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Unread 04-24-2016, 03:15 AM   #1
ED.SJ
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Default Grounding Comet RS720 mount

I have a Magnum 257 radio and K40 antenna that looks like the firestick and its not adjustable. My antenna mount was mounted on the lift gate, I had it grounded between the mount and cable to a bolt under the lift gate cover. The SWR was very high, so how do ya recommend grounding it? mount.jpg
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Unread 04-24-2016, 08:04 AM   #2
bulldog
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You typically want to use braided cable between the mount and the body. Don't ground to the liftgate.
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Unread 04-25-2016, 03:05 AM   #3
gm350reratliff
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That is probably the best way to ground it. I run a Comet HD-5 mount for my cb and grounded to the gate by scraping off all the paint and primer where the mount is then applying a generous amount of di-electric grease to the bare metal. I don't seem to have any grounding issues.

I will say that, the Comet mount isn't as sturdy as I hoped it would be so I will be moving the antenna to the rear bumper that I am planning to build.
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Unread 05-05-2016, 12:55 AM   #4
ED.SJ
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I notice that my antenna moves position after few weeks with comet, I added blue lock tight so ill see how that holds up. So I don't need to add ground wire to antenna mount just scrape paint from hatch and antenna mount?
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Unread 05-05-2016, 07:30 AM   #5
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I would recommend adding a grounding braided cable if the SWR is still high and see how that works.
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Unread 06-29-2016, 02:20 AM   #6
gm350reratliff
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Quote:
Originally Posted by ED.SJ View Post
I notice that my antenna moves position after few weeks with comet, I added blue lock tight so ill see how that holds up. So I don't need to add ground wire to antenna mount just scrape paint from hatch and antenna mount?
My antenna also moves position if running a rough trail. In fact, it completely came apart last year on Imogene during the FJ summit. I had to stop and bolt it back together. I do have an idea that may hold it in place a little better. I'll share it if it works out. Still planning on building a rear bumper that will eliminate the need for the Comet mount ( I pass by and look at the steel in my garage everyday ).

Also, just to clarify, I haven't tuned my CB yet so I don't know if the SWR is high or not. It is clear on my end and everyone else says it transmits clear as well. Hopefully this coming weekend I can work on that. Who knows, a ground strap may be in my future as well.

Honestly, I don't want to put to much $$ or effort into the Comet or CB because of the bumper I have planned and also I want to move to HAM anyway.
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Unread 07-31-2016, 06:57 AM   #7
gm350reratliff
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A small update to this.

No, still haven't built my bumpers but I did make a reinforcement bracket for the Comet mount which seemed to help keep the Comet from coming apart again. Along the way I sanded off some of the paint on the Comet to help it ground better. When all was said and done, I tuned it and had decent SWR numbers. My CB worked great for the FJ summit this year.

Anyway, here are some pics of said bracket;



Cut this from a piece of Aluminum 1.5"x1.5"x1/8" angle then cut it to fit around the Comet mount.


I put some 3M VHB double sided tape on the two "feet" of the bracket where it sits on the Comet mount and drilled out the Comet mount to use a longer 1/4" stainless allen head bolt and SS acorn nut.


The result is the mount feels much stronger and doesn't move at all. The CB antenna spring flexes instead of the mount and the bracket doesn't stick out much further than the Comet mount.
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Icons, Camburg UCA's, SAW coils, Ridge Grapplers, BudBuilt sliders, some other stuff. Build thread: http://www.toyota-4runner.org/5th-ge...ld-thread.html

Last edited by gm350reratliff; 07-31-2016 at 07:00 AM.
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