Freesat reception - all about dishes

Published on 10th September 2006 at 12:42 by Brian Butterworth on UK Free TV

Satellite reception has both advantages and disadvantages compare with terrestrial (aerial) reception.

By using much higher frequencies (gigahertz, compared to terrestrial televisions megahertz) more transmission channels called transponders (the satellite equivalent of multiplexes) can be provided. For example, there are only six Freeview multiplexes, but Sky or Freesat users can access two hundred satellite transponders.

Aside from exceptional weather conditions (very heavy rain for example) digital satellite provides stable pictures and audio. Where Freeview transmitters are no more than 732 metres above sea level, the geostationary satellites used for television are 35,800,000 metres above the equator so reception is possible even where buildings, trees and hills make terrestrial reception impossible.



The downside of the transmitters being 22,300 miles up in the air is that the signals are very, very weak - so standard TV aerial is of little use. When the signals are sent to the satellites, huge dish transmitters are used to uplink the signal to the satellite. These are tens of metres from side to side, and feature an emitter that generates the signal, which is first bounced of a mirror (called a reflector) and then off the surface of the parabolic dish.



There are many satellites in the sky over the equator. Often these are in clusters over a particular position, for example there are four used for UK television are at 28.2 degrees east. There is another cluster over the 19.2 degrees east positions that are used for German television.

To receive these very weak signals from the satellite, it is necessary to use a dish for reception too. By using a reflective dish, this concentrates the signals onto a small device called a LNB. This is held in front of the dish by a metal arm.



The size of dish for reception is typically much smaller; often 60cm to 100cm in diameter, but the exact size depends upon the transmitting satellite transponder. To keep the transmission power levels down to levels that can be powered by the satellite's solar panels, each beam is focused on a particular area of the Earth's surface. If you are trying to receive the signal at the centre of this zone, a small dish is required. At the outer edges, you may need a 5 metre dish. Maps of these zones are provided by the satellite companies, and are called satellite footprints.

When the dish is installed it must be aligned carefully as the signal is very weak. The installer needs to know the inclination and the azimuth from the ground location to the satellite. If you install yourself you will find that there are markings on the dish that are used to point the dish in the correct position. It is important that the view of the satellite will not be blocked, so must take into account leaves growing on trees and potential building works.

For many people the LNB will have a single cable connected to it, however if you have Sky+ or a multi-room installation the LNB package will actually contain four receivers a quad-LNB. Unlike terrestrial television where you can split the aerial cable to feed more than one Freeview box or television set, with satelite reception you cannot. So, a Sky+ box with two receivers (so you can watch one thing and record another) has two cables connecting the box to the dish.

The cable that connects the dish to the receiver must be satellite grade cable. Whilst this looks superficially like the cable used to connect and aerial to a television, a higher grade cable is required for satellite reception.

Here is an image of a co-axial cable. This sort of cable is used to connect any type of receiving aerial to the reception equipment.



RG6, PF100 and PH100 are all types of coax cable that are suitable for the very weak signals that are received by a satellite dish. (The power is the same as you would receive from a one-bar electric heater on the moon).

The conductor in the centre passes the signals received from the dish to the set-top box. This is made from steel in RG6 cable, and from copper in the RF100 and PH100 types. This makes RG6 less suitable in the UK where rain can damage the cable.

The shielding is responsible for keeping unwanted external interference from damaging the signal. In the cheaper cable this will be a foil wrap, in better specified cables this is a braid (or mesh) of copper wires. The sheild in the RF100 covers 58% of the cable.

The non-conducting layer between the shield and the conductor is called the dielectric. This can be either a solid (RG6), foam (RF100) or air-spaced (PH100) dielectric. This makes the cables progressively more flexible (ie bendy without damage).

First comments Earlier comments  ◊ 

Your comments are always welcome. Please use the form below to add your thoughts or questions to this page. We will get back to you as soon as we can.

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jb38
Friday 26 April 2013 9:36PM

Gordon Brockley: Speaking in general terms smaller dishes are more critical to align by the fact that they aren't gathering up that much of a signal to start off with, this meaning that the slightest movement past the ideal spot will cause the signal to drop down again under the sat receivers minimum level for reception, this resulting in the classic "no signal" warning being seen.

