Hi, I'm at the stage in the house restoration where I can wire for TV & Sat. It's a 3 bed terrace and I'd like the following circuits.
Loft ariel to splitter 1, located under landing floorboards. Landing to splitter 2, and then to lounge and office outlets. Landing to splitter 3, and then to dining and kitchen outlets.
I've read that the use of splitters can weaken the signal so I may need an aerial amp. How are these connected? Would one serve the whole circuit?
Satallite. Can this be split like TV cable? (I'd probably only want two outlets for sat).
If I use twin VHF/UHF + sat sockets (eg page 185/quote 13740 of Screwfix), can I connect the radio and TV simultaneously with a splitter?
Cable. Can I use screened coaxial for sat or do I need sat cable (they look similar in the Screwfix catalogue)? Yes I'm on a tight budget.
Are there any fancy products where by TV and sat are combined in one cable?
Their range is sold in the UK by (amongst others) CPC at
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They do a multi-input amp that permits separate inputs of TV, sat, DAB, and FM radio with umpteen outputs. I have one of the 'lesser' types and am very satisfied with it.
BTW the satellite isn't that simple to split and distribute. This is because the sat LNB, assuming the ASTRA Sky system is sourced via four states in the LNB that is High band, and Low band, and Vertical polarised signals ,and Horizontal polarised signals so there are 4 differing modes, the SAT LNB that's the thing that's on the end of the arm that sticks out from the SAT.
These receiving states are signalled from the receiver via differing voltages and a superimposed tone signal so only One sat can control one LNB use Two sat receivers and it won't go if they want different things at the same time. Let alone the 18 odd volts to supply the LNB
The answer is to have a couple or more LNB's combined in the same unit or even 4 known as a Quad LNB and run SEPARATE cables to each receiver. For more outputs a specialist amplifier is needed that takes a Quad LNB and does some very clever switching but these are rather specialist..
The method for distributing a VHF/UHF system is very different from that required for satellite distribution.
It's probably easiest if I take each of them separately first and then illustrate how you could combine.
VHF/UHF ========
It is reasonably easy and not expensive for a basic system to distribute VHF/UHF to a lot of outlets using a central amplifier and splitters as you describe.
First of all forget anything that you can buy in a DIY shed. It is poor quality and consists of cheap signal boosters intended for delivering signal of a sort to up to about 8 outlets in total.
You need to have a distribution amplifier with a high level signal output which you then feed to the splitters as you suggest.
As an example, have a look at the Antiference A281 or A261
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is an illustration there on how to hook it up to take input from VHF and UHF antennas and then to distribute via splitters.
Always use satellite grade CT100 cable for this. The TV coax sold by various places is absolute garbage and will not give good signal results and moreover be sensitive to interference. It is not worth skimping. The components such as amplifier and some splitters should cost no more than about £60 and then whatever it is for the wall plate outlets.
If you wanted to combine VHF radio and UHF TV and have outlets for both but fed with one cable you can do it, but the Screwfix products aren't it. You need a diplexer to do this, which is a filter and two outlets. Basically the VHF signals go one way and UHF the other. These cost £6-7 such as Maplin YB54J
A system like this will not take account of differing signal levels between channels, nor will it improve a poor signal. Before starting make sure that you have good, clean signals.
If you have signals for different channels that are not equal (usually this is the case) you may get too much signal on some channels (leading to overloading with patterning on pictures etc. or not enough, leading to grainy pictures. It is possible to correct this but it does cost money. You can get filters matched to your channels and adjust them individually. These are normally about £50 a channel and it really needs test gear to set them up (i.e. professional job.
You can get really good results but it does depend on what you are willing to spend.
Satellite ======
Most of the satellites with a footprint including the UK operate on a range of frequencies known as Ku band. This includes the Astra 2 constellation, operated by SES and used by BskyB.
Unlike UHF TV, the first part of the receiver, is actually in the LNB (the device sitting in front of the dish. Because of the way the technology works, the receiver has to send power to the LNB and also some control signals to select between two frequency ranges and vertical and horizontal polarization. The satellite is transmitting on frequencies from about 10 - 13 GHz, whereas the cable carries signals in the range from about 900 MHz to about 2000MHz (2GHz).
This means that for a simple system, there is a one to one relationship between receiver and LNB. You can't just put the signal through a splitter - it won't work.
If you want to have up to four receiver outlets you can do it by replacing the LNB with a Quad (not Quattro) type. You home run cables from the LNB to up to four satellite receiver outlets - it does not go through the UHF distribution system.
