is a Cable Amp and Why do I need one?
Simply put, a cable amplifier is a box that boosts your antenna or cable TV signals. When your cable signal comes into the house, it is generally strong enough to provide a good signal to two or three televisions. However most homes have many more than three TVs - and that doesn't even include all of the TV accessories! Cable TV boxes, VCRs, TiVo, ReplayTV - all of these boxes require a good strong signal to provide you with a good picture.
When your cable comes into your house, it starts getting split into different directions. It is these splits that cause your cable signal to suffer. Every time your cable signal is split, the signal gets weaker - causing graininess and in severe cases, SNOW. If you've had these same problems in your home you probably went on a search for a good product to give you strong, clear reception. Like other people, you probably have several TVs in your home, and in some rooms you have a TV, VCR, and a cable box. In order to feed a signal to those three devices, you probably had to connect a three-way splitter to the cable coming out of the wall. You didn't think twice about all those splitters in your house at all or at least until you started having problems. Your TV picture might have started getting "grainy", and when you recorded TV programs on the VCR, the picture would be blotchy and lack good clarity. You probably didn't realized that this was because you were not getting a strong enough signal at the TV and VCR to give you a good clear picture.
Once you figured out the signal issue your first try at fixing things was probably to go to local electronics store and buy one of their standard amplifiers. They cost about $35-40. When you hooked it up to your incoming cable, you probably noticed a couple of things - the TV picture did not appear to be any better, and possibly now there were ghosts and other strange interference appearing on various channels. So you might have ended up taking it back, or not using it at all. Next you might have gone to the local building supply to see if they had anything better. They had a couple of different brands, so you might have bought one of each and took them home to try out. Often neither one of them made the picture significantly better, and in most cases many channels actually appeared to be WORSE. Now your stuck, you realize at this point that there has to be something better - better than the cheapie amplifiers sold at local electronics stores. Viewsonics amplifiers are top of the line amplifiers. I have always been a believer in "you get what you pay for" and with this product - its true. Viewsonics cable TV amplifiers cost more than the "cheapies", but they are well worth it.
Why are they better? The quality amplifiers are made totally differently than the cheapies. They use high quality components and a sealed PC board (PCB) design. They incorporate a Gallium-Arsenide (Ga-As) semiconductor with PCB surface mounted components. The Ga-As technology was developed by Viewsonics many years ago. This technology has become the industry standard for the major manufacturers of cable amplifiers (drop amps) in the last five years.
In Cable company terms, each customer has a cable running from a utility pole or pedestal to their home. The "pedestal" is a cable company distribution box - where they hook up a whole bunch of homes to one place. It is generally where you see the cable guys working a lot. The cable company refers to the connection from their "box" to your home as a cable "drop". Years ago when the signal was too low at a customer's house, the cable company used to go out and install a "drop amplifier" pretty much for free, just inside the customer's house. Nowadays, Drop Amplifiers are available from the cable company to compensate for weak signals or multiple TVs, but they charge you a premium for them, and generally don't give you a choice of models (1,2,4, or 8-port models).
So the term "Drop Amplifier" is a cable company term. Now you learned something new!
There are four basic kinds of amplifiers: "cheapies", Bi-directional amplifiers, Bi-directional amplifier/splitters and Reverse Path amplifiers. I will describe each type so you can understand what you need to make your TV or cable signal better:
Cheapies are the types of amplifiers typically purchased at local building supply, department stores, and general electronics stores. These amplifiers will usually boost a TV signal in the 50-900 MHz range. They are generally constructed of very inexpensive parts, made in China (overseas), and in most cases (in my experience) they they typically do not improve television pictures. The reason for this is that because they are made of cheap materials and not well engineered, so instead of improving your picture they actually add what is called noise (distortion) into your TV signal. I personally have tried several of these amplifiers (of various brands) and found that they seemingly don't do a darned thing. At least none of them seemed to make my TV picture any better. That is the whole reason I looked around for a better product. The CHEAPIES are ok for maybe a small TV/VCR, in an area where TV reception is OK, but could use a little boost. They might also be OK for regular Outside Antenna TV if you have a particularly long cable running from your antenna to your TV.