On the other hand large dishes are capable of gathering up more of the signal and with this being why the signal strength levels seen on sat boxes with larger dishes are always that much higher to that on a box using a standard mini-dish, a knock on effect of this higher level signal making these type of dishes "slightly" (and only) easier to align.

The reason for this being, that if the dish is being swept across from one side to the other then once a signal of a sufficiently high enough level to produce a picture is found it will be held for much longer before dipping down again on the other side, in other words by them having a slightly flatter response in the pick up zone to that experienced with small dishes and their almost razor sharp responses, the smaller the dish the worse it gets.

Of course the higher signal levels associated with larger dishes is why heavy thundery type downpours do not have the same effect on satellite reception in the way they do with smaller dishes, basically because the signal has further to drop before reaching the receivers lower threshold cut off level.

The secret of success when aligning satellite dishes is really by adopting slow motion movements.

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Peterpiano
Monday 29 April 2013 4:48PM

Two questions:
1. Is it possibe for a competent DIYer to realign a sat. dish?
2. Are suppliers of satellite equipment legally bound to give the purchaser the password to reset the system, etc.?
I bought three Freesat systems three years ago and had them fitted by a local firm. They have never been satisfactory. I can only get a few TV channels and even fewer radio channels.
My sat. boxes have a 'signal strength' and 'signal quality' page and the channels that come as 'no signal' have correspondingly low quality and strength readings. I've had the firm back to sort it out twice - once for free, but the second time for £35.00. I asked for the passwords and was told they were put in, but patently, they do not work - I can't access the boxes. I think they have witheld the passwords deliberately, fobbing me off with technical jargon, thus forcing me to pay them to come and sort out any problems.
can you help, please?

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jb38
Monday 29 April 2013 5:16PM

Peterpiano: I dont quite understand where passwords come into the equation, as satellite boxes whether Freesat or Sky do not have such a thing, although Freesat boxes do require a post code to be entered during the initial set up procedure or after any subsequent resetting of the box, although the post code is only required to enable the viewer to have the correct regional news services.

Does your dish face into a tree or any other building or structure? because thats about the only thing that can cause problems with satellite reception other than the dish being misaligned.

Further advice dependant on reply.

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jb38
Monday 29 April 2013 5:19PM

Peterpiano: Also meant to request if you could mention the model numbers of the Freesat boxes in question.

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jb38
Monday 29 April 2013 6:33PM

Peterpiano: On having a rethink about your question regarding passwords, and although Freesat boxes generally do not request this I do appreciate that whatever you are using must request it be entered otherwise you wouldn't ask, and so should this apply then I would try the standard default of 0000 or 1234, although if either of these do not work then there is always the possibility that your installer has changed it, that is should the box allow this to be done, but though if you can provide the model numbers of the models involved this can be checked.

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Neil Bell
Monday 29 April 2013 7:37PM

Peterpiano Just to add that my old free to air satellite receivers do require passwords to enter the menu system to do retunes, add or delete channels etc. so if that is the case with yours I can't see how the original suppliers could possibly justify withholding the passwords. As JB38 says try 0000 or 1234 to start with. Also just out of interest did they fit a quad LNB and run 3 separate cables - one to each receiver - or have they tried to use some form of splitter?

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Leslie Pugh
Saturday 1 June 2013 1:11PM

I .live in france and get good freeview with my sky system
But get a no sygnsl when I connect myDVB-T MINI BOX
And a data base empty sygn
Thanks for any advice

LES PUGH

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Dave Lindsay
Saturday 1 June 2013 1:31PM

Leslie Pugh: "DVB-T" stands for "Digital Video Broadcasting Terrestrial"; If it is satellite you are using then you probably require DVB-S (Digital Video Broadcasting Satellite).

Freeview is the brand name of terrestrial system in the UK and its Crown Dependancies.

The "free-to-air" channels are those which you're referring to, I think.

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sam mott
Sunday 2 June 2013 9:50AM

Hi all,
I have a strange issue with my new Freesat set-up.

