Satellite Dish Types Explained - What They Do & How They Work
If you are thinking about having a satellite dish installed or just want to know more about the satellite dish types that there are, the differences between them and which one should you get. Read this article for all you need to know. In this blog, we discuss the types, shapes, sizes, construction material and many other things. So, let’s begin!
Component Parts of A Sat Dish
Although there are many different designs of satellite dish the principle is the same. The idea is to reflect a received a signal from satellites in space onto the LNB(or equivalent), which does various things to the signals and then relay these to a some sort of satellite TV receiver or modem etc.
The parabolic reflector is the big(usually) round part of the satellite dish that reflects the radio-waves onto the LNB. These are usually a circular or elliptical design, but some designs of dish will have other types of shape. For instance Fracarro do a quadrilateral-type diamond shape on some of their dish antennas. These can come in a variety of different materials and also be a solid or mesh design, both of which we cover later. The mesh design has small holes which are just small enough to not allow the short-waves lengths straight through without being reflected.
Depending on the service and satellites you would like to receive depends on the satellite dish size that you require. The weaker the signal, the larger dish required. This is because the greater the surface area the more of the signal can be reflected back to the LNB. Most satellite services can be received with a dish antenna size of less than 1m. The dish size is the effective reflector size of the parabolic reflector. Sometimes people choose to have a larger dish size than is necessary to offer a more reliable signal and to reduce the amount of pixelation.
LNB Feed Arm
The LNB Feed Arm on a satellite dish attaches to the main reflector and extends off the front onto which the to the LNB Collar/ LNB is attached holding it in the correct position. On an offset style dish this extends from the bottom of the main reflector to just in front of the dish. On a prime focus dish this is different as the LNB sits centrally in front of the main relator and there are usually more than one arm holding it in position.
Low Noise Block(LNB)
LNB stands for Low Noise Block and it's part of the satellite dish that captures the signals via the LNB feedhorn. There are many LNB types, too many to explain the differences between them all here but typically a sat LNB will oscillate the signals down to a more manageable frequency that connecting coax cables can handle and the connects these to a satellite TV receiver, a Sky box or something similar. Most LNB's for satellite TV are known as LNBf, with the F indicating an inbuilt feedhorn. These also nearly always come with an F coaxial connector.
The LNB collar is the part of the dish that attaches the dish LNB to the LNB arm. These are different for most satellite dishes so you need to make sure that the collar size on the LNB you have purchased corresponds to that of the LNB collar. Most LNB collar sizes for satellite TV are 38mm and 40mm but there are also sizes. It doesn’t sound much but you would have a job trying to fit an 40mm collar LNB in a 38mm collar, if you try to fit a 38mm collar LNB in a 40mm collar it will be loose and you will be unable to secure the LNB and skew adjustment in position. It’s not ideal, but in practice a few wraps of insulation tape around the LNB collar will be sufficient to be able to build the extra couple of millimetres for a secure fixing.
Depending on what type of dish you have purchased, you may or may not have a wall mount included. For Sky style mini-dish the wall mount is part of the design but for others you have clamp/ bolts to attach to a tube or mast. There are specific brackets and mounts for this purpose, usually some sort of L arm that come in varying diameters and stand-offs which may be required for larger dishes and alignments. You could alternatively use TV aerial brackets, like T and K wall brackets. I recommend purchasing galvanised steel wall brackets where needed as these large longer than painted steel versions. I’m not sure why, but they are very rare, stainless steel would also be suitable. I had a customer who didn’t want rust on his walls and manufactured his own bracket. He had a company that manufactured such things, but I appreciate this isn’t always going to be an option for most.
Satellite Dish Materials
There are several materials that satellite dishes can be constructed out of, each having their own advantages and disadvantages. When referring to a material that the satellite dish is made of, generally speaking is primarily referencing what the main parabolic reflector is made out of, you will often find other parts, bolts, screws, LNB holder are made out of something else. For instance the clamping and fixing parts on a fibreglass dish are usually made out of aluminium or something similar.
Steel is the most common material that satellite dishes are made of. This is nearly always a painted steel, I honestly can’t recall ever coming across a galvanised, anodized or stainless steel dish but they may well exist somewhere. The upside of steel dishes is that they are strong and relatively inexpensive to buy. The major downside of painted steel dish antennas is that they rust relatively easily meaning that the expected dish life-span is less than other types and may leave rust stains down your wall. They can also be unsuitable for seaside and marine type environments where they won’t last very long at all. For instance, I live near the seaside and a Sky dish installation on a seafront property, you will be lucky to get five years out of it. You may want to even consider painting the dish to hold back the rust and prolong it's life.
