Hello. I do apologize about the length of this, but I didn't want to be too vague and leave you needing me to answer many other questions before you might be of help to me. Again, please forgive me for the length.

Previous to the past few days, I assumed one cable was roughly as good as another and a splitter was a nasty fastball. Now, my parents have purchased an HL61A750 that will be arriving Tuesday, and they have decided to purchase the Comcast Triple Play package in Houston, Tx, with the top tier commercial broadband available from Comcast in the area (16Mbps down/5Mbps up).

After Hurricane Ike, they had to have a new drop line installed (that is the correct term for the aerial cable that runs from the cable company's source line on a utility pole to the home, correct?), and it was installed by a subcontrator hired by Comcast to handle the additional repair work caused by the hurricane. Checking their internet speeds after installation a few times, I notice they definitely receive diminutized upstream and downstream speeds than previously.

That preface leads to this: they are about to call Comcast to have them come out and install HD digital cable service, and I want to be sure that they get top quality cabling at the time of installation. For now, the drop line runs roughly 50ft to 60ft from the utility pole to the house, connects to a two-way splitter, and from there, one cable runs into the house and is split 5 ways to various outlets throughout the house and the other cable runs dedicated to the modem for internet service.

The only designation I can find on the drop cable that describes it type is "TFC-T10". The only other information on the cable are length markers every two feet which I presume are there to measure out a 1000ft spool. The cable that runs from the splitter for broadband internet is "JT2617211 Commscope Cable 5740 RG6 Type Quad F6SSVCMG 9900963 cm, c (ETL) us or CATV (ETL) us 18 AWG". The other cable running from the splitter into the house is at least twenty years old and so I assume that it all needs to be eventually replaced--at least before they get any HDTVs in those rooms.

Now, their new TV will be in the same room as the main computer, and it appears to me that they should run the drop line through a quality three-way splitter, with a dedicated line to the computer's modem, a dedicated line to the new HDTV, and the final line to all of the other SDTVs in the house, either to be eventually upgraded to a quality cable by Comcast, or to be upgraded by myself. The cable length from the splitter to the outlets on the dedicated lines are roughly 40ft for the internet line and would be roughly 30ft for the HDTV cable.

Having attempted to do a bit of research, it appears that the Commscope cable is 75 ohm and the quad shielding helps to avoid RF and electrical interference keeping the signal purer or stronger. I tried to research the TFC-T10 cable, but the description printed on the cable seems far too generic to determine its properties compared to the specs I did find. Add to that what discussions I found of others talking about this cable seemed to always include a more precise description on the cable itself. It makes me wonder if this cable is a knockoff used by the subcontractors to save money considering the degradation in performance, besides my inability to determine if actual TFC-T10 cable is as good as the Commscope cable.

So, my questions:

1. What type of drop line should I ask the technician to install in replacement of the current drop line?

2a. What kind of splitter should I purchase so as to have a top quality splitter for the distribution of the incoming signal?

2b. I have read that the technician should have splitters and that they are better than the ones I would likely find for purchase locally. Is this true and should I ask the technician to supply a three-way splitter?

3a. Is the current Commscope cable that my parents have for the internet line sufficient and future-proof, or should I be asking the technician to replace the drop line, add a new dedicated line for the HDTV, and replace the cabling in place for their internet connection?

3b. Should they be offering better cabling than the Commscope cable mentioned above?

4a. Should I feel confident that the cabling the technician will have is of acceptable quality, assuming they are in permanent employ of Comcast as opposed to being subcontractors hired in an emergency?

4b. If I should be skeptical of the cabling provide by Comcast, what cabling would you suggest I get?

5. Seeing as it will be a bit before I can have the other cable to the regular TVs replaced, is it wise to run a dedicated cable from the splitter to the HDTV? It would seem to me that it would be as the length of cable the signal would have to travel would be greatly reduced and undergo less divisions of the signal than would be so if it was run through the labyrinth of existing cable connecting the other TVs, nevermind the likely inferior quality of the cable through which it would have to run.


