Mobile Scanner Antenna/Ground Plane Issues

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415dispatcher

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Ventura County, CA
I've got a 396T in my truck and i've been using a cheap, Radio Shack mag mount/all-band antenna...and i'm ready to have a more permanent mount using a new antenna. I like the Austin Spectra...and I am planning on mounting it on a mirror mount screwed into the bed rail directly behind the cab. Then I started reading about ground planes and how the best possible location for the antenna would be the middle of the roof of the truck. I am not opposed to holes...i don't want it up there for clearance issues. My truck is already raised and the Austin Spectra is quite tall as you know.

So my question is...would i be better off getting a shorter antenna (Comtelco which is 17 inches) and putting it on the roof? or stick with my original plan? It seems like a lot of folks mount antennas to luggage racks, bumpers and such without any regard to ground plane.

Also...if i go with the bed rail mount....do i need to run a grounding wire down to the chassis? I know this doesn't have anything to do with ground plane...but does it improve performance that much?

Thanks!

p.s. I mainly monitor these frequencies: 450-512, vhf high and low. nothing in the 800+ range.
 

KT4HX

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Dec 19, 2002
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Spotsylvania County, Va
In your case, because of clearance issues, I highly recommend the Larsen 150/450/800 antenna. It is about 17 inches tall, which will meet your specs there, and I have found it to be a very good antenna. Been using one for close to four years, and have been totally satisfied. This was covered in part by this thread: http://forums.radioreference.com/antennas-coax-forum/170918-mobile-antenna-larsen-150-450-800-maxrad-bmax-scan-1000-a.html

Certainly worth you checking out. You will need the NMO mount for it obviously. Hope that helps.
 

prcguy

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So Cal - Richardson, TX - Tewksbury, MA
The Larsen is ok for 150 and 450 but the big Spectra will work much better on VHF lo. The antenna will work best in the clear with a large flat sheet of metal under it and mounting to the bed rail will loose some performance over roof mounting. You don't need a separate ground wire, the antenna will not know its there unless its part of the ground plane.
prcguy
 
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