What currently works:
- Sky dish connected to sky box
- LNB coaxial cable in another room (from the Sky dish) connected to a Freeview-SD box (at the LNB-IN)

What does not work:
- LNB coaxial connected (via LNB-Antenna Female adaptor) to the Antenna-In of a new Freesat Box. I get 'No signal' message on the TV screen.

I also connected the LNB-Antenna-F-adaptor directly to the Antenna-IN of the back of the TV (no box involved), and auto-scanned for signals, but got no signals.

Where could the problem be?
Many thanks to all, in advance.

Sam

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Neil Bell
Sunday 2 June 2013 11:41AM

Sam Mott Could you confirm that you have at least a dual LNB with a separate cable run to your Freesat box? Each sat tuner requires an LNB connection so e.g. a Sky plus box and a dual tuner freesat box would require a quad LNB and 4 cables. Only TVs or set top boxes with satellite tuners will work with coax connections from LNBs

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sam mott
Sunday 2 June 2013 1:31PM

Neil Bell: Thanks Neil.
I got an engineer to come over last year to connect my Sky dish to 3 rooms. Each room has a coax cable (with a single LNB at the end). He also left me with a fully functional Freeview SD box.

I now like to use the coax cable and connect a Freesat HD. The Freesat box I bough, unfortunately does not have a LNB-IN, but has an Antenna-IN.

Not sure if I can answer your question - bit too complicated for me, but I hope the above information might be helpful?
IF you need me to get you more specific information, just let me know what to look for. Many thanks.

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jb38
Sunday 2 June 2013 2:00PM

sam mott: Any box with an "Antenna" in socket is a Freeview box intended to be used with a normal aerial, as "all" satellite devices are connected with what's known as an "F" connector that fits into the boxes LNB input socket.

If you have just recently purchased the box and its still in its original "and unmarked" packaging then you may be able to change it for the correct Freesat type.

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Dave Lindsay
Sunday 2 June 2013 2:14PM

sam mott: You can't use a "Freeview" receiver with a satellite dish.

If you are using an adaptor such as this then you will still not be able to use the Freeview receiver with the dish:

 F Type Screw Connector Socket to RF Coax Aerial Male: Amazon.co.uk: Electronics

As jb38 says, a Freeview box is for use with a normal aerial.

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sam mott
Sunday 2 June 2013 2:21PM

jb38: Thank you very much. That explains it.
Aerial antenna -> Antenna-In
Dish -> LNB-IN
Iäll have to return it and get the one wit a LNB-IN.

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jb38
Sunday 2 June 2013 3:31PM

sam mott: Yes, best policy! as a Freeview box is of no use to you unless you had a normal loft or roof aerial installed as well as residing in a reasonably good reception area, but remember that anything you purchase has to have "Freesat" printed on the box and NOT "Freeview", the emphasise being on "sat".

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Neil Bell
Sunday 2 June 2013 4:15PM

Sam Mott although you do say you have a fully functioning SD Freeview box so presumably you have an aerial and a signal? In which case have you tried replacing the SD box with the new HD box. That would show you definitely if it is a Freeview and not Freesat box. If that works you could try a splitter on your aerial & run a cable from the splitter to the new HD box instead of from the LNB.

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chad
Thursday 6 June 2013 2:24PM

Hi
can you tell me if a easy find lmb will work with a humax
receiver

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chad
Thursday 6 June 2013 2:29PM

Hi
will a easy find lmb work with a humax receiver
i go away in the caravan a lot

thanks

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MikeP
Thursday 6 June 2013 5:44PM

chad:
I assume you mean an LNB? Any LNB designed for reception of Sky or Freesat will work with your Humax Satellite receiver when mounted on a suitable dish aimed at the satellite carrying the desired services. If you need to buy a dish, perhaps look at Amazon but there are other suppliers. To aim you dish, there is some good advice at  The Art of Aiming a Satellite Dish - UK Camp Site Articles

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jb38
Thursday 6 June 2013 9:14PM

chad: In addition to that said by MikeP, if you are referring to one of these LNB's thats fitted with a red and green LED to assist finding a satellite such as are supplied along with portable sat dish kits of the type that fit on a tripod then yes! as LNB's will work with any Sky of Freesat system.