Just to reitierate, I would like for them to have the best quality that they can have through Comcast, whom I am dubious of in the first place as it relates to service and quality. I would like for the HDTV to receive the best signal it can and for the broadband internet to receive full use, at least potentially, of its broadband capabilities with as little latency as possible.

I am truly appreciative of any help you may be able to provide me, and I will try to keep a close eye on this thread in case there is any additional information you need to be of assistance.

1) They don't need to replace a newly installed drop to give you HD, I highly doubt they will either unless they determine something is wrong with it.

2a-b) It's Comcast's responsibility to insure the HD cable box they install is receiving sufficient signal. Let them supply whatever is needed.

3) See 1

4) See 2

5) That's up to you, again it's the technician's job to make sure the newly installed HD STB is getting a proper signal.

I highly doubt the new drop is the cause of your reduced cable speeds, nor is that last whatever feet from the pole to your splitter going to make that large of a difference in speeds and latency. It could be a number of things causing speed drops, different test sites, increased load on the local node, time of day, etc etc.. What speeds were you seeing before and now?

The speeds they were receiving before, based upon roughly 40 tests at various times over a number of months tended to be between 3 and 4 Mbps down and 1.5 to 2 Mbps up, well below what they were paying for--8Mbps down and 2.5Mbps up. Now, their speed has reduced to 1.5-2.5 down with the same speed as before up, based upon 10 tests at various times on various days since reinstallation of a new drop line after Hurricane Ike.

They intend to pay $10.00/month more for a bump to 16Mbps down and 5Mbps up, but, seeing as how they were never even getting over 50% of what they were paying for previously, I am concerned that they will not even get to the bandwidths for which they are already paying. The 40%-50% drop they have experienced since the new line was installed, on top of already receiving only roughly 50% of the contractual bandwidth previous to the new drop line bothers me.

I have run these test over various bandwidth testing sites and taken an average across the whole set of data. Also, when I say that I have run a test, included in each individual test are bandwidth ratings from the numerous sites, then averaged. So basically I have tested their bandwidth more than 200 times previous to the hurricane and 50 times since. They do not use anything suspect like **********s nor do they download a lot of material or use large monthly amounts of bandwidth, so they shouldn't be experiencing any deleterious packet shaping or purposeful capping or "crimping" (the proper term evades me at the moment) of their bandwidth.


As far as the rest, thank you for your advice. I do think I should have them run a separate cable for the HDTV as there is no way they will be able to get to the other cabling to do any necessary replacements at the moment--the attic is very cramped and very full at the moment until I can clean it out for my parents. It is probably just my ignorance, but the installation of that drop line with the subsequent degradation of service seems more than coincidental.

The only designation I can find on the drop cable that describes it type is "TFC-T10". The only other information on the cable are length markers every two feet which I presume are there to measure out a 1000ft spool. The cable that runs from the splitter for broadband internet is "JT2617211 Commscope Cable 5740 RG6 Type Quad F6SSVCMG 9900963 cm, c (ETL) us or CATV (ETL) us 18 AWG". The other cable running from the splitter into the house is at least twenty years old and so I assume that it all needs to be eventually replaced--at least before they get any HDTVs in those rooms.

T10 is TimesFiber's series of drop cable. Can't get any better than that. The materials used by subcontractors is provided to them by the local cable company.

one suggestion - the cable modem should be connected at the very first spliter, so your system wiring is split into TV and internet access at the first opportunity after entering your house. What happens to the TV signal after that will not effect the quality of signal available to the cable modem.

one suggestion - the cable modem should be connected at the very first spliter, so your system wiring is split into TV and internet access at the first opportunity after entering your house. What happens to the TV signal after that will not effect the quality of signal available to the cable modem.
Absolutely!

Good afternoon, and thank you to everyone who has offered me help. I cannot tell you how fortunate I feel to have stumbled upon what appears to be the the standard bearer for websites that deal with home theater and signal clarity issues. Again, you people are a wonderful boon. I have been proselytizing for this website for the two or so weeks since I have stumbled upon it every chance it seems appropriate to do so. All of you helped me to make a studied decision on the equipment I have suggested for my parents to date, and, of course, I will come here when they decide they wish to put out additional money on a sound system.

