Mediacom → Re: [AL] Low receive power in Huntsville/Madison AL

Thanks for the reply Burner. I'm in a related industry (I actually design DSLAMs and ADSL line cards, but I can't get DSL in my area, isn't that a laugh), so I understand a lot of your network but I don't know some of the fine detail. Where exactly are the amplifiers physically located? In my neighborhood we have all underground utilities and Mediacom has a metal outside plant box at the front corner of every other house on my side of the street. I assumed that these boxes are entirely passive and that the line amplifier is located a bit further up the network. Right or wrong? How are the amplifiers powered? Through the coax I assume (RG11 maybe?). I'd really like to learn more about how cable networks are layed out.

Thanks again,

Michael

»Cable Modems and Wiring Issues

That FAQ Is more comprehensive than i have time to post, Just got home from an outage It also has some pics

The worst part about Coax is that you have to worry about "Signal Flow" (Much like plumbing) and Signal loss. Every Time a cable is split there is less signal. The further you run a cable the more loss there is in that run.

The coax is anywhere from .500" to 1.25" Diameter Coax usually with a hard aluminum Shield, This shield may be wrapped in black plastic so the lines may be silver or black. The small boxes in every other yard are Taps, Entirely passive, These connect each drop to the hardline. There are differnt value taps. The value is the amount of signal "loss" going from the hardline into the drop, Normal values are from a 26 right next to an amp all the way to an 8 or 4 when you get close to hitting another amp. The value and how far away the next amp is depends on the distance you need to go, the size of cable , and the number of houses you need to feed. So there is usually +30 to +45dB in the hardline.

There is 2 differnt uses for cable in a modern HFC Plant, Trunk and Feeder. Trunk is a thicker diameter cable and has no passives in it. It is used to get the signal past the current neighborhood to another with the lowest signal loss possible. Feeder is usually a smaller diameter cable and has all the passives in it. It is used for feeding homes.

You ever see an electric meter on a utility pole With a line going to a box a little higher up? Usually a power supply for our amps. Most amps take 60VAC. That goes into a Power inserter and can be back fed into the Amp or can be run directly into the amp.

There are generally 3 kinds of amps
1.) Line extender - Usually 1 feeder in One feeder out.
2.) Bridger Amp - Usually 1 Trunk in and several feeder out. Can also have a Trunk out.
3.) Node - Turns IF into RF and Vice-Versa, Usually 1 fiber in and several trunk or feeder out depending on the situation / location.
The power is easy to control. There is a fuse for each in/out on every amp. Obviously there is a fuse for the line with the AC in (Not necessarily the RF Input leg) If there are Amps further down the line that need Power you put in a fuse for each output with more actives and in those actives when you get to the end you simply dont put a fuse in the output side of the amps.

I think i covered most of it....Any questions? And any other techs if i'm wrong in any of this info PLEASE correct me

EDIT: Found the pic on another FAQ

Thanks again Burner50. That does give me a better handle on what the network looks like. So you think a receive signal power of -10 to -7 dBmV is not too low? I seemed to have less sync drops when I was running a db or two below zero.

I'll call customer service again. The problem I had with customer service is that the person I spoke to didn't seem to be too technically savvy with respect to cable modems. They pretty much seemed to be speaking off a standard script and the 1st thing they wanted to do was schedule a four hour window for me to be home to wait on a tech to show up. In my opinion there really isn't any reason that I should have to be home nor do I think the tech needs to come inside my house. I think they should just take a look at the signal level at the demarcation (what we in the telco world call the NID - Network Interface Device). And I think it goes without saying that the drop outs that appear to be temperature related are extremely unlikely to be anything in my house. Work is pretty busy for me right now and taking half a day to wait on a tech to show up probably isn't in the cards any time soon.

Thanks again for your info. Most appreciated.

Michael

-10 to -70 is about as low as you want to get

a few issues with your explanation, but for the most part pretty good, but trunk cable will contain passive as line splitters which are often found in trunk cable are passives. and if you get down to an 8 or 4 value tap there better not be another amp after it as a 4 value tap is a self terminating tap and an 8 value tap if a 4 port tap is also self terminating, other than that pretty good.

Yea, Sorry Brain-fart.......forgot about splitters on the trunk, but that should be the only passives on the trunk