All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
geoffrey o'neill:
It seems that for 'normal' HD a download speed of at least 5 Mbps is needed to avoid annoying 'buffering' so as 4k TV is at least fours times the amount of data that suggests it will need a service running reliably at 20 Mbps or better. Bear in mind also that actual speeds experienced varies with the amount of traffic use on the internet so it tends to slow somewhat at heavy use periods. That is not a function of your own download speed but of the way huge amounts of data are shared across the internet and provided through servers. If any server is experiencing a heavy demand, the rate of delivery tends to slow down.
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L Stevenson:
You need a 'flylead' with male coaxial plugs on both ends, such as TV Aerial Coax Flylead Lead Male Plug to Male Plug by: Amazon.co.uk: Electronics (others are available). They come in various lengths and colours and most DIY or electrical stores sell them.
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CJ
No. There is no right in laws concerning development for any consideration to be given to TV reception, nor even a general 'right to light', contrary to common belief.
Consequently, there is no way you nor anyone else can claim from the developer.
When Canary Wharf in London's Docklands was built many years ago, it all but destroyed UHF TV reception for large areas in the Lee Valley as that is directly the opposite side of the towers from Crystal Palace. A Court case rejected the need for the developers to either compensate locals affected or even to do anything to right the problem caused.
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Dave Kirk:
You would be better putting it/them close to the aerial input socket of the TV. That way the signal strength in the downlead is greater and therefore less susceptible to interference if there is any locally. As MikeB suggests, put a short flylead into the TV socket and then put the attenuator on the end of that and then connect the downlead to the attenuator.
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Aiden Clifford:
If you want to watch or record any TV service while it is being broadcast you must have a TV licence. Look at Official TV Licensing website - Check and you will see they say "You need to be covered by a valid TV Licence if you watch or record TV as it's being broadcast. This includes the use of devices such as a computer, laptop, mobile phone or DVD/video recorder."
Does that answer your question?
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Dave Lindsay:
It's worth noting that if a passive splitter is used then all the outputs need to be connected to the input of a tuner all the time or have a 'dummy' load connected. This because a splitter is designed so that the impedances of inputs and outputs remain at 75 Ohms to ensure proper matching and that can only be maintained with all outputs having the correct 75 Ohms load connected. Leaving just one output unconnected will give rise to unexpected results and may cause partial or total loss of reception being reported.
That was a problem in analogue days and seems to be worse, or at least more critical, with digitally encoded signals - perhaps because of the way the decoding is performed.
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Dave Lindsay:
When I was working in TV Servicing during the analogue days we had male and female plugs with 75 Ohm loads built in, but I haven't seen them advertised for some years. Correct termination is crucial when dealing with RF. An aerial is designed to present a 75 Ohm impedance at the connections and the input to any TV tuner is designed to 'see' that 75 Ohms so that the full amount of signal passes into the first stage of the tuner, usually a tuned RF amplifier. If the tuner does not 'see' 75 Ohms, there is a significant loss of signal being transfered into the tuner. Added to that is that mismatching can give rise to internal signal reflections in the cabling, which can mean total loss of signal at the tuner input! And that loss could be frequency specific so you might get good signals at, say, 500 MHz but little or nothing at 510 MHz! Plus you can get some very strange effects due to standing waves in the cables! (Isn't RF fun to play with?!)
Passive splitters are always designed to maintain the impedance matching but only when all outputs and inputs are connected to 75 Ohm devices. Unplug any one and the matching is lost, often resulting in the mismatch effects I described above. Using Ohm's Law you can calculate the values of resistors needed for each leg of the splitter, remembering that all of them must be the same value else the signal is not shared equally.
You can make a terminating plug easily though, all you need is a plug of whatever gender you require and a 75 Ohm wire-ended resistor. One lead is connected to the inner and the other to the outer - simple but can be a bit fiddly. Depending on the actual construction of your chosen plug you may want to solder the wires to the centre pin and the star-shaped fitting that usually connects the outer sheathing of the coax cable to the outer body of the plug. The centre pin wire can usually be passed right down the bore of the pin so there is no risk of it shorting to the outer and it can be trimmed so it does not protrude beyond the pin.
When you assemble the terminating plug don't worry that the end of the resistor and its wire are a little visible, they are at 'ground' potential.
If though you don't want to fiddle with a plug and resitor, you could always get a 75 Ohm F terminator and an F-Coax adapter, such as the ones shown at IEC Spiral Connector 75 Ohm Terminator, (other sources are available).
Note that all references to 75 Ohms in this context is to the presented impedance of the device(s) at the rated RF and not to any DC resistance (an aerial often measures as a short circuit to DC!).
Does that help?
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Dave Lindsay:
Glad to be of assistance. Using passive splitters can give some unexpected problems so I would suggest that if you still want to use a passive, rather than an active that gives gain but isolation between outputs, then it might well be worth having the terminators available and connected to unused outputs to prevent odd events. Note that you always get some loss of signal strength with passive splitting, even when all outputs are properly terminated into 75 Ohms.
Such is the fun of electronics technologies, especially when working with the higher frequencies. When you start looking at the signals in the 10 -100 GHz bands it gets even more critical to have properly designed distribution. I well remember a taxi firm in Nottingham using an improperly set up VHF transmitter that spread interference across not just the VHF radio signals but badly affected local reception of UHF from the Kimberley transmitter and also some immediate neighbours' satellite reception! And all because the transmitter was not 'matched' to the dipole aerial they used.
Let us know how you get on with the signal distrbution.
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Mark Heselden:
The 'measure' of signal quality is a very subjective matter dependent entirely on how the software used in the particular TV/STB has been written. They all vary, even within the same make but different models.
It is meant to give some indication of how well, or otherwise, the decoder system is sorting out the actual data carried within the multiplex signal for the programme that you are watching/'measuring'.
I have a TV with a DVB-T2 tuner/decoder built in and a STB that is DVB-T only. If I check the signal quality of the same programme, I used BBC1 SD from Mendip for my check just now, the quality is shown as 90% on the TV and 75% on the STB, both being fed from the same log-periodic aerial through an active splitter. Swapping the feeds round so the STB had the input that was originally to the TV (so eliminating any variance due to cabling, etc) gave exactly the same figures. That shows the software design and implimentation is the variable factor.
All you can deduce from the quality indication is whether the signal is able to be decoded or not. Elsewhere on this site is a discussion about what happens when you have too much signal, usually shown by a 100% strength reading. In some cases the TV/STB shows a message suggesting there is no signal when in reality it has too much signal and it can't decode it so the quality is shown as 0, hence the 'No Signal' message that is actually incorrect. A similar situation occurs when there is too little signal though most receivers will show some programmes but not others, the weaker ones not being decoded. In that scenario the strength is usually well below 40% but I've seen quality as much as 60% even though it is having problems decoding!
So, to summarise, it's only an approximate hint but can be misleading. All you do know is that if it shows a very low quality you could have problems viewing some programmes. You also know that if the signal is too strong then that could lead to reception problems as well.
Hope that helps?
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Saturday 17 January 2015 8:46PM
geoffrey o'neill:
To watch any satellite channels you need to have a satellite receiver connected to the computer. This could be a USB plug-in unit, such as WinTV-NOVA-HD-USB2 Product Description (others are available), or else arrange a suitable feed from you existing satellite receiver, how to do that depends on youyr equipment. It is of course necessary to have a suitable dish and LNB installed properly aimed at the required satellite orbital location. The alignment of the dish depends also on where you live, any good satelite dish installer will know all about that.