So, it appears that the drop line is top notch. Good. That eliminates a bottleneck for me; after Comcast comes out to upgrade their cable service and after they send new operational protocol to my parents' modem, I will be able to develope a better knowledge base as to if there is a problem and what to do next.

The signal from the drop is on a two way splitter that separates the TV signal for the entire house from the internet signal to the modem at the point of connection to the drop right now. I believe the splitter is fairly old, besides not being a three-way. When the installer comes out, I will ask him or her to install a three-way splitter, with the signal to the modem on a dedicated line, the signal to the HDTV on a dedicated line, and the rest of the SDTVs on the remaining line of the splitter.

Then, if there is a problem with internet speed and the HDTV signal, I can probably assume the issue is either an unfortunately faulty piece of new drop cable, or something anywhere from the source line on the utility pole all the way back to the headend of the source itself. If the problem only arises with the internet, I can begin to look at running some diagnostics on the modem to see if it is problematic or possibly look into replacing the cable in place with a new cable, assumedly of the same type as it seems nobody thinks that it is any type of bottleneck. If I do all of that and yet the internet signal is weak, I can begin to seek more intensive help from Comcast.

Thanks again for all of the help, but please feel free to add any advice or even differing opinions on this thread if you think it is valuable. I have noticed that two or three people will get into very respectful debates about the central themes of various threads, with everyone reading becoming the beneficiary of the knowledge that emerges from various experts. So far, this may be the most respectful forum of highly knowlegeable people I have come across on the internet. The benefits that arise from that for the noob to the expert are obvious and very significant.:)

Out of curiosity, what are the levels (upstream and downstream) and SNR of the cable modem as found at http://192.168.100.1?

By the way, welcome to AVS Forum!

Thank you for the welcome egnlsn. I hope after some time that I might possibly be able to be useful to other novices like myself once I become better educated in the various subject matters that pertain to the equipment I or my parents or friends own.

I went out to the Motorola site, and I believe that the numbers are good, from what I understand:

http://img219.imageshack.us/img219/6128/modeminfokl0.png (http://img219.imageshack.us/my.php?image=modeminfokl0.png)


In case that pic doesn't load:

Downstream:
Frequency: 591MHz
SNR: 36.7 dB
Power Level: 1.2dBmV

Upstream:
Frequency: 24MHz
Power Level: 45.5 dBmV

Now, mind you, I cannot say that I am knowledgeable in the theory as to why these numbers are good, but, from what I could find, a downstream or reception power between -10dB and 10db is good, with the closer to 0dB being best, and an upstream or transmission power between 8dB and 55dB being desireable, with most lying within the forties. From what I could find on the SNR, a good ratio should be 30+dB, with ranges below 30dB leading to performance degradation, and massive to total malfunction occuring at 23.5dB or below.

So, it seems that my modem should not be the issue. Thank you for the link. I really need to read up on modems, but had not yet gotten around to it. You provided me with useful information and gave me confirmation that my modem should be acceptable. Thank you again.

Downstream:
Frequency: 591MHz
SNR: 36.7 dB
Power Level: 1.2dBmV

Upstream:
Frequency: 24MHz
Power Level: 45.5 dBmV


Nothing at all wrong with those numbers. DOCSIS calls for the downstream level to be within -15 to +15dBmV, and most systems like to keep their's at least a few dB from each outer limit. With digital, either it works or it doesn't -- there are no varying degrees of it working as there are with analog. A downstream level of 0 is just as good as +10, which is just as good as -10dBmV.

There was no suggestion that your cable modem was at issue. knowing what your downstream level is lets you do the math to design your distribution system. Take the downstream level and add 6 to it (The signal for cable modems is QAM, which is run at 6dB below analog). Then add the splitter loss to determine the signal level at the groundblock (or at least the input to the first splitter (tap). So, you take your 1.2 and add 6 to it to get the analog level of 7.2dBmV. You then add 3.8 (the loss through a 2-way splitter) to get 11dBmV at the input of the 2-way splitter.

