Radio antenna ground plate - Team Camaro Tech
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post #1 of 8 (permalink) Old Nov 20th, 14, 12:11 PM Thread Starter
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Dave
 
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Radio antenna ground plate

Does the radio antenna ground plate that goes just under the antenna opening in the fender serve any actual electrical purpose? As in "grounding" the antenna to the body?

I would think, if it did, there would have to be some bare metal on the bottom of antenna opening in the fender for the ground plate to make contact with. Leaving bare metal there doesn't seem like a good idea.

The antenna assembly instructions in the AIM don't mention anything about it.

I am wondering what the right thing to do is.

Thanks.....Dave

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post #2 of 8 (permalink) Old Nov 22nd, 14, 07:11 PM Thread Starter
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Re: Radio antenna ground plate

Is there anyone who can comment on this?
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post #3 of 8 (permalink) Old Nov 22nd, 14, 08:42 PM
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Al
 
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Re: Radio antenna ground plate

The plate is there so you can tighten the antenna to the fender, not for grounding.


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post #4 of 8 (permalink) Old Nov 23rd, 14, 07:02 AM Thread Starter
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Re: Radio antenna ground plate

Ok, thanks......I figured the antenna was already grounded through it's coaxial cable but just wanted to be sure.

The use of the word "ground" in the description something related to an an electrical item had me wondering.

Dave
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post #5 of 8 (permalink) Old Nov 23rd, 14, 07:46 AM
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Re: Radio antenna ground plate

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Originally Posted by daven1256 View Post
Ok, thanks......I figured the antenna was already grounded through it's coaxial cable but just wanted to be sure.

The use of the word "ground" in the description something related to an an electrical item had me wondering.

Dave
I'm not 100% sure on this but I thought the mounting plate usually had little teeth on it to "bite" into the underside of the body sheet metal, reason being if you rely only on the outer shield of the coaxial antenna cable and there is resistance the end result will be reception that is not as good as it could be. Can't remember when I was made aware of this bet it was years and years ago and I've always tried to make sure the antenna base was grounded well on it's in addition to the ground bathe from the cable shield.

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post #6 of 8 (permalink) Old Nov 23rd, 14, 08:30 AM
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Re: Radio antenna ground plate

My radio theory is more than a little rusty, but here goes. Car radios use what is known as a Marconi half wave antenna, which utilizes ground for part of the antenna circuit. In a car, the antenna element forms one quarter of the antenna, and the skin of the car (and capacitance to the road) forms the ground plate, and provides the other required quarter wave. So, the antenna should be grounded to the body.

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post #7 of 8 (permalink) Old Nov 23rd, 14, 09:26 PM Thread Starter
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Re: Radio antenna ground plate

Thanks for the replies so far.

What I was trying to find out from this was.....do I need to leave some bare metal on the bottom side of the fender's antenna hole to make good contact with the ground plate. I don't want to give rust a place to start but don't think the teeth on the ground plate are sharp enough to penetrate the paint.

Now I am not sure again.
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post #8 of 8 (permalink) Old Nov 28th, 14, 01:59 PM
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Re: Radio antenna ground plate

The "plate" you are referring to is designed to "bite" into sheet metal by piercing through any primer and/or paint on the underside of the fender. This essentially links both ends of the outer shield in the coax cable to chassis ground to prevent radio frequency interference from the ignition system from getting into the signal conductor that links the antenna to the front end circuitry into the radio.

I know it pains those who spend $$$ on rust repair and concours restorations, but you do need to ensure it's "bitten" into metal when the base assembly is tightened down. You can do this by taking an ohm meter and see if you read continuity (zero ohms) between the outer housing of the antenna plug after you pull it out of the radio and a convenient sheet metal ground.

If you have grind a bit to get bare metal on the underside of the fender, once things are assembled you can smear dielectric grease around the "plate" where it mates to the sheet metal. This will discourage moisture from penetrating the bare spots and prevent premature corrosion.
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