Frequently Asked Questions
I want to have multiple satellite points around the house and multiple receivers. I also want to distrubute the TV from one receiver to all TVs how can this be done. How can I use a multiswitch for multiple satellite outlets in every room and include a motorised dish?
There are two parts to this question.


To provide many Sky or freesat dish points around the house you either need a quatro LNB on your dish or a quatro LNB dish kit. see dishes with quatro LNBs and a 5 input multiswitch (multiswitches are usually situated in a loft or cupboard or central area.) see multiswitchs The quatro LNB (with 4 outputs) feeds the multiswitch using 4 LNB cable - see 4 LNB cable Best to put two outlets in each room as it may be that twin tuner receivers (record one channel and watch another) may be needed. If so use the twin wall plates see outlet plates then scroll down to the twin units. Use twin cable to each room. see Twin cable For (e.g.) 6 rooms a 12 output multiswitch would be used. Twin cable to each room. An aerial can be fed into the 5th input of the multiswitch if required. Using a wall plate which has a diplexer built in, two satellite points and an aerial point is available. The UHF Aerial signal is added to the satellite signal by the multiswitch and goes down the same wire as the satellite signal. If two or three aerials are required e.g. TV, FM and DAB radio, a 3 way combiner can be fitted on the roof and the one cable from that unit goes into the 5th input of the multiswitch. Again the appropriate wall plate is needed to separate them all out again. see multiswitch combiner Standard Sky, Sky+ Sky HD freesat and freesat HDR and other receivers can then be connected to the F connector wall plate.


distribution round the house needs a 2, 3, 4, 6 amp or (preferably) professional 8 way amp and cabling. see Professional 8 way amp and Offer 1 but read the whole page. This is to distribute TV from one receiver to other TVs around the house (one channel) This can be done by feeding a cable from the room containing the sat receiver to the multiswitch location and into the 3 way combiner then into the multiswitch. However, the problem with this method is that the multiswitch will not permit the 9 volts to go through and the TV Eye or omni link system to work for control. It is better therefore to have a completely separate output system with separate cabling for the distribution system This would mean 3 cables to each room, two for the satellite and one for the distribution. TV eyes for Sky receivers Sky accessories or omni link systems for freesat receivers etc. see omni link kit (and a modulator is required - same page) This will allow full control of the Sky or freesat system from all of the rooms. How to use mutiswitches and motorised in multiple rooms. Using a 9 input Delta multiswitch,, two satellites can be made available in every room. This multiswitch could be fed from (e.g.) a dish on 28E for sky or freesat. This dish would have a quad (not quatro) LNB. These multiswitches are designed for quad or octo LNBs. A good example of a dish for this purpose would be - The Triax 60cm solid dish with quad option see Triax 60cm. (with quad LNB option) The Triax heavy duty 60cm or 70cm dish with quad LNB option see Triax heavy duty 60cm or 70cm dishes (with quad LNB option) The clear 60cm dish with quad LNB option. see Clear 60cm dish (with quad LNB option) This dish would be fed into input 1 of the 9 input multiswitch (this is 4 inputs), 1-4, for the quad LNB. Input 2 (i.e. from 5-8) would be fed by a motorised dish. The motorised dish (e.g. 90cm Triax - see Triax 90cm motorised dish (with octo LNB option)) would have an octo LNB option (8 outputs) 4 of the outputs would feed into input 2 of the multiswitch (5-8) A 5th output would go direct to the motorised satellite receiver. (or outputs 5 and 6 to a twin tuner motorised receiver.) This receiver would be placed in the house where it can easily be accessed as it will control which 2nd satellite it being offered to the multiswitch. Let us assume the 9 input multiswitch has 16 outputs. That is to say twin cable to 8 rooms so that every room has the capability of using a twin tuner receiver. The system would then work in the following way - Using any receiver into a twin satellite point in a room, 28E (Sky and freesat) would be available even if the receiver was a dedicated receiver (like a Sky receiver) and does not have Diseqc switching PROVIDING 28E goes into input 1 of the multiswitch. Input 1 is the "relaxed position" of the switches (Input 2 is the forced position) therefore the signal will go through input 1 whether the receiver has Diseqc switching or not. If the receiver DOES have diseqc switching, then the second satellite can be selected. If the motorised dish is (e.g.) on Hotbird, the second satellite available in every room would be Hotbird at 13E If the motorised dish is (e.g.) on Astra 1, the second satellite available in every room would be Astra 1 at 19E this system insures that everyone in the house can easily select the main UK satellite (Astra 2 at 28E) but would also be able to access a second satellite and that satellite would be determined by the position of the motorised dish. This system eliminated a particular problem. Within the menu of a satellite receiver you can't select Diseqc switching (Diseqc 1.0 or 1.1) AND motorised (Diseqc 1.2) AT THE SAME TIME. This is why an octo LNB must be used with these special quad / octo multiswitches. This system keeps the diseqc 1.2 separate from the multiswitches and so it all works. It would not work with quato LNBs as the motor would not work between the LNB and the multiswitch. There has to be a 5th output to separately route through the motor to a control receiver. Twin wall plates are needed in every room. The motorised receiver needs it's own cables directly from it's own dish. This system also works for a 36 volt motor, here a V Box is used in the cable from the 5th output of the octo LNB to the main motorised control receiver otherwise everything else is the same.
What are the differences between an offset dish and a prime focus dish? How do they compare?
The differences between prime focus and offset dishes.

