# POE filter in an apartment



## Kerwin51580 (Sep 20, 2012)

Before I ask my question, here's some background:
We live in an aprtment and have two Premiere XL4s, one in the living room and one in the bedroom. The living room XL4 is connected directly to the router. This one is also serving as a moca bridge to the one in the bedroom. I can stream between the two just fine. The Tx/Rx rates hover around 142 Mbps/112 Mbps. 

The way the cable is configured in my apartment is as follows:
Point of Entry ==> Splitter 1

Splitter 1 connects to cable modem and Splitter 2

Splitter 2 connects to both Tivos.

I read on tivo.com that a moca network in an apartment wouldn't work because a POE filter couldn't be installed where the cable comes in, but it obviously works in my situation without it. Just to be doubly sure that my neighbors can't access my network, I set an encryption key in the moca settings.

So, my question is whether or not installing a POE filter where the cable comes into my apartment is a good idea or am I just trying to fix something that isn't broken?

Thanks in advance!


----------



## NotNowChief (Mar 29, 2012)

I would put in the filter. I understand you set up encryption, but why not prevent the issue in the first place?

It seems you have clear and open access to all of your wiring in the apartment, if you can readily identify your POE, try it.


----------



## CoxInPHX (Jan 14, 2011)

Yes, place the POE MoCA filter where the cable comes into your apartment, The POE filter not only prevents your network from reaching your neighbors.

It also reflects the MoCA signal back into your coax making your signal stronger. 

It also prevents the MoCA signals from causing excess noise issues for your neighbors that could potentially cause them signal problems.


----------



## dianebrat (Jul 6, 2002)

I'd install it, there are many positives, and CoxinPHX's last reason is actually a big deal in an apartment, my Dad did MoCA and didn't do POE and the neighbors in the next house over were having issues because his signal was back filling to them and causing issues.


----------



## unitron (Apr 28, 2006)

Kerwin51580 said:


> Before I ask my question, here's some background:
> We live in an aprtment and have two Premiere XL4s, one in the living room and one in the bedroom. The living room XL4 is connected directly to the router. This one is also serving as a moca bridge to the one in the bedroom. I can stream between the two just fine. The Tx/Rx rates hover around 142 Mbps/112 Mbps.
> 
> The way the cable is configured in my apartment is as follows:
> ...


Where to put what depends on exactly what it does.

What does a POE filter block and what does it pass?


----------



## steve614 (May 1, 2006)

This sounds like a similar situation that I had with getting DSL internet in my apartment.
Once you get DSL, any peripheral device that uses the phone line requires a DSL filter.
In my case, the phone jacks throughout the dwelling are wired to a central location, and I only need one filter at that junction. 

In contrast, some houses are wired to a central box only accessable to the phone company. In this case you need a filter at each location.


----------



## CoxInPHX (Jan 14, 2011)

unitron said:


> Where to put what depends on exactly what it does.
> 
> What does a POE filter block and what does it pass?


http://www.cisco.com/en/US/prod/collateral/video/ps8806/ps9095/ps10163/7016817.pdf

http://www.soontai.com/MoCA-POE-h.htm

http://www.soontai.com/MoCA-LPF-M3.html


----------



## Kerwin51580 (Sep 20, 2012)

Thanks for all of your input! I'll definitely get one soon. I've noticed that the Tx/Rx rates have actually increased since I posted. As of this morning, I'm getting steady rates of 150 Mbps/142 Mbps and I don't know why they would've increased dramatically without any sort of intervention on my part.

So should I just buy the POE filter from tivo or just get one from ebay for slightly cheaper?


----------



## unitron (Apr 28, 2006)

Okay, now that I know it's basically a low pass filter with a knee at about 1,000MHz, it should probably be the first thing the cable company's cable sees on the way in, unless MoCA screws up the cable modem, in which case cable to splitter, splitter out 1 to cable modem, splitter out 2 to POE filter, filter to second splitter.


----------



## CoxInPHX (Jan 14, 2011)

Kerwin51580 said:


> So should I just buy the POE filter from tivo or just get one from ebay for slightly cheaper?


If you have walk-in stores for your Cable Co. I would go there and ask them if they have one, It will probably be free. As the Cable Co benefits and probably requires you to use one with a MoCA set-up.


----------



## NotNowChief (Mar 29, 2012)

unitron said:


> Okay, now that I know it's basically a low pass filter with a knee at about 1,000MHz, it should probably be the first thing the cable company's cable sees on the way in, unless MoCA screws up the cable modem, in which case cable to splitter, splitter out 1 to cable modem, splitter out 2 to POE filter, filter to second splitter.


