110V line running in parallel with LMR400 and Cat5e cabling

Everything Else
#1

Background:
We have a set of on-pole antennas and Peplink equipment (a BR1 and a AP One Mini). They are connected with the in-house network by LMR400 coax antenna cabling and CAT5e Ethernet cabling running in a conduit in a trench to the house, feeding an HD2 (antennas and Ethernet both).

In the same trench there is another, smaller conduit, currently not in use.

Set-up:
We need to run a 110V/20A circuit from the house to the pole. There is a proposal to use the second (empty) conduit for that purpose. The two conduits are close to each other.

Question:
Would the power line be likely to interfere with the existing coax/Ethernet setup? (I am most definitely not an RF person)

Any knowledge or suggestions would be welcome.

Be well,

Z

#2

I am assuming the buried conduit of both is non-metallic. If so I would highly recommend the installation of your 20A circuit to use an armored cable (foil jacketed) just to ensure there isn’t an issue. The LMR should be okay provided the load on the 120V 20A circuit isn’t noisy. Alternatively, upgrade the CAT5e cable to a CAT6 shielded and terminate the ends correctly so that it does not pickup any noise from the AC lines.

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#3

I’ll give you a slightly different take on this but I can’t disagree with what @EM724 suggested.

In general 60Hz hum (and that’s really what we are talking about here) is not much of a problem in such an environment. I’d suggest three things which you may try in order, all inexpensive.

  1. If the power you really need at the end is DC run DC rather than AC. Example: Don’t run 120VAC out to a switching (or linear) power supply to convert it to DC to run a Peplink device. Rather, feed the power line with DC.
  2. Just do it and try. I’d expect the isolation of the “LMR” to provide a “noise barrier” of >100dB (without checking spec sheets.) Add to that results of the inverse square law which considers the distance between the origin of the noise/potentially interfering signal and the ethernet cable – there won’t be much interfering emissions left.
  3. Do as Eric said – run a length of direct bury (even if in conduit if its underground) Cat6 or better. The “throughput” of Cat6 is no better than 5E but the manner in which Cat6 cables are constructed (twist, manner in which the pairs are stabilized inside the jacket, etc) results in greater isolation.

Let us know what happens! :blush:

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#4

@Rick-DC makes a good point, depending on the distance and needs of the end-point DC could be a better solution (you could actually use the LMR-400 to carry that with a DC Coaxial Injector). We use these for tower-top amplifiers in the Amateur Radio world. However, DC does have limitations and heavier conductors will be required to carry the voltage and current over longer distances. Remember Ohms Law E over I times R. Great calculators online make sizing conductors for DC circuits easier. Alternatively, determining the power need and running a higher voltage at input and allowing the conductor run to drop the voltage at the other end. DC-DC buck-boost converters are trivial to purchase and could be an easy solution.

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#5

If running DC on a cable like this, I recommend changing the supplied 12V PSU to a 24V PSU this is assuming that the product on the end can handle the range and a lot of our products accept from 12V DC up to 40-52V DC, just check the specifications first!

The reason for this is the voltage drop on the extended cable can mean that only 5-10V DC is actually been received on the far end which is not high enough to reliably power the device but if you give it 24V, then 15-20V should be successfully delivered tot he end device.

Please note the the numbers will depend on the distance and cable used. Please do your own testing!

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#6

The advice is appreciated. In our particular setup the Peplink devices are powered using POE, and have been functioning quite well. The new component is the addition of the 110V line for some other equipment to be powered off the pole.

Cheers,

Z

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