If I were the technician, I would install a DC-12 (perhaps a DC-9) for the cable modem (cable modem on the TAP leg) and everything else (including the HD) to the distribution splitter.

Unfortunately my the focus of my time is a bit fractured at the moment, so I could not do as much research on the things you have mentioned as I would like to have done, or at least successfully so that I could understand everything you said. So, please forgive me if a few of these questions seem to have self-evident answers or appear redundant.

I had thought that the broadband internet was digital. What types of internet access are digital as opposed to analog?

What is a DC-12 and a DC-9 and what is the difference? I am assuming that this refers to directional couplers, but I was unable to find them referenced as DC-12 or DC-9 with any clarification as to what that meant. I did research directional couplers (it seems like a two-way splitter is functionally similar to a 3dB directional coupler, with the signal split evenly), and, as I understand it, the higher the dB rating, the greater the amount of signal that goes to the through port and the less that goes to the coupled port. But I didn't find any directional couplers rated at 9dB or 12dB, so I am uncertain as to what you mean.

I followed the rest of what you were saying. Let me give you a bit more info as to what my situation is and what I planned to do, and, hopefully, if my longwindedness has not driven you mad, you might clarify some things for me a bit more.

Below, I will use "DC" to mean "directional coupler".

Right now, the drop line, TFC-T10 cable, is connected to a Genesys II two-way splitter, 5-1000 MHz, -130dB RFI, equally distributed 3.5 dB to each through port. One port is a dedicated connection via a Commscope RG6 Quad Shielded cable directly to the modem, and the other port is connected to really old cable for which I cannot find any specs upon it. This cable is over two decades old and is visibly smaller in diameter in comparison to the RG6 and Times Fiber cables previously mentioned. It runs through the walls and attic in some labyrinthian manner, with I could not tell you how many splitters, inputing to five outlets with four SDTVs connected, all of which receive an excellent signal. I know that the cable throughout the house needs to be replaced, and done so more efficiently; however, at the moment, it is not something we can do.

When the cable installer comes out to connect the HDTV to an HD signal, it is my wish to have that particular television run off of a dedicated through port, as the modem now currently runs, instead of being distributed through all of the cables on which the other televisions run, as I would imagine the signal to the HDTV run through the same route as the other televisions would receive an unacceptable signal, due to the antiquated cable and likely inefficient setup.

So, now, with that preface, I would like to ask you some questions.

1.) How much of the signal do I likely need outputting through the coupled port to the regular televisions in order to continue to maintain their strong signal....in other words, should I end up buying a directional coupler, would a signal divison of 75% split between the modem and HDTV with the remaining 25% being distributed to the other televisions be sufficient?

2.) Could I go with a greater imbalance, like, say, a 7dB (80/20) DC or even a 10dB (90/10) DC?

3.) Is there such a thing as a three-way DC which would distribute three outputs at imbalanced amounts, for example 50%/25%/25%, 50%/30%/20%, etc., or would I need the drop line to connect to, for example, a 6dB DC and then either a two way splitter to divide the the through port evenly to the modem and HDTV, with the remaining 25% going to the coupled port for the other televisions?

4.) Could I and should I possibly run through two DCs, so that the the majority signal distributed to the modem and HDTV is again distributed in a majority and minority amount to either the modem or the HDTV?

5.) The frequency range on the current splitter I have is rated up to 1GHz, but I have seen splitters and couplers with higher frequency ranges. To what does this range refer? Do I need a higher range to gaurantee a quality signal?

5a.) Right now, my router operates on a 2.4GHz frequency, but I am about to upgrade the router to an N-draft gigabit router that will operate on a 5.0GHz frequency, along with upgrading the computers receivers to to N-class cards. Does the frequency range of the splitter or DC have any effect on the productivity of input and output from the router?

