Read Feedback Read the Blog Cookies!
Checkout Can't Find It? Shop Index All Aerials Aerial Amplifiers Aerial Attenuators Aerial - Best Aerial Boosters Aerial Diplexers Aerial Filters Aerial - FM/DAB Aerial Hardware Aerial Meters Aerial Splitters Alarm - Garage Amplifier - aerial Amplifier - earphone Amplifier - LNB Amplifier - UHF Attenuators Attic Box Audio Index Bargains Batteries Battery Tester Blu-Tack Bolts - wall Bolts Books to download Boosters, Amps Boots - Rubber Box - plastic Brackets - aerial Brackets - satellite Brackets - TV Bypass Amplifiers Cabinet Fan CABLE+PLUGS Cable - CAT5/6 Cable - Coax Extens Cable - Coax Reels Cable - computer Cable Decouplers Cable - HDMI Cable - hole covers Cable Joint Cable - loudspeaker Cable - mains+plug Cable - modem Cable - telephone Cable Tester Cable - thin coax Cable Threader Cable - toslink Cable - twin flex Camping Light Capacitors Capacitors Low ESR Caravan/motorhome Car Radio Adapters CAT5-HDMI Children Games Chimney Brackets Compass Components Computer Batteries Computer Leads Craft Knife Cutters - wire Decoupler DC Blocker DC power inserter DC Power Plug DC Power Socket Denso Tape Digibox spares Digital Aerial Digital Link eye Diodes DiSEqC Switches Dishes Dish - alignment Dish - caravan Dish Hardware Dish Motors Dish - Omnisat Dish - upgrade Dish - zone 1 Dish - zone 2 Dish Paint DTA adapter Duct Tape DVD Players Earphones Earphone Clip Earth rod Electrical - mains Electrolytic low ESR Electronic components Electronic Kits Electronic Kits 2 Epoxy Adhesive Ethernet RJ45 CAT5 Extension - Coax Extension - mains Faceplates Filters electrical F Plugs Fly Leads Freesat Digiboxes Freesat Magic Eye Freeview cable FTA Digiboxes Freeview receivers Fuses Gadgets Gaming Accessories German Sat TV Glue Grease H-H Motors Hardware HDMI / Audio HDMI Splitters HDMI Wallplate Headphone Amp Heat Gun Heatsink gook Heatshrink tube Home Cinema HomePlug PLA IC Sockets InfraRed LED Installation kits Invacom LNB iPhone Accessories Jack Plugs Krone Tool Leads + Plugs LEDs LED Torches LED Torch Probe Lightning Protect Litz Wire LNB amplifiers LNB Boots LNB cable LNBs for Sky LNBs 40mm LNBs C120 LNB Holders LNB Splitter LNB switches LNB Upgrade Loft Aerials Loft Boxes Log-Periodics Magic Eyes Magic Eye Kit Magnifier loupe Magnifier stand Mains Electrical Mast Caps Meters Microphone clip Mobile Accessories Modulators - RF Motorhome Motorised dishbits Multimeter Multiroom Kit Multiswitches Notch Filter Omnisat Dish Orbital Dish Oscilloscope Phone Surge Phono Adapters Phono Plugs Piping Freesat Plugs - 'F' type Plugs - Phono Plugs - RJ45 Plugs - TV Pliers Poles Power Inserter PowerLine Adapt PowerMid XL Power supplies Raspberry Pi Relays Remote Controls Remote extenders Resistors RF Cable RF Modulators RF to Scart DTA RJ45 CAT5 Ethernet Satellite Cable Satellite Meters Scart Leads Screen Cleaning Screwdrivers Self Amalg tape Signal Combiner Silicone Grease Sky Digiboxes Sky Eye Kit SkyLink Amplifiers SkyLink Bypass SLxLink "eye" Slingbox Fan SPC4 Combiner Solder Solder Sucker Solder Wick Soldering Iron Spade connects Spanners SPC4 combiner Splitters Stripboard PCB Surge Protection Switches Tape Telephone cable Terminal Posts Thomson PSU Tools Grease Glue Toys Educational Transistors TV cable TV Eyes TV Plugs TV Wall Brackets U Bolts Videosenders Video/Leads VisonLink "eye" Wall Bolts Wall plates 1 Wall plates 2 Washers Wire Cutters Wire - coaxial Wire - Kynar PTFE Wire - Litz Wire - Loudspeakr Wireless Eye Wireless Phone ad Wireless Remote Zone 1 minidish Zone 2 minidish Technical Index Product Instructions 4G problem ADSL problem Aerial Advice Aerial+LNB 1 Cable Aerial amplifier Aerial Amps Aerial Booster Aerial - DAB Aerial Filters Aerial Groups Aerial Points Aerial - Which? Amp Adder Amp Choice Analogue Switch-Off A18QR aerial Arcon Dish Atticbox Audio Adapter USB AV equipment BBC/ITV outside UK Bedroom sound Best aerial Brick Burst cover Cable Info. Cable Kinked Cable specs Cable-Thin Coax Cable - Which? CAMs etc. Capacitor Kits Channels Chimney Brackets Chimney Strap Coaxial Cable Cooling fan