prime focus dish A 1.4m prime focus dish is shown to the left. This type of dish is circular NOT oval. It has 3 feed support arms (some use 4 arms) and the 3 arms converge in the centre. Each arm is 120 degrees apart. The feedhorn uses concentric scalar rings. The concentric scalar rings reduce noise and improve signal to noise ratio when fitted to a prime focus dish.

An offset dish (See below) is oval and is higher than it is wide (some are wider than they are high). They use either one feed support arm (at the bottom of the dish - see bottom left hand picture) or 3 feed support arms (again all in the bottom half of the dish - see bottom right hand picture). Many offset dishes use a standard 40mm clamp LNB but some more expensive specialised offset dishes also use a feedhorn If a feedhorn is used, a c120 flange LNB is bolted to it. An offset feedhorn is a flaired horn without scalar rings

offset dish prime focus dish

Shown above on the left is an offset dish with one feed support arm and on the right above an offset dish with three feed support arms.

As a general rule the two types of dishes are simply two ways of doing the same job, however, an offset dish, if well engineered, can have more gain than the prime focus dish. It is never, however, that simple. It is true that petalised offset dishes usually have poor gain but a one-piece well engineered prime focus dish can be better than a poorly engineered offset dish and some very good prime focus dishes can have the same gain as a good offset dish of the same size. As usual you get what you pay for. Cheap prime focus petalised dishes are to be avoided and we don't sell them. Prime focus dishes probably look better than offset dishes as they point upwards. Below we compare the two types of dishes in much more detail. Read on ....

