How to replace lnb on satellite dish?

• Loss of some or all Sky TV channels. Depending on the nature of the LNB fault.
• Loss of horizontal or vertical polarised Sky channels.
• Missing Sky channels.
• Replacing a Sky dish LNB.
• Sky reception problems in cold weather.

Satellite dishes need to be aligned very accurately to get a signal, because of the way the work and the frequencies that they use. It is not easy to align a satellite dish by eyesight alone or by looking at the direction of the neighbour’s satellite dish. An adjustment of a millimetre of two can be the difference between a good reliable satellite signal and no signal at all. If you’re going to attempt to realign your satellite dish if it has been knocked off direction or you believe it to be the reason why your satellite TV is not working.

It is worth noting that you need to get this correct on three planes, the east and west direction, the elevation and the skew adjustment on the LNB itself. This is the part that makes allowance for the deviation off due south. For example, Sky and Freesat both use the Astra 2 satellites at 28.2 degrees East off due south, because it is beaming the signals down to earth from an angle adjustment must be made at the satellite dish to make allowances for this and so the LNB itself can differentiate between horizontally and vertically polarised signals. If you are aligning to foreign satellites from the UK, here are some guides on French, Polish and Italian satellite reception.

If you’re going to attempt this yourself it is extremely advantageous for this to be done with a TV spectrum analyser as you can literally see on screen the when the strongest signal has been obtained. I understand that this is highly unlikely that average “DIYers” are going to have one of these, in which case satellite alignment tools can be purchased at a very reasonable price from many local DIY shops. When using these you need to have a rough idea of what direction you are going to point the dish as most “satellite finders” won’t tell you which satellite you have founds and there are loads up there.

In any case you will need the satellite co-ordinates so where you know where to point your dish. For this I recommend using Dishpointer, you simply enter your postcode in and the satellite you wish to use, and it will give you the east/west alignment angle, the elevation and the screw adjustment. It will also give you a helpful red line on the bird’s eye view may which represents the line of the satellite signal for you to use as a reference. When aligning your satellite dish, I recommend using a compass and inclinometer. You will also need to take into consideration the difference between due south and magnetic south as these are often different and often change.

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Trees can be a pain, it is possible that since your satellite dish has been installed that a nearby tree has grown and is now blocking the satellite signals. For satellite dishes to work they need a clear unobstructed view of the satellites in space. If trees are blocking your satellite signal the only option to get it working really is to move it. If you’re lucky you will be able to move the dish itself higher up the same way and the connecting coaxial cables will be long enough to reach, however more often than not these will need to be either joined and extended with a weatherproof join if the join itself is going to be outside and you will probably need to do more than one join if you have recordable satellite recorders like Sky+ or Sky Q boxes or if you have satellite receivers in more than one room.

If you are unlucky and the tree is still blocking the satellite dish even when it is as high as it could go on the wall already, maybe it was already installed at fascia and soffit level already because of this. In which case it will either need to be installed higher still, maybe on T and K wall brackets and a tall mast or onto the chimney stack. If neither of these are possible it may have to go onto a wall that is further away from the tree so that the signal can pass over the top of this. If this is going to be on a wall that is not south facing you may also need to install the satellite dish on a pole that looks over the roof or building so that the building itself doesn’t block the signal.

Because satellite dishes must be install outside and because LNB required a currently provided from the satellite receiver itself, it is imperative that all connections onto the LNB itself or any outside coaxial joins that may be in place adequate weatherproofing measures have been made to prevent any rainwater onto the inside of the cable. There are many ways in which this can be done but here are some of the most common ways.

1-      Ensure that the weatherproofing cover on the LNB is pulled down, this isn’t 100% reliable as a weatherproofing measure especially in seaside or coastal towns but if this is left up and not pulled down it is very easy for water to enter the coaxial cables.

2-      Use weatherproof F connectors. There are many compression type F plugs that are rated up to 2 bar, in water pressure, these are ideal for the connections on the LNB itself. The down side of these are that the connectors themselves are quite expensive and required a specialist tool to put them onto the cable.

