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I have a satellite communication system at office running on C-band. The C-band is downconverted to L-band and carried to the l-band modem. With this RF coaxial waveguide/cable, +12V DC power cable for the outdoor amplifier is also routed tied together. I know ac power cable shouldn't be laid along with the RF/coaxial cables. But I am not sure with the DC cable. So my first question is Can we route RF cable along DC power cable? And what is the minimum separation to be maintained if we have to.

For the second question, I read researching on the subject that power cable can laid in perpendicular with the RF cable but not parallel. I have a guess for the reason being that the magnetic field vector from the power cable shouldn't effect the electric field vector of the RF cable, but sure. So can someone please explain the reason for laying the power cable with RF cable in perpendicular (if needed) but not parallel?

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    \$\begingroup\$ Just send the DC up the same cable as the RF. It's commonly done, because it's a simple matter to separate the DC from the RF at each end. \$\endgroup\$ – Dave Tweed Jan 25 '16 at 15:40
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    \$\begingroup\$ You worry about this too much ! The RF signal and the DC signal will not bite each other. Many systems even share the Coax cable for RF and DC. At in and outputs AC and DC are separated by filters. You can just run a DC cable in parallel with the Coax, the Coax is shielded so the DC cable cannot harm the RF signal. \$\endgroup\$ – Bimpelrekkie Jan 25 '16 at 15:41
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Phantom power for satellite dishes means DC and signal are the same cable: -

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The only care you need to take is to ensure that the power superimposed is not noisy and that currents taken from the cable are kept quite well constrained. This applies also to DC power cables run next to antenna coax.

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  • \$\begingroup\$ Could you elaborate on "currents taken from the cable are kept quite well constrained" a bit please - constrained in what way? \$\endgroup\$ – pjc50 Jan 25 '16 at 16:40
  • \$\begingroup\$ @pjc50 I'm thinking that the power cable is unspecified in terms of what type so no big switching current impulses is what I'm getting at. \$\endgroup\$ – Andy aka Jan 25 '16 at 17:56
  • \$\begingroup\$ What if the power cable is carrying 240VAC, 6A current? \$\endgroup\$ – sk1 Jan 26 '16 at 5:19
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    \$\begingroup\$ @sk1 Your question is entitled to ONLY cover "DC power cables". AC power cables can cause a lot of problems and if you are interested then you have to look-up the effects of the 6A inducing voltages into the coax and what this might mean for any electronics attached to the coax - too much to generalize here. \$\endgroup\$ – Andy aka Jan 26 '16 at 8:25

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