Combiners Compass use Cupboard Control DAT45 aerial DC inserter Decouple cable Denso Tape Digibox Problem Digibox Internals Digibox in loft DigiEye (obs) Digilink (obs) Digisender Digital Ariel Digital Link Diplexers DirecTV Disconnect safely Disguise a dish Dish indoors Dish - Orbital Dish Painting Dish Sharing Dish Size Dish Upside Down E-books Electric shocks Electronic Kits Electronic Parts Epoxy resin glue Expats Extend cable Extender Plate Extenders Fan - cooling Fan - cabinet F1 for Free Filter-notch Fire Hazard Firmware D-load Fit F Connectors Fit TV plugs Foxsat HDR Foxsat unicable Free channels Freesat Install DIY Freesat Sky Dish Freeview/Freesat Freeview Problem French sat TV German sat TV Glossary Greek sat TV HDCP Support Heatshrink Sleeving Hole Cover Humax PSU Inside Sky Digibox Instructions Interference Invacom LNB Irish sat TV Italian sat TV IR sensor-locate Large Dishes Lightning Protect Liquid Spilt LNBs - about LNBs - add more LNB amplifier LNB Boots LNB - extra LNB Fitting LNB no signal in sun LNB - Quad-output LNB-Replace Sky LNB Reset LNB skew LNBs-Switching two LNBs 2 in 1 cable LNB-waterproof your Loft Boxes Macrovision Magic eyes Make Fly-Lead Multiroom phone Multiswitches No Satellite Signal Notch Filter Omnisat Semitronic Orbital dish Phone Connection? Phone Socket Wires Phone surge protect Phono Leads DIY Plate-Twin-F Plugs-which? Plug-Top PSUs Plus Combiner Powermid+cable TV Powermid XL Raspberry Pi Reboot Digibox Reed Switches Relay Timer Remote Codes Remote Doubler Remote Eyes Remote extenders Remote versions RJ11 phone wiring RJ45 plugs Satellite Advice Satellites-where SatMeter Scart leads Self-Amalg Tape SelfSat Antenna Signal Boosters Signal Combiners Signal Meter Silicone Grease Sky x2 same room Sky+ batteries Sky Digital Sky fire hazard Sky HD Sky in Europe Sky Install DIY Sky LNB Sky LNB-extra Sky Multiroom Sky Remote Probs Sky room wiring Sky Plus SlxLink Slingbox Fan Solder - How to Split Digibox RF Split Dish cable Split satellite signal SPS1 switch (obs) Stacker-Destacker Stuck in standby Terminology Thin Cable Thomson Problems Tree blocks signal Triax minidish TV Interference TV Interference 2 TV/VCR faults TV Links tvLINKplus TV set Fix TV set New TV eyes USALS USB Audio adapter UXF4 Videosenders VisionLink Wall Plates 1 Wall Plates 2 Wall Plate twin F WF125 Plugs What Channels What is TouView? Which plugs Wire my house X-Ray Remote 304114 wall plate FAQs BLOG Contact Us		TV Amplifiers / Boosters Send this page address - CLICK HERE - to a friend !   Contents Will an RF amplifier improve my signal/picture? What is "Gain" and how much do I need? Where does a booster go? What does a SkyLink Compatible Amplifier do? Where does a masthead amplifier go? Where does a set-back amplifier go? Where does a distribution amplifier go? What is signal/noise ratio? How can I install a Digibox in my loft? Do I need a Loft Box? Do I need a Multiswitch? IMPORTANT: When a power supply is used to feed an amplifier upstairs, any wall plate MUST be a non-isolated type, otherwise the aerial signal will get through but the DC power won't. An isolated (decoupled) plate is often marked with a capacitor symbol -||- so if yours has this (or obviously has capacitors fitted inside) don't use it unless you short-circuit the capacitors. In addition, any "TV plug" between the PSU and amplifier must be soldered to the cable, otherwise a poor or intermittent connection is likely to interrupt viewing now or in the future, SAFETY NOTICE: Electrical equipment which is installed in a loft or roof space should, wherever possible, be mounted on a brick or concrete surface. There have been rare instances of equipment catching fire so every precaution should be taken to prevent spread of fire. Powered equipment needs good ventilation and should be kept away from flammable materials such as cardboard, paper, plastic etc. Where a separate power supply is used, mount it on a wall with good ventilation. On no account lie it on a carpet or rug. Note that an amplifier can only amplify what's there. It's always better to use a better aerial located above the roof instead. The amplifier must always be near the input end of a long cable. If you put it at the output end, you are simply boosting the signal and the noise it has picked up, so you are hardly any better off! An amplifier's ultimate performance is limited by the cable quality. We recommend CAI approved WF100 coaxial cable.   