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Old 09-19-2013, 10:05 AM   #1
HazelW
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Satellite Diplexer vs. POE filter?

In my system I use a satellite diplexer to combine the MOCA and the cable modem signals upstairs, and the diplexer feeds the MOCA signal into an 8 way splitter downstairs while the cable signal goes to the incoming cable feed. There is also an amplifier before the 8 way splitter. So the MOCA signal gets blocked by both the amplifier and the diplexer. Do you any need for a POE filter in this setup?
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Old 09-19-2013, 12:16 PM   #2
FrodoB
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In my system I use a satellite diplexer to combine the MOCA and the cable modem signals upstairs, and the diplexer feeds the MOCA signal into an 8 way splitter downstairs while the cable signal goes to the incoming cable feed. There is also an amplifier before the 8 way splitter. So the MOCA signal gets blocked by both the amplifier and the diplexer. Do you any need for a POE filter in this setup?
Sounds more or less like my setup, and in my case, adding the POE filter actually kills my cable modem (for reasons inexplicable; maybe there's already one inside it and something just goes haywire?). The amp should do plenty to nuke the MOCA for you (assuming it's not a MOCA-compatible amp) without the need for the POE filter, IMHO.
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Old 09-19-2013, 01:17 PM   #3
Scooby Doo
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So the MOCA signal gets blocked by both the amplifier and the diplexer. Do you any need for a POE filter in this setup?
The diplexer isn't blocking the MOCA signal and the amplifier probably isn't doing much either; there are several people on this forum running MOCA through an amp. So yes, you still need a filter. Remember it's for your benefit as well as your neighbors. And it's $5.

Regarding cable modems, the recommend installation for a MOCA filter is not to insert it upstream of your cable modem. How easy this is depends on where exactly in your installation you have your cable modem.
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Old 09-19-2013, 02:33 PM   #4
FrodoB
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Regarding cable modems, the recommend installation for a MOCA filter is not to insert it upstream of your cable modem. How easy this is depends on where exactly in your installation you have your cable modem.
At the risk of taking the thread a bit on a tangent relative to the original question...

I'm always a bit perplexed by how the recommended installation of splitting out the cable modem from the rest of the cable signal is supposed to play out in practice. Maybe houses in other parts of the country have their cable runs come in different places that make it more convenient, but the two houses we've owned here in Wisconsin brought the cable in through the furnace room, which is a crappy place to stick a router generally. Sure, I could run a bunch of Ethernet cable from a cable modem there to a place where a router stands to get signal, or I could make a second parallel coax run for the cable modem separate from the existing one that feeds the cable modem and the MOCA adapter for getting the router's network through the house, but neither of those seems like an option that most cable companies are going to be willing to do "standard" (since "standard" means not running more extra cable than is minimally necessary, at least for Charter). Do cable companies actually do this sort of thing generally in other parts of the country, or are cable runs more conveniently located?
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Old 09-19-2013, 02:44 PM   #5
Scooby Doo
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My cable entry is in the attic, which is actually quite a good place to locate a modem and router. I agree it's a bit harder if your cable entry is in the basement. One option is to have the modem and a Moca adaptor in the basement and then install a router for wifi somewhere upstairs. No need for parallel coax.
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Old 09-19-2013, 04:39 PM   #6
HazelW
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My cable comes into a box on the side of the house. It goes to a two way splitter. One side goes to an amplifier connected to an 8 way splitter that then feeds all the TV outlets in the house. The other side goes up to my office where the cable modem and router are located.

The MOCA adapter connects to the router in my office and since the coax side would go to the two way splitter on the other side of the amplifier, the MOCA signal would be blocked by the amplifier. Thus I use a satellite diplexer to combine the MOCA and cable signals in the office, and another diplexer to separate them outside the house. The MOCA side of the diplexer goes to a port on the 8 way splitter where it gets fed to all the other outlets in the house. The other side goes to the two way splitter.

Since a diplexer is essentially a low pass filter (as is a POE) I believe they accomplish the same thing.

If the router was in the basement, I could not connect it to my computer in the office.
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Old 09-19-2013, 05:15 PM   #7
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Originally Posted by HazelW View Post
My cable comes into a box on the side of the house. It goes to a two way splitter. One side goes to an amplifier connected to an 8 way splitter that then feeds all the TV outlets in the house. The other side goes up to my office where the cable modem and router are located.

