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grounding ?

B

brash

Member
Apr 22, 2012
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new to this cb scene, so i have a question about antenna grounding. all my buds at work like me just have there antenna mounted to the mirror bracket or use a mag mount on the roof. my situation is my mirror bracket is painted with heavy paint. couple other trucks are like that also. seems like nobody has a problem but most of them use cobra 19's and such. think the one guy has a 29. thats about it. if i run a wire from the bracket down to the frame somewhere and mount it should i be fine. what size/kind wire. would 14thhn wire be fine. will i notice a difference or will it just be with the swr settings.
 
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First things first, the type of radio has nothing to do with an antennas ground system. It doesn't matter if you are running the $20 Walmart special or that $1000 heavily modified unit, a ground system problem will affect all of them exactly the same.

Running a wire to the chassis like that is great for DC. However, when talking about radios I really don't like the term "ground" because at radio frequencies a "ground" doesn't act like most people are sure a ground acts. Time and time again I hear of people running a wire between the antenna and the chassis, and then wondering why their SWR is off the charts.

The problem is that wire, if long enough, will act as part of the antenna (at least it will try to), and it has the ability to actually change the antennas feedpoint impedance.

Copper straps are the best, the wider the better, and the shorter the better. For more info I recommend looking up "rf bonding", as articles on RF bonding are a good source of info on lengths and widths of wire/straps.


The DB
 
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brash said:
if i run a wire from the bracket down to the frame somewhere and mount it should i be fine.
Click to expand...
No. Doesn't work like that. OK for DC, not OK for RF.

what size/kind wire. would 14thhn wire be fine. will i notice a difference or will it just be with the swr settings.
Click to expand...

You will notice a difference on receive, transmit and with noise.

Basically mounting it on the bracket even if you're using bits of wire to connect to the frame you only have half a circuit. If you take the light in your living room at home and disconnect one of the wires in the fitting it'll light but only half as bright. With poor grounding this is effectively what you're getting with your radio signal both on receive and transmit..

Magmount on the roof is better than bracket on a mirror arm. Permanent fixed mount on the roof is the best of all.

Bit of reading.

Grounds, RF & DC
 
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where do you suggest i run the strap to, anywhere that has a bolt/screw going through to good metal?
 
Not if it is a magnet mount.

If it is a solid roof mount; then bonding of the doors and hood may help considerably. Solid mounts are better than mag mounts. Mag mounts are an option for temporary placement. Is it your vehicle or a company vehicle? Got any pics of your installation we can see?
 
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Have you check the swr? If its way off then maybe straps but I would say magmount would be the easiest.

Sent from my GT-S5690M using Tapatalk 2
 
Since that cab is that high; no matter what antenna you choose to put on it will still be high. Yeah, that Sirio 5000 has that tilt function and may work out. But the whip on it is ~70in and you can't change its length w/o ruining its RF properties. I can appreciate the problem you have, as the mirror bracket would be the logical choice.
 
M0GVZ said:
Not if you use the Sirio magmount. I've gone under low height barriers with the magmount and Sirio on the roof and the barrier has only been a few feet higher than the roof. The whips bend quite well and spring back.
Click to expand...

which model do you have
 

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