3-      Use silicone grease on the LNB connections. This is a personal favourite, I love silicone grease and it is a satellite engineers best friend. I recommend spreading some silicone grease over all outside connections. I personally even spread it over the top of weatherproof plugs as it keeps the outside of the plug in good condition.

4-      All outside joins should be made within an outside enclosure or be done with self-amalgamating tape. This tape extends and pulls into position around outside joins and when done properly provides a good weatherproof join. I personally spread a bit a silicone grease over the top of a join using amalgamating tape just to be on the safe side, not that it needs it. Here is a video showing you how to perform a weatherproof coaxial join.

If your satellite signal is not working and you notice that the connectors themselves are waterlogged, you may get away with cutting a bit of the cable off and remaking the cable connectors. If the inside of the cable has got very wet, it may be wise just to completely replace the cable altogether.

It is possible that the LNB itself has become faulty, this is very common like all electrical equipment can just develop a fault for seemingly no reason. Faulty LNB’s can be responsible for a lot of intermittent type faults where the satellite TV signal can be fine for long lengths of time and then fail suddenly. It can be difficult diagnosing these type of faults, even with expensive test equipment as often when you examine the satellite signals they seem to be all OK, only to fail again later. If your satellite dish is aligned correctly with no obstructions blocking the signal and there are no signs of weathering and evening seems to be okay when visually inspected. I would suggest that the LNB would be the next thing to tick off your list. Having said that faulty LNB’s can also be very easy to diagnose in certain situations and can be responsible for you only losing a proportion of the satellite TV services, like a half or a quarter because of the way satellite signals are broadcast.

It is very common that coaxial TV cables haven’t been terminated properly which would result in a poor satellite service or no signal at all. The most common problems with the incorrect termination of satellite connections is when there is a cable short, this is where the cable braid is allowed to touch the centre conductor of the coaxial cable, this would stop the DC flow up to the satellite LNB and result in a complete loss of signal or when the cable braid has been cut away altogether and is no making permanent contact with the main plug body, this could result in complete loss of signal or an intermittent signal.

Other common termination problems are:

1-      Plug is too loose

2-      Plug is incorrect size for the coaxial cable

3-      Centre conductor is too short and not making a reliable connection

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If you need help performing common coaxial cable terminations please see out DIY Video guides

Another common problem that can cause loss of satellite signal is when something is temporarily blocking the satellite dish. This is most common with satellite dishes that have been installed at low level where a parked vehicle could potentially block the signal.

Perhaps the most common temporary obstruction of a satellite signal is the erection of a nearby scaffold, this may be on your property or neighbours building. The only solution here would be to temporarily or permanently moving the satellite dish. A temporary fix would involve clamping the satellite dish itself onto the scaffold so that it can obtain a satellite signal. Then, once the work has been completed and the scaffold can be removed you re-fit the satellite dish back in it’s original position. When temporarily moving scaffold dishes to scaffolds it is also common to have to temporarily join the cables so they can reach the temporary dish position, but these joins can be out back in position when the dish is put back to the wall.

Tip- If you are relocating a dish to the scaffold yourself, when moving it back to the wall there is often marks left on the wall mounting bracket by the dish bolts that you can use to get the satellite dish fixed back in the right position again.

Satellite signals are beamed down to earth from the satellites in space and are reflected by the bit round or oval part of the satellite dish towards the receiving LNB.  If for whatever reason the round part of the satellite dish is misshapen or bent or very rusty. This can cause the satellite signals to bounce off at different angles than they otherwise would and not be received by the LNB as they should be which can cause poor satellite reception.

The same effect can be happening the LNB is not sitting perfectly in it’s intended position if you have a broken LNB holder or not the correct LNB holder for the satellite dish.

So, if your dish has been hit by a ball or received any form of damage and still looks as if it is in the correct position there is a chance that you have a broken satellite dish. If you live in a seaside or coastal town you could consider isntalling a satellite dish that is better suited for the environment, like a fibreglass satellite dish.