The only snag about these being, that they cannot distinguish between a satellite positioned at 19.2 degrees over those used for Sky and Freesat at 28.2 degrees and although these may appear on paper to be well separated, however in practice they only represent a nudge away from each other.

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E SABERTON
Monday 10 June 2013 4:21PM Bournemouth

Hi I have a humax freesat box which has suddenly started to want rebooting after I have watched a recording and try to change to watching tv no signal comes on screen . so I then have to reboot. can you help me please?

19 posts

•  Recepition map
•  Terrain plot
•  Reception list
•  R+T Investigation
•  Digital UK tradeview
•  DAB radio checker

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Jerry Smith
Wednesday 12 June 2013 11:50AM

Hello

I have just moved house and the previous owner had sky installed. He has left the chimney mounted dish in situ together with a small amplfication box (uses f connectors) which he used to provide sky to 4 separate points (lounge, kitchen, study and bedroom). I would like to use the dish and existing cabling to feed freesat hd signals to 3 of the 4 points. Could I do that simply by buying three Freesat HD equipped TVs or am I being too optimistic?!

Thanks

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MikeB
Wednesday 12 June 2013 2:30PM Peterborough

Jerry Smith: Not optimistic, but it will cost you a great deal of money!

Freesat equiped TV's are not common, and tend towards the middle high end of the market, and the smallest they've ever been made in is 32". The only 32" being made this year with Freesat is the Samsung 32" Six series - which is currently £599. Its actually a very nice TV (400hz screen, etc), but is a little over the top for a bedroom TV. Other than that its 40" plus.

I would start by looking to see if you have an aerial, aerial points and the strength/ quality of your Freeview signal, since every TV sold for at least the past five years should have a Freeview tuner built in. If you get a decent signal, and even better, have a number of extra points, then you have the choice of either Freeview or Freesat, and of course you can use your existing equipment immediately with no extra cost.

Check your TV's to see if any of them have Freesat built in. About 4 years ago, a fair number of Panasonics had them, and some LG's (there was only one Sony). Samsung started putting them in in the 8000 & 7000 series, and then the 6 series a couple of years back. If they have one, then they are good to go.

Its slightly strange that the previous owner had what sounds like Sky multi-room, but only had one connection into the living room - if you want to record/watch on Freesat or Sky you need two cables (one for each tuner) - so your fine to watch using a Freesat box, but you'd have to have an extra cable coming in to use a Humax Freesat PVR (the de facto standard).

If you do want to use the connections from the dish, you'll need to buy a Freesat box, which connects to the coax from the dish, and then uses scart or (even better) HDMI to your TV. They are around £70, depending on the brand. A recorder can start from £150ish, but the Humax Freetime (basically You View but Freesat) is £249, but a PVR does need two connections.

Bottom line - if you've got Freeview, then use that first, and you can attach Freesat tuners as well if you want. If you've got (or are buying) a TV with Freesat in, then thats useful as well, but its not essential. And if you want to record on Freesat (in the lounge), you'll need two cables coming in, not one. If your reception on Freeview is awful, then the dish will be very useful.

47 posts

•  Recepition map
•  Terrain plot
•  Reception list
•  R+T Investigation
•  Digital UK tradeview
•  DAB radio checker

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jb38
Wednesday 12 June 2013 5:01PM

Jerry Smith: Completely apart from the advice given by MikeP as far as your various options are concerned and purely centring on the dish, how many coax cables can you see connected to the underside of the dishes LNB?

And with regards to the connection points in the other rooms, are these screwed type male "F" connectors or standard female coax sockets?

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paul sankey
Wednesday 12 June 2013 9:05PM

Les Nicol, I have the same problem as Ken Sims, I just had my dish realigned by a sky fitter, he said its fine now, wasn't far out anyway, but there is a small tree in line of sight about 15ft away, like ken, mine worked fine until the leaves grew, now signal quality is up and down, picture is pixelating all the time, would cutting the tree down solve this? Thanks, Paul

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