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I am trying to decide which location would be the better spot to mount a cable modem.

Cable modem jack will be home run to the cable box.

Current Coax run is ~50 Foot thru crawl space.

Location #1 is small hall linen closet and would re-use the existing Coax run. Install a Coax jack and a CAT6 jack in hall closet, then run CAT6 ~30 feet up into the attic to a patch panel in another bedroom closet. Panel would connect to a pfsense router with maybe a 7 foot patch cable

Location #2 is the bedroom closet mentioned above. I would have to re-run a new longer Coax drop to the hall linen closet, then up into the attic, and along same path as the CAT6 to reach the bedroom closet, estimate ~80 foot Coax run. From where Modem would be mounted to where the router would be mounted might need a 10 foot patch (maybe 7 but overestimate the 10)

So which run would be better:

  • 50 foot Coax main, short Coax patch to modem, short CAT6 patch to jack, 30 foot Ethernet run to panel, 7 foot Ethernet patch from panel to router
  • 80 foot Coax main, short Coax patch to modem, 10 foot CAT6 patch from modem to router
  • Any time there is a splice you have a power loss. Are you talking about changing from coax to cat 6? this will have an impedance mismatch causing a degraded signal if I understand your plans. The best way would be coax with no splices to the cable box. – Ed Beal Jun 21 '16 at 23:09
  • There will be no splice of the Coax. Coax jack will be a home run directly to the Cable companies utility box outside the house – user45041 Jun 21 '16 at 23:50
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    Ed - the coax (in either case) connects the modem directly to the cable box. The cat 6 (in either case) connects the network to the modem. And which location does not matter at all in the given example, so pick the more convenient one. – Ecnerwal Jun 22 '16 at 1:23
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I think your configuration (despite the apparent confusion in some earlier comments) is: coax to cable modem, then CAT6 from cable modem to a router, then CAT6 from router to point of use.

RG6 coax, which is used by CATV systems, has an attenuation of ~ 6dB per 100ft (@ 1000MHz). CAT6 has an attenuation of about 9dB per 100ft (@ 200MHz). All other things being equal, coax will suffer less attenuation of relevant signals.

However, the signal strength margin (how much stronger than the minimum acceptable input for your cable modem) your CATV signal has when it enters your house is unknown, and could conceivably be just enough for your present 50 ft coax run, so that adding an additional 30ft to it could push your cable modem "over the edge". The Ethernet signal is starting at a known strength coming out of your router, and has enough margin to travel 100m (as long as you use good quality CAT6 and connector terminations), so the 40-50 ft you need is well within published expectations.

All said, I think Option 1 is slightly lower risk. but make sure your Ethernet cable, patch panel, and connectors are high quality, or you may compromise the published 100m range dramatically.

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Ethernet is designed to carry a digital signal with no measurable degradation over runs of 100 meters or less. Television coax was designed to carry analog signals over thousands of feet with signal degradation kept low enough that humans won't notice it. It's used to carry digital signals now, but it wasn't designed for it.

In general, a long Ethernet run is preferable to a long coax run (as long as you keep within Ethernet's length limits), but more important than either is to keep the number of splitters and connectors between your cable modem and the outside world to a minimum.

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It doesn't matter.

Both solutions are within normal operational parameters, so they'll all be fine. There are some issues worth considering but they're not technical:

  • Convenience of placement. Put modem as close to the router as possible, so you wouldn't have to keep running between them every time the internet is down and you need to tell if it's your router's fault or the cable company.
  • Convenience of wiring. Coax length needs to be more or less accurately calculated to account for the loses, while Ethernet is very straightforward. If the cable guy can do the coax for you - take it. If you have to do the wiring yourself - stick to the Ethernet.

Also note that cable modem transmit power needs to be adjusted to the losses of the coax cable. So it's usually not possible to change the length of coax without calling the cable guy in.

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Coax is designed to carry cable TV for hundreds, even thousands of feet. Ethernet not so much.** Though for a <50 foot run it's not going to make much difference either way - the smart play is to favor the most convenient and least intrusive location which produces [edit:] harmony among the occupants regardless of gender, race, creed, color, sexual orientation or national origin.

** By which I mean modern Ethernet. Old Ethernet used either thick Coax, thin Coax or twisted pair. Thick (10Base5 as in 500 metres) had the longest range, thin (10Base2, 200m) was second, and twisted pair (10baseT) was the shortest and resembles what we use today.

  • I agree with coax being able to carry the signal but cat6 is not coax – Ed Beal Jun 22 '16 at 0:46
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Since I don't think it will make much difference either way, performance wise. I'd think about convenience, and ease of troubleshooting.

To me, it makes sense to have all the equipment in a single location. If you have a problem, the provider is going to ask you to reboot all the equipment. If doing so requires visiting multiple locations, it's inconvenient.

When running coaxial cable, you want to avoid splices. Adding splices also introduces a point of failure. Because of this, you'll want the coaxial run to be continuous from utility box to modem. So while in wall jacks look good, they're an unnecessary point of failure.

Finally, if you don't have a convenient way to run the cable, i.e. a conduit or chase. Consider installing one. Installing conduit from the utility box to the point of use, will allow you to more easily upgrade when new technology becomes available (fiber optics).

If it were me:

  • Pick a location where all the equipment can live together.
  • Run conduit from utility box to equipment location (make sure to install pull boxes where required, to make pulling the cable easier).
  • Pull a single length of coaxial cable from utility box, through conduit to the modem.

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