Question about running Rg-58 antenna cabling and heavy gage power lines under vehicle

[rayra]

Concerned about interferences in either. Will be wiring my Suburban for a couple different projects, one a multi-flavor power module and extra battery(ies) as part of my storage drawer setup and running multiple antenna cable runs to the back bumper corners and back of the roof rack.

I'm considering running everything underneath, on top of the chassis / under the body. Most all of my off-road travels with be desert environments, some alpine mountain.
Working in my IT career the guidance was always to avoid running ethernet cable adjacent / parallel to power lines, preference being to cross them at a right angle. My surmise is that this is also true for CB and HAM radio antenna cabling? Other than the usual concerns about kinks, crimps, sharp edges, and hot places under the chassis, and protection from flying rocks / gravel, is there anything else I should be worried about in these conditions?

I'm not adverse to running the majority of the cabling inside the vehicle, part of my buying an older vehicle is greater willingness to drill some holes in it. I'll run this vehicle until it's dead. I am considering running the antenna cables into the vehicle around / thru the rear hatch seal edges and down the side interior trim panels. I should be able to run my power cables down one side of the vehicle and the antenna cables down the other. Any issues laying 2-3 RG58 cables side by side, are there any interference issues with that arrangement? It will be CB and 2m, no plans for HF.

Looking for pros / cons, inside vs outside. Thanks for your time and any technical or empirical info.

 

[4x4junkie]

I've never had any trouble with coaxial cable runs that are parallel (or even bundled together) with other wires. As long as it's good quality cable (95% or better shield), and the shields are terminated well, you shouldn't have RF leaking out through them.

Ethernet cables OTOH are usually unshielded. These no doubt can be affected by other cables right next to them (for telephone cabling it was referred to as "crosstalk" or something like that IIRC).

 

[AlbanyTom]

I don't think you'll have any trouble running them side by side, actually I'm sure you won't, as long as you're not running high power. By that, I mean that CB is HF, and HF with a marginal antenna means you have signal traveling on the shield, and past 5W or so that could couple to your power lines in a bad way. But as long as you're 5w or less CB, and good antenna for 2m, you'll be fine.

I'd be more worried about physical damage, corrosion in connectors mostly. And maybe water in the coax. I believe rg-58C is solid PE dielectric, instead of foam, and stranded instead of solid center. The would be my choice in a vehicle, as it's more rugged. Loss at the lengths you have in a car don't matter at HF and VHF. Also would put it in split loom, for physical protection. And no splices outside. Maybe that would be OK in the desert, but in the NE, they wouldn't last a winter.

 

[BigJimCruising]

It's not the fact that your running 12v next to coax that is a problem, it's what that 12v is hooked up to that might be a problem. Some devices can be very noisy while others won't be a problem. I run Siamese coax hundreds of feet without any issues, but if I added a 12v refrigerator inline I could have a real mess on my hands. Even worse a cheap inverter. It mostly is about what your hooking up that makes the difference. I have coax's and high amp power lines running all over my truck but except for HF there isn't a problem. That being said if you can run your coax separate from your power your odds of less problems increases the longer the runs. Since you don't plan to run HF your probably going to be just fine. But just remember that CB is at the higher end of the HF bands.

 

[AlbanyTom]

Big jim - If you mean interference from the 12v to the radio, then I completely agree with what you said. Just would add that if it's the radio itself, or just lights or something quiet on the 12v line, that there shouldn't be any interference to the CB.

What my concern was, is high power HF/CB inducing enough RF into the power line to wreck the trucks electronics. Thinking the combination of a marginal antenna, which will put RF on the coax shield, close to the 12v power line, with both capacitive and inductive coupling going on. 100W radio, bad antenna, I wouldn't run them tied together. Decent antenna, 5 watts? I wouldn't worry about it.

 

[mm58]

Ethernet cables OTOH are usually unshielded.

I always thought Ethernet/CAT cables were shielded passively by the fact that they are twisted pairs. Am I wrong on this?

 

[98OzarksRunner]

I always thought Ethernet/CAT cables were shielded passively by the fact that they are twisted pairs. Am I wrong on this?

As I understand it, in theory, if the source and load impedence are exactly the same, there will be no emission from the transmission line (and I guess no reception either), which is why ethernet 'works' (as well as twin lead transmission line). Ethernet hardware can provide close impedence matching, though no cable or load is ideal (and twisting helps with with noise rejection and emissions due to mismatches). Getting the source and load exactly the same (1:1 SWR) is a challenge wiith antennas, especially in a mobile setup.

 

[rayra]

'passively shielded' from the low-energy fields of adjacent like cables. high volt / amp lines is another thing.


