Dear Big Picture Big Sound,
FOR A RECENT REMODELING PROJECT FOR A RELATIVE HE WANTED CABLE JACKS IN ALL THE BEDROOMS AND LIBRARY,(JACK IN LIBRARY FOR CABLE MODEM). WE HAVE A MAIN FEED GOING TO THE UPSTAIRS WITH A FOUR-WAY SPLITTER TO EACH ROOM, IT HOOKS TO A SPLITTER IN THE BASEMENT WHICH ALSO CONNECTS TO THE FAMILY ROOM WHERE HE DECIDED TO HAVE A FLATSCREEN HDTV. NOW THE CABLE COMPANY SAYS HE NEEDS DEDICATED LINES FOR THE HDTV AND THE MODEM UPSTAIRS BECAUSE FOR THE BEST RECEPTION YOU CAN'T HAVE ANY SPLITTERS. IS ALL THIS TRUE AND IS THERE A AFFORDABLE SIGNAL STRENGTH TESTER.
Thanks for your note. First off, PLEASE TURN OFF YOUR CAPS LOCK KEY BECAUSE IT LOOKS LIKE YOU'RE SHOUTING! THANKS.
As to your questions, it is absolutely possible to split a cable signal and still have enough signal strength to operate a cable modem and feed HDTV signals to a QAM tuner (assuming the signal strength coming into the house is sufficient). And the Cable Act of 1992 means that it is legal to do so. But every time you split a cable or antenna signal, you lose at least 3 to 4 dB of signal strength. So if you're splitting the signal 5 times, you could have as much as 15 to 20 db of loss in the signal by the time it reaches your modem or tuner. And this may be too much signal loss in order to lock into the data or QAM signal.
The cable companies compensate for this by amplifying the signal all along the way to your home, and (presumably) they do so with high quality splitters and amplifiers, minimizing the amount of noise being introduced into the system.
So the best approach, if you want to distribute the cable signal within your own home, is to use a high quality signal amplifier as close to the source as possible (i.e., where the initial cable feed comes into your home), then make sure to use high bandwidth low-loss splitters on the signal once inside your home. The amplifier has to support a "return" feed in order to work with cable modems so be sure to look for an amplifier that supports this. Also use high-quality RG-6 cable with good shielding and high quality connectors to prevent any additional loss or interference. And keep these cables away from high voltage power cables to prevent any additional interference. If you must cross over power cables, then do so at right angles to minimize interference.
Your best bet, assuming you have already laid the wires, is to buy a high quality signal amplifier and place it in-line before the splitters, and replace any cheap splitters with high quality high bandwidth splitters that can support the high frequency QAM and digital modem bandwidth. Also, try to split the signal only once if you can, particularly for the most "important" sources like your primary HDTV and cable modem feed. In other words, never use a 2-way splitter, followed by a 3-way splitter (if you can help it) because each level of splitting introduces additional signal loss. Instead use a single 4-way splitter (in line just after the amplifier) so that each feed has a consistent, but acceptable level of loss.
We have seen good results with cable amplifiers from Motorola and Channel Master but there are other good ones out there. A few of our specific product recommendations include:
The Motorola BDA-S2 and BDA-S4 and the Channel Master 3044 all include built-in signal splitters so you can save yourself having to buy a separate splitter if you're using this with a modem and HDTV or with multiple TVs. All of the above include high output, low noise amplifiers and support return feeds for cable modems and interactive cable offerings such as PPV (pay per view).
I am not aware of any inexpensive, high quality RF signal strength meters, but with a good amplifier, good quality splitters and cables, and a decent quality cable feed coming into your home, you shouldn't need one. Good luck!