C12537 masthead amp Will an RF amplifier improve my signal/picture? Try it without! Connect your equipment with just a short length of coaxial cable. (Take the TV into the loft if necessary). If it still doesn't work, then an amplifier won't help.   The main purpose of an amplifier is to counteract losses in a long cable. The second purpose is to allow you to split the signal without incurring losses. The third purpose is to get the Freeview signal level above the tuner "threshold" without swamping it with analogue signal. If your Freeview receiver works near the aerial (e.g. in the loft) but not further away, you probably need an amplifier to overcome the signal losses in the cable. If the Freeview receiver does not work near the aerial, try a low-gain amplifier. It may just boost the signal enough to overcome what's called the "tuner threshold". (This is often expressed as a negative figure like "-80 dBm". The larger the negative number, the more sensitive the tuner). If you can't get the Freeview receiver to work near the aerial, connected by only a short length of cable to the aerial, with an amplifier, then the aerial signal is no good. You may be able to improve it by aligning the aerial better, by raising the aerial higher, or by fitting a better aerial. For masthead aerial amplifiers see page 11c. aerial signal amplifier amplified signal cable attenuates signal T = tuner threshold Blue area represents noise. Yellow represents usable signal. A digital tuner has a critical "threshold". If the signal (yellow) is below this level, the tuner will not "see" it. So an amplifier will help if you can boost the signal above that threshold without also boosting the noise (shown in blue) above it. We sell a lot of variable gain masthead amplifiers for this reason. You can set the fine balance between not enough signal and too much noise. For UK Freeview there is an additional problem. While analogue TV transmissions continue, you must keep the analogue signal low enough to avoid "swamping" the digital tuner. For this reason, a correctly adjusted digital signal is likely to register 75% or less, otherwise the analogue signal (typically 14 dB higher) will "blind" the tuner. A (low-noise) amplifier can be useful in some circumstances. But, if the gain is not adjustable, it's wise to connect an adjustable attenuator at the input of each Freeview receiver. Look at the table of cable specifications mentioned above. 860 MHz is near the top end of the frequency band used for TV transmissions in the UK. You will see that 100 metres of WF100 attenuates a signal at 860 MHz by 18.7 dB. That's 0.18 dB per metre. So you would need an amplifier of approximately 18 dB gain to compensate for 100m of WF100 used for an RF connection. Or 6 dB to compensate for 33m. The amplifier must always be near the input end of the cable. If you put it at the output end, you are simply boosting the signal and the noise it has picked up in the cable, so it's not as good. What is "Gain" and how much do I need? Gain is the "amplification factor" measured in dB. The Amplifier should have enough "gain" to overcome the losses in the cable it is feeding. See notes above about this. For example, assuming good quality cable like WF100 which loses about 0.18 dB/metre at high UHF TV frequencies, a cable length of 39 metres will lose 7 dB of signal. So the amplifier gain should be roughly the same (7 dB). In the case of an analogue RF signal, over- or under-amplification can result in a poor picture that may be "grainy" or have interference lines. In the case of a digital (e.g. Freeview) signal, over- or under-amplification can result in breakup of the picture or no picture at all. What does a SkyLink compatible amplifier do? T140 Global amp It provides a 9 volt supply for a "magic eye" remote extender and also passes the remote control signals back to the Sky Digibox. See page 3 for a choice of remote extenders. See page 15 for a choice of SkyLink compatible RF amplifiers and Loft Boxes. (A SkyLink amplifier should not be connected directly to an aerial as its noise figure is usually too high.)   