How to install a masthead amplifier and power supply unit

July 13, 2017
by
Tom Smart

How to install a masthead amplifier and power supply unit

 

Something that is regularly used with the aerial and satellite sector but not commonly known outside the trade. It is not common knowledge that the same coaxial cable that feeds the TV or set top box can be used to power active devices. Such as masthead amplifiers, Line amplifiers, LNB’s on satellite dishes and so on. It can!

 

The following guide will show you the uses of and how to install a masthead amplifier and power supply unit.

 

How does a masthead amplifier work?

 

A masthead amplifier is an active device which requires power to operate. It takes an aerial signal in and then sends the signal out at a higher level.

 

The amplifier itself is powered via the coaxial cable that feeds the TV by a power supply unit. Usually a 12V DC supply which connects into the output of the masthead amplifier but 5V, 18V and 24V versions are sometimes used with the 18V and 24V versions usually not for domestic style masthead amplifiers but for powering of distribution equipment in communal systems for blocks of flats.

 

The coaxial cable which runs between the amplifier and power supply must be either uninterrupted with no joins, wall plates, amplifiers, filters or splitters incepting the cable on route, or if it does pass through any these they need to be DC passing varieties.

 

What types of masthead amplifiers are there?

 

As with most TV aerial amplifiers they are separated by the following:

 

Frequency band

 

Most masthead amplifiers are wideband these days, up until a few years ago this was UHF channels 21-69. Nowadays since the release of 4G which operates on channels 60-69 the 800Mhz band a masthead amplifier will only generally go up to channel 60. Beware when working on transmitters that use UHF channels 57-60 such as the Whitehwak transmitter in Brighton and the Dover transmitters which as many models will filter out these multiplexes. So beware that the masthead amplifiers only a few years old may take accept 4G signals in at a level which may not be a problem and amplify them to levels which may cause interference on Freeview and newer models may actually filter out some channels which you want to keep.

 

It is worth noting also that when 5G is rolled out which is looking like will happen ahead of schedule, scheduled for 2020 but could happen in 2018 more of the UHF frequency band will be set aside for this. 5G will operate on a 700Mhz band and UHF channels 50-60 so it is almost certain that wideband masthead amplifiers will only operate on channels 21-50. Finally please be aware that amplifiers which are LTE ready and designed to remove unwanted 4G signals may actually suffer from similar problems when 5G is rolled out.

 

Like I said most amplifiers are wideband but that’s not to say that grouped versions exist. I often come across group A, Group B and Group C/D masthead amplifiers which are only intended to pass that frequency band.

 

How many outputs the amplifier has

 

 

 It is common to practice to install 4, 5, 6 or even 8 output versions when running multiple TV’s. A one way masthead amplifier and DC passing passive splitter could be used but often it looks a lot neater just to have the one piece of equipment especially when installing the amplifier outside.

 

It is also very important to note that many multi-output amplifiers will need the power supply to be connected to one particular output so be careful when moving PSU’s from room to room as it may not work. The majority these days however allow the PSU to be connected to any output – certainly the models we use.

 

How much signal gain the amplifier has

 

Different makes and models of masthead amplifiers will output the signal at greater or smaller levels that others. Some have a fixed gain and others have a variable gain. A typical masthead amplifier we will use will have about 10dB of signal gain. But we commonly use a variable version that operates between 15-27dB. We would use this in a weak signal area and when we are running into a high output passive splitter where the extra signal is desirable. The adjustable gain also helps us balance the system where needed.

 

Many amplifiers will have a maximum input of output. This should never be exceeded as this could cause the amplifier to become faulty and cause loss of TV reception or pixilation. Please also beware that this maximum input/ output should be de-rated when carrying numerous multiplexes or channels through the amplifier so you should never test this is its maximum capacity as it’s likely it will still be overloaded.

 

Power consumption

 

As already previously mentioned most domestic masthead amplifiers will require a 12V DC power supply but some operate at 5V DC. The power supply needs to be matched to the amplifier.

 

 

Why might you want to install a masthead amplifier?

 

You may need to amplify a signal in a place that doesn’t have mains power, obviously it’s great if you have a mains point in a loft but that isn’t usually the case and you almost certainly won’t have a mains point outside such as on walls and the aerial mast itself.

 

You may be in a weak signal area and want to carry as much as the signal as possible down to the TV before any cables losses or losses occurred as a result of splitting you multiple TV’s. If you are intending to install an amplifier or “Booster” at the TV end of the cable the signal may already be too weak to amplify. By amplifying nearer the aerial end you are carrying the signal at a higher level at all times and it will work better.

 

There may be nowhere else where a TV aerial amplifier can be installed inside so if you are going to install this outside you will need a masthead amplifier which are designed to live outdoors.

 

If you are concerned about installing the highest quality equipment. Mains amplifiers are widely available to the general public but the ones that can be purchased in your local DIY store are a load of crap and should never use where possible. Although good quality amplifiers can be found it is a little bit more difficult to those outside of the trade. As masthead amplifiers are aimed at the trade and largely not available to the general public they are made to a much higher standard. Such as having far lower noise figures.