In effect the LNB now consists of four logical LNBs in one box. Each receiver can select a different frequency/polarisation independently of the others.
For outlets you would really need to have a diplexer filter fo rUHF and VHF and a separate connector fo rthe satellite. I am not sure that these are made. Alternatively you would use two plates.
More than 4 satellite outlets and ========================== Combined Satellite and UHF/VHF distribution. ====================================
To achieve more than four satellite outlets, a switching device called a multiswitch is used.
Instead of a Quad LNB, a Quattro type is used. This has four outlets, with each representing one of the polarisation and frequency options. It is connected to the multiswitch with four cables. You then home run a cable to each outlet. The receiver sends its control signals in the usual way but instead of them going to the LNB, the multiswitch interprets them and connects through the appropriate signal out of the four. Each receiver thinks that it has exclusive LNB access.
Moreover, it is possible to combine in VHF and UHF signals and deliver them down the same cable. The wall outlet can then be a triplexer - e.g. Maplin L72AN.
These types of system are used in multiple occupancy dwellings to avoid large numbers of satellite dishes and are expandable up to several tens of outlets.
A multiswitch costs from about £15 to £25 per outlet, plus the outlet plate.
for example
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a switch able to allow selection between two LNBs and access to two satellites at the same time.
You can work out from this that to get something able to distribute satellite and UHF/VHF to a fair number of outlets, you will need to spend around £500
Well, it "sticks out" on the arm in front of a satellite dish. The SAT (assuming that's intended to be an abbreviation of satellite) is the thing that's in free-fall 22,236 miles above the equator.
It's actually a shortened version of the complete description, which is Low Noise Block Convertor.
So it's called a block convertor because it converts a block of frequencies to a lower range.
In the case of Ku band it is . 10.7GHz - 11.7GHz and 11.7GHz to
12.75GHz - i.e. two bands.
These are converted down to a range of 950 to 1950MHz for the lower band and 1100 to 2150MHz for the higher.
The reason for doing this is that the signal level as received at the dish is tiny. Even with some of the powerful new birds such as the Astra 2 constellation with power levels of around 100W per transponder, it is still small.
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Imagine looking at a light bulb at 20-odd thousand miles away and you can see the point......
Signals at the satellite transmission frequencies would not survive being sent through CT100 type cable, so having the first stage electronics out on the dish means that they can be amplified and down-converted to a range more suitable for the cable.
It's important that as little noise is added to the signal as possible, so great care is needed in the LNB design and hence the term, "Low noise". Considering all that, these things are remarkably cheap, at least at the consumer market level.
It's a Quattro LNB in those circumstances, rather than a Quad.
A Quattro feeds all four combinations (High/Low, Horizontal/Vertical) to the amplifier, which then allows any or all of the boxes to select any one of the four options.
is a manufacturer that I picked at random. The design of this isn't exactly what is normally used in Europe but it's useful as an illustration of the principles.
Near the bottom of the data sheet there is a block diagram, which shows in simple terms the functional pieces. In practice, the designs can be quite complex, but this is good enough to describe how it works.
The arriving signals go first of all through a low noise amplifier (LNA) to bring them up to a reasonable level.
They are then filtered so that signals above and below the bands in use are not going to interfere. There is a local oscillator which generates a signal at a fixed frequency of good accuracy and stability. It runs at a frequency close to those of the received signals.
This local signal is mixed with the received ones. The effect is to produce resulting signals in two ranges. One is the sum of the received and local signal frequencies and the other is the difference. It is the difference frequencies which are used. These will be in the 900MHz to 2GHz range I mentioned earlier. They are further amplified before being passed down the cable at what is called the I.F. or intermediate frequency range.
The principle is very similar to that of a basic radio receiver. In a radio, only one frequency (in practice a very small range) is passed through and the filtering is adjusted as well as (in most cases) the local oscillator frequency. This is tuning.
In an LNB we want a range or block of frequencies to pass down the wire so we fix the local oscillator. The remainder of the tuning happens in the set top box.
LNBs can be a lot more sophisticated. For example some have two local oscillators etc. but the principle remains almost the same.
If you are wiring a house from scratch I'd highly recommend running ethernet cable to a few rooms and terminating them in a suitable cupboard or cellar. For devices that are likely to come on the market in the future that would benefit from an internet connection it would make things very tidy. It might sound frivoulous now but for the expense and effort required it's worth it.
Not forgetting that you are supposed to have a minimum 50mm between data and power circuits. You shouldn't run the cables in the same space or thru a shared hole.
According to the regs.
Andrew
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