Weekend project. I’m moving the [del]DNC server [/del] tower computer to a [del]more secure[/del] different location further from the cable entry. Primary object is to get the damn thing out of the bedroom and will also help whole-house coverage which is actually okay. I have access to the attic for routing cable/coax.
Should I extend the coax cable from the ISP to the modem (a Motorola Arris if important)? I’ll need a male to male and about 20 ft of coax based on the routing to the new room.
Leave the modem alone and use a longer CAT 6 cable to the router (Netgear AC1750)?
Is there any difference in signal loss between 20 ft. of coax or 20 ft. of CAT 6?
In principle you would leave the modem as close to the point of entry as you can. It is signal loss in the feed to the modem that matters for speed. Once your connection is terminated in the modem you are now running a different network, and whilst there might be losses in the Ethernet cabling, it won’t really matter. Once your connection losses have lost you speed from your ISP, there is nothing that gets it back.
OTOH, it probably actually won’t make any difference, if your connections are good, and the cable good quality, and you don’t kink it, losses will be minimal compared to the entire run, and you are better served by getting everything out of living space. Your main problem is going to be the bit you can’t control - the run into your house.
CAt6 is good for up to 100 metres - the differences in performance between 10 metres and 70 metres are so small as to be unmeasurable to mortals (assuming the cables are properly made* and their quality is good)
*‘properly made’ here means proper observation of twisted pairs in the cable - some people bodge this and get away with it for short cables. If you’re buying cables with fitted plugs, it’s not a worry - they’ll be right - if you’re terminating cables yourself, research it and do it right.
I was asked once to diagnose a DIY setup for a small office. The front counter PC’s near the router worked fine - the ones at the back failed. I couldn’t see a reason for it to fail… It never occurred to me that someone would not know the proper configuration of ethernet twisted pairs - 12, 36, 45, 78; but this guy had just done 12,34,56,78. So a cable run of 5 to 10 feet still worked, but 50 feet into the ceiling and then to the back of the office - total packet loss. Mind you, this was in the days of 10/100 ethernet, I suspect 1GB is a lot more sensitive.
But yes, using a proper cable from modem to router - I guess it depends on the router. Unless you are pushing 300 feet you will have no problem. (I originally recall the limit being 300ft, 100yards, or 90m) Until recently, routers would do 10 and then 100Mbps since ISP feeds rarely reached that. But I am seeing some feeds claiming to break the 100Mbps mark, and the tech is so cheap there’s no reason for a modern router not to use 1GB for the WAN feed.
Don’t scrimp on the cable. CAT5 is for 100Mbps, CAT5e and CAT6 is for 1GB. For distances inside a house, who really cares - either tech will work fine. (Can you even find CAT4 or CAT5 today?) Your old cable from 10 years ago may be CAT5.
I don’t make cables or wire structured cabling often enough to ever have memorised it, but I learned early on that it matters (and I just have to look it up whenever I need it) - but yes, I’ve met people who didn’t know about it, and others who had been told, but didn’t really believe it, and argued that it makes no difference. Weird.
You’re more likely to have bad connections than bad cables, so if I understand you correctly, if your two options are adding an additional coax segment or replacing a short ethernet cable with a longer one, then the latter is going to be better.
Also as Francis mentions, your internal network is going to be way faster than the cable link to the ISP, so that also points to leaving the coax alone and extending the ethernet cable.