Cables overtime can generate faults. This is very common for cables that have been installed outside, this could be where a cable hasn’t been secured properly and developed a split which will allow rainwater in, this is common where cables have been installed running down and over roofs. When doing this every few tiles a piece of lashing wire should be inserted in and around the cable and under a tile to stop the cables flapping about. It is possible that in today’s Health and Safety conscious world that the cables were left loose to prevent the need for someone to physically get onto your roof and secure them.

Another common problem with cables installed outside is that over time the cables will begin the perish. This does take many years to happen but if your satellite dish is connected to a particularly old cable it is possible that the cables has come to the end of its life and it’s time to install a new cable.

Internal cables can still become faulty as well. This could be physical damage like where a rodent has chewed through it or an electrical type fault where a the cable has carried too large of a current that it is intended to, like an electrical surge or nearby lightning strike.

There is also the possibility that an incorrect cable has been used to connect your satellite dish to your satellite receiver. I recommend using WF100/ CT 100 coaxial cable or equivalent for use with satellite signals, but the slimmer WF65 type twin cable or “shotgun” as it’s more commonly known is perfectly fine for short cable lengths. I would suggest at an absolute minimum that you should use a double screened coaxial cable with a solid centre conductor. If you’re currently using a single screened cable I would suggest that you replace this as it is not designed to carry the frequencies that satellite TV uses, the cable losses will be immense and the same goes for a cable with a stranded centre conductor, but I would assume that this would have never worked in the first place.

As satellite signal are beamed down to earth from satellites in space, atmospherics and weather conditions can affect your satellite TV reception, particularly heavy rain and cloud cover and electrical storms. This is because the radio waves must travel through all of this and with water (rain) being an electrical conductor and electrical storms themselves being well, electrical. This can cause all sorts of havoc with your signals.

The good news is that this should only happen ever so often so when the rain goes, or the storms eases the signal should come back. If you’re satellite signal is being lost every time that there is the slightest drop of rain you may benefit by having a larger satellite dish installed to increase the amount of signal that you have or by double checking that your dish is aligned for peak reception, remember every millimetre count! You could of course have a connection that is not properly weatherproofed in which case you would need to fix this.

It is possible that the signal is just too weak, if this is happening for any other reason than the cable length is too long I would suggest that something else is causing your signal to be weak that has already been mentioned in the sections above. If you have a cable length of more than 50m (normally fine for WF100 type cable) you may benefit from installing a larger cable size or taking a shorter cable route to your TV. So, if you have a smaller type shotgun cable running a long length you may benefit by replacing the cable for a WF100 type cable and like wise for a WF100 coaxial cable that is losing a lot of signal because of a long cable length, you many benefit by installing a WF125 cable.

I would suggest though however for domestic installations rather than installing cable sizes you will be better off installing line amplifiers instead. This is because satellite dishes and wall plates are not designed to receive a cable size above this. When installing line amplifiers to improve your satellite signal placement of the line amplifiers is very important. The amplifier should be installed not too near the satellite dish so that it overloads the line amplifier and not too far away so that the signal is already completely lost before it is amplified. Usually around halfway is a good spot to install the line amplifier.

Believe it or not this is a thing! I always get looked at strange when I tell my clients that their signal is too strong. This is unlikely to happen is a domestic type environment as the LNB’s are designed to output a signal at a usable strength, but I have come across this once when a customer was using a high gain LNB with a very short cable run.

The most likely time this will ever happen is when within a communal system environment and the system hasn’t been installed or designed properly and the signals delivered to the flats are in fact too strong. This can be rectified often with a signal attenuator that will pass DC and the frequencies that satellite TV uses but I would suggest that you would be better off contacting whomever is responsible for the up keep of your communal TV system.

There is a good a chance that your satellite dish is in a working order, despite the “no signal” message on your satellite receiver like your Sky or Freesat box. You must remember that these boxes although are very sophisticated in what they do only have a few in built messages in the software, so any problem could leave you with a no signal message, despite that not being the problem.

If you have a spare satellite receiver to hand it might be worth disconnecting your existing satellite receiver and trying the spare one. You should also bear in mind that if you are receiving encrypted TV services like Sky that you will not be able to receive these without a compatible box and viewing card. This will only affect the encrypted TV services however, like Sky 1, Sky Sports etc but could still be used for the free unencrypted services like BBC, ITV and to see whether your satellite dish is working.

