----------------------------------------------------------------- THE CABLE CONNECTION c) 1989 by Marc Wielage All Rights Reserved ----------------------------------------------------------------- Let's have a quick show of hands of everybody out there who has cable TV. Okay, now, everybody who actually their reception, keep your hands up. Not many, are there? That's what I thought. Most videophiles I know have a love-hate relationship with cable TV: they the selection of channels and the convenience, but they the mediocre picture quality, the rolling lines, the static, and the periodic cable outages that only seem to come up when you're trying to record the last showing of your all-time favorite film from pay TV. Can anything be done to improve the quality of cable TV? Plenty...but unfortunately, most of it has to be done at the , which is the central receiving office of the cable company. Without a good signal to begin with, the best-quality cable amplifiers and wires in the world can't bring a decent picture into your home. In addition, many cable companies operate under- less-than optimum budget conditions, preventing them from using state-of-the-art gear, for everything from inadequate line amplifiers on the telephone pole to shoddy channel-selector boxes in your home. There are a couple of things you can look for to help the cable repairman solve the usual problems: perhaps the biggest is or video noise, which is generally caused by inadequate signal levels. Most experts advise that an average tuner needs at least .1 millivolt of signal to produce an acceptable picture. A little more, like around .3 mV, is even better. Cable TV companies routinely use amplifiers in their lines placed at regular intervals so that people far away from their headquarters will get reception just as good as the people who live a block from the head end. If a little signal is good, then a lot of signal must be even better, right? Wrong. In VHF/UHF transmissions through cable, the biggest loss is with the high frequencies, especially channels 25 and up. The cable company's amplifiers use special "tilt" equalization to help peak these frequencies, which helps reduce the loss over a long distance. If the cable amps are improperly adjusted, the lowband channels (2-13) suffer, resulting in a lot of ghosting and intercarrier interference. The latter is the typical "buzzing" you hear when bright titles pop on the screen. Another problem is "tearing," when bright signals streak or smear from one side of the screen to the other. You can cut back on the cable line's signal with a inexpensive device called an . This is an in-line metal barrel that screws directly between your cable and the tuner input. An attenuator works by reducing signal strength with an electrical filter, sort of like using an adjustable spray nozzle on a garden hose. Attenuators are rated in decibels (dB), and range from as little as 5 dB all the way to 20 dB and up -- the higher the number, the more severe the effect. Sometimes, just the signal to several TV sets or VCRs will help cut down the signal to a proper level, too, using a multi-output RF splitter, available for about $20 from Radio Shack and other companies. If your cable pictures are marred by snow and ghosts, you've probably got the opposite problem: signals. Radio Shack, Recoton and several other accessory companies make consumer VHF/UHF signal amplifiers which can help strengthen weak cable signals. But it's easy to misadjust these amps and create some of the problems mentioned above. Experiment carefully, and make sure the reception is clean on channels to determine the best setting for your system. This is especially important when connecting more than two or three devices to one cable signal. Another common cable TV problem is , which looks like large horizontal bars rolling through the picture. Usually, these roll rather slowly, which are a sign of 60 Hz hum (the same frequency as AC current). Hum in cable systems like this happens when your house current is grounded differently than the cable system's current. This visual hum is often accompanied by low- frequency hum or buzzing in the audio, and is particularly annoying when heard through full-range speakers. One solution for this common cable ailment is the , which you can make yourself for less than $5.00. This fix consists of two 75-ohm to 300-ohm transformers, also known as "baluns," which are included free with virtually every VCR to help connect them to older TV sets with 300-ohm jacks. To make this device, simply connect the four 300-ohm leads together so that the round 75 ohm terminals are open. The cable TV signal goes into one end, and the other end goes to your VCR or TV set. Voila: the hum is gone, since this double-transformer breaks the cable's ground and isolates it. With my own local cable signal, I use Sony's EAC-25 [shown in the photo], which neatly fits a variety of conventional baluns. The only drawback with this fix is that you'll lose about 3 dB of signal, which may introduce a small amount of snow in the picture if your signal is weak to begin with. Another potential problem is that the 300 ohm wires may pickup stray transmissions in your area, which means that strong local stations may affect similarly- numbered channels on the cable. But that's a small price to pay, considering the immense improvement for the rest of the stations. Some cheap baluns that don't use transformers may not fix the hum problem, but there is a company called Gemini Electronics who manufacturers a direct 75 to 75 ohm "ground breaker" called the model #CV89. Their address is Gemini Industries, Inc., 215 Entin Road, Clifton, New Jersey 07014. This device is a more attractively packaged and is virtually guaranteed to get rid of the hum from all but the worse cable systems, with a little less signal loss than the above method. And there's one more device you can use to get better cable quality: the telephone. If you're having severe cable reception problems, make sure your cable company and local utilities are aware of the situation. Sometimes, a call to the chief engineer of your local cable company can work miracles. Just as a squeaky wheel gets the grease, even the best cable TV company in the world can't fix problems they don't know about. [Special thanks to reader Bob Katz of New York, NY for providing some of the background information for this column.] # # # # # # # # # # (Portions of the above appeared in the October '88 issue of VIDEO REVIEW magazine.)