Bi-Directional Amplifiers: Bi-directional amplifiers are the kind that you typically do NOT find on the store shelves, even at your favorite video/electronics store. These amplifiers are different from the cheapie amplifiers for a number of reasons. First, they are generally made of high quality components - and in the case of Viewsonics are produced right here in North America, NOT in China. Many other brands of cable amplifiers are produced overseas. Bi-directional amplifiers use expensive, high tech components which allow them to amplify the TV signal and at the same time allow your cable box to send signals back to the Cable Company. Bi-directional amplifiers operate in the 50-1000 MHz range, making them PERFECT for Standard Cable, Digital Cable and interactive services - including Cable Modems. Bi-directional amplifiers only amplify the signal going TOWARD your TV or Cable box. They DO NOT amplify signals going back to the cable company, and for that reason they may not always work well with cable modems. Only 1-port or 2-port amplifiers are recommended for use with cable modems for the best results.
Path (Reverse) Amplifiers:
Return Path (Reverse) amplifiers are almost the opposite of the bi-directional described on this site. Return Path amplifiers amplify ONLY the 5-42 MHz (return band) signals going back to the cable company. A Reverse Path amplifier will help in situations where the RETURN signal going back to the cable company needs to be boosted, or where the digital cable box (or cable modem) is unable to consistently transmit information back to the cable company. Usually this is because of long cable runs which tend to decrease the signal. Either way, a Reverse Path Amplifier will not make your cable modem FASTER, it will only make it more RELIABLE. Better reliability may make it seem like it is faster. Only your cable company can "speed up" your cable modem access by adding new equipment.
Path Equalizing (Tilt) Amplifiers:
Equalizing Amplifiers come in only 1-port versions. They are specialized equipment designed to overcome some of the problems associated with very long cable runs. When a cable signal travels over a long cable run (>150 feet), the higher channel (high-band) signals tend to lose strength faster than the lower channel (standard-band) signals. If you use standard amplifiers over long cable runs, you end up with very strong standard-band signals, and very weak high-band signals. Essentially you will be able to see the lower channels, but the higher channels may be weak. The opposite may also happen: the standard-band signals may be so strong that they OVERDRIVE your TV or cable box, and the high-band channels may be just fine. The solution to this problem is to install an equalizer rather than a standard amplifier for long cable runs. Some amplifiers boost the signal more on higher channels than on lower channels, so that this "long cable run" problem does not occur.
When shopping for an amplifier, bigger dB numbers are not always better. Too much of a good thing can actually make things worse for you. It is easily possible to make your TV signal WORSE by boosting the signal too much. This is called OVERDRIVING the signal. It is bad because it causes buzzing, bleeding or blotchy colors, and white streaks - among other problems. The best strategy is to keep the signal strength as close as possible to the signal strength provided by your cable company. In the real world this is done through painstaking calculations of cable lengths and cable splits throughout the house. However, most people don't know how to compute gain/loss so they take a SWAG (simple wild-ass guess) at it by throwing an amplifier in place, in the hope that it does what they want. Believe it or not, this actually works most of the time! Fortunately a good guess works for most of the simple situations out there.
|dB Boost/Loss||dB Power Factor||Voltage or Current Ratio|
(also known as dB boost):
Amplification is the process of boosting a signal. Amplification is generally needed for homes with multiple TVs, or where long cable runs (>150 feet) are used. Amplification is generally a good thing, except for the fact that cheap TV amplifiers don't do a real good job, and can actually make the TV signal worse. Cheap amplifiers add "noise" to the signal, which can then be seen as ghosts, buzzing, snow, lines through the picture, and other annoying things. Good amplifiers do their job so well that they don't add ANY noticeable noise to the TV signal. Good amplifiers make your picture look BETTER, and don't cause side effects like ghosts, lines, or snow. The boost is measured in dB.