Where does a booster go? The low-noise amplifier/booster must always be near the input end of the cable. If you put it at the output end, you are simply boosting the signal and the noise it has picked up, so you are hardly any better off! The purpose of an amplifier is to compensate for signal loss in the cable before it happens! NEVER plug a booster in the downstairs feed from the aerial. The only time a "set-back amplifier" or booster should be used downstairs is when it's amplifying the signal to send it somewhere else via a LONG cable (bedroom, kitchen, conservatory). Also see our "I live in a flat" example, below. Note that current flows up the "drop cable" to the amplifier so the cable must not have any poorly made joints. If there's a wall-plate socket, it must be a "DC pass" type. There are two types of amplifier: 1. The low-noise* masthead amplifier which can boost the faint signal from an aerial while adding the minimum amount of unwanted electrical "noise". This type is normally installed on the aerial mast or in the roof space close to the aerial. Ideally the cable between the aerial and masthead amplifier should be 1 to 2 metres long but a little longer will be OK. The masthead amplifier receives its power through one of its outputs - usually any one of its outputs. The power supply unit (PSU) will provide between 5 and 25 volts DC, dependent on the amplifier design. More modern low-noise amplifiers tend to use a very low voltage PSU. The power supply can be located near any convenient mains power socket since the length of coaxial cable between the PSU and the aerial doesn't matter. (The voltage drop will be immeasurably small). *Beware so-called "aerial amplifiers" with noise figures above 3 dB (or not even mentioned). These are often cheap, pretty boxes sold in DIY shops. They may not give truly professional performance. Apart from adding too much noise to the signal, they may also introduce harmonic interference, causing "picture dropout". 2. The "Set-Back" amplifier which is used to boost the fairly strong RF signal from your receiver to another TV set. You can buy multiple output types called "distribution amplifiers". We recommend you use the T120/T140/T180 range. This type of amplifier normally includes a power supply and may be designed to plug directly into a power socket. A "Loft Box" combines both types of amplifier. It has a low-noise masthead amplifier as well as a distribution amplifier inside. Short lengths of cable (less than 20m) probably won't need an amplifier unless the aerial signal is really weak. The cable from the power supply to the amplifier has to carry a low current, low voltage supply. This is not dangerous but it needs a DC path so you must NOT use a wall plate or connector which "decouples" (removes) the DC path. All of the TV wall plates that we stock are proper DC coupled types. An attenuator may be required at each receiver where the cable run is short or the amplifier gain is too high. See our "Piping TV..." eBook for details. Where does a masthead amplifier go? Position the mastamp close to the aerial. The ideal cable length is 0.5 to 1.0 metres but a longer cable will work OK. However, the longer the cable, the more noise it will add to the signal before amplification.   