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Old 10-10-2013, 11:55 PM   #1
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CB power?

Hi all. I am going to be installing a cb soon, and I am getting a game plan worked out. Pretty sure on how and where to run the power and antenna. My question is the type of wire to use for power. I am going to run direct to the battery. I know 14-16 gauge should be ok and I will have a 30amp in-line fuse as close to the battery as possible.

I found this link online:
CB Wiring Basics

that talks about using coax cable for power. The center wire is power and the shielding would be ground. Supposedly it would cut down on interference due to the shielding, though I know going direct to the battery will do a lot of that anyway. Does this seem like a good idea? Has anyone tried it? Will RG-6 be able to handle the current, specifically the shielding. I know cable doesn't have a lot of current flowing through it, about 12-20 when used for cable TV, but would the differences in wattage and amperage have any ill effects using it for cb power?

Thanks in advance.

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Old 10-11-2013, 10:53 AM   #2
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I'd use 14 gauge with a 5 amp fuse, a 30 amp fuse wouldn't protect the circuit. An RG type cable could be used for power but likely won't be needed for a Jeep which typically has an electrically quiet ignition system when the right spark plugs & wiring are installed.

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Old 10-11-2013, 11:12 AM   #3
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Originally Posted by geeknik View Post
Hi all. I am going to be installing a cb soon, and I am getting a game plan worked out. Pretty sure on how and where to run the power and antenna. My question is the type of wire to use for power. I am going to run direct to the battery. I know 14-16 gauge should be ok and I will have a 30amp in-line fuse as close to the battery as possible.

I found this link online:
CB Wiring Basics

that talks about using coax cable for power. The center wire is power and the shielding would be ground. Supposedly it would cut down on interference due to the shielding, though I know going direct to the battery will do a lot of that anyway. Does this seem like a good idea? Has anyone tried it? Will RG-6 be able to handle the current, specifically the shielding. I know cable doesn't have a lot of current flowing through it, about 12-20 when used for cable TV, but would the differences in wattage and amperage have any ill effects using it for cb power?

Thanks in advance.
You could use coax for power. Since you are going to use RG58 for transmission line I'd use same foe power if that is what you want to do. Or you could just put some auto wire in a drill. Other end in a vise and make up some twisted wire. RG58 has about 28.5 pf per foot. Just add a capacitor to ground if you have problems. Easier and cheaper
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Old 10-11-2013, 01:35 PM   #4
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Thanks for the advice guys.

Uhm, whats pf per foot?
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Old 10-11-2013, 04:23 PM   #5
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Thanks for the advice guys.

Uhm, whats pf per foot?
Coax has capacitance per foot. As frequency goes up like in the CB band capacitive reactance goes down. What happens is basically noise on your power line is by passed to ground. i.e. noise goes away. On twisted wire less noise is picked up because of inductance in power line. Noise has an AC componet like your house power. Adding inductance by twisting and capacitance to shunt it to ground works better. I have had mobile ham rigs since 1956. However, there is a noise componet at 10 & 11 meters that is tough to deal with. 11 meters being CB band & 10 meters the ham band. In the old days we constructed traps for engine noise. Now we have better noise limiters in the radio that helps. If you twist your wires and put a 100 pf capacitor from B+ to ground at the CB rig you will have much better results. Assuming you are using 4 ft of wire. Add about 28 pf for every extra foot of your power line length. You could just guess. Put a .1 micro farad between B+ and ground at your CB. ( that is 1000 pf) Don't think that is where noise is coming from. It is through antenna from engine. If I recall gas engine noise frequencies is about 29.6 mcs where noise is at. Feeds ant not power line to rig. The battery has lots of capacitance that dampens noise. I've only been doing this since 56 so have lots to learn about it.
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Old 10-11-2013, 04:33 PM   #6
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So twisting the wires, that would be the power and ground twisted; positive and negative wires? Kinda like in ethernet.
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Old 10-11-2013, 04:54 PM   #7
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So twisting the wires, that would be the power and ground twisted; positive and negative wires? Kinda like in ethernet.
#12 wire. twist. I use elictric drill.. Causes inductance on line that resists RF but not 12v dc.. If any rf left capacitance to ground eliminates it.. Noise is from engine. I said 29.6 but is about 28.6 mcs. It cones through antenna not DC power from battery.
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Old 10-11-2013, 05:12 PM   #8
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Ok cool. I really appreciate your help. A lot of the info is above my head lol, but I get the gist of what you're telling me. I'll just use #12 wire...I have a power plug for my cb on order so i will just twist them, zip tie every couple inches, (not tight), install the 5amp fuse and call it good. If there's any noise after Ive got the system together Ill look into installing a capacitor if needed. Again, thank you so much for your guys help. You're experts!
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Old 10-12-2013, 06:54 AM   #9
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Ok cool. I really appreciate your help. A lot of the info is above my head lol, but I get the gist of what you're telling me. I'll just use #12 wire...I have a power plug for my cb on order so i will just twist them, zip tie every couple inches, (not tight), install the 5amp fuse and call it good. If there's any noise after Ive got the system together Ill look into installing a capacitor if needed. Again, thank you so much for your guys help. You're experts!
Don't need zip ties. Use #12 automotive wire. May have to put knot in end if it falls out of electric drill chuck. Other end in a vise. Run drill until it is twisted. Give a yank on wire. Presto it will stay a twisted pair & very easy to work with. You end up wasting a little wire on both ends but does a great job.
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Old 10-12-2013, 01:44 PM   #10
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I've got an electrical engineering background and a LOT of 2-way radio installation experience over the past 48 years (since I was 18) and in my personal experience with installing ham and CB radios in many Jeep models, I really don't believe you will need to use RG cable for power & I don't believe power & ground wires would need to be twisted to cancel noise either.

Such techniques are sometimes needed for some installations but not usually for a modern Jeep.

When a CB is powered by an adequate wire gauge that is connected directly to the battery, noise is seldom a problem in a modern Jeep running the proper factory resistance style ignition wiring & resistor spark plugs as specified. Of all the CBs & ham radios I have installed into modern Jeeps, which is quite a few, none needed RG cable for their power connections or twisted power wiring.

The usual causes of noise in a CB radio are normally just from getting power from a random (noisy) power source, improperly/inadequate grounding of the antenna mount, inadequate wiring gauge, or someone having swapped the OE resistor type wiring & spark plugs for non-resistance or low-resistance ignition components.

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