Freeview modes
Brian Butterworth published on UK Free TV Two of the Freeview multiplexes (collections of channels) broadcast in one mode known as "64QAM mode, FEC=2/3,", and the other three broadcast in another mode called "64QAM mode, FEC=3/4".
The " FEC=2/3" mode provide a more reliable signal than a "FEC=3/4" mode signal at the same power level, but there is a trade-off that means less digital data can be carried.
This diagram shows the current channels carried on the Freeview system. The wider the box, the more bandwidth is used to carry the pictures. The more bandwidth used for a service, the better the picture quality.
Boxes split horizontally denote channels that occupy the bandwidth at different times of the day.
The third line shows the configuration of the BBC "B" multiplex switchover which is used for HD and is in another mode DVB-T2 256QAM.
64 QAM (3/4) mode
In this mode, the digital TV signal is transmitted in groups of 64 symbols. The "forward error correction" is 2/3, and this results in a bitrate of 24M.1b/s (megabits per second). This can be used to carry up to eight simultaneous television channels.64 QAM (2/3) mode
In this mode, the digital TV signal is transmitted in groups of 16 symbols. The "forward error correction" is 3/4, and this results in a bitrate of 27.1Mb/s. This can be used to carry ten simultaneous television channels.Help with Television sets?
Monday, 15 August 2011
Tim
9:12 AM
9:12 AM
Street Light is interesting, Briantist. I'll look for a correlation between lighting uo and interference starting. If that is not the case it's time to get a man in with a meter. My TV recorder (Not TIVO, hard disk thing from Panasonic like the TV) is tuned to a different xmitter, and is less affected (the TV refuses to tune to it) And I am currently watching TV after 9pm by record and watch!
We used to be able to report interference to some statutory body, didn't we, and they came out and investigated it reasonably fast?
Confusing that we have twin Tims right now. I'm the UK chap in TQ6
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Tim: Yes, you can report such interference via the BBC reporting tool - Radio & Television Investigation Service - Diagnostic form .
However, you might find that replacing your aerial "fly leads" for ones of higher quality will also help.
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Tim
9:30 AM
9:30 AM
I have a loft mounted aerial with booster and untraceable cables down to my aerial socket (Very old and much fiddled with house). Which are the fly leads?
I'll report the interference anyway after seeing time correlations or not tonight
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Tim: The "fly leads" are the ones that connect from a wall socket to the set or set-top box.
Loft aerials are not really suitable for reliable Freeview reception - moving the aerial to the roof and removing the booster would be a much better option.
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Tim
9:40 AM
9:40 AM
Roof is impossible - GII listed building. But the problem has only just started and I've been in this house 20 months. Tenant for 12 months before that reports no problems then either.
So, unsuitable or not, it used to work and now doesn't. So something has changed approx 10 days ago. Must be a timed event since it's a regular thing.
Didn't we used to report interference to the then General Post Office as a statutory body? BBC is (surely) just interested in being the BBC?
Tks for info re fly leads. Always expect me to be ignorant, coz I am :)
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Tim: Tim, it hasn't been the post office (GPO) for a couple of decades I don't think.
There used to be a team at Ofcom, but they delegated the investigation of interference to the BBC, so you access it via the link I provided above.
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Tim
1:20 PM
1:20 PM
Tks my new friend. I did say "the then GPO" you know ;)
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J
jb385:44 PM
Tim: (Dartmouth) Although local conditions are most probably coming into the equation in a negative sense, but you are shown as being 1 mile away from the very low powered freeview "light" transmitter at Dartmouth, but only 6 miles away from a 20Kw "full service" one at Beacon Hill, why dont you try a test using that one?
Your aerial should presently be roughly at 202 degrees "vertically" mounted for Dartmouth, whereas for Beacon Hill it should be pointing at 348 degrees and be "horizontally" mounted.
You will likely have to manually tune your set to use Beacon Hill, and the channels used are Mux Ch60 - 53 - 57HD - 42 - 45 - 51.
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Tuesday, 16 August 2011
Tim
7:16 PM
7:16 PM
Ah, I did try the big one, but there is what is technically known as a flirping great hill in the way. I need a different physical aerial for the other one, too. WHen I moved in we were tuned to the other, then the set gave that idea up :)
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J
jb389:38 PM
Tim: I did suspect that there must have been some dastardly local obstruction in existence, or the powers that be wouldn't have found it necessary to build what is in effect a fill in transmitter.
The only thing you can really do is to make sure that your loft aerial is actually mounted vertically and not positioned horizontally, likewise its not mounted facing into, or running parallel to a water tank, at least with it not being any nearer than about a metre or so away from it, and finally the aerial not sitting anywhere near to power cables. (with same separation as with water tank)
Another procedure that frequently brings results is to try moving the aerial as much as possible to positions either side of its present one, which if your post code reasonably reflects your true position should presently be pointing at approx 200 degrees for the Dartmouth transmitter.
Any movements made to your aerial should be carried out whilst the TV is showing the signal/quality strength indications on one of the channels, in your case either Mux Ch41 or 47.
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