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Author Topic: Antenna  (Read 213 times)
N8PAY
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Posts: 17




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« on: April 10, 2004, 12:01:13 PM »

On a Force 12 flagpole antenna, how do you attach multiple ground plane radials to the base? Many more than the standard 4 that come with it. Thanks Louie N8PAY
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K1CJS
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Posts: 5871




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« Reply #1 on: April 10, 2004, 12:26:29 PM »

You have to custom make the radials that attach to the points on the base the original ones do, but consider:  You're changing the design specs of the antenna as you do this--you may degrade performance more than improve it.
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N8PAY
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« Reply #2 on: April 10, 2004, 12:38:00 PM »

I realize the potential for degrading the performance, but how do you attach them to the pole at the one screw provided at the base? N8PAY Louie
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KA5N
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« Reply #3 on: April 10, 2004, 01:56:52 PM »

Well you could form a ring of heavy copper wire (at least #12) 6 or more inches in diameter and screw this to the one screw and solder the radials around on the ring. Make the connection as short as possible.  Should work.
Gud luck Allen KA5N
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N8PAY
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« Reply #4 on: April 10, 2004, 01:59:32 PM »

Thank you Allen for a great solution idea . Louie N8PAY
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K0ZN
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Posts: 1531




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« Reply #5 on: April 10, 2004, 06:15:05 PM »


Hi,

Quick comment: I am not intimately familiar with your antenna, but I can positively assure you that if that antenna is monopole (i.e. a 1/4 wave vertical), you can only improve the radiation efficiency by adding more radials. DON'T confuse SWR readings with radiation efficiency. With a poor ground radial system, the SWR will be "better" because of the higher ohmic losses (R) in the ground system yielding a feedpoint impedance nearer to the 50 ohm Z of the coax. If you put in 100 quarter wave radials (e.g. a "perfect" ground radial system), the feed point impedance will DROP to 36.5 ohms, the SWR will go UP (as the feed point Z moved away from 50 ohms) and the radiation EFFICIENCY (which is what counts) will also go UP. You can confirm this in any ARRL or other good antenna book. More radials are BETTER for a gound mounted vertical antenna. (A true ground plane, which is NOT electrically connected to ground is a little different deal). If you are limited in the length of radials you can install, more short ones are better than a few long ones because the highest current is closest to the base of the antenna. i.e. you would be better off with thirty 1/8 wave (on lowest band) radials than 15 quarter wave radials. In my experience in installing a couple of ground mounted verticals, the points of significant improvement come at 32 (about the true minimum number for "decent" performance), 64 radials will give "good" performance and 75-100, depending upon your location and soil conductivity will give "excellent" performance. Installing radials is a lot of work, but based on my experiences and what the books show, if you want to work DX, it is worth the effort. Good luck on your system!

73,  K0ZN
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