Exactly. My understanading has been that MoCA uses the unused frequencies below 1ghz to run network traffic. The filter just blocks those low frequencies so the modem and OnDemand will work without a problem.


----------



## poppagene (Dec 29, 2001)

NotNowChief said:


> Exactly. My understanading has been that MoCA uses the unused frequencies below 1ghz to run network traffic. The filter just blocks those low frequencies so the modem and OnDemand will work without a problem.


MoCA channels are located at different frequency bands between 875
MHz to 1500 MHz


----------



## Kerwin51580 (Sep 20, 2012)

I ordered a filter on ebay. I should have it by Monday. I've noticed that since my PHY rates magically increased the other day, I've gotten a few packets with errors. Not so many to make me believe there's a problem with anything (82 on the living room TiVo out of the 7+ million it's received; 10 for the bedroom TiVo).


----------



## unitron (Apr 28, 2006)

NotNowChief said:


> Exactly. My understanading has been that MoCA uses the unused frequencies below 1ghz to run network traffic. The filter just blocks those low frequencies so the modem and OnDemand will work without a problem.


The television channels should be below 1GHz (1,000MHz), and the cable modem for internet access should be below them, since they don't start until 54MHz or thereabouts, which leaves 7 TV channels worth of bandwidth underneath.

The MoCA stuff should be going on above 1GHz.

Perhaps the specs on both the MoCA adapters and the POE filter should be taken into account together, since there seem to be POE filters with a knee down around 850MHz as well.


----------



## NotNowChief (Mar 29, 2012)

unitron said:


> The television channels should be below 1GHz (1,000MHz), and the cable modem for internet access should be below them, since they don't start until 54MHz or thereabouts, which leaves 7 TV channels worth of bandwidth underneath.
> 
> The MoCA stuff should be going on above 1GHz.
> 
> Perhaps the specs on both the MoCA adapters and the POE filter should be taken into account together, since there seem to be POE filters with a knee down around 850MHz as well.


Thanks for the info and clarification, now I have plenty of reading to do today!

I found this to be interesting and very informative:

http://www.ieee802.org/1/files/public/docs2007/at-sovadia-MoCA-overview-0507.pdf


----------



## Kerwin51580 (Sep 20, 2012)

My POE filter should be arriving today. Just an updated on things: Originally, the TA in the bedroom was connected to the TiVo by a 25" long coax cable -- couldn't do anything about the length. I was desperate and that was the only size the local drugstore had. I swapped it out on Monday with a 9" quad shielded cable from Monoprice. It bumped up my Tx/Rx rates about 20Mbps in each direction.

I just want to make sure I install this filter the right way. I figure I should power down both TiVos, both TAs, the cable modem and router and THEN install the filter. Then, power everything up in the reverse order? Does that sound right?


----------



## Kerwin51580 (Sep 20, 2012)

Well I guess I was overthinking everything! POE filter is in place and my Tx/Rx rates are now the same. And they've jumped quite significantly hovering between 235 - 238 Mbps.


----------



## NotNowChief (Mar 29, 2012)

Glad to hear it worked.

Dont worry about the cable length, its only 25 feet, not 250. Even if its RG-59, its not the end of the world. Hopefully, its RG-6.


----------



## Kerwin51580 (Sep 20, 2012)

NotNowChief said:


> Glad to hear it worked.
> 
> Dont worry about the cable length, its only 25 feet, not 250. Even if its RG-59, its not the end of the world. Hopefully, its RG-6.


Yeah, the new cable is RG-6. Looks like I'm finally all set.


----------



## bsd (Sep 30, 2002)

Any idea where I can find a filter in NYC? Tivo has them, but I will pay almost as much for shipping as the filter itself costs. I tried calling Radio Shack and Best Buy and they had no idea what I was talking about.


----------



## CoxInPHX (Jan 14, 2011)

bsd said:


> Any idea where I can find a filter in NYC? Tivo has them, but I will pay almost as much for shipping as the filter itself costs. I tried calling Radio Shack and Best Buy and they had no idea what I was talking about.


Does your Cable Co have retail stores? They should have them probably free.

Or (several w/ free shipping)
http://www.ebay.com/sch/i.html?_sacat=0&_nkw=moca+filter&_frs=1


----------



## Dan203 (Apr 17, 2000)

I'd put it on the input side of Splitter 2. Since both TiVos are connected to that splitter they'll be able to talk just fine and then there is no chance the POE filter will interfere with your cable modem. (it shouldn't anyway, but some people report slight drops in cable modem speeds after installing a POE filter)

Dan


----------



## lrhorer (Aug 31, 2003)

CoxInPHX said:


> Yes, place the POE MoCA filter where the cable comes into your apartment


It can be anywhere before the root splitter. If I read his topology correctly, the root splitter is splitter #2, so anywhere before that should be good.