The next option you could choose is an aluminium dish. These typically cost a bit more than steel dishes, meaning your satellite dish installation cost more. I have always said to customers that aluminium doesn’t rust which after doing some research for this article that is technically true as rust is a type of corrosion specific to iron/ steel but aluminium does oxidize. This is not a problem as this ultimately can protect the underlying metal. Aluminium is also very light weight, which might make an otherwise difficult installation high up a ladder or on roof more easy.
Fibreglass is a fibre reinforced fabric made of plastic. The main advantage of a fibreglass satellite dish is that as it is not made of a metal or corrosive material so you do not have to worry about rust or other type of weathering associated, this makes them the perfect choice for seaside installations and installations within marine environments. The biggest downside of fibreglass dishes is the cost, the are a lot more to purchase than the other types. For instance, when I do fibreglass installations for UK satellite TV like Sky or Freesat, the installation will cost the customer almost double due to the extra material cost. Another downside of fibreglass, is that it’s typically not as strong as steel, this is not really a problem with satellite antennas though as once they are installed they are rarely touched again, only really by high winds.
Sat Dish Types
The are many types of satellite dish, below I describe some of the most common designs, like offset vs prime focus dishes. We also discuss dishes for different frequency bands and parabolic reflector types among other things.
Offset Satellite Dishes
Offset satellite dishes are far and away the most here in the UK. If you were you look at the satellite dish, offset satellite dishes do not look like they are pointing up at the sky. This is because the LNB feed arm and LNB are sited to a side(usually the bottom) or the parabolic reflector and the the signals are reflected to the offset position. This is usually around a 20 degrees offset but this will vary between manufacturers. As the LNB & feed arm are not directly the way of the parabolic reflector like is the case with a prime focus dish, they do not block or impede the signal in any way meaning that you can usually get away with a smaller dish size. You can often tell when someone has attempted their own dish-alignment by using something like the Dishpointer App as the dish has been angled up the the satellites with no consideration of the offset angle. Generally speaking, offset dishes are more suitable for wall mounted installations over prime focus dishes. When aligning offset dishes for some of the satellites lowest of the horizon. like Turksat the dish antenna can look like it’s angled slightly down and pointing to the floor.
Prime Focus Dish
A prime focus dish points directly towards the satellites, there is no offsetting of the LNB or of the reflected signal. Because of this the LNB is sited directly in the middle of the focal point of the antenna and is held in position with more than one LNB feed arm. As the LNB and feed arms physically get in the way of the signal before it is reflected back to the LNB feedhorn you typically require a slightly larger dish size to compensate for this. Prime focus dishes are not very common in the UK because of the low angle of the satellites and satellite arc, but they come more common as you travel south into countries nearer the equator. This is where the geo-stationary satellites which orbit around the equator on the Clarke Belt are significantly higher in the Sky. I remember a trip to Tunisia where most of the satellite dishes were installed on roofs and looked like they were almost pointing directly up. Generally speaking offset dishes are more suitable to be installed on top of things, like the roof rather than a wall mounted installation.
If you see the term “solid” when comparing satellite dishes,this refers to the parabolic reflector. It means that it has no holes in it, whereas the other types, mesh/ perforated satellite dishes do. Solid satellite dishes are the most popular and generally much better for seaside and marine environments where the rainwater and moisture has less places that it can enter where it can rust/ corrode the metal. Solid dishes are also more popular and more suitable for higher frequencies used by satellite TV and satellite broadband services.
Mesh/ Perforated Dishes
Most satellite dishes for Ku band reception have a solid reflector, but some that you will see will have holes in them. These are called mesh and perforated satellite dishes. As the holes are smaller than the wavelengths of the satellite signal meaning that they do not pass through the holes and are reflected back to the LNB. Most dishes for Sky TV are often referred to as mesh dishes but they are in fact perforated satellite dishes. Mesh satellite dishes were typically large satellite dishes used for C band reception which were broadcast at much lower frequencies than most satellite TV services, as the wavelengths were much larger meaning larger holes than those of perforated dishes could be used. Mesh dishes had a solid outer ring with several various solid arms back to the centre and the mesh installed onto this. A perforated dish is one with an otherwise solid parabolic reflector but with small holes in it. Mesh and perforated dishes become less suitable the with the higher the frequency you wish to receive, like for Ka Band reception. They do have some advantages however, as they are typically weigh less, use less material and have less wind-loading.
