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Author Topic: vertical ground radials  (Read 764 times)
AI4WX
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Posts: 26




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« on: March 05, 2013, 12:19:38 AM »

i just finished building a mobile vertical bugcatcher design antenna to cover 6-20m. I have been reading about rf grounding the antenna and i'm more confused then ever. I have the antenna mounted on top of a camera tripod stand that i modified, and the so239 fitting is beside the antenna. From the so239, i soldered solid wire from it that leads to the bottom loading coil. The antenna itself sits on a metal bracket. How many radials do i need and what length do they need to be??
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K2DC
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« Reply #1 on: March 05, 2013, 03:04:20 AM »

The radials will be layed out on the ground, so they don't need to be resonant.  The number an length is up to you.  What you've built is a poor-man's copy of the Alpha Delta Outpost tripod (no longer available) which was very heavy and pretty expensive.  I did something similar with lightweight aluminum angle stock from a big-box HW store.  The radials were basically more angle stock that folded out from each leg, so I had 3 radials about 3-1/2' long.  My hamsticks matched better on the tripod than they did on the car, and seemed to work very well.  I suppose performance might have been a touch better with more and longer radials, but there's a hard limit to how much you can expect from such a small antenna.  Your mileage may vary.

73,

Don, K2Dc
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KB4QAA
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Posts: 2407




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« Reply #2 on: March 05, 2013, 07:34:19 AM »

Reminder:  radials need to attach as close as possible to the antenna base/feed point. 

-You can work contacts without radials.
-Any radials you add will improve performance
-Any length is better than none

-Radials close or in contact with the ground will be detuned so precise length/resonance is not critical
-Still radials about 1/4wl long at the lowest frequency would be great
-Personally, I think 8 radials are the level of effort I want to put into setting up a portable operation.  You may have different ideas.  This number should do a good job of providing a stable impedance and ground plane, in my opinion.

http://www.antennasbyn6lf.com/
Rudy N6LF has done some wonderful and easily readable work on vertical ground planes.  bill
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