CB Antenna Grounding Question

[ree]

When I put my new H2O rack on, my old CB antenna mount over the DS window on the rack rail didn't fit any more. I finally got around to mounting it up on the new rack this weekend and grounded it to the frame via a screw in the OE rack rail.

But I was wondering if I should also attach the new rack itself to the ground? This is easy to do since the rack has several pre-tapped holes in it that conduct very well. But I don't know enough about this stuff to know if it will help or hurt performance of the antenna to do this.

[CslRkH2]

Originally Posted by ree

When I put my new H2O rack on, my old CB antenna mount over the DS window on the rack rail didn't fit any more. I finally got around to mounting it up on the new rack this weekend and grounded it to the frame via a screw in the OE rack rail.

But I was wondering if I should also attach the new rack itself to the ground? This is easy to do since the rack has several pre-tapped holes in it that conduct very well. But I don't know enough about this stuff to know if it will help or hurt performance of the antenna to do this.

Are you sure the rack is not already grounded. My GOBI is grounded to the roof track.

[ree]

I'm 99.872% certain it's not since:
1) the mounting clips are powder coated
2) the the bolts through the clips don't pass through a tapped hole (ie exposed steel) in both the rack and the clips (ie can't conduct through the bolt)
3) the nut plate holding it in the rails is powdercoated
4) the rails themselves are coated and I did no prep where the mounting tabs are to scrape of the coating to allow conduction because of (1-3)
5) I did not wire any exposed portion of the rack's metal to a ground on the frame.

Does the GOBI have a grounding strap on it that you attach to the frame somewhere/somehow?

I know how to ground the rack...that's easy. I just don't know if it's the right thing to do to make the antenna perform well.

[dochummer]

The CB won't tune if it's not grounded right....if I remember right. Just try tuning it...

[ree]

Well, it is grounded right (see "grounded it to the frame via a screw in the OE rack rail."). I already did tune it with my SWR meter and it's working just fine.

But, what I really want to know is if, by grounding the rack, I've enhanced the ground plane. Or because it's a large mass of metal high up (relative to the frame) does grounding the rack actually have a detrimental effect on antenna performance?

[ree]

Here's what the folks over at Firestik told me:

Normally ... metal on the horizontal plane aids the antenna. However, anytime you change the environment around the antenna .. you need to put an swr meter on the set up and retest it because it could change how the antenna performs. If the rack is causing any problem at all ... it will show up on the swr meter ... any thing else is only a guess.

So I guess I'll ground the rack try retuning the antenna and see if I can get the SWR lower and leave it at that.

[KenP]

I didn't ground our rack, but I did ground the antenna just as you did and didn't have any problems.

[CslRkH2]

My GOBI is electrically grounded without any extra wires.

The Ground Plane is not Electrical Ground. It is the RF ground. The RF ground is created by the perpendicular metal vehicle roof. The closer you install your ant. to the roof and to the center of the vehicle the better the ground plane. My ant. is on the Driver rear corner of the Rack and my readings as of Sunday (tuned new antenna)

Ch 1 = 1.8
ch 20 = 1.3
ch 40= 1.7

'they' say anything less than 2 is good/operational, under 1.5 is great.

[CslRkH2]

Originally Posted by ree

Well, it is grounded right (see "grounded it to the frame via a screw in the OE rack rail."). I already did tune it with my SWR meter and it's working just fine.

But, what I really want to know is if, by grounding the rack, I've enhanced the ground plane. Or because it's a large mass of metal high up (relative to the frame) does grounding the rack actually have a detrimental effect on antenna performance?

I don't think grounding the rack made any difference to your ground plane good or bad. Moving the installtion location would make a difference and call for a re-tune.

[JoeHummer]

Okay so help a Newbie. I just added a CB with the antenna mounted to my Manic rack. How do I ground the antenna and what is the "S??" tuning?

[CslRkH2]

Originally Posted by JoeHummer

Okay so help a Newbie. I just added a CB with the antenna mounted to my Manic rack. How do I ground the antenna and what is the "S??" tuning?

This would be a good place to start learning about CB antennas.
http://www.firestik.com/Tech_Docs.htm

Your antenna should have come with instructions on how to mount it. Generally you electrically ground the mount first (not the antenna), which you might be able to do by just clamping it to your rack. A multi-meter will tell you if you have a good electrical ground or not.

The SWR meter is used to tune the antenna. Because your installation environment is different than everyone elses you have to adjust the antenna (tuning screw at the top). The Firestik website does a very good job of explaining all of this. If you buy a 102" whip, then no tuning is needed but you'd have a ~9' antenna on your truck