Thanks for the info folks. I wanted to run the antenna cabling without tearing up the vehicle interior, so I could get the radios in and operational. But other projects are leading to that, and progress is so slow on multiple items that I'm likely to just do it all at once, after piling up all the prerequisite gear. Just one big gutting and modification. And then I'll have full access to route everything. OnStar antenna replacement / conversion, high dash cam, replacing the dash onStar panel with a multiple switch array, roof rack antenna, bumper antennas, power feeds from the vehicle charging system to the rear power module, and possibly even a roof solar panel install. And a roof LED tight bar and backup / rear area lights. Even thinking about some marine-grade 12v sockets in a few places around the bottom edge of the roof rack, allowing use of some portable area lights that just plug into those ports. The Z71 roof rack mountings are so oversized I think I can easily add such ports in the housings.

 

[technoweenie]

Skip RG coax and go with LMR-240..

Lower loss, better shielding, usually about the same price, and YOU control the length, quality of connections, etc.

 

[AlbanyTom]

I always thought Ethernet/CAT cables were shielded passively by the fact that they are twisted pairs. Am I wrong on this?

It's not really shielding, but it is a degree of interference rejection, that under some circumstances is very effective. Twisted pair wiring is normally used with balanced signals. Ethernet over twisted pair works like that, as does balanced audio in analog pro sound systems. Twisted pair does pick up outside interference, but since the receiver only is supposed to pay attention to the difference in the two signals, and the interference affects both lines in nearly the same way, there's not much noise. The noise is canceled out.

If the systems aren't balanced, but instead are ground referenced, like normal consumer audio gear, or RS-232 signals, or even 12v power distribution, then twisted pair doesn't help any. The receiver picks up the noise just like signal.

Even if the systems are balanced, like twisted pair Ethernet, it's not perfect. The cable isn't perfect, and the receivers aren't perfect. Common mode noise can affect balanced systems. This is why they make shielded twisted pair for some applications.

In addition, 98o is correct, if your terminations aren't balanced, then twisted pair will radiate noise, and they will pick up common mode signals as differential noise, because the terminations will convert it. Or in other words, as the impedance match gets worse, it acts more and more like an unbalanced system, because that's what it's becoming.

But that's all about twisted pair cabling, which doesn't have anything to do with trucks. And because there's nothing balanced about automotive electrical anything, using twisted pair won't help anywhere. Just putting this in, in case anyone is thinking of using twisted pair to reduce electrical noise in a truck. Won't help any, unless you convert whatever you're talking about to balanced line at each end..and that wouldn't be worth it.

 

[rayra]

Making some progress on the custom console fabrication for my future radios. Found some upholstery pleather that matched the factory console quite closely. Dusting off 30yr-defunct upholstery skills. Radio rack is 1/2" MDF, easy to work with, strong enough for this application. Cutting all kinds of ventilation and access holes in this subchassis. Has removable exterior panels which are padded and upholstered.
Once this is done I'll get the radios and the rest of the related hardware. By then I should have my wiring runs figured. And have my HAM Tech license.

 

[AlbanyTom]

That looks sharp. Do you put the pleather right over the mdf, or is there padding in between? Staples to attach?

 

[rayra]

1/2" foam, 1/2" MDF, 3/8" staples work well.

Just finished making the rolltop-style door, it's slides down into the body. Couldn't find the right metal or styrene C-channel, so I just made the guides out of MDF too. The slats for the door are cut from oak veneer plywood left over from making cabinet door centers. It's a bit under 1/4" thick. Trying to stain that ebony-black, but it's coming out more like dark brown. Didn't want to paint, want to see the wood grin. Might have to buy some real ebony. Did a bunch of fiddly sanding to round the edges of the plywood slats. Gonna try anothe r3-4 coats of stain on them and see what I end up with.

 

[BettysNephew]

I used a semi transparent black stain from Cabot and it came out very black with grain showing. May be too late but it did work for my project.

 

[rayra]

Thanks, I'll have to look into that if this staining doesn't satisfy. Today I finished four applications of stain, finally getting dark enough. Maybe one more for good measure. Still have to figure out what sort of handle to use on the door.

Working on the last bit of upholstery, the front panel, with it's semi-circle cutout for factory wiring runs to the central console

All covered, need to working on the top piece fitment, and still haven't figured out a quick attachment method for the side panels. MIght default to velcro, can't find the snaps I had intended to use.

Back view, showing the fan arrangement. A silent 120mm 12vdc computer fan, pushing ~40cfm+. The cardboard boxes are dimensional mockups of the radios I've picked. Their arrangement gives a nice stagger and I've put two 1" wide slots across both radio shelves. This arrangement should blow cooling air at the underside of both radios. Just a stray idea. Don't even have the radios yet. Don't know how they are arranged / vented.

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I'm looking at more antenna mount hardware, more cabling options. I have to dismantle the rear interior trim on the Suburban and get a good look at various structures and arrangements. I've had the front and mid / 'B' pillar trim apart already, excising a defunct 10yr old backseat TV / video / entertainment system. I'll be running some heavier cabling from the vehicle battery to the cargo area for some additional battery and power conversion options, so I'm likely to perforate the floor anyway. And doing that, I can just run the antenna cabling from the back bumper to the same entry point, but running forward. So I'm considering crossing paths in the same opening. But if I'm drilling one hole then what's two? Need to really investigate adn figure that stuff out next.