Based on our Decibel Table above, a 1-port amplifier provides 15dB of forward signal gain, which means that the signal is almost 32 times stronger coming out of the amplifier than the signal going in. In addition, a 1-port amplifier has a return path loss of 0.5 dB, which means it causes an 11% loss on any signal going back toward the cable company. Here is a quick summary table:
|# Amplifier Ports||Signal Gain (dB)||Forward Signal Boost Factor||Return Path Signal Loss (dB)||Return Signal Loss Percentage|
|4 (UG model)||0||1.00||7||80%|
|8 (UG model)||0||1.00||10.5||91%|
The frequency range (bandwidth) determines what range of signals the amplifier can handle. Basic outdoor Antenna TV and Cable TV signals go from 50~800MHz (Megahertz), Digital Cable services can go as high as 1000MHz (also known as 1 Gigahertz - GHz). Digital Cable and Cable Converter boxes also require what is called a return path. Most cable amplifiers do not provide a return path unless they explicitly advertise that they do. If the amplifier does not support a 5-42 MHz return path, it will not work with cable boxes or cable modems. When buying an amplifier, always ASK if the frequency range is not advertised. It is generally not advertised if it is a CHEAPIE amplifier.
The Return Path is a special frequency range used by the cable company to transmit signals FROM your cable box BACK TO the cable company. Ever wonder how the cable company can allow you to "talk back" using your cable TV box? How about ordering a Pay-Per-View special using your cable box remote control? The cable TV boxes actually transmit signals BACK to the cable company to tell them that you want to watch the "Wrestlemania 25" pay-per-view event. Then the cable company sends a signal back to your cable box to "turn on" the pay-per-view channel. That's how they do it. Cable companies also require the return band for use with cable modems. If the cable amplifier does not support the return band, the cable modem won't work with it. The standard return path is in the 5-42 MHz frequency range. A bi-directional amplifier is required to allow these special cable company signals to travel back to the cable company. CHEAPIE amplifiers will not work with Cable TV Digital services, Multimedia (Cable Modems), and Cable TV boxes.
Bi-directional means that signals can pass in both directions. This means that the cable company can send signals to you, but you can also send signals back to the cable company. Bi-directional has nothing to do with Amplification. Cable signals can be amplified in one direction only, by ONE amplifier. If an amplifier is advertised as amplifying in BOTH directions, be aware that these products are relatively uncommon. Some people selling cable TV amps on eBay do not know the difference, and will incorrectly advertise bi-directional as full 2-way amplification. The cost of a Return Path Amplifier is significantly different than a standard bi-directional Amplifier. If you're not sure, drop me an email with the model number of the product you are looking at, and I'll tell you what it is if I know.
Amplification vs. Unity Gain:
4-port and 8-port amplifiers come in two versions - those WITH forward gain, and those with UNITY gain. The Unity Gain amplifiers generally have the letters "UG" right on the label. A unity gain amplifier acts just like a big splitter. It breaks up a cable signal, but does not provide a boost to the signal. This means that "signal strength IN = signal strength OUT". Unity Gain amplifiers are generally used for special applications where you specifically do NOT want any amplification of the signal. Standard amplifiers will provide Forward Gain, which is expressed as a dB number. 4-port amplifiers generally provide 7dB of "forward gain", and 8-port amplifiers generally provide 4dB of "forward gain".
Splitters (above) are used to break your incoming cable or antenna signal up so that it can go to more than one TV. Everyone has at least one splitter somewhere. The problem with splitters is that every time you use one, you cut your signal strength down. It's like putting one of those Y-splitter things on your garden hose... These drops in strength are also measured in dBs. A high quality two way splitter will generally make you lose 3.5dB. A 3-way splitter will make you lose 5.5 dB, and a 4-way splitter will make you lose at least 7dB of signal strength. What does that mean? Well if your signal drops enough, you will get snow or a fuzzy picture. If you use multiple splitters, you actually degrade your TV signals a LOT. Splitters also have a Frequency Range. Always use high quality, 1000 MHz DC PASSING splitters. If you use high quality splitters you will save yourself a lot of headaches. They cost more, but they are worth it. Cable-Amplifiers.com only sells high quality splitters.