The MOCA adapter connects to the router in my office and since the coax side would go to the two way splitter on the other side of the amplifier, the MOCA signal would be blocked by the amplifier. Thus I use a satellite diplexer to combine the MOCA and cable signals in the office, and another diplexer to separate them outside the house. The MOCA side of the diplexer goes to a port on the 8 way splitter where it gets fed to all the other outlets in the house. The other side goes to the two way splitter.

Since a diplexer is essentially a low pass filter (as is a POE) I believe they accomplish the same thing.

If the router was in the basement, I could not connect it to my computer in the office.
Wow, that's actually pretty cool. And I agree no POE required.
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Old 09-19-2013, 05:16 PM   #8
FrodoB
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Originally Posted by HazelW View Post
My cable comes into a box on the side of the house. It goes to a two way splitter. One side goes to an amplifier connected to an 8 way splitter that then feeds all the TV outlets in the house. The other side goes up to my office where the cable modem and router are located.

The MOCA adapter connects to the router in my office and since the coax side would go to the two way splitter on the other side of the amplifier, the MOCA signal would be blocked by the amplifier. Thus I use a satellite diplexer to combine the MOCA and cable signals in the office, and another diplexer to separate them outside the house. The MOCA side of the diplexer goes to a port on the 8 way splitter where it gets fed to all the other outlets in the house. The other side goes to the two way splitter.

Since a diplexer is essentially a low pass filter (as is a POE) I believe they accomplish the same thing.

If the router was in the basement, I could not connect it to my computer in the office.
Aha. Sounds like your layout is almost identical to mine if I added in a splitter before the amp and then another diplexer instead of running the cable modem/MOCA line through the 8 way after the amp. (Explains how you have the cable modem/MOCA on a single line and still have the recommended split.) I should think about doing that; I know best practice is to not have cable modem traffic going through the amp. I just hope it doesn't kill my cable signal, which was marginal even with the amp in some rooms.

My understanding is the same as yours, that the POE filter would be redundant to the diplexer. Either way, I don't see how, with your setup, you could put the POE filter at a point before there'd hypothetically be MOCA traffic (assuming it really does bleed through the diplexer somehow) and yet not be upstream of the cable modem. If you put it before the amp input, it's after the splitter and therefore doesn't stop this hypothetical leaked signal. If you put it anywhere on the line that feeds the diplexer or before the splitter, you hit the cable modem upstream. So without running a dedicated cable for the MOCA adapter, I don't think this can be done. (Of course, if your cable modem isn't impacted by the POE filter like mine apparently is, you could just put it before the splitter and call it a day. )
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Old 09-19-2013, 05:29 PM   #9
HazelW
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Aha. Sounds like your layout is almost identical to mine if I added in a splitter before the amp and then another diplexer instead of running the cable modem/MOCA line through the 8 way after the amp. (Explains how you have the cable modem/MOCA on a single line and still have the recommended split.) I should think about doing that; I know best practice is to not have cable modem traffic going through the amp. I just hope it doesn't kill my cable signal, which was marginal even with the amp in some rooms.

My understanding is the same as yours, that the POE filter would be redundant to the diplexer. Either way, I don't see how, with your setup, you could put the POE filter at a point before there'd hypothetically be MOCA traffic (assuming it really does bleed through the diplexer somehow) and yet not be upstream of the cable modem. If you put it before the amp input, it's after the splitter and therefore doesn't stop this hypothetical leaked signal. If you put it anywhere on the line that feeds the diplexer or before the splitter, you hit the cable modem upstream. So without running a dedicated cable for the MOCA adapter, I don't think this can be done. (Of course, if your cable modem isn't impacted by the POE filter like mine apparently is, you could just put it before the splitter and call it a day. )
The POE filter could go between the cable drop and the first two way splitter.
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Old 09-19-2013, 05:49 PM   #10
FrodoB
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The POE filter could go between the cable drop and the first two way splitter.
Wouldn't it still be upstream of the cable modem, then?
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Old 09-19-2013, 05:59 PM   #11
Scooby Doo
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Wouldn't it still be upstream of the cable modem, then?
Yes it would. Thinking about it some more, you could put the POE filter just before the amp since you may be leaking some Moca back through the amp. But I'm going to guess you experimented and found that your particular amp blocks the Moca frequencies, since otherwise your design could have been simpler.
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Old 09-19-2013, 06:27 PM   #12
HazelW
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Wouldn't it still be upstream of the cable modem, then?
No, the POE attaches to the cable that comes into the box from the cable company. Its the first thing the cable signal passes through before it comes into your house.
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Old 09-19-2013, 06:33 PM   #13
Scooby Doo
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No, the POE attaches to the cable that comes into the box from the cable company. Its the first thing the cable signal passes through before it comes into your house.
Meaning it's upstream of the modem (i.e between the modem and the cable head end.). So not ideal.
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Old 09-19-2013, 07:03 PM   #14
HazelW
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Meaning it's upstream of the modem (i.e between the modem and the cable head end.). So not ideal.
That is where it should be. it just keeps MOCA from going back out of your house. Cable signal will pass through.
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Old 09-19-2013, 07:32 PM   #15
Scooby Doo
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That is where it should be. it just keeps MOCA from going back out of your house. Cable signal will pass through.
The general advice is to not put the POE between the modem and the cable head end because it may block channels used by the modem. Whether this matters or not depends on the frequency assignments used by your cable operator.
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Old 09-20-2013, 08:03 AM   #16
HazelW
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The general advice is to not put the POE between the modem and the cable head end because it may block channels used by the modem. Whether this matters or not depends on the frequency assignments used by your cable operator.
Take a look at the examples in this document:

