adding CATV jack-question

[jeffmoss26]

I am going to add a CATV jack in my basement. Since it is near all of the cabling that I put in down there, I might want to use the CATV jack for my cable modem, hook up the modem to a wireless router, and hook up the switch ports to a patch panel so I can use the data jacks I already have in my workshop.

Anyway, do I need to do anything special so I can hook up my cable modem to this CATV jack? Are there special connectors I should use? I am assuming that I need to use RG6 cable.

Thanks,
Jeff jeff moss
jeffmoss26@adelphia.net

 

[executone]

It has to be RG6 cable. The modems have trouble if splitters appear in front of modem. It did not like signal booster either. I had to put a two way splitter where all my connections are. One went to modem and other went to all the other TV connections.
Good Luck!!

 

[jeffmoss26]

well i will need to install another splitter. So would the modem work or not if it is attached to a splitter? jeff moss
jeffmoss26@adelphia.net

 

[daronwilson]

It does not have to be RG6. Belden for example makes a very nice RG11, RG59 swept to 3.0 Ghz and even a smaller diameter coax for patching that is swept plenty high to accomodate cable modem services. RG/11 will provide less loss than RG6, RG59 and the smaller stuff will be more lossy. Depending on the length of run, one needs to take that into account when designing the system.

There is nothing inherit to a splitter that will cause a problem with it in front of a modem. Unless you live at the headend, that signal is 'split' and 'tapped' many times before it arrives at your house.

There ARE two things regarding splitters that WILL make a difference with your cable modem. Those two things are the bandwidth of the splitter itself, and the attenuation associated with the insertion of the splitter.

Keep in mind this is all two-way radio frequency stuff. On my particular system the cable modem downstream signal is about 650 MHz and the upstream frequency is about 24 Mhz. Now, for the system to work, ANY device you install in the line must be able to pass signals in excess of 650 Mhz. Decent splitters should have a range up to 1 Ghz. Many cheap and/or old splitters were designed for broadcast signals or early CATV systems that did not have channels in the 650 MHz range so they may only pass signals up to 550 Mhz or so. So, first and formost, any splitter you use needs to pass everything you are going to send through it. Secondly, splitters are very lossy. A 2-way splitter will make both signals go down 3 dB. 3-way and 4-way splitters are even more lossy. So you can see that you could easily reduce the signal by 1/2 just by popping a splitter in there. However, it is done all the time. Many DOCSIS modems allow you to point your web browser to the modem (my motorola bitsurfer is at 192.168.100.1) and see what the signal strength is of the downstream signal. When I installed mine, the cable technician and I experimented with different signal levels. We found that putting a splitter in first, sending one port to the modem and the other port to an 8 way amplified splitter for the rest of the house was too much signal for the cable modem. It actually performed better when a 6 dB attenuator was added before the modem.

I believe your best solution is to run a new piece of quality (I prefer RG/6) cable from the CATV interface to your basement patch panel. That way, you can put a splitter in out there and get as much of the signal as you can downstairs. From there, you can work with different devices and get the signal level you need to make your cable modem work. Like any radio, the modem is expecting a certain level of signal to function properly. You can either experiment while looking at the web interface to get that correct level or put a signal strength meter on it and adjust it that way.

Hope that helps!
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[jeffmoss26]

here's the problem:
a main line runs from the street to the back of my house.
it hooks up to a splitter. one leg goes directly to my modem, the other leg goes into the basement. in the basement is a 3 way splitter. one cable goes to the family room, one goes to my parents room, and another goes to a 2 way splitter outside that feeds my room and my dads office.
so i dont have a direct line coming inside. There is no CATV interface in my house, and I am not going to have a CATV patch panel, I just want to add another outlet that can be used for TV or Cable Modem.

plus my dad wont let me run anything outside or drill any holes outside.

I went to RadioShack to look around. The guy said I need a $10 DSS Splitter, that will "work for data"
I wasnt sure so I didnt buy it.

What I will have to do is disconnect one cable from the splitter and connect a jumper to a second splitter. Then I will hook up the cable I disconnected and the new cable I will run to my workshop.
I guess to make it easy I could just forget about using this jack for the Cable Modem
I am out of ideas... jeff moss
jeffmoss26@adelphia.net

 

[wires]

Barrel (double female F connector) the main line from the street to the line going to the basement and remove the splitter. This connection needs to be somewhat weatherproof so use a pair of 7/16" wrenches to "snug" the connectors

In the basement connect the input of the 2way splitter to the wire from outside. Connect one output the the input of the 3way splitter and the other to your cable modem. The signal level will be about the same as it was before as long as the run from the outside to the basement is a reasonable length.

Since you are unfamiliar with all of this you might want to mark wires, make notes and take pictures before you start. That way you can put everything back the way you found it if things don't work out.

Daron - Do you have any idea what the minimum signal level is for the downstream signal?

 

[daronwilson]

Just a correction, as I check my modem the downstream is 669 MHz and the upstream is 30.8 Mhz. My current downstream signal is reported by the bitsurfer as 3 dBmV. As I recall it ran with a much hotter signal, but the tech said they seem to do better with a lower signal. I've not tried changing the attenuator so I don't know the precise minimum. Some day when I have time I'll drop the signal 3dB at a time or something and see how it does.
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[jeffmoss26]

well i dont want to mess with anything outside. a few years ago it was screwed up and they had to run a new line to the street. they actually ran it to where the power meter is and then barrelled it to the cable that is already there. so we dont even have a direct line without splices.
jeff moss
jeffmoss26@adelphia.net

 

[wires]

Daron;

Thanks for the measurement. Here is what I have found on my several installs with a spectrum analyzer.

On the local system there are two upper areas of digital signals 547 - 670 and 710 - 749 MHz. I am not sure which is cable modem and which is digital cable. On systems that are trouble free I get a trace peaking along the -50dBm (-3dBmV)line for the lower frequencies and around -55dBm for the higher frequencies. I have had some problems with systems where the lower frequencies peaked at -55dBm and the higher ones around -60 dBm (-13dBmv). The dropoff in signal I attributed to some old RG59 from the 32 channel days.

I never really went looking for the upstream frequency but it must be fairly narrow since a 0 - 1GHz saved trace shows no sign of it.

Where did you find the 669 MHz and 30.8 Mhz frequencies?

 

[daronwilson]

When I point my browser at my Motorola bitsurfer modem, the status screen reports the downstream and upstream frequencies as well as signal levels. I let my spectrum analyzer go with my communications service monitor and a bunch of two way radio gear when I shifted work focus, so I am limited to a CATV signal meter for testing.

If I had a spectrum analyzer I would be able to give you more info, guess I'll check out ebay

It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[fs483]

Hello,

I want to mesure my line before I go out and purchase my cable modem (100$ CAN non refundable). The Ip for the config page on Atlanta DXP110 is 192.168.100.1 but the feature to measure signal strenght is disabled. Does anyone know how to activate this (ISP won't give out any info). Would someone know the IP for a Samsung cable modem (don't have model number yet) and I haven't tried the ip 192.168.100.1 yet, my friend is out of town for now.

Thanks.
anthony