 

Where should you install a masthead amplifier?

 

The clue is in the name itself. It’s a mast (aerial pole) – head amplifier, so it’s designed to live happily on the aerial mast and should for maximum performance be installed s close to the aerial as possible but no closer than 1 meter to the aerial. It can in reality go closer but 1m worth of coaxial cable should extend out of the aerial before entering into the amplifier. The vast majority of models come with a cable tie or strap so this connected directly the aerial pole.

 

You should also consider servicing so it may not be always be a good idea to go 1m away from the TV aerial where they work best. Tied to the bottom of the aerial pole is usually a good serviceable position if you have access to where the aerial is. If your aerial is high on a chimney then you want to put this as close as possible but accessible such as high up on a wall or within a loft if it’s not too far away from the aerial.

 

Where should you install the Power Supply Unit (PSU)?

 

I prefer to install these in positions where they are not likely to get switched off or unplugged. A mains point in the loft or within a cupboard. If you can cable directly into a fused spur unit to prevent it being disconnected or turned off great, but make sure that you consult a qualified electrician before attempting such a task. It also makes the installation tidy not having to plug a bit of equipment in one of the rooms.

 

The PSU can otherwise be installed behind the TV or anywhere that intercepts the aerial cable with a nearby mains point that feeds between the TV and the masthead amplifier. If you are going to install this behind the TV I recommend screwing this down or labelling it saying “TV power do not remove”. It is so common that when people move house they take these with them thinking that they are “boosters” and can be re-used where they are going. What they are actually doing is removing something that is worthless on its own so unless they move into a property that has a missing PSU, not impossible if they are in a chain and the person who has last the property did the exactly same thing and secondly leaving the TV system not working for the new occupiers of the property. I often hear “it was working when we left” and they would be right up to the point where they disconnected and packed the TV with the PSU with it.

 

I recommend installing the PSU on it’s into its own mains socket where possible and it not into a trailing extension socket or adapter. This is just so that it is less likely to get switched off by accident and no signal throughout the system and so other equipment which you may want to un-power or disconnect can be done without messing around switching over plugs.

 

Step by Step guide to installing a masthead amplifier

 

1- Connect aerial input into masthead amplifier

2- Install a cable between the room where the power supply will go and connect into the output of the masthead amplifier.

3 – Connect PSU, plug into mains supply and connect masthead amplifier output cable into the section that distributes the DC. This is usually labelled ‘12V’ or ‘Aerial’ and switch on.

4- On PSU connect remaining output coaxial cable to TV or onto distribution system.

 

Common problems with installing masthead amplifiers

 

Faulty electrical related problem

 

The equipment can just go faulty like any other bit of electrical equipment. It’s USUALLY the power supply unit which goes wrong so I advise changing this before changing both parts. That’s not to say that the masthead amplifier can go faulty.

 

Power unit switched off – Missing power unit

 

This should be the first point of call when investigating no signal where masthead amplifiers are in place. You would not believe the amount of times I have turned up at emergency call outs only to find the power unit switched off.

 

Weathering

 

As the masthead amplifiers often live outside and especially seaside towns some efforts should be made to ensure that the DC coming from the PSU can get to amplifier as any water penetration into the cable has the ability to stop this. This may include installed weather proof F connectors or smearing the outside connections with silicone grease to prevent water ingress.

 

It is good practice when installing masthead amplifiers outside or on the aerial pole itself these are taped shut or cable tied – Tape is better as it’s very common when installing outside for these to flap open and let water in or for the cable tie included to snap and for the amplifier itself to turn upside down and fill with water.

 

The cable which the PSU is connected to must be of good condition as if this cable is to fail you will lose signal to every TV attached to the system.

 

Power not reaching masthead amplifier

 

This usually occurs when passing through wall-plates or splitters.

 

All wall plates that are attached to the PSU cable must not be isolated. If they are you need to either relocate the PSU or change the wall plate for a version that allows the DC to pass through.

 

Splitters must be off the DC passing variety and the power unit must be connected to the output that allows the DC to pass as many splitters are DC passing but only on one output. The vast majority of DC passing splitters are diode protected which will only allow a current to flow from output to input. If you need the DC to pass the other way, uncommon with masthead amplifiers but common with remote eyes for Sky boxes you will need a splitter that allows you do this.

 

All amplifiers must be of a DC passing variety but it is uncommon again for these to pass from output to input.

 

A multi-meter could be used at the masthead amplifier end to check for voltage if you are in doubt whether the power is flowing through or not.

 

Overloading of signals

 

You should never add an amplifier for adding an amplifiers sake. Where possible you should avoid amplification where possible as you never get something for nothing with an amplifier. It is possible when you install a masthead amplifier in a strong or moderate signal area that the signal will be too strong and overload the distribution or viewing equipment.

 

I hope that this blog was of some use to you. Please do LEAVE A COMMENT if you liked it, are having any problems or would like to make any further requests for future blogs.

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