Signal combiners are used to combine local off-air channels from a TV antenna with the modulated channel 3 or 4 signal output from a satellite receiver, VCR, DVD player or other audio/video device. This allows you watch any of the local channels from your TV antenna or the satellite channel from your satellite receiver on any TV in your house. However, signal combiners are often poorly made and can cause interference on not only channel 3 or 4 from your satellite dish or other device, but on some or all of your local "off-air" channels. These problems will be addressed in this tutorial along with some different solutions to solve these problems.

Problems With Combiners

Channel 3 or 4 signal combiners are a major cause of interference and have created a lot of service calls for us in the past. We recommend to our customers that they replace their channel 3 or 4 signal combiner with a high isolation A/B switch, such as the Regal model RABS A/B switch or a UHF modulator, such as the Cable Electronics 2000SD stereo modulator.

Signal Combiner

A/B Switch

Cable Electronics 2000SD MTS Stereo Modulator

The channel 3 and 4 combiners just don't have good isolation from adjacent channels and they aren't "active", which means that all they do is simply combine the relatively weak channel 3 or 4 signal coming out of your satellite receiver or VCR and combine it with the local off-air channels. Even if there is an adjacent off-air channel 3 or 4 over 100 miles away there can be enough signal there coming in off of your antenna to make your "in house" channel 3 or 4 bad. Since your device's signal is usually weak and only strong enough to provide a good quality signal to only one or two TVs, an amplifier has to be added to increase this weak signal level. But this can lead up to even more problems and can actually make matters worse if your "in house" channel 3/4 is a lot stronger than your local off-air channels.

Some of the newer models of signal combiners have a built-in amplifier, but these amplifiers are almost always low quality amplifiers and can add "noise" or imperfections to the signal. Also, channel 3 and 4 combiners typically are not constructed very well and sometimes even tapping on them can make the picture on the TV better or worse. This is why we strongly suggest not using these channel 3 and 4 combiners.

A/B Switches

While high quality A/B switches are effective at switching between two sources, they are often a nuisance. Because the A/B switch is most often located at the main TV where the satellite receiver and the lead-in coax comes in from the off-air TV antenna, each time that someone in another room wants to switch between a local channel and satellite, you have to go back to the A/B switch. This is why modulators have gained popularity in residential installations in recent years.

Modulators - The Best Option

A modulator is a device that actually "creates" a new channel on your TV system, unlike signal combiners that simply take the device's channel 3 or 4 signal and combine it with your local off-air channels. Modulators are "active" and feature a built-in amplifier that will provide a good clear picture to any room in your house. Most residential type modulators create this new in-house channel in the UHF TV band, which moves the A/V device even further away from the VHF-LO frequencies that are often prone to power line interference that can be picked up by an outdoor TV antenna.

While they do cost considerably more than a simple A/B switch or signal combiner, they make watching TV in any room of your house a breeze. Modulators allow you to watch a satellite channel from your satellite receiver, VCR, DVD player, or other A/V device on any TV in your house by simply putting the TV on your newly created in-house channel. You can even combine multiple modulators or purchase a multi-channel modulator so that you can watch more than one device located at your entertainment center anywhere in your house by simply tuning the TV to that device's assigned channel. Plus, a stereo modulator can make true surround sound stereo available to every TV in your house without having to run audio cables to every TV.

Until recently, stereo modulators were very expensive, starting at around $300. But thanks to a partnership between Cable Electronics and Motorola Semiconductor, they have built the first MTS stereo surround sound audio encoder integrated circuit. This has dramatically reduced the cost and size to allow RF transmission of MTS stereo and surround sound audio signals from consumer electronics products to stereo TVs to be economically possible. For more information on the Cable Electronics 2000SD MTS stereo surround sound 1-channel modulator click here.

View our tutorial on how to install a modulator