Comparing a prime focus dish with an offset dish.
Which has the most gain? Assuming two dishes have exactly the same area, which is unlikely as dishes of the same quoted diameter are rarely the same (more about that later) but assuming the same area, and (for the sake of this discussion) the same efficiency (same accurate parabolic shape, again unlikely) the offset dish should produce more signal as the arms, feed support, feedhorn and lnb are not in the signal path. However, it is never that simple. A prime focus dish produces a very precise focal point. (Just like focussing the sun with a magnifying glass), the electromagnetic microwaves can be focused to a very exact well defined position into the feedhorn. In addition, any unwanted radiation, (e.g. infra red heat) that approaches the feedhorn from around the edge of the dish are rejected around the edge of the feedhorn by the scalar rings. These rings produce destructive interference and therefore maintain a high signal to noise ratio. The focal point on an offset dish is not as precise and the feedhorn needs to be flaired to collect the radiation. There are no scalar rings and so it is more likely that noise (eg infra red from around the edges of the dish) can enter the feedhorn. It is possible that this effect, (improved signs to noise ratio) can, to a greater or lesser extent make up for the shadows on a prime focus dish due to the feed assembly. Some manufacturers, when they quote dish diameter, quote maximum, others quote average and some quote useable. Does the dish work all the way to the edge or is there a roll off area resulting in a much smaller useable area? Petallised dishes or dishes in several segments tend to have low efficiency as they usually do not form a very good parabola. once assembled they often lack accuracy. The quality and rigidity of the feed support arms can also affect the amount of signal being received Flimsy arms may not hold the feedhorn and lnb in the exact optimum position. It may be possible for the arms to flex to a position that gives better results but then they spring back again. Paying more for a dish usually provides a higher build quality. Petalised dishes are usually cheap and have a very disappointing performance. One piece dishes tend to work really well if manufactured by specialist companies that make quality a priority. Dishes can be made of steel, (steel needs to have a good coating to stop corrosion) aluminium, or fibre glass / plastic. The type of material is not really an issue. What can be a problem is if the material is too thin. If it can be damaged or warped in transit or in high winds. The backplate needs to be very strong. Here steel is ideal and the best covering is "dipped galvanised". All bolts, nuts and u clamps should be stainless steel. Brass is a good material for long threaded elevation adjusters. The gain of a dish should be specified at (at least) 3 frequencies. The feedhorn should be designed for the dish, or have an adjustable f/d (scalar rings on a threaded adjustment) that can be matched to the dish. 40mm universal lnbs may not be a good match. All prime focus dishes should use a prime focus feedhorn with scalar rings. A prime focus or offset matched feedhorn should provide an improvement over an LNBF (An LNBF is an LNB with an intergrated feedhorn, more commonly these days called a 40 mm LNB. Technically only an lnb without an integrated feedhorn e.g. a c120 LNB or a block type should be called an LNB) if the dish size is 1.2m or larger. (Larger dishes have a narrower acceptance angle) Whether prime focus or offset, a matched feedhorn should improve the signal to noise ratio. To summarise, there are good well engineered offset dishes and low cost mass maket offset dishes. There are high quality prime focus dishes and some poor quality low cost petalised prime focus dishes. As usual "you get what you pay for". Which look the best? This is a matter of opinion but the prime focus dish points upwards to the satellite and looks purposeful. When domestic satellite TV started in the UK in 1985 all dishes were prime focus. The offset dish reflects the radiation downwards and so the dish face is more vertical (there is an offset angle). There is a great deal more to this subject than most people realise, hopefully this discussion clarifies some of the differences. Cost, build quality, the right matereials and good design are the key to maximum useful signal (High signal to noise ratio.) quality dishes.

Getting more signal - a series of related questions. - How much difference do low noise LNBs make and why do some LNBs have a C120 flange and a feedhorn? How can I get more signal from my dish? Would a better LNB help or a more sensitive receiver? Problems with signal through trees. Why does my lower noise LNB produce less signal?
There are many parts to this question.

Dish size is everything. LNBs only have a very very very very .... small effect as does receiver sensitivity. Dish size is everything! Changing from a 0.9dB to a 0.1dB does not have the effect of 5mm of dish diameter! and then the lower noise LNB will only help in good weather, virtually no effect in bad weather. Bigger dishes provide more signal in all weathers. BUT .. if the dish size cannot be increased for any reason, the lower noise LNB can help a small amount and it MIGHT be just enough to pull in a difficult to receive channel that was just coming in but maybe pixilation or freezing (a common fault caused usually by lack of signal) was a problem and may be stopped. 0.1dB LNBs! To achieve 0.1dBs over a significant frequency range, manufacturers would need super cooling to slow the electrons down! Simply not possible at normal temperatures in the UK. It may well be the case that the latest 0.1dB LNBs have the lowest noise figures. They are very good LNBs. Possibly even be the best, but they really can't be as low as 0.1dB or 0.2dB over any kind of useful frequency range if at all. It is however true that a new LNB can provide a significant improvement over an old LNB. This is because old LNBs, several years old, have been temperature cycled through winters and summer and my now be rather "noise" (i.e. poor noise figure and not up to original specifications. Clearly a new LNB in this circumstance can have a very good impact on "getting more signal". Some of us are getting old (!!) and can still remember being young - back in the late 1950s early 1960s - not sure exactly when - but being told it is possible to achieve a good picture on the TV with an aerial shaped like a PLANT POT that could be stood on top of the TV! (even with a plastic plant inside it!) We all now know that what was really needed was a decent sized aerial on the roof (and preferably not in the loft - which can produce reflections!) Many people would like technology without wires in sealed boxes. Sometimes they will insist on having the electronic equipment in cabinets with doors on. This is better known as an cooking the technology in an oven as it stops ventilation and creates a fire risks. Many also want the smallest possible dish so the question is - "is it possible to find an alternative solution to receiving more signal" BUT ... no matter how much people might want to ..... YOU CAN'T CHANGE THE LAWS OF PHYSICS! "Dish size is everything." It is a question that is asked every day and sometimes customer think that if they ask the question in 4 or 5 different ways, they will eventually hear a different answer. To repeat - Dish size is everything! Dish size is everything!

