We have a customer that is remodeling an entire apartment building and has their construction office in one apartment. As the project moves along, they need to relocate the construction office accordingly. They have their telephone and Internet service provided by Comcast using hardware located within the apartment.

The customer now needs us to move everything to the next temporary office location in a different apartment. My thought is that as long as they remain on the same node, we should be able to plug in the modems to any working CATV outlet in the building.

Am I correct in my assumption? It is my understanding that Comcast communicates with these devices using MAC addresses, so the modems should work pretty much anywhere on their network, correct?

Ed,

We had to do the same thing with one of customers several times during the different phases of construction. Comcast didn't actually care that we moved it because I checked with them. They told me that they would have to charge each time they came out to move. We moved it from it's original locations 2 times before it landed in its final destination. I would say you should be good as long as your coming from the same entrance cable and can tap off. I have seen when they are using multiple devices on the cable network they use different .db level splitters (i don't know if that is just something that I've noted and is normal or if that was just what they had on the truck) and that would be my only concern.

I was always told that the modem needs to be as direct a line as possible...connected to one leg of a 2 way from the main drop, and the other leg would feed the TVs.

Jeff that was alway my understanding as well, not that it would not work but speed may suffer

I've always seen it done that way by Time Warner so that's how I've done it.

Ed, is there a way for you to leave the modem in one place (in the basement or other utility area) and just transport the voice and data via twisted pair to each apartment, as it's needed?

Not really Arthur. The apartments only have a three pair feed from the riser closets and we need six. All solid sheetrock.

Hmmm...

As my old Grandma would say, you're S.O.L.

I guess you don't want to set up a short-haul T1 line from the basement to the apartment. Put an Adtran 750 channel bank at each end, and send data and voice over two pairs.

I can lend you the channel banks with FXO and FXS cards, but I don't have any data cards to go in them.

I see no problem with moving the modem as long as it's still within the same physical address. Keep in mind that it's registered to the E911 database. Move it across town and that will be a problem.

-Hal

Have the customer call Comcast and inquire as to the costs? I would think a TR wouldn't be much. Yes you don't get the work, but you won't get blamed if it doesn't work or the calls are choppy, etc.

We did the move yesterday and everything went just fine. The new apartment was actually served from the same set of riser taps that the original one was.

The reason that the customer asked us to do this was because Comcast had told them that there was a three-week window to schedule the dispatch of a technician. They were more than willing to pay, but three weeks was too much of a delay.

I got a chance to scope out the riser and tap arrangements for this complex of three high-rise apartment buildings. Yes, each building does have a physical street address, but they all share a single telephone/CATV room in the basement of one of them, so a nodal issue in any apartment won't be a problem.

Thanks for the reminder about 911, Hawk. Didn't think about that one. I'm sure that the customer can change this information with Comcast for minimal (if any) expense.

Thanks for the reminder about 911, Hawk. Didn't think about that one. I'm sure that the customer can change this information with Comcast for minimal (if any) expense.

It was me Ed. I don't believe the customer can change the E911 location for liability reasons. That information is entered when the modem is installed by the cable tech at the physical address and the account is activated.

-Hal

The differing taps are so that they can compensate for cable losses in the outside plant, and maintain a consistent level to each customer. The tap attenuation decreases the farther you get from the last amplifier on the trunk cable.

Lets say that you have a trunk amplifier that puts out +30db, and you want to maintain a level of 0db at the customer set. Lets say for the sake of argument that 1/2" hardline has a loss of 1db/100', and RG6 has a loss of 6db/100'.

Lets also assume that you are trying to maintain 0db +/-2db, and that the average drop length to a customer is 75', with a splitter, and 50' drops to the sets. Taps off the trunk cable are every 100'. Lets assume that the splitters have 4.5db loss.
That's ~12db loss from the tap to the set.

If your first tap is at the amplifier output, you would need ~18db of attenuation at that tap to feed the first set of drops, 17db at the next tap 100' downstream, 16, 15, etc.. Taps come in 3db increments, so you would probably have 17, 17, 15, 15, etc.
Plug-in attenuators are also available, which can be used to compensate for asymmetric drop lengths, etc.

The large tap housings used on hardline have interchangeable inserts, so they sometimes put a couple housings in series, with different tap values. There are also large housings which can accommodate half a dozen tap plates for structured wiring applications such as apartment houses.