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Running Ethernet over existing coaxial cable

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Re: Running Ethernet over existing coaxial cable

#21

Post by Dylan16807 »

sidewndr46 wrote: post #10
PlutoIsAPlanet wrote: post #4

I have tried MOCA, but it runs at higher frequencies than cheap European coaxial was designed for (lower frequencies for terrestrial television) and had stability/performance issues due to this. There's an alternative called G.hn over Coaxial, that runs at 100-200Mhz which seems to fair much better on crappy coaxial, at the cost of max bandwidth (500Mbps-1000Mbps) and harder to get hardware. The manufactures of G.hn2…

Given that WiFi is meant to work over the air, you could probably get a set of access points, RP-SMA to type-F adapters, and a set of attenuators and connect them back to back over basically any random coax. The loss is higher in the coax than in the air but there should be a noise floor consistent with transistor noise at room temperature. You'd want to start with as many pads as possible, so something like >80 dB o…

> The loss is higher in the coax than in the air

Oh, I did the math on this before.

So you technically don't have much loss from the air itself, but you lose 6 decibels every time you double the distance from the antenna. So at the distances people normally use wifi, the loss from distance alone is higher for air than for coax. And that's not counting the 40+ decibels of loss you start with for adjacent devices with antennas.

Re: Running Ethernet over existing coaxial cable

#22

Post by sidewndr46 »

Dylan16807 wrote: post #21
sidewndr46 wrote: post #10

Earlier quoted context omitted.

Given that WiFi is meant to work over the air, you could probably get a set of access points, RP-SMA to type-F adapters, and a set of attenuators and connect them back to back over basically any random coax. The loss is higher in the coax than in the air but there should be a noise floor consistent with transistor noise at room temperature. You'd want to start with as many pads as possible, so something like >80 dB o…

> The loss is higher in the coax than in the air Oh, I did the math on this before. So you technically don't have much loss from the air itself, but you lose 6 decibels every time you double the distance from the antenna. So at the distances people normally use wifi, the loss from distance alone is higher for air than for coax. And that's not counting the 40+ decibels of loss you start with for adjacent devices with…

it really depends on the coax involved. The old stuff put in homes is abysmally bad for cable TV at 700 or so MHz. So at triple the frequency it is really bad. The APs are nominal 50 ohms, and the coax is 75 ohms. So that alone is a huge loss that is present twice in the system.

Also sometimes the coax takes insane routes because the installer couldn't be bothered to run it the shortest distance.

It isn't hard to find a scenario where two APs with dipoles technically have less loss than a run of coax. The advantage the coax has is noise floor, which is what actually determines the bandwidth of a communications channel.

Re: Running Ethernet over existing coaxial cable

#23

Post by avery17 »

Spivak wrote: post #17
franga2000 wrote: post #7

Earlier quoted context omitted.

If the cables were run in conduits AND if there aren't any sharp turns AND if you own the place or got your landlord's permission.

I will eat my hat if anyone installing coax actually uses conduits, the kind of people doing the installation -- your cable provider gives zero shits. Avoiding "sharp turns" should be no issue since in your average home you're not gonna need >4 quarter turns that would necessitate a junction box.

Our cable provider just drilled a hole into our house through the exterior siding, through the floor moulding and right into the dining room. Hooked it straight up, no box, no wall plate. Didn't even seal the hole. They dont give a shit.

Re: Running Ethernet over existing coaxial cable

#24

Post by Dylan16807 »

sidewndr46 wrote: post #22
Dylan16807 wrote: post #21

Earlier quoted context omitted.

> The loss is higher in the coax than in the air Oh, I did the math on this before. So you technically don't have much loss from the air itself, but you lose 6 decibels every time you double the distance from the antenna. So at the distances people normally use wifi, the loss from distance alone is higher for air than for coax. And that's not counting the 40+ decibels of loss you start with for adjacent devices with…

it really depends on the coax involved. The old stuff put in homes is abysmally bad for cable TV at 700 or so MHz. So at triple the frequency it is really bad. The APs are nominal 50 ohms, and the coax is 75 ohms. So that alone is a huge loss that is present twice in the system. Also sometimes the coax takes insane routes because the installer couldn't be bothered to run it the shortest distance. It isn't hard to fin…

> The APs are nominal 50 ohms, and the coax is 75 ohms. So that alone is a huge loss that is present twice in the system.