Dish efficiency.
This can be important. Especially among large dishes. Check the gain fugures. The Andrews (Channel Master) 1.8m and 2.4m have a very high gain due to very good design and so do our own Primesat dishes. Always avoid metal petalised prime focus dishes as they can be warped when they are new due to bad assembly or damage and tend to be very in-efficient. Matched feedhorns can pull in more signal than better LNBs. See below.

A normal 40mm clamp LNB has an integral offset feedhorn for offset dishes. The correct name for these LNBs is "LNBF". It means LNB with integral feedhorn dishes. A prime focus dish like the Primesat range on this site must have its own feedhorn with "scalar rings" on one side and a C120 flange on the other. Also read questing 2 above for more details. i.e. The Invacom feedhorn, here you should use the C120 flange LNB which fits the c120 flange on the prime Focus feedhorn. If a prime focus dish does not have a proper feedhorn then it should have one. The scalar rings on a prime focus feedhorn are a very important part of the design. The feedhorn should really be designed and made by the dish manufacturer for a perfect match but if this is not known or possible, fit a the invacom feedhorn as this has adjustable F/D and can be adjusted to match the F/D of the dish. The Raven (formally Andrews and before that Channel Master offset feedhorn - Customers in several countries have found it made a worthwhile improvement. If an LNB feed is not a perfect match, like a standard 40mm clamp LNB, it may illuminate (say) 1.1m of a 1.2m dish. (less signal) OR, It may (try to) illuminate 1.3m of dish. This will cause infrared (noise) to be picked up round the edges. The result is a poor signal to noise ratio. (poor picture) Feedback from customers suggest that the matched feed on a Raven 1.2 as far west as Belfast brought in all of Sirius. Before it was fitted this was not possible. More feedback suggested it can make a difference in southern Spain For Sky TV and the BBC using a Raven 1.8m dish and using the 2.4m Raven dish from the Spanish offshore islands.

Receiver sensitivity.
This has only a very small effect on the signal. Most CI and free to air receivers are sensitive anyway. Some Sky digiboxes, however, do not have particularly sensitive tuners. Not a problem in the UK but in Spain a sensitive satellite receiver can help a little.