I have deliberately left this at the end of the blog as it is perhaps the most unlikely. Outside electrical interference can affect your satellite TV reception, but this is only usually happens under fault conditions and should be reported to whomever is responsible for investigating this type of thing in your area. It used to be Ofcom here in the UK, but I believe it is the BBC now (don’t quote me on that).  There are also some mobile phone and cell phone operators that use frequencies with the satellite Intermediate frequency band (IF). Because of the way that satellite dishes receive their signals these are very, very unlikely but still a possibility. If you are in the unfortunate position where it is affecting your satellite TV reception you may need to relocate your satellite dish, install an LNB with a built in LTE filter and/ or report this to whoever is responsible for this type of thing in your county.

I hope you like this article, if you have any comments of questions please LEAVE A COMMENT and I will get back to you in the soonest.

Of course, if you are East Sussex based and would like to book Smart Aerials in to fix your satellite dish please do get in touch today. Until next time.

A key component in your satellite TV system is the satellite LNB [Low-Noise Block Downconverter]. The LNB is a critical component in the satellite reception system as it is responsible for amplifying the signal received at your dish. In most cases a problem with your satellite dish can be traced to the LNB and replacing it is not only easier than replacing the whole dish but a lot cheaper.

Upgrading the LNB can help you to receive 4K or change to a SWM (Single Wire Multi-switch) setup.

The LNB is mounted pointing back at the satellite dish and collects the weak signals transmitted from satellites via its feed horn. It consists of a low-noise amplifier to boost the signal and a local oscillator which combines with the amplified signal transmitting this stronger signal via coaxial cable to the receiver.

LNB’s don’t go wrong very often, but a lot of common problems stem from being exposed to the elements too long. This casues cracks to appear letting moisture into the unit. Symptoms of a faulty LNB can range from interference and pixilation to complete signal loss (especially in heavy rain) or missing channels.

You can check an LNB in several ways to see if it needs replacing, for safety and to prevent shorting its best to disconnect the receiver unit from mains electricity. Also, disconnect the coax [As the LNB is powered from the receiver via the coax connection]. Assuming you can get up a ladder to access your satellite dish safely, you can start with a visual check.

Before inspecting the LNB its worth testing the sturdiness of the dish mountings and pole. If they move easily, this could be the root of your reception problems.

The LNB is mounted on a protruding arm that sticks out and points back at the dish. It looks cylindrical or horn-shaped. Check the plastic casing for any cracks or other damage. If the housing is damaged, it is most likely that the electronics inside are compromised by water ingress. Over time even small hairline cracks can “suck” water inside the unit via capillary action.

Check that the coax mountings (usually F-Connectors) are secure and that you can’t see any rust or dirt on the connections that may interfere with conductivity. If rusted through, then you will most likely have to replace the unit. If the coax is loose but not rusted, try cleaning and tightening the connections to improve reception.

TIP: Add some grease before reassembling to reduce future corrosion problems.

As your LNB is powered via a DC feed from the receiver, it’s worth noting that the longer the cable length to the LNB, the greater the voltage drop which may be. Source of problems. Also, longer the cable runs mean higher signal attenuation.

RG 6 cables with a solid copper center conductor are recommended due to much lower DC voltage drop properties compared to copper-coated, steel conductors. To avoid the need for additional AC boosters cable runs should ideally be less than 100 feet from receiver to dish. I’ve found that shorter runs also help with fade due to rain / bad weather.

To test the LNB operation, connect a current meter, and check that the LNB is drawing the requisite amount of current and is within normal operating range in mA (milliamps). Carrying out this test can be a bit tricky up a ladder, especially as you’ll need to test the current in series. You may need to create a jumper cable to allow this.

If you can obtain a satellite signal strength meter, you can try removing the existing coax connections to the LNB. Unscrew the signal output jack and connect a jumper cable between the LNB and meter. If there is a strong signal present, it means the fault is elsewhere in the system, i.e., the coax or receiver unit.

