be easy to do if you have a pully on the top end so you can easily drop the wire to change the shorting straps. With the 50 foot wire, I would be concerned about getting high angle radiation on 10/15/20 metters. Dog bone insulators might put less capacitive loading on the top of the disconnected section. Tam/WB2TT Also, you can't have too much ground area, within reason. More aluminum foil or copper is always better. If you have access to an SWR analyzer such as the MFJ 259, so much the better. They are highly recommended for making and troubleshooting antennas. -- 73, Bill W6WRT |
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