CB Radio Information and Installation

Every antenna and mount location is different, so just make sure you read how yours should be grounded. If it needs to be grounded through the mount (some Firestik) and the mount is not grounded in the location you want it, then there is no harm in running a ground wire from the mount to a ground point. If the ground wire isn't grounded, you would end up with high SWR and would know there is a problem.

Grounding from a mount to something else with a wire won't be an issue as long as the wire just connects to the mount.

For example, my antenna (Wilson) comes with a ground wire so it is not dependent on the mount plate for ground. It doesn't matter how long I run that ground cable as long as it eventually gets to a ground point.

 

Always keep the ground wire as short as possible because you're basically making a dipole antenna with it and you will transmit and receive through it.

 

Oh, I thought as long as it wasn't longer than your (uncoiled) antenna it wasn't an issue.

EDIT:

So, now I am reading that as long as it is grounded well and isn't causing SWR issues (or, reflecting back into the antenna) then it's not an issue.

Looks like I may need to read more about ground wire lengths and issues.

 

Alright, I found an equation to figure out the max length of ground wire from here:

http://www.radioworks.com/nbgnd.html

Seems that DC just sees impedance linearly with added length of wire. But RF grounding should be limited to (much) less than 1/4 wavelength at the highest freq operated. So for most of us that's not going to cause a problem (unless you are running a ridiculously long ground wire > 2').

So you are right, lower is better, but it would have to be awfully long to see enough impedance to be a problem. I am going to update the posts with that.

 

They come with a wire for those that can't ground the mount to the body. If the SWR is too high 3:1 all over the band it could be a bad part, a bad junction, poor ground or bad location. If the SWR is 1:1 across the band (1 to 40) it indicates a low efficiency antenna or a lossy component. Anything below 2:1 is an OK match 1:5 and below is achievable.

 

That's what Joelt had to do since he was running the antenna off his toolbox. Also with a powdercoated BAMF tailgate mount (like mine) there is not sufficient ground. Thus, a ground wire is run. As long as you keep the ground wire under 2' you shouldn't see any issues.

To test this, when I get home I am going to run a 3', 5' and 9' ground wire on mine and take readings to see how they differ. My guess is I won't see any negatives until I get to 5'.

 

Yes if you have no choice you have to run a ground wire any odd multiple of 11 meters will work as far as length. Fiberglass, paint plastic makes a lousy ground so you have to provide a return ground to the radio some how. I doubt if you will see much difference with any length of ground wire with a 4 watt output.

 

So, which is it, first you say the length of ground wire may cause problems. Then you say it won't...

And what do you mean by "odd multiple of 11 meters" and in relation to what?

EDIT: Are you talking about not getting a ground wire that is quarter wavelength? I think it would have to be 9' for that to match...

I think you need to work on getting your messages across clearly...

 

I cut 3 pieces of 12 gauge wire last night to test the antenna grounding lengths at 3' 5' and 7'.

At 3' I was 1.1 and 1.2.

At 5' it was the same.

And at 7' it went to 1.6 and 1.7.

I didn't go all the way to 9'.

In each case I tested talking to a guy that is roughly 2 miles away. There was only slight degradation of signal with the 7' ground.

So I think it's safe to say as long as you keep it under 2' it should be good to go.

 

In the radio world, "grounding", isn't electrical as you'd think a light or a winch would work....

 

It's both, RF and DC ground right? I was trying to focus on the RF, since DC ground shouldn't be an issue once you find a good ground to the frame.

 

an RF ground isn't necessarily a DC ground. Read up on capacitive coupling.

The antenna doesn't need an electrical ground per say. An electrical ground CAN BE an RF ground but doesn't need to be a DC ground.

image plane in rf terms can be a very abstract concept

 

I know they aren't the same thing, but I thought our antennas need both DC and RF grounding.

Either way, for the purposes of simple truck CB setups, I don't think ground wire length is going to come into play.

 

Antennas don't need DC grounding. There are DC grounded antennas, but that is for lightning protection

What is happening is that you don't have enough metal near the antenna, running that wire helps couple the antenna to the nearby image plane.

The ground lead length comes into play if you decide to use them as radials.

 

Ah, right on. Learning has occurred.

But for the sake of keeping this as a simple CB setup thread, it's safe to say keep the ground wire (if required) under 2' to prevent any SWR issues? That's what I am assuming with the test I did yesterday.

 

It doesn't really matter. It's like the 18' of coax thing CBers have in their heads. It's trickery of how SWR works

Everybody's setup is slightly different. The plastic bed is what makes tacomas so interesting to install HF radio into.

 

Subd

 

A 1/8 wave wire a 1/16 wave wire can resonate a 1/7 wave will not.

 

I have no problem with my plastic bed my radio works fine from 10 to 75 meters. The answer is in the details a proper install will get you on the air. No matter what you do a vehicle is a terrible ground plane you just got to do the best you can.

 

This antenna is a motorized unit all though not designed to be used in the 11 meter band it still will tune it. The SWR is pretty much right where it should be if you have a 1:1 match there is some thing wrong with the antenna. I tuned it on ch.20 and then switched to 19 with out a retune so as you see it is not a perfect world.The mount is bolted to the body it is well grounded the coax braid is bolted to the mount behind the tail light assemble. The meter is not from Radio Shack it is a $1700 Bird AT100.