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#1 WRAF233

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Posted 19 January 2020 - 01:16 PM

Going to install a Kenwood mobile GMRS in my '18 F350 (aluminum) and 1/4 wave antenna.  I have a back-rack/headache rack on the truck that has a slot for accessories and I have a mounting plate to go with it (also aluminum).  The mounting plate is 8" square.  I would drill the plate for an NMO mount.  It would make a clean installation but I'm wondering if that's a good enough ground plane or will performance be a lot better if I mount the antenna directly to the roof?

Obviously, a magnetic mount won't work on an aluminum roof so would have to drill into the roof, which is not a big deal, but prefer not.

 

Is the ground plane only the surface the antenna is grounded to and not surfaces around it (like the roof)?  Would the width of the backrack (same as truck bed width) contribute to the ground plane?


Gary

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NE NV


#2 Jones

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Posted 19 January 2020 - 01:34 PM

6 inches or more is a near perfect ground plane for UHF, so your proposed 8 inch plate would be great just as it is.  You should get good results from that.

Make sure your headache rack is grounded to the truck's frame and body to avoid static. as in, if it is mounted on rubber bushings, run ground straps or wires as needed.


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#3 Elkhunter521

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Posted 20 January 2020 - 05:48 AM

Hi Extreme,

Keith T here. I have a similar mount setup. Headache rack with gmrs antenna on. A 8"x8" x 1/8 plate center top.
Also , cophase cb antenna at 1/8 wavelenth o edges of rack.
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Be vewy vewy quiet.
I'm listening to my wadio!


#4 kb2ztx

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Posted 20 January 2020 - 08:48 AM

I installed a back rack on my new JT as its a soft top. It has the bracket also. It works OK, but not as good as my F150 with a drilled NMO with same 1/4 wave antenna. I mostly talk simplex and it is noticeably different although both sweeps show the same on a VNA. Its the only solution I have on the JT so it is what it is. I would prefer a roof mount NMO. In regards to the NMO mount get the good sealed mount. I run the Larsen thick mount as the standard NMO wont fit the steel plate. I got mine from antenna farm - https://www.theanten...mokhfcxthk-1161

 

 
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#5 berkinet

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Posted 20 January 2020 - 08:51 AM

...Is the ground plane only the surface the antenna is grounded to and not surfaces around it (like the roof)?  Would the width of the backrack (same as truck bed width) contribute to the ground plane?

 

 

For a little more information on ground planes take a look at this page from stackexchange. Note in particular the first answer.


Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.

-- Marcus Aurelius


#6 WRAF233

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Posted 20 January 2020 - 09:36 AM


delete


Gary

WRAF233

NE NV


#7 WRAF233

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Posted 20 January 2020 - 09:48 AM

For a little more information on ground planes take a look at this page from stackexchange. Note in particular the first answer.

Link brings me to the top of this thread. 

I did however go out and Google for more information.  I'll learn a lot by the time I get to the answer.

 

https://www.electron...eory-design.php


Gary

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NE NV


#8 berkinet

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Posted 20 January 2020 - 10:12 AM

Link brings me to the top of this thread. 
...

Fixed. Thanks for noticing that.
 

I did however go out and Google for more information.  I'll learn a lot by the time I get to the answer....

  :)


Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.

-- Marcus Aurelius


#9 WRAF233

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Posted 26 January 2020 - 01:50 PM

Hi Extreme,

Keith T here. I have a similar mount setup. Headache rack with gmrs antenna on. A 8"x8" x 1/8 plate center top.
Also , cophase cb antenna at 1/8 wavelenth o edges of rack.

Keith,

 

..and the GMRS works well with this setup?

 

Thank you.


Gary

WRAF233

NE NV





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