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Author Topic: Running cables together in mobile installation  (Read 2681 times)
KK4IKO
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Posts: 67




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« on: April 02, 2012, 06:09:02 AM »

Has anyone seen any sort of interference issues with running antenna coax, DC power, aux. speaker wires and head control cable in the same raceway through the vehicle?  I'm doing a new installation and the only convenient raceway is the floor molding along one side from the dash to the cargo area in the rear.  It's possible the coax won't have to run under the door with the other cables, just down one side near the radio location.
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AA4PB
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« Reply #1 on: April 02, 2012, 06:34:57 AM »

I haven't had any problem. RFI problems can occur when there is RF flowing on the outside of the coax shield. That can happen if you don't have a very low impedance RF ground (bond to the vehicle chassis) at the base of the antenna where the shield is connected.
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K6LCS
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« Reply #2 on: April 02, 2012, 09:12:10 AM »

>> ...  interference issues with running antenna coax, DC power, aux. speaker wires and head control cable in the same raceway through the vehicle?

No - just use excellent quality coax for the project, and you should be fine.
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Clint Bradford, K6LCS
http://www.k6lcs.com
NA4IT
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« Reply #3 on: April 02, 2012, 10:06:38 AM »

I always use a snap on ferrite on both ends of the head separation cable, and on the power cable right at the radio. That is for HF. For VHF / UHF I have never had a problem.
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M6GOM
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« Reply #4 on: April 03, 2012, 07:17:32 AM »

>> ...  interference issues with running antenna coax, DC power, aux. speaker wires and head control cable in the same raceway through the vehicle?

No - just use excellent quality coax for the project, and you should be fine.


And decent RF grounding.
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KK4IKO
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« Reply #5 on: April 04, 2012, 07:57:36 AM »

Thanks everyone.  Wish me luck, I'm taking my test on Saturday.

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N6AJR
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« Reply #6 on: April 07, 2012, 12:46:26 PM »

good luck on the test, you'll do just fine.  Also when you run the mix of wires, try to get a random sort of twist to them as they run so they are not  parallel the whole length, sort of scramble  twist so they don't have all cables perfectly aligned to each other a single twist or two will cause them to add noise here and reverse the same there.  I hope this makes sense.
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M6GOM
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« Reply #7 on: April 09, 2012, 09:02:11 AM »

Also when you run the mix of wires, try to get a random sort of twist to them as they run so they are not  parallel the whole length, sort of scramble  twist so they don't have all cables perfectly aligned to each other a single twist or two will cause them to add noise here and reverse the same there.  I hope this makes sense.

It doesn't because it is completely nonsensical. If it does cause issues, you've got inadequate grounding on your antenna and have common mode on the co-ax which then ends up going through the power wiring, remote head cable etc. With a properly installed antenna and feeder there should be no common mode to cause a problem.
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AA4PB
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« Reply #8 on: April 09, 2012, 09:54:55 AM »

If your coax has common mode currents coupling energy into other cables then that's energy that isn't being radiated by the antenna and you should fix the problem at the antenna rather than trying to minimize coupling between cables.
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N6AJR
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« Reply #9 on: April 10, 2012, 01:39:27 PM »

So twisted pairs are not there to prevent cross talk??  I am not saying that other  cautions should not be taken, just that  organizing the cables in a non parallel manner may help avoid  cross talk problems, and it does not cost a penny to do so why not  take the extra twist when you can.
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AD7GU
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« Reply #10 on: April 11, 2012, 05:08:18 PM »

only rf problem i've run into was on school buses. the antenna coax was run along with the camera power cable. when the coax got old, rf would show up on the videotape.
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M6GOM
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« Reply #11 on: April 11, 2012, 05:49:55 PM »

So twisted pairs are not there to prevent cross talk??  I am not saying that other  cautions should not be taken, just that  organizing the cables in a non parallel manner may help avoid  cross talk problems, and it does not cost a penny to do so why not  take the extra twist when you can.

Yes they are. But look at the typical length of a phone line and compare it to a head separation cable. Also on shorter cables you'll find it done for data but look at the speed of the data being transferred and the tolerance required.
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N6AJR
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« Reply #12 on: April 19, 2012, 11:15:46 AM »

in the car I only have 2 cables running through the trunk for antennas, and the power comes from the front. but in the pickup I have 4 cables coming down one front post together and in the back there are 2 sets of 2 antennas coming up either side of the bed.  so as long as I have to run them , I am careful not  to run the cables in parallel I intentionally let them twist as they may.  so far no problems, except for a noisy fuel pump in the rear tank on the truck.
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