There are high chances that this is the first time you hear about a TV/SAT attenuator. However, as an Aerial Fitter in Preston we do use these from time to time.
Before diving into this subject, I am aware that for most people, a lot of what is discussed in this blog are terms and subjects that are only of interest to other aerial & satellite engineers. The general public don’t really care how their TV works, so long as it does! It is only when they experience a problem, that some begin to take an interest. With that in mind, I will be discussing about a small often overlooked piece of equipment that does on occasion come in very handy. This is the Attenuator.
What is a TV/SAT attenuator?
So, what is an attenuator & what is it used for? Well in simple terms an attenuator is the reverse of an amplifier. Whereas an amplifier amplifies or increases a signal or sound, the attenuator reduces the signal or sound. In our case we look to it in order to reduce a satellite or digital signal from an aerial.
They are only small pieces of equipment and come with differing rates of signal reduction. It acts like a resistor and depending on the strength it is set to. There are attenuators that have a fixed amount set, such as a -10db reduction or there is the variable type that allows the amount to be set manually. They are designed in a way to provide a reduction or resistance in the signal without distorting it.
Why are they used?
The reasons they are used is to reduce the strength of a signal going to the television if the signal is too strong. The reason a strong digital signal can be a problem, is that if the signal going to the TV is over 90db then most TV’s will struggle to deal with that signal. This is known as over signalling.
Over Signalling
When this happens, the result is almost identical to having a very poor signal. Picture break up, freezing, sharp loud noises. On the odd occasion I come across this, I am called out because the customer thinks their aerial is failing and the signal is too weak. The ability of an attenuator to reduce the signal is a very simple solution and cost effective.
Why can a signal be too strong. Well, in my experience, one of the most common reasons, and in reality, it isn’t that common, is due to the set up of either 1 or more amplifiers. Not all homes are set up have a nice neat and orderly set up of its aerial system. Larger homes and businesses such as rest homes and hotels will quite often have one system on top of another.
Due to this I will often come across a set up where a set back amplifier is feeding into another amplifier and then into another. All of this is a complete no no when it comes to providing a trouble-free distribution system, but it happens never the less. In most cases a complete redesign and installation is not affordable, and a quicker and cheaper solution is required for the TV’s suffering from over signalling.
This is where I will employ the use of an attenuator for each of the TV’s suffering with over signalling. It would be better to remove the amplifier distributing to the TV’s but sometimes this isn’t always the cheaper solution for the customer.
Why?
- Firstly, it can be very difficult to track the cable back to the amplifier (particularly within hotels that have dozens of rooms with TV’s in them)
- It maybe the case that only a few of the outputs from the amp result in over signalling due to the run of the cables coming from and going to the television. (A shorter run of cable loses less db than a longer run).
So, for these reasons, using an attenuator each of the TV’s can sometimes be the best solution.
Digitec Aerials Preston
The Watermark,9 – 15 Ribbleton Lane,Preston,PR1 5EZ
Telephone: 01772 369629