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?
Saturday, 20 August 2011
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Brian Rawlinson1:26 PM
PHILIPS DVD Player / Recorder / SET TOP BOX (DVDR5500)ANALOGUE / DIGITAL.
Prior to switchover I had both analogue and digital reception. Now after switchover I have to retune every time I power up. It loses all channels on power down.Most annoying as otherwise it works fine with tendency to drop or switch channels. I contacted Philips support but all they could suggest was a complete 'factory' reset which I have done many times already. I send this in the hope that someone somewhere has had something similar. I wonder if the fact that it still has the analog capability has an effect. At boot up I get the message 'no signal' which would be true if it is looking for analog channels first. An analog scan produces nothing naturally as we went digital in May 2011.
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Tim
2:30 PM
2:30 PM
ah, JB, the man is coming today. He will be here before I can find my radio. Cross your fingers for me.
Good luck Brian R, this is a great place for answers. Be patient and try the things the guys here suggest. It's a process of elimination, often. WHat might help them is a full postcode. I know they usually ask for it. It helps them ID which transmitter you are nearest to
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J
jb383:13 PM
Brian Rawlinson: It would have been of assistance to know your location as reception checks etc could have been made, however apart from that the problem you are experiencing could possibly be linked to the fact that when transmitters change powers at switchover they go onto an 8K transmission operating mode, this causing problems with many sets, and with on some occasions it not being a rectifiable problem.
I tried to check the spec on your device but it doesn't give that info, but the fact that you have actually received something since switchover suggests that it is capable, but exactly how efficiently is another thing all together, as many sets have to have software updates to allegedly cure a range of 8K derived difficulties.
I will say that your particular model is no stranger to firmware updates, as many people experience problems with it and other Philips devices of this nature.
If you come back with your location (pref post code) the transmitter transmissions details can be checked on, as dependant on which transmitter is involved 8K might not be applicable to all Mux channels, and a manual tune for testing purposes can then be carried out on that ones that aren't.
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jb383:14 PM
Tim: Yes, post an update on whats found, or maybe suspected anyway!
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Tim
7:16 PM
7:16 PM
We have the answer. It was a Labgear transformer that powered the amp that was dying. The nice man said they are well known for it. So, to replace and make me a shiny new signal only cots £85 which pleased me mightily. No idea at all why it was time dependent. That part makes no sense since the transformer is always on.
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J
jb389:17 PM
Tim: Thanks for the update on the final situation and pleased to learn that all is now OK.
However on the subject of the booster, that's why I brought it into the equation emphasising about trying its power off test AFTER the picture went faulty, because trying the test whilst the picture was OK wouldn't really have shown any fault up as it was obviously working then, but if the same test was tried after the picture went downhill it wouldn't have made any difference by switching it off, this positively indicating the fault being associated with the booster circuit, which in this case was its power supply failing on a regular basis through thermal reasons, likely because of nightly heat build up in the loft.
Main thing is though that all is now OK!
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Tim
10:57 PM
10:57 PM
The thing is that this is the Labgear power pack with the adjustable gain control. Apparently it is known for such things.
Oddly it loved the heat of the day. Much hotter in daytime with a good picture than night time with bad. And it failed your most excellent diagnostic test with flying colours. Go figure!
I blame gremlins.
Just discovered I can see the transmitter from my back garden, too
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Wednesday, 21 September 2011
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nigel1:34 AM
no channels at all in central region after 2nd retune 21/09/11
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lisa wesmacott1:48 AM
Malvern
Absolutely no channels in Malvern working. Tried retuning my Echostar T101 set top box 4 or 5 times now and absolutely nothing. Thanks digital switchover.
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lisa's: mapL's Freeview map terrainL's terrain plot wavesL's frequency data L's Freeview Detailed Coverage
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