TV Aerial / Sat Antenna Attenuators – Why Would You Need One?
Here is a term and product that may not be in your vocabulary but, to successfully install your own TV systems whether DIY or professionally it's important to have a knowledge of TV signal attenuators and purposeful signal reduction. As a professional installer, it's not something that I use every day but it's important to keep a bunch of them stocked on the van. In this blog I discuss the different types you can buy, what these do and how to install them correctly. Let's begin!
What is an Attenuator?
An attenuator in from a TV Aerial/ Sat perspective is something that is used to attenuate a signal, in simple terms this means to reduce the strength of. This usually plugs into your coax plug but there are a wide variety of different types for different purposes.
Why Would You Want To Reduce Signal Strength?
I always get a funny look when I say that the TV isn’t working properly because the TV strength is too strong, but this is actually very common. A TV signal is actually a voltage/ current and some of the circuits in TV tuners & distribution equipment like TV aerial amplifiers are only designed to carry a certain amount so you may need to reduce the signal strength for a reliable TV signal. This is most common where a high amount of signal is coming off a TV antenna, the closer you’re to a TV transmitter the stronger the signal is usually or when an amplifier has been installed which boosts a signal above maximum levels.
Types of Attenuator
There are various types of attenuator that you can purchase and it’s important to buy the correct one or your could ruin your TV signal. If you buy one which offers too much attenuation you could reduce your TV signal to a strength that is too weak, or you could buy one that does not offer enough attenuation which means that the TV signal is still too strong which will not prevent the signal strength from overloading the TV tuner or distribution equipment.
Coax IEC Type
This usually just inserts onto the end of a coax plug which can be plugged directly into the RF input of a TV or distribution equipment like splitters/ amplifiers. The input is nearly always a female connection and the output a make connection.
Most F type attenuators will be fitted in the inputs of splitters/ distribution equipment or satellite receivers which has F type connections. In instances like this, it saves the job or having to install new plugs and/ or adapters. Most F plug models have a female F connection for the input and a male F connection for the output but some models are “in line” meaning that they have female connection on both ends and a link lead or male to male F plug will be required to connect it into a F type input.
Satellite Attenuators / DC Passing
A attenuator for satellite TV signals must have the following characteristics, it must be able to pass the satellite IF frequencies, most will go up to the frequency of 2400Mhz and it must also be DC passing allowing the DC voltage to pass through it to power the satellite LNB or output on a multi-switch amplifier. If you have a set up where DC voltage is required to power a masthead amplifier or Sky magic eye a DC passing attenuator will be required too, however it would usually make more sense to move the attenuator to a different location where line power is not required to pass through it, like the input of the masthead amp or the input of the aerial input of the Sky box to which the remote eye is connected to.
An adjustable attenuator can be very useful if you not sure how much that you reduce a signal strength by. Most adjustable type models offer 1-20dB attenuation which is adjusted with a screwdriver on the side. Being able to control the attenuation, unlike a conventional model allows the user to monitor the effect that this has on TV reception. If attenuated too much it’s likely that this could cause TV pixelation and not enough will not solve the issue of too much signal.
Attenuator Signal Losses
It’s important to buy an attenuator that reduces the signal to the correct amount. It’s not easy to do this without test equipment that can measure the strength of your TV signal. Attenuators typically come in 3dB, 6dB, 9dB, 10dB, 12dB increments but you could find some in between that offer more or less attenuation.
Minimum & Maximum Signal Strengths
You want to buy an attenuator that will keep your TV signals at your TV receiver somewhere comfortably in between the minimum and maximum suggested signal strengths. Depending where you go you will get different information,but I recommend the following:
MinimumSignal (dB) MaximumSignal (dB)
DigitalAerial/ Terrestrial 45bB (Ideally50dB) 80dB
Satellite 47dB(Ideally 52dB) 80dB
Analogue TV 60dB 80dB
FMRadio 60dB 75dB
DAB 40dB 70dB
Temporary Use of Attenuators For TV Tuning
Attenuators can be used to solve TV tuning issues, by in large they are not needed but on occasion some make/ models of TV’s do not store the correct TV services. Sometimes when you run an auto-scan on your TV you will get duplicate channel results. This is when there are more than one TV transmitter being picked up on a TV aerial cable, even when you align a TV aerial in one direction sometimes signals will be picked up off the sides and back of the antenna, this is accentuated with amplified TV systems. Problems arise when the TV stores the incorrect signal which may be very weak signal and unreliable reception. This problem is usually solved with a manual tune of your TV receiver but some do not allow this. In these situations a correctly sized attention could be installed to reduce the strength of the unwanted duplicate signals which are usually weaker so that when the TV automatically it scans through it goes straight past the signals that you might be storing by accident. Once the tuning is complete the attenuator can be removed as this would be also be reducing the strength of the signals which you want to keep.
TV Signal Attenuator Installation Best Practices
Installing an attenuator needs to be done correctly, if done incorrect it could cause other problems with your TV signal. If you follow the guidance below you should be okay.
Remove Unnecessary Amplification First
If your TV aerial amplifier is being overloaded or is causing your TV signal to become too strong. It makes more sense to remove the amplifier from the system altogether as you do not get something for nothing with an amplifier. If you have a distribution amplifier serving multiple TV’s this could be removed and replaced with a multiple output passive splitter which itself could be used to reduce the signal strength in the system. This isn’t always possible though with systems feeding a very large amount of TV’s and/ or long coax cable runs and the signal loss could become too great, not only will you get signal losses through the splitter you will also lose the signal gain from the amplifier.
In regard to satellite reception, this might also mean turning down the signal gain on satellite launch amplifiers or not installing high gain LNB’s for very short cable runs.
Pick The Right Type
You need to buy one that has the correct amount of signal losses and if you get one with the correct corresponding coax connectors it will save you a job of having to install new coax or F plugs. Remember satellite attenuators must be able to pass the frequencies used by the satellite IF band and a DC voltage.
Don’t Let The Signal Get Too Strong
The purpose of an attenuator is to drop the signal so that it does not overload distribution equipment or TV tuners. If the attenuator is not installed in the correct place it may not work. For instance, if a TV aerial amplifier is being overloaded by a too strong signal then plugging an attenuator behind your TV set will not resolve your signal problems as the TV amplifier will still be overload.In this instance the attenuator must be installed before the input of the amplifier to resolve signal issues.
Don’t Let The Signal Get Too Weak
It’s important when installing attenuators not to let the signal get to weak at any point in the system, even if an amplifier is to be installed afterwards to give the signal a boost in the right direction. You should never let the signal drop below the suggested minimum signal level for reliable TV reception, at any point in the system. Just make sure that if you’re attenuating into an amplifier that it doesn’t do this.
You Might Be better Off Installing a Filter
Where TV tuners and distribution equipment are being overloaded with interfering signals, like 4G interference or Tetra, you will most likely be better off installing a filter instead to reduce the strength of the interfering signal while preserving the signals that you want to keep. An attenuator could work in situations like this but it could also ruin your TV signal.
Install A Link Lead To Reduce Stress On The Cable
If you have an attenuator plug direct into the back of the TV tuner input, you may want to consider installing a link lead to reduce stress on the TV input. The last thing you want to do is damage the TV. The is particularly important when your TV has been installed close to the wall and there is limited space to fit it in, do not try and squash it in. Instead, install a link lead or use an inline attenuator. Right angled coax plugs could also be used to reduce the cable bend radius and to fit into limited spaces.
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That's it for this one, until next time.
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