http://www.cisco.com/en/US/docs/vide.../4031235_B.pdf
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Old 09-20-2013, 10:21 AM   #17
Scooby Doo
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I stand corrected. There have been people on this forum who have had problems with POE filters stopping there cable modems working, but these could well have been user error.
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Old 09-20-2013, 11:30 AM   #18
FrodoB
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I stand corrected. There have been people on this forum who have had problems with POE filters stopping there cable modems working, but these could well have been user error.
I'm one of them. I tried the POE filter on the main line into the house and every step past it that would still allow the MOCA inside the house, and it took the cable modem out each time. Confused the heck out of me at first, because the installation of the POE filter was part of a larger rewiring. The previous house owner used OTA only and so the cable line inside the house was 20 year old RG6 (basement, post remodel) or over 20 year old RG59 (upstairs) and so had god-awful signal everywhere. I upgraded everything I could easily access to RG6 quad shield, replaced the 8 way amp that Charter had installed with a one way amp feeding an 8 way splitter so it wouldn't block the MOCA, and installed the POE filter per the instructions on my new Premiere 4. (I got in on the "transfer your $6.95 MSD" deal from June and now am wishing I had the spare funds for a Roamio, although since I'm used to S3 and S2 hardware, the Premiere doesn't seem *that* slow. ) And lo and behold, substantially better wiring leads to dead Internet?!? And the cause turns out (after an hour of futzing while my wife was "patiently" awaiting the return of the Internet) to be the POE filter. I have a suspicion that the DOCSIS 3 modem Charter gave me earlier this year has MOCA blocking built-in and something's just going weird from having a second (well, third with the amp) line of defense.
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Old 09-22-2013, 05:09 PM   #19
HazelW
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I believe that the internet traffic to and from the cable company is below the TV band, i.e. < 5 MHz. I can't see how a POE filter would affect this in any way except perhaps your cable company is using high frequencies for internet.
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Old 09-23-2013, 03:00 PM   #20
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I believe that the internet traffic to and from the cable company is below the TV band, i.e. < 5 MHz. I can't see how a POE filter would affect this in any way except perhaps your cable company is using high frequencies for internet.
There is insertion loss on a POE filter, but it is a low pass filter by design.. Diplexer is the exact same thing, just don't know the frequency cut off. It's probably passing < 1 GHZ.. I REALLY don't expect that anything is above 1GHZ anyway.. DOCSIS channels are all over the place, i see one at 254MHz, 404mhz, even one up in the 850mhz range..

My plant comes into home, go into a POE.. Out of POE is 3 way splitter..
1) -7DB into eMTA, 2) -3.5GB into Cable Modem, 3) -7DB into a 10DB amp.. AMP has two legs, which are each split again.. Truth be told, this is about balanced as you can get.. My eMTA and Docsis power levels are +5dBMV Receive, 46dBmV on transmit.. (Across 4 bonded channels)

I didn't want to depend on my AMP to keep my eMTA and Cable modem functional. MOCA on my Elite works fine, even to my 2 mini's that are on the other leg of the amp.. The only downside is, i have my eMTA and Cable modem (and a UPS) up in the attack... Probably limiting their life, due to heat... But lots of signal all around and moca works like a charm.
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