I realize that was possibly a bit long-winded, and that I asked many questions, but I hope you will understand that I wish to be a bit more informed than I already am, which is not much. I thank you very much for taking the time to read and respond to this.

I had thought that the broadband internet was digital. What types of internet access are digital as opposed to analog?[/QUOTE

It is digital. Analog was mentioned because that's what the FCC gave specifications for. It is much easier to do a calculation once than 3 or 4 times. you take the reading off the cable modem, add 6 to it, and you're done.

[QUOTE]What is a DC-12 and a DC-9 and what is the difference?

A Directional Coupler is sort of like a very unbalanced 2-way splitter. The loss through the TAP leg is the value of the thing, while the loss through the OUT leg is minimal. With an input level if 11dBmV, a DC-9 would give you +2dBmV (analog) to head to the cable modem (cable modem is connected to the TAP leg). Subtract 6 to get -4dBmV (QAM). Perfect.

A loss through the OUT leg of a DC-9 is 1.6dB (Holland DCG-9FRC), which leaves 9.4dBmV to go to your video distribution system.

I didn't find any directional couplers rated at 9dB or 12dB, so I am uncertain as to what you mean.

Directional Couplers (http://www.cencom94.com/gpage.html)

I followed the rest of what you were saying. Let me give you a bit more info as to what my situation is and what I planned to do, and, hopefully, if my longwindedness has not driven you mad, you might clarify some things for me a bit more.

...This cable is over two decades old and is visibly smaller in diameter in comparison to the RG6 and Times Fiber cables previously mentioned. It runs through the walls and attic in some labyrinthian manner, with I could not tell you how many splitters, inputing to five outlets with four SDTVs connected, all of which receive an excellent signal. I know that the cable throughout the house needs to be replaced, and done so more efficiently; however, at the moment, it is not something we can do.

Sounds like the outlets are daisy-chained with RG 59.

Directional Couplers do not work as you had previously thought, so I will not address questions 1-4.

5.) The frequency range on the current splitter I have is rated up to 1GHz, but I have seen splitters and couplers with higher frequency ranges. To what does this range refer? Do I need a higher range to gaurantee a quality signal?

Cable TV goes up to 1000MHz. (Very few actually go that high. The vast majority are 750 or 860MHz). That being the case, you don't need anything that goes higher than 1000MHz.

5a.) Right now, my router operates on a 2.4GHz frequency, but I am about to upgrade the router to an N-draft gigabit router that will operate on a 5.0GHz frequency, along with upgrading the computers receivers to to N-class cards. Does the frequency range of the splitter or DC have any effect on the productivity of input and output from the router?

The router is ethernet. It has absolutely nothing to do with CATV.

Now that you have explained that your current distribution system is daisy-chained, I would probably have to go with a different configuration than previously mentioned. An unbalanced 3-way splitter at the beginning, with the 7dB legs going to both the cable modem and the HDTV outlet and the 3.5dB leg going to the existing distribution system.

Perfect! Earlier today I stumbled around through various forums and learned a bit more about DCs, but maybe more significantly, I found a number of individuals who had situations similar to mine that were resolved by quality installers who disigned their signal distribution in just the way you suggested with the 7dB/7dB/3.5dB splitter. Having you confirm that at the end of your last reply takes a lot of stress out of the upcoming installation for me.

All of the information you have provided me has been invaluable to me. Now, I can set up this install and proceed forward with no worries, as I know enough to understand the basics of what the installer will be doing. Life has been extremely stressful for me lately, so anything that alleviates some area of stress is a true blessing. I cannot thank you enough for your kindness and patience. If you do this for a living under somebody else's employ, is there any place and person to which I might be able to send a letter commending their judgement for retaining your services?

Given a particular speed limit, set in the cable modem by its internet provider according to its subscription plan, download speed can't go higher than that limit. But download speed is affected by Cable Modem Downstream Power Level? The less the power, the less SNR becomes, and the slower same internet connection will be, as smaller number of packets will be able to reach destination without being lost and retransmitted during a given time period. Is that correct? How power level affects actual download and upload speeds (within limits of subscription speed)?