Sky/ Freesat Satellite Dishes
There are a couple of satellite dishes used for Sky/ Freesat in the UK. These are a Zone 1 “mini-dish” and a Zone 2 dish. Both have an elliptical, perforated reflector and it made from painted(dark blue) steel. I recommend reading my previous blog Zone 1 vs Zone 2 dishes for more detail but the mini-dish has a 43/45cm reflector and the Zone 2 a 60cm one. Zone 1 dishes are for England/ southern UK and Zone 2 dishes are intended for Scotland/ northern UK where the signal is weaker and a larger antenna size is required, to protect against things like rain-fade. Owing to their mass production, they are usually relatively inexpensive to buy.
VSAT Satellite Dishes
VSAT stands for Very Small Aperture Terminal. VSAT is used for data links, typically where traditional fibre or cable is not required and can be used for internet and VOIP (Voice Over Internet Protocol) traffic. There are many types of VSAT system which I will address in a separate article, but the dishes that people are most familiar with are those used for satellite broadband services like Tooway or SES Broadband, these dishes both transmit and receive unlike most other types which just receive. VSAT dishes used for satellite broadband operate within the satellite Ka band which is a higher frequency than the Ku band meaning that mesh and perforated dishes are completely unsuitable.
Sqish dishes are a rather clever design where you can have a dish that doesn’t look like a dish. A Sqish dish is a rectangular dish with no front extending LNB, this mounts at the rear. They are of a rectangular design that looks not dissimilar to a small solar panel. Although these are usually white, the have a front cover which can be used to change the colour and even one that has a brickwork pattern on it to help blend into a wall. Sqish dishes are perfect where you wish to keep the sat installation discreet or where you are otherwise not supposed to have them, like on a balcony of a block of flats.
C Band Satellite Dishes
C Band dishes are dishes that are designed to receive lower frequencies in the C band which is approximately 3.7-8GHz. As the C Band frequency is lower the wavelengths are larger than Ku/ Ka band reception, the dishes are quite a bit larger than dish-sizes we have become accustomed to and were most commonly a mesh design where the larger wavelengths would not penetrate through the parabolic reflector. In North America they were often referred to as “Big Ugly Dish”. C band dishes were most commonly used for free-to-air, mainly analogue satellite TV services.
Motorised Satellite Dishes
A motorised satellite dish is a dish that can be moved to point in different angles or can be used to automatically find the satellite signal based on your co-ordinates and the satellites you wish to receive a signal from. Most motorised satellite dishes for satellite TV are not motorised dishes at all, but rather a normal satellite dish mounted onto a dish motor than can be moved by commands from the satellite receiver. DiSEQc 1.2 and 1.3/USALS refers to this type of system. Other types are where satellites can be auto-located are typically much more expensive. These are fairly common of higher end motor homes where the vehicle could be parked up in different locations, facing different directions and the satellite dish will find the signal with the pressing of a button or two.
If you’re familiar with multi-sat reception of a single fixed dish, you will already know that the further you offset the LNB the weaker the received signal will be. You will also be restricted between how far you can bridge between satellites. For instance Hotbird to Astra 2 is just over 15 degrees which can be difficult to align/ set-up and obtain reliable reception. Toroidial dishes overcome this by having two reflectors set up so that the signal bounces off the main parabolic reflector, onto another reflector roughly where the LNB position would be on an offset satellite dish and back to the LNB(s)which are sited just below the main parabolic reflector. By doing this the dish has an effective larger size meaning there is little signal drop across 20 degrees each way making it perfect for multiple LNB installations. You can also add significantly more LNB’s than you would be able to with other type multiple fixed LNB installations.
Satellite Dish Questions – In Blog Comments Only Please
I hope you liked this blog, if you have any questions or comments please do post them within the blog comments section and I will endeavour to respond to these as soon as possible. Please be patient when waiting for a response as answering blog comments is not the top of my to-do list. Please also check out other blogs on our site.
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All that being said, I will help where I can and please check back for future articles.
Until next time,
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