[Battlemesh] Ethernet over Coax

[Jonathan Morton]

> On 19 Jan, 2018, at 3:03 pm, Philipp Borgers <borgers at mi.fu-berlin.de> wrote:
> 
> I would like to use the old coax cable in our building to extend our local
> community network from the roof to the tenants in the building. Has someone
> experience with ethernet over coax and can recommend hardware for such a setup?

Originally, Ethernet was *designed* to run over coaxial cable.  However, I believe that is limited to 10Mbps and half-duplex, which is likely to be inadequate to serve any significant number of subscribers at anything more than "basic e-mail" standard.  Putting even an office's worth of computers in the same collision domain is a recipe for disaster.  Additionally, typical Ethernet hardware uses 50-ohm cable and terminators, whereas typical UHF antenna cable is 75-ohm; you'd need to find some way to match the interface impedances.

Technically speaking, a miniature DOCSIS setup would be ideal for the hardware, but I assume that would be beyond any reasonable budget for a single-building deployment.

In principle, it might be possible to use wifi hardware to communicate over the cable, but I wouldn't hold my breath.  Wifi operates at significantly higher carrier frequencies than the UHF broadcast band, so the cable probably isn't efficient at transmitting it - *especially* in the 5GHz band which offers the best data capacity.

Ultimately you might find that running fresh twisted-pair cable is easier.  You can shorten cable runs by providing switches on each floor.

 - Jonathan Morton