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I'm running a feed line from the end of my amplifier to the antenna for HF transmissions. I'm using RG8x / mini 8. There's an existing pathway through my house I'd like to use that has a cat 5e ethernet cable.

I'd like to just push the coax through the same conduit as the ethernet, they'll be laying on top of each other for maybe 10 feet, outer jackets touching. In a couple of areas they'll end up zip tied next to each other. Does this create any interference that would be detectable? I'll be running up to max legal power (US / FCC).

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  • $\begingroup$ What is the maximum power that your amplifier is capable of? And what is the highest band? A correct answer depends on knowing that information. $\endgroup$ – Mike Waters May 28 at 18:28
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    $\begingroup$ BTW, welcome to this site! Check your email. $\endgroup$ – Mike Waters May 28 at 20:21
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No.

In fact, you shouldn't use RG-8X at all. Belden's specifications put the maximum power at 1000 W at 10 MHz, and 370 W at 50 MHz. The maximum power on most HF bands is 1500 W, so you'll be significantly exceeding the ratings of the cable.

Also keep in mind a cable in an enclosed space will run hotter than one with natural convection, so some derating may be appropriate.

Provided however you operate within the cable's specifications, use a high quality cable, and the cat 5 isn't connected to something extremely sensitive to RF, running other cables bundled with the coax is probably fine. See the datasheet for the isolation the shield provides: if there's not a datasheet then it's not a high quality cable. Do be sure to check for common-mode current, and mitigate as necessary, as this is likely the more significant coupling mechanism compared to leakage through the shield.

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    $\begingroup$ If the cable is hidden behind a wall or similar this would be even worse, as there would be nowhere for excess heat to dissipate. This could lead to a lot of heat in an enclosed space, and the consequences of that don’t bear thinking about $\endgroup$ – Scott Earle May 28 at 15:43
  • $\begingroup$ I submit those consequences "do bear thinking about"! $\endgroup$ – K7PEH May 28 at 15:50
  • $\begingroup$ @Phil if I keep it to 100 watts (I can run without the amp at home) that would take care of the cable rating, but what about the interference side? $\endgroup$ – Eric May 28 at 16:09
  • $\begingroup$ There could also be an issue with the zip ties if you tighten them enough to pinch either of the cables. $\endgroup$ – mrog May 28 at 18:13
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    $\begingroup$ Phil's answer and the comments here so far are most likely correct. However, until we know what power and the maximum frequency the OP with be using ... For all we know, he's only on 160 thru 40 and running 500 watts. :-) $\endgroup$ – Mike Waters May 28 at 19:01

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