There’s no end to the arcane products you’ll find in the serious antenna enthusiast’s toolbox. One of the least expensive is the lowly attenuator. An attenuator is really nothing more than a volume control. They come in variable ones, which inevitably have a respectable “old-school” look to them, or fixed ones, which look like the ends of cables. They serve a specific purpose and when you need one, you’ll be glad you have it.
The purpose of an attenuator is to keep a certain amount of signal from passing through. While rural and distant antenna users erect ever-larger arrays to pull in super-weak, distant signals, city and suburban dwellers often have more signal than they need. While the hobbyist with a giant aerial antenna may scoff, those close to the towers may find that stray signals are ruining their viewing experiences.
Too much signal can cause ghosted images or a wide variety of other problems. A very strong signal can bounce off nearby buildings, interfering with the stronger primary signal and creating what is called “multipath interference.” This continues to be a problem, even with digital signals.
If you suspect that you’ve got too much signal, an attenuator can help you by reducing the amount of signal that travels through the line. Attenuators aren’t just for antennas, though; they are also used with satellite amplifiers to guarantee that “just enough” signal gets through. Overamplified signals can cause distortion that can overload a satellite receiver’s tuners.
The point of an attenuator is that it lets some signal through, just not all of it. An attenuator that stops all signal from getting through is more properly called a filter or a trap. Filters are used for a variety of reasons, such as limiting amplification to one part of the spectrum while leaving another untouched, or allowing two antennas to happily coexist.