Low-noise masthead amplifiers are available with one or more outputs. Sometimes these outputs are provided in the amplifier itself and sometimes they are in a separate power supply. These are handy where, for instance, you want only Terrestrial Freeview in each room. If you also want satellite TV in each room, a Loft Box might be more appropriate. To make sure the signal reaching every socket is the same, use the same length of cable for each. That way you can adjust the gain ("amplification factor") and be certain that every socket is receiving exactly the same signal level. Coil up any extra in the roof space. (Big, loose coils kept away from any source of interference.) Alternatively, you can use different lengths of cable and see how it goes. If you have problems then you can either add extra cable to equalise the signal losses OR you can fit appropriate value UHF attenuators at the bottom end of each short cable. (Never fit an attenuator close to the amplifier output; a weak signal is more prone to interference so it's better to keep the signal strong as far as possible.) Another example where a two-output masthead amplifier is feeding two TV sets via Freeview boxes. Note that an attenuator must be fitted to any aerial input where the signal is too strong due to short cable length. You can calculate, as explained previously, on the basis that 1 metre of WF100 cable loses 0.18 dB of signal. Note that current flows up the "drop cable" to the amplifier so the cable must not have any poorly made joints. If there's a wall-plate socket, it must be a "DC pass" type. WARNING! Are you using a wall plate that looks like this? Read why you should replace it, click HERE. "I live in a flat. The signal is fine for my Freeview integrated TV but I need to feed the signal to the bedroom. If I fit a splitter, the picture breaks up!" Answer: Fit one of our set-back amplifiers. This splits the signal but boosts it at the same time. You should also fit a 6 dB attenuator to the nearest TV aerial input if it doesn't require the extra boost. If the bedroom TV is not far away, it may also require an attenuator to avoid overloading (which can cause picture break-up just like insufficient signal). We offer high-quality 2-output and 3-output set-back amplifiers. Where does a distribution amplifier go? A distribution normally goes in the loft as this is the most convenient place for connecting the signal to bedroom TVs. But there are many possibilities. A low-noise masthead amplifier may be required if the aerial signal is too weak to travel down a long "drop cable" to the main room. A set-back amplifier may be required if the cable run up to the distribution amplifier is very long. The gain of the distribution amplifier is usually only around 6 dB to send the signal down the cables to the bedrooms. An attenuator may be required at the end of short cables. The Digibox output is added to the aerial signal for distribution to other rooms. (The Digibox requires an RF modulator in order to combine signals like this, otherwise the aerial signal will simply pass through without having the currently selected Digibox channel added. (The "Digibox" can be any sort of equipment - Satellite, terrestrial or a player. Several may be "daisy chained together" if required, but all must have internal or external RF modulators.) Why can't I simply put an amplifier next to my TV/Digibox to boost the signal? Look at the graph, above. The dotted area "N" represents the background noise which is always present with any transmitted signal. The diagonal hatched area "S" represents the actual signal. An amplifier will boost both the signal AND the noise. You can see that the amount of signal above the noise "D" remains the same. So the signal + noise is boosted but the available signal that is free from noise is no better. In fact it will be slightly worse because all amplifiers add a little noise of their own. So an amplifier is useful ONLY for compensating for losses in a cable. But an amplified signal will always have more noise than an unamplified signal. The best place to put an amplifier is next to the TV aerial or, in the case of an LNB, as close to the LNB as you can get without overloading the amplifier input. An LNB signal is quite strong so you may need to put the amplifier after several metres of cable but before the signal is too weak and noisy to be any use. Send this page address - CLICK HERE - to a friend ! Here's a useful site that gives you dish sizes: http://www.satmania.com/eng/satchannels