CABLE / COAX Question for any gurus out there

[Rezzin]

Is it possible to have the coax feed into the house split more than twice before reaching my cable modem? I currently have the feed split once before the router. I tried using another splitter (my router and cable modem is in the garage and I just put a TV in there) and after doing so, my connection drops. Removing the splitter takes care of the problem. I'm wondering if it's the splitter I'm using, if it's the cable I'm using (i bought some gold plated 3' coax cable from Radio Shack), or if it's impossible since it's the 2nd 'split' before the coax feed reaches my cable modem. Any insight into this is GREATLY appreciated!

 

[redbeard1]

Any connection or split creates a signal loss. With higher quality parts it is diminished, but there is still a loss. How the cable techs usually try to do it, is to have the cable modem connection come out of the first splitter in the house, going direct to the modem, sometimes with a filter, then the other side of that splitter goes to the tv's, taking the rest of any needed splitting on that line.

Having a splitter between the feed and the cable modem is not good, two can't help. The splitter may not be made for the higher mhz that they usually use for digital signal. It seems to me that they are up to 1000 mhz, and you can still buy splitters that are only rated for 650. Old ones are even slower than that.

 

[Rezzin]

I appreciate the fast response redbear - only problem is the main coax feed comes into my living room (where the first split occurs.. one to the TV and the other runs to the garage where the cable modem / router is located). Can you recommend any high quality filters by chance? My only option that I can see to getting the extra TV in the garage to work is to use another splitter.. so maybe high quality filters will do the trick for me?

Thanks again..

 

[KenGr]

OK, right now I've got completely separate cables for Internet and TV so I can't give you first hand experience. However, I think you are best to split only once before the modem since data is a lot more sensitive than TV. Once you split, split the TV signal as much as you want to. I've seen cable TV signals split a half dozen times with no major problems. Plus you can always amplify the TV signal but I'm not sure if an amp would work on the data signal.

 

[ScottMac]

OK, here's for background:

If you are using a two-way splitter, you have divided the signal power by half + the loss of the connections and the splitter. If you use a three-way splitter, you are losing more than 75% of the signal per connection, because of the way a three-way is done. A four-way loses a little less than a three way, because it's a "natural" split.

Most splitters will have the loss noted at each connection: 3db is half (then you add the losses of the splitter), 6db is 25% (then add the losses)....

New cable TV systems are all under 1Ghz (ending somewhere in the mid-900Mhz as the highest frequencies), so you want a splitter rated for 1Ghz. Anything above that is unused spectrum, and may even allow more noise into the system.

The data channels used by a cable modem are transmitted just like video, on two "channels" of the broadband (usually one @ low freq, one @ high freq , like VHF and UHF - one for transmit, one for receive).

Now, the "usual" method is as mentioned above: one split where one branch goes to the cable modem, one to a video feed. Either can be split again and again AS LONG AS YOU COMPENSATE for the losses, usually with an amplifier. In the case of the Data side, it must be a two-way amplifier (so the return signal - your transmitted data - can make it back into the system above the noise floor). On some cable systems (like digital cable TV ... boxes with pay-per-view, etc) may also need a bi-directional amp.

The amps are available, but your better choice (IMHO) would be to have an installer come out and do the compensation for you. Run the cables (or figure out where you want 'em), then have the installer come out and adjust the system. The installer has a signal strength meter and can adjust the signal strength coming into your home to match the cable layout you have.

If you add equipment to their system, they are not responsible for it, and they may (read: almost certainly) blame your equipment if something isn't working right, and make you remove it.

Just dropping in an amp may not help: an overamplified signal is typically worse than a weak signal; most systems (Cable modems or TVs) can amplify to some extent, but can only reduce the signal so far...the target is a 0dbm signal to each device.

Using a high-quality cable can reduce some of the loss. The minimum standard these days is RG/6; a better grade is quad-shield RG/6. Radio Shack cable is OK, but there's much better available for probably less cost through a commercial electronics supply. Connectors will also make a difference. A good quality connector conducts the signal with a minimum of loss, and helps to "seal the noise out." Snap & Seal (IMO) are absolutely the best.

There is no such thing as a "decent" screw on connectors (for any medium). They suck. They suck really bad. They're unquestionably the worst thing you can use for anything other than a temporary connection.

Again, bottom line, (imo) you're much better off calling the cable company and having them send out a tech. He has the right tools and equipment, and can make the adjustments in the signal strength of the feed to give you the best data and video signal.

Of course, they are some real, um, stoooopid installers; they are generally the exception rather than the rule. If something isn't working correctly, call the cable company back out to make it work right. Since they do/did the work, they are responsible for it.

Good Luck

Scott

 

[Rezzin]

Scottmac,

This is exactly what I've been looking for. I can't thank you enough for the informative post. I think I'll call my cable company to send a tech out - even if it costs me. Thanks again!