CoxInPHX said:


> It also reflects the MoCA signal back into your coax making your signal stronger.


That is utter nonsense. A reflection would be deadly to the MoCA network. A reflection only doubles the signal amplitude at the reflection point. Everywhere else all you would be doing is producing ghosts - seriously bad ones. If a node is, say 15 meters from a reflection, then it would receive a particular bit in the bit stream at time t = 0, then it would receive the very same bit again at t = 0.05 microseconds later, or at 100Mbps or 5 bits later. The resultant signal would be nothing but a string of garbage consisting of adding together every bit in the stream with the bit that was transmitted 5 bits earlier. What's more, the two carriers would collide, causing alternating nodes of virtually zero signal and a carrier almost twice the level all the way down the line.

The filter *terminates* the signal. It does not reflect it to any extent, as best the manufacturer can mange given the price of the filter.



CoxInPHX said:


> It also prevents the MoCA signals from causing excess noise issues for your neighbors that could potentially cause them signal problems.


This is also incorrect, although not quite as badly. By definition, those carriers represent intentional signals, not noise. They could hypothetically interfere with something on your neighbor's system - most likely their MoCa system. but by definition they are not noise.


----------



## lrhorer (Aug 31, 2003)

NotNowChief said:


> Exactly. My understanading has been that MoCA uses the unused frequencies below 1ghz to run network traffic. The filter just blocks those low frequencies so the modem and OnDemand will work without a problem.


Not. It's a high pass filter, not a low pass filter. Upstream frequencies on the CATV system are 5 - 40 MHz. Downstream frequencies are 55 to either 550, 750, 850, or 1000 Mhz. MoCA will be above that.


----------



## lrhorer (Aug 31, 2003)

unitron said:


> Where to put what depends on exactly what it does.
> 
> What does a POE filter block and what does it pass?


It depends on the filter. Most probably play it safe and block 1000MHz +. Some might block frequencies as low as 850 MHz, but doing so risks losing video channels on some CATV systems.


----------



## Dan203 (Apr 17, 2000)

lrhorer said:


> That is utter nonsense. A reflection would be deadly to the MoCA network. A reflection only doubles the signal amplitude at the reflection point. Everywhere else all you would be doing is producing ghosts - seriously bad ones. If a node is, say 15 meters from a reflection, then it would receive a particular bit in the bit stream at time t = 0, then it would receive the very same bit again at t = 0.05 microseconds later, or at 100Mbps or 5 bits later. The resultant signal would be nothing but a string of garbage consisting of adding together every bit in the stream with the bit that was transmitted 5 bits earlier. What's more, the two carriers would collide, causing alternating nodes of virtually zero signal and a carrier almost twice the level all the way down the line.


If MoCa uses MIMO like Wifi N then the ghost would actually improve the signal. Not sure if it does though, haven't read up on how exactly the MoCa standard works.

Dan


----------



## unitron (Apr 28, 2006)

A reflection on a cable may strengthen an analog signal if the reflection is in phase with the original, but the chances of that are perhaps only one out of 360.

Terminate cables and transmission lines properly and save the phase shift for Hammond B-3s and Leslie cabinets.


----------



## CoxInPHX (Jan 14, 2011)

lrhorer said:


> That is utter nonsense. A reflection would be deadly to the MoCA network. A reflection only doubles the signal amplitude at the reflection point. Everywhere else all you would be doing is producing ghosts - seriously bad ones. If a node is, say 15 meters from a reflection, then it would receive a particular bit in the bit stream at time t = 0, then it would receive the very same bit again at t = 0.05 microseconds later, or at 100Mbps or 5 bits later. The resultant signal would be nothing but a string of garbage consisting of adding together every bit in the stream with the bit that was transmitted 5 bits earlier. What's more, the two carriers would collide, causing alternating nodes of virtually zero signal and a carrier almost twice the level all the way down the line.
> 
> The filter *terminates* the signal. It does not reflect it to any extent, as best the manufacturer can mange given the price of the filter.


So Cisco is putting out misinformation:
http://www.cisco.com/en/US/prod/collateral/video/ps8806/ps9095/ps10163/7016817.pdf
Features
● Prevents interference between adjacent subscriber homes that use MoCA technology
● Minimizes MoCA energy on the cable TV feeder
● Acts as a reflector to increase the MoCA signal level within the subscribers home


----------



## Kerwin51580 (Sep 20, 2012)

bsd said:


> Any idea where I can find a filter in NYC? Tivo has them, but I will pay almost as much for shipping as the filter itself costs. I tried calling Radio Shack and Best Buy and they had no idea what I was talking about.