Every time you put a splitter or amplifier into your cable line, it causes the signals going BACK to the Cable Company to weaken. This is particularly problematic if you are using a cable modem or Digital Cable Services. If the signal that the cable modem or Digital Converter sends back to the Cable Company is too weak, your services may not work. Each splitter or amplifier is rated for (return) loss, which basically tells you how much signal strength you lose when the signal goes back through the splitter or amplifier. Here are some approximate Return Loss numbers for common situations:
|Splitter Type||dB Loss||% Signal Strength Lost|
These numbers are all based on HIGH QUALITY 1 GHZ splitters. Lower quality splitters will likely have higher loss numbers. What about the Amplifiers? Amplifiers also cause return path signal loss. Those numbers are listed in Table 3. Bottom line, this means that even if you use an amplifier, you could end up with weak signals going BACK to the Cable Company. That's why the cable company usually uses a dedicated cable line for your cable modem, so that the signals traveling back to the cable company stay as strong as possible.
These terms describe the physical cable used in your home. RG59 is thinner and cheaper, and allows more signal loss. RG6 is a heavier cable which comes in 2 flavors - standard and quad-shield. If you are installing new cables in your house, use quad-shield cable. it costs about 20-30% more than regular RG6, but keeps SIGNAL LOSS at a bare minimum. You should not use RG59 cable unless RG6 is unavailable. Home Depot carries both RG6 and RG6 quad-shield cabling in 100 and 500 foot spools.
An F Connector is the standard screw-on connector used on the back of your TV, VCR, or Cable box. It is a standard for all TVs, VCRs, and Cable Boxes. Cable amplifiers use F Connections to connect into your system. When replacing cable ends or installing new cables, always use high quality crimp on cable connectors. There are different sizes for RG59, RG6, and RG6-quad - so be sure to buy the right ones. You will also need a cable stripping tool for coax cable - they are available at Home Depot. The same thing applies to the crimping tool. Make sure that which ever tool you buy supports the cable size you are using, since there are different crimper sizes.
A Cable modem is a piece of equipment which receives data from your cable company (your Internet provider) and also sends data from your home back to the cable company and out onto the Internet. It is always used with your home computer. Cable modems allow you to send information to and from the internet just like a regular modem, except you are using the Cable Company's cable lines instead of the Phone Company's phone lines. Cable Modems use the same signals as your regular Cable TV Converter box. The only difference is that the Cable Modems use different frequencies which cannot be seen by your television set. Cable modems generally require a pretty strong signal, which also means that they require a fairly unrestricted path back to the cable company. This is why the cable company will put in a totally separate cable connection dedicated to the Cable Modem. Cable Modems will GENERALLY work in conjunction with a Bi-directional amplifier or a Splitter... I guess it would be better to say that they TOLERATE bi-directional amplifiers and splitters. Depending on the situation, a bi-directional amplifier may improve or degrade your cable modem performance. The best rule here is " If it ain't broke, don't try to break it". If your cable modem is fast and generally reliable, you don't need an amplifier for it. However you might still need an amplifier for the rest of your TV equipment in the house.
Cable Modem Setup #1: This is normally the way the cable company will install your cable modem. Adding in the amplifier as shown in the picture will not hurt your cable modem, and will improve your TV picture.
Cable Modem Setup #2: Put an amplifier in BEFORE the splitter for the cable modem. It will help the cable modem operation as well as improve your cable TV picture.
Cable Modem Setup #3: Put a 2-port amplifier in place of the 2-way splitter. It will help the cable modem operation as well as improve your cable TV picture. This setup is somewhat "cleaner" than the 1-port amplifier used with a 2-way splitter.
Standard Cable/Digital Cable Setup: Put an amplifier as close as possible to where the cable comes into the house (to prevent signal degradation), and then split the cable off to various TVs and cable boxes throughout the house.
Outdoor Antenna Setup: Put an amplifier as close as possible to where the antenna wire comes into the house (to prevent signal degradation), and then split the cable off to various TVs throughout the house.