Solved Coax cable vs Ethernet

March 24, 2020 at 16:48:09
Specs: several
I do not have an electrical engineering degree, nor
do I play an EE on YouTube.

I'm helping to select a new security camera system for a
large building. It currently uses coaxial cable to connect
16 analog cameras to a DVR. We will probably have 24
cameras in the upgraded system. We could save money
by using the existing coax cables, but that means using
analog cameras rather than digital cameras, which are
normally connected by Ethernet cables.

My understanding is that coaxial cables are higher quality
than any Ethernet cable. To me that means they should
be able to carry a digital signal as good as or better than
an Ethernet cable. Ethernet cables have four conductors.
I gather that two carry the signal and the other two can be
used to carry power to the cameras. Power for analog
cameras has to be (and currently is) provided separately.

Aside from the lack of built-in conductors for power, could
the existing coaxial cable be used to connect digital cameras
via Ethernet communications protocol? If so, would that be
dangerously nonstandard? Is putting Ethernet connectors
on coax cable a difficult practical problem?

-- Jeff, in Minneapolis

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March 24, 2020 at 21:00:39
✔ Best Answer
Either stay with analog or go digital with Ethernet but do not try bridging them together.
Ethernet cables have four pair of twisted wires or 8 conductors, not four.
Cat 5e or Cat 6 cable are much easier to run than coax is so rewiring is not a real hassle.
You power the devices with POE or Power Over Ethernet with POW power injectors or a POE Switch (like a hub) which injects the standard 48 Volts (or is it 50 Volts, well certainly between 48 & 52) into the cables from that point forward to the devices. If the runs are not too distant the Switch will be used, for the more remote ones a more local POE Injector will be used.

You have to be a little bit crazy to keep you from going insane.

message edited by Fingers

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March 24, 2020 at 21:18:52
It is possible to use Ethernet to Coax converters at both end of the coax cable. But I doesn't come cheap. Plus these converters need power too. You can weight the advantages against the cost of new Ethernet cables. Be aware that power is needed at endpoints of the coax cable if converters are used!

Some examples:

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March 24, 2020 at 23:00:09
> Ethernet cables have four pair of twisted wires or 8 conductors, not four.

Ooops! Yes, right you are!

If I had remembered that there are 8 conductors, not just 4,
I would have realized that more than two conductors must be
required for the signal, so a coaxial cable wouldn't do. The
converter boxes obviously do some complex processing to
squeeze the signal into the coax. Since they can do that, I
expect that my "understanding" that coax cables are higher
"quality" (capable of greater bandwidth per conductor) is
probably correct.

I didn't think it would be practical. Looks like it isn't.

Thank you!

-- Jeff, in Minneapolis

message edited by Jeff Root

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