More information about LNBs.
An LNB is the box of electronics on the end of the dish boom arm. It acts like a aerial masthead amplifier. The signal (microwaves) reflect off the dish and into the feedhorn to the LNB. Here it is amplified and the frequency is lowered. The lower the noise figure the better. i.e. in simple terms, it pulls in the signal better. The signal is then sent down the coaxial cable to the satellite receiver. Quality digital cable should be used. A universal LNB covers the KU band from 10700 to 12750Ghz with LO frequencies of 9750 and 10600. There are Single LNBs, Twin LNBs, Quad LNBs, Octo LNBs and Quatro LNBs. Single LNbs have one output, twin - two outputs, quad - four outputs and Octo - eight outputs. All outputs are the same and are equivalent to a single LNB. All outputs carry both bands and both polarities. A twin LNB could be used for two single tuner satellite receivers or a twin tuner satellite receiver Quatro LNBs have 4 outputs and they are all different. Quatro LNBs can only be used with multiswitches. Each output carries only one band and one polarity. All four outputs carry all of the four components. There are also 40mm clamp LNBs and C120 LNBs. This refers to the way they fit on a dish. A 40mm LNB has an integral offset feedhorn and fits to the most common types of offset dishes. C120 flange LNBs fit on a separate feedhorn and could be used on either offset or prime focus dishes. They are usually used on specialist high quality dishes. Both 40mm and C120 LNBs could have single, twin, quad or quatro outputs. At the moment only 40mm LNBs have octo (8) outputs. Using a quatro LNB and a multiswitch it is possible to have many many outputs. Even 42 outputs or larger. That is what multiswitches do. They provide many outputs so that a single dish can be used. A Sky mini dish LNB uses a fixing that is none standard and a tongue fits into the end of the boom arm. Sky have changed the design of their dishes many times and new LNBs will not fit older dishes. Standard dishes have a 40mm clamp (and sometimes 23mm to fit a feedhorn) and the fixing has never changed since domestic satellite started in 1985

To conclude,
"Dish area is everything". Other small gains are possible but they are small. Large increases in signal are possible in all weathers with bigger dishes. A large gain can be made if a dish is found to be warped and then corrected. More efficient dishes provide gains but not as much as manufacturers claim they do. When a manufacturer says their 50cm dish is equivalent to other 60 or 80cm dishes, remember this is marketing not science! (or to put it another way this is simply sales jargon for lying!) A more efficient dish might have the effect of being as good as a dish 1cm diameter bigger but not the sort of silly claims some manufacturers (or dealers) make. Small gains are possible with matched feedhorns Very small gains might be possible with better LNBs or more sensitive tuners but they may be too small to be significant. A new LNB is likely to help as LNBs do deteriorate with age. If older than 4 or 5 years it is a good idea to replace the LNB. They are not expensive.

If trees are in the way, the signal will not get through them, however, if they are on the fringe of being in the way - maybe only a thin band of branches and leaves with a good proportion of the signal actually getting through, a bigger dish will collect more signal and compensate for the problem.

Better LNBs can producing less signal (as measured on a meter) but have more "good" signal
This is a very common question. The important point here is that only a higher signal to noise ratio matters not the total signal level. The total signal level is shown on a satellite meter and is NOT relevant. Meters do NOT measure the quality of an LNB as meters are NOT measuring signal to noise ratio (over a frequency range.) Satellite meters are to help find a satellite, not assess an LNBs performance. A high (signal) output LNB is good for driving a signal down a long cable (e.g. over 40m) But a high signal to noise ratio pulls in weaker signals. Remember - Looking at the meter reading in a satellite receiver TELLS YOU NOTHING AT ALL as far as this particular question is concerned. It only shows you the total signal and not the difference between the signal and the noise. A poor 0.9dB (but high output) LNB on a short cable (not much attenuation) can produce a large reading on a signal strength meter than a low output 0.1dB LNB. A low output LNB on a longer cable can show a low signal on a signal strength meter. So what?!! it has nothing at all to do with the ability to pull in a weak channel - nothing at all. At a technical level, if you draw a graph with a horizontal line representing the signal and a lower horizontal line representing the noise, the meter is simply showing the level of the top line. With a high output LNB on a short cable the two lines move up equally BUT the height difference between the two lines does not alter. With a low output LNB on a longer cable the two lines move down equally BUT the height difference between them again does not alter. With a lower noise LNB or bigger dish the height difference between the two lines INCREASES - we say there is a better SIGNAL TO NOISE RATIO. A signal strength meter does not measure this parameter. Anyone who says it does, probably has a no technical background in electronics. It is like saying that the signal to noise ratio of a Hi Fi system is better if you turn up the volume. Your ears would be equivalent to the signal strength meter and this statement would be total rubbish as well - but it is an interesting, accurate analogy. The only test is to check out the capability of pulling in weak channels - do not use the meter for comparing LNBs. The meter is designed to help to locate the satellite accurately and not to test the LNB.

Copyright © 2012 Vision International. All rights reserved.
Primesat is based in the United Kingdom.