Is the impedance mismatch worse than the 40 decibels of loss you get just by having antennas? Shouldn't it be pretty small? And you can correct for it, can't you?

> The old stuff put in homes is abysmally bad for cable TV at 700 or so MHz. So at triple the frequency it is really bad.

What kind of cabling should I assume? RG-59 loses about half a decibel per meter at 2.4GHz. So if someone is 30 meters away, but it's 60 meters via coax, both methods should give them 30 decibels more loss than at 1 meter away. The total loss is still over twice as bad for the antenna connection. And that's with no walls.

What does a situation look like where the antenna technically has less loss?

Re: Running Ethernet over existing coaxial cable

#25

Post by tguvot »

phil21 wrote: post #13
zcw100 wrote: post #8

Earlier quoted context omitted.

Yes. All true. I just hate the coax in my house. It pisses me off every time I see there they installed it by just drilling a hole in the facade.

I bought a house in a locality that requires conduit for all in-wall wiring (including low voltage) by code. This annoys most people, but I love it since it means you can upgrade stuff easily in the future if you desire. This house did not have cat5 installed anywhere, but it had both coax and cat3 for the old school phone lines/intercom system. During the inspection I removed some wall plates and noted that there in…

conduits aren't that magical, especially in concrete walls. they tend to break/bend too much in plane transitions making it hard or impossible to pull anything through them even if there is pull string inside

Re: Running Ethernet over existing coaxial cable

#26

Post by khaki54 »

I have these in my house. They work super good, and I usually plug them in to a switch that can do 2.5Gb and then from there any media devices or AP. What's interesting is they are not point to point, they're like a bus topology or something. You can have 5 and they will all work fine.

Re: Running Ethernet over existing coaxial cable

#27

Post by riehwvfbk »

Dylan16807 wrote: post #16

I bet there was something physically wrong with the cat5 wiring as the actual reason it couldn't do gigabit.

Was going to post the same thing. I had a new construction townhouse in the Bay Area that had Ethernet. The max speed was either 10 or 100 Mbps depending on which jack was used. Opened up the jacks to discover that the cables were stripped of the jacket for at least 6 inches, the twisted pairs were untwisted and this mess was jammed into the wall behind the jack. At every single location. The worst offender wouldn't connect at all. That had a foot of jacket stripped off. Re-crimping all the jacks made everything work at 1 gigabit.

In summary, general tradespeople don't know how to install Ethernet.

Re: Running Ethernet over existing coaxial cable

#28

Post by runjake »

dmw_ng wrote: post #2

AIUI the minimum latency on these is always measured in milliseconds, with 6-7ms apparently commonplace, which you're going to immediately feel using e.g. a block or network storage protocol. No references, but did look at moca for exactly the same reason a few months back. The physical size of the models I looked at also suggested you'd want to check power consumption before stuffing a home full of them - custom dev…

I have the same set of ScreenBeam MoCA adapters that are in the article and I get Most home users aren't going to really notice or care about a 6-7ms latency for even network file protocols. They're probably using Wi-Fi anyway.

Re: Running Ethernet over existing coaxial cable

#29

Post by Symbiote »

mrkstu wrote: post #12
PlutoIsAPlanet wrote: post #4

I have tried MOCA, but it runs at higher frequencies than cheap European coaxial was designed for (lower frequencies for terrestrial television) and had stability/performance issues due to this. There's an alternative called G.hn over Coaxial, that runs at 100-200Mhz which seems to fair much better on crappy coaxial, at the cost of max bandwidth (500Mbps-1000Mbps) and harder to get hardware. The manufactures of G.hn2…

I have ancient coax in the US on my house built in the 70s, leading to syncing at lower bandwidth often on my moca, sometimes as low as 100Mb. Luckily it runs outside the house, so at some point I’ll replace it with newer cable and actually get the theoretical 2.5 Gb.

If you're replacing the cable, you may as well install an ethernet cable.

Re: Running Ethernet over existing coaxial cable

#30

Post by gkfasdfasdf »

zcw100 wrote: post #6

There’s something even better than MOCA. Black electrical tape. You tape the cat5 to the end of the coax and then pull really hard and then you get great performance.

If cables are running through holes drilled through studs/joists those may be filled with flame-retardant foam, which could make pulling tricky.
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