Got mine of off ebay for about $8 with free shipping.


----------



## lrhorer (Aug 31, 2003)

CoxInPHX said:


> So Cisco is putting out misinformation:
> http://www.cisco.com/en/US/prod/collateral/video/ps8806/ps9095/ps10163/7016817.pdf


Apparently so. It would not be the first time. Such nonsense is rife throughout industry, and Cisco is no exception. I suggest the last place anyone should seek technical information is an advertisement. Poorly supported statements, glossing over details, and even out and out lies are the norm for advertising. Most ads, even for a lot of technical companies, are written by people who have never even taken an engineering course or any physics at all, and haven't a clue how the item they are hawking works.



CoxInPHX said:


> Features
> ● Prevents interference between adjacent subscriber homes that use MoCA technology
> ● Minimizes MoCA energy on the cable TV feeder


All of that is true, and perfectly implied by what I said.



CoxInPHX said:


> ● Acts as a reflector to increase the MoCA signal level within the subscriber's home


Utter nonsense. In fact, because of its very nature, MoCA is very susceptible to problems caused by impedance mismatches. The first thing anyone who experiences issues with their MoCA system should do is make sure every port on every directional coupler is properly terminated. Note there is an excellent chance (in fact it is almost certain) the S/N of the MoCA signals will increase significantly, perhaps even drastically, which may be what the ad was trying to convey. In their technically deficient minds, this might have been what the advertising folks understood to be the case. Even if it were ultimately true, the increase in signal would not help, at all, since it is the S/N which determines the throughput, not the absolute signal level, and a signal increased by a simple physical reflection has precisely the same S/N as a properly terminated one. What's more, doubling the signal (even if it did somehow help the S/N, which it doesn't) would only result in an absolute maximum gain of 3 dB. Properly terminating the line, however, could easily result in an increase of S/N of more than 20dB, which is huge.


----------



## lrhorer (Aug 31, 2003)

Dan203 said:


> If MoCa uses MIMO like Wifi N then the ghost would actually improve the signal. Not sure if it does though, haven't read up on how exactly the MoCa standard works.


That is specious. First of all, by definition MIMO requires radiators that are spatially diverse, which would require dual ports on the MoCA adapters. MoCA does indeed employ spread spectrum modulation which makes interference from reflections less impactful to signal levels in a certain sense, but it does not mitigate the fact that the reflected signal arrives later in time than the primary signal. If the reflection is close to the radiator, then it can help, yes, although in a coaxial system usually not. The fact the carrier is spread out in frequency and not entirely dependent upon any single small section of the signal means the awful spectral response generated by the reflection is not an issue for the receiver, and the sections that are received have a higher S/N, giving better throughput and fewer errors. If the space-time displacement of the reflected signal results in a phase angle in the payload of greater than 90 degrees, however, it will tend to completely destroy the information in the bit stream. Only if the level of the demodulated ghost is typically at least 6dB lower than the demodulated primary can the ghost ordinarily be electronically rejected for phase angles larger than 90 degrees.

To put it a different way, again assuming a 100 Mbps payload, if the reflection is less than about .75 meters from one of the nodes, then the signal presented to that node will have up to a 3 dB higher signal level than if the line is properly terminated. Any node further than that away, however, will receive a horribly degraded bitstream from any node other than the one right by the reflection. Indeed, if the node is 1.5 meters from the reflection, then it is likely no other node on the system will be able to receive anything at all from that node for a 100Mbps payload. If the nodes drop the bit rate to 50 Mbps, they should all be able to talk once again. Note even the node that is half a meter or so from the reflection won't benefit much, however, since while the signal level may be higher, the S/N won't usually be.

The bottom line is the last thing anyone wants in any coaxial transmission system and most especially in a MoCA system is reflections.


----------



## lrhorer (Aug 31, 2003)

Kerwin51580 said:


> I just want to make sure I install this filter the right way. I figure I should power down both TiVos, both TAs, the cable modem and router and THEN install the filter. Then, power everything up in the reverse order? Does that sound right?


I know the horse has already left the barn on this one, but for future reference, there is no need to power anything down. Disconnecting the inoput cable won't send anything into a permanent tizzy. Of course, while it is disconnected, you won't get any cable service for the duration, but as soon as it is reconnected, everything will come right back up.


----------

