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Author Topic: Can ground radials be used while stationary?  (Read 1283 times)
KD5AIU
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Posts: 12




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« on: August 08, 2008, 11:06:29 AM »

I'm trying to get the mobile bug going and have read a
lot about antenna installation.  

The easiest for me would be a hitch mount but that's one
of the worst locations for ground under the antenna.

Would adding radials around the vehicle be of much help
if one were operating stationary?  

Would they need to be connected at the antenna base or could they be added to any well bonded part of the vehicle?

Thanks.
Dave
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K0BG
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Posts: 10248


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« Reply #1 on: August 08, 2008, 03:17:37 PM »

If you do this, you needn't make them any particular length. Six or 8 is usually enough if they're at least 30 feet in length. There can be a problem, however. If you properly matched the antenna with a shunt coil, when you add the radials the input impedance will go up. This means you'll have to readjust the coil slightly. It isn't a big deal, just a little messy.

The real question is, does it help? Yes, but I'd bet you won't notice the difference unless you measure it with an impedance bridge. And... the real difference in efficiency isn't all that great, unless you install about 25 or more radials.

Alan, KØBG
www.k0bg.com
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WB2WIK
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Posts: 21837




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« Reply #2 on: August 08, 2008, 07:09:41 PM »

Add the radials directly to the "ground" side of the antenna at its base/mount, not "other places" on the vehicle!

I had a trailer hitch mount for several years on the back of my Volvo wagon.  True, not the best location, but it was very STRONG which was a big plus and maybe worth 3 dB or more in worry reduction.  I had my hitch mount bonded to the chassis using six 3" wide copper flashing straps bolted various places under the vehicle after scraping paint or undercoating (the nasty part of the job) from those places.  It was very well grounded, but still "low" compared with a higher location.

I also had a standard Motorola SS "ball" mount up high on the right fender, only maybe 6" below the roof line, so I could move my whip from  the hitch mount to the ball mount in 30 seconds.  True, the higher elevated ball mount location did work better but then the whip was tall enough it would catch low tree branches in residential neighborhoods, etc.  So, most of the time, I actually used the hitch mount and sacrificed a few dB for the better good.

I figured, either the band is open, or it isn't.  3-6 dB one way or the other won't open a band that's not.

:-)

WB2WIK/6
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