If there is a weak signal, it may mean that either the LNB is faulty or the dish has become misaligned. Try moving the dish alignment according to your satellite networks instructions to see if the signal strength improves. Sometimes if the fixing bolts aren’t tight, strong winds can misalign your satellite dish.

Another way to test signal strength if you don’t have a meter is to use the signal strength facility usually built into your satellite receiver. Depending on the model of the receiver, you’ll often find a signal strength setting in the setup tools menu.

Unfortunately, this isn’t a very accurate way of doing things. You’ll also need someone else to communicate strength readings to you while you move the dish to various positions. [A walkie-talkie can come in useful here].

Move the dish bit-by-bit until you get the best signal strength. Use the 3-axis of movement that the mounting bracket should give you, i.e., azimuth (side-to-side), elevation (up-down), and tilt (dish reflector rotation). You can usually verify the Azimuth, Elevation, and Tilt angles for your location by ZIP code – check your satellite providers website for details.

Some of the more premium mounting brackets will come with a built-in bubble/spirit level and graduated markings to assist with alignment. One of the most significant alignment issues can be traced back to the fact that the pole isn’t perfectly upright. I’ve seen several installations where people swear azimuth, elevation, etc. are spot on but the pole is either not vertical or bent!

If your TV reception has been gradually degrading over time, check the location and growth of any trees which may be restricting your signal reception. Similarly, check if any new buildings or cell towers have been erected nearby.

If you find a fault with the LNB, you’ll need to locate a suitable replacement. Sometimes proactively replacing your LNB for a higher quality component can be an excellent way to improve your TV signal. It can seem like a complicated endeavor; it’s not as complex as it may seem.

Almost anyone can switch out an LNB unit in minutes with just a socket wrench and a screwdriver. Upgrading your LNB is a good way to improve on the standardized LNB that comes by default with your satellite dish. In a lot of cases with the addition of 4K or SWiM technology introduced by DirecTV, you can keep your existing dish setup.

A lot of older satellite receiver boxes use dual LNB’s as standard so that you can record from one channel while watching another.  If you are replacing your LNB, it’s worth thinking about upgrading to a quad LNB or SWM to drive more than one receiver unit and distribute your TV viewing around the house. There are other ways of distributing TV signals around your home with multiswitches / splitters etc.

When looking to replace your LNB, there are several factors to consider. Noise, Gain, Microphonics Resistance, and Cross Polar Rejection. If you are going to go to the trouble of fitting a new LNB, you might also want to consider installing a satellite dish heater. Dish heaters are especially useful if you live in areas with a lot of snowfall in the winter.

The level of noise generated by an LNB degrades the signal and therefore, the picture quality displayed on your TV. If you are amplifying weak signals (from space) an undesirable side effect of that is the amplification of noise. You should aim to get an LNB that produces the least noise possible (LNB noise is measured in Kelvin). Typically, C band LNB’s tend to have the lowest noise temperature performance, and Ka band LNB’s have higher noise.

C band is 3.4 – 4.8 GHz.

Ku band is 10.7 – 12.75 GHz.

Ka band is 19.2 – 21.2 GHz

The gain is the amount by which the signal is amplified. It is feasible that gain can be too high and overload a receiver, but this is unlikely.

We’ve all had the irritation of satellite TV signal disappearing in bad weather. Wind / Rain etc. cause small disturbances in electrical performance of the LNB called microphonics. Severe wind vibrating the dish or rain hitting the LNB can add up to a total loss of signal if your LNB is susceptible. Unfortunately, there is no standard measurement for microphonics, making it challenging to compare LNB’s. Some groundwork on the manufacturer’s tech specs to find out the LNB’s ‘resistance’ to microphonics will is required before making a choice.

Cross polar rejection refers to how LNB’s handle interference between the different horizontal and vertically polarised signals. A lot of LNB’s can switch between the horizontal and vertical polarised signals satellites send.

You also need to consider how many tuners your existing setup uses and make sure you obtain an LNB to suit.

Check out our recommendations for replacement DirecTV, DISH, and FTA LNB’s below.

#ad Recommended Replacement DirecTV LNB

#ad Recommended Replacement DISH Network LNB

#ad Recommended Replacement FTA LNB

Summary