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Topic Title: Digital vs Analogue TV
Topic Summary: Is digital broadcasting all it's meant to bel?
Created On: 05 October 2012 05:37 PM
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 05 October 2012 05:37 PM
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bille1319

Posts: 6
Joined: 25 July 2008

In N.Ireland we're expecting anologue TV transmissions to cease on the 10th Oct. I'm for one am not relishing the prospect for several reasons.
Apart from the extra 200+ programmes consisting mostly of rubbish my concerns in the main are:

1. The transmission time lag is very noticeable and could be anything up to 2secs delay behind analogue.
2. Teletext is cumbersome and slow with the pages slow to load in comparison to analogue plus the time clock is always out.
3.The picture quality is not much better even when the High Definition programmes are broadcast and tend to suffer from interference much more readily which either freezes the screen or pixilates it.

At the time of analogue TV closedown will the digital TV signals be boosted to give better coverage otherwise I should invest in a new antenna system? IET members living in UK mainland should have experienced this.

I don't know a lot about Digital Radio but I understand it's quality is not all it should be either with FM radio winning hands down as regards audio quality. perhaps this has something to do with the restricted bandwidth requirements.

Let's hear your views on this one.
 07 October 2012 10:56 PM
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ectophile

Posts: 544
Joined: 17 September 2001

200 channels of rubbish? I don't get anything like that many here in England. I only have about 70-odd channels of rubbish to wade through.

The short delay is largely irrelevant while watching TV unless you really want to set your watch by the start of the BBC news. The exception is where you have several TVs on, each with different digital tuners, because each will have a slightly different delay.

I always found the text on analogue TV painfully show as you had to wait until it got round to transmitting the one you wanted. The version on Freeview isn't particularly fast either, but I rarely use it for anything but the weather.

I don't have HD, so can't comment on that. If you get frequent interference or drop-out then there are two things to look at. The first is a better aerial, and the second is to hunt down sources of electrical interference. Domestic appliances with thermostats can be a particular problem when they turn off.

They should be re-shuffling the channel allocations and boosting the signal once the analogue one is turned off. You may find that any interference problems fix themselves at that point.

DAB digital radio is notorious for its low bit-rate and poor sound quality compared with good FM reception. Strangely, radio on Freeview has a higher bit-rate and so better quality than DAB.

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S P Barker BSc PhD MIET
 09 October 2012 07:01 AM
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normcall

Posts: 8122
Joined: 15 January 2005

Yep, digital is only as good as the space it takes up.
So to get more in, the quality goes down. They made a slight mistake with Freeview as the sound bit rate is almost double the 'high digital quality sound' of DAB.
Freeview HD is about 2 seconds later than Freeview SD which is about 2 slower than analogue.

I'm not sure they thought all this digital stuff through, as we have had to retune about half a dozen times (including the one on the 17th as the numbering is wrong!!) due to changes in assignments etc. It wouldn't be quite so bad, but we use an old T1 system, whereas almost everyone else uses the T2 standard (as used for HD).

Just remember live FM radio is better than most CDs, recorded FM 'record' quality and most digital is like medium wave without the drifting. No wonder they want to phase out FM radio. Like most things now, reduce down to the lowest standard that most will accept.

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Norman
 09 October 2012 07:44 PM
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bille1319

Posts: 6
Joined: 25 July 2008

I think the 200 freeview TV channels count was an overestimate right enough as a lot are blank. I wish I could block off the adult ones some way.

If I require a better TV antenna to receive digital, I presume I could replace my yagi with one with a better gain; i.e more directors. However I notice that most of my neighbours to receive digital use either what looks like a 14 element log periodic or a 12 element yagi crossed x element type antenna which should have similar gain to a yagi. This seems strange but unnecessary given that digital TV is transmitted on the same frequency band as analogue. I can see this on a retune. In our region it's around 750-820Mhz. The transmitted signal would still be transmitted using the same type of polarisation I take it; in my case horizontal. Or have they started to use some other method?

I also notice a difference on the latency depending on the model of TV Im watching. I notice there is less delay on newer models which must be to do with their faster processing ability. However a 2-5s delay is unacceptable e.g'I could depend on the BBC1 Teletext clock to synchronise certain little experimental projects I had in my shack now I need to used my satnav if I want a reliable time signal. Of course there are other ways and means but the BBC1 teletext was the handiest for me.

I wonder is there similar sorts of latency issues with digital comms such as Tetra. I surmise that's why aircraft continue to use good old a.m for comms because of its simplicity and reliability.

Talking about broadcast radio quality, I have driven through various regions in my car and in certain rural areas all I could receive were some stations on MW. FM had all but disappeared and as most car radios don't have long wave there was nothing to listen to but my old CDs. I presume DAD radio when mobile is an even worse proposition with reports of fading after just 5 miles of coverage.
____________________
Bill

It was long ago and far away And so much better than it is today....
 10 October 2012 06:53 AM
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normcall

Posts: 8122
Joined: 15 January 2005

You can always delete any channels you don't want, but do it after next Wed (17th) as one again a retune is required owing to a 'program renumbering' .
Considering all the time in the gestation period, then someone should have got it right from day one.
TETRA suffers the same delays in the set up - like all trunking systems. You can see the effects of delay by just watching outside news items with all the head nodding while they wait to hear the question etc.
Polarisation is mainly horizontal as they have reduced the number of 'in-fill. transmitters (don't laugh, lack of available frequencies) which generally are vertical.
We have noticed that newer TV receivers are more sensitive, but much slower on decode.

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Norman
 10 October 2012 09:29 AM
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ectophile

Posts: 544
Joined: 17 September 2001

Most Freeview boxes have a "favourites" system so you can ignore unwanted channels. You may even be able to set a PIN to block some channels - check the manual.

Is your existing aerial a wideband one, or one tuned to the specific frequency range used for analogue TV in your area? The modern "digital" aerials are all wideband, as they have moved all the channels around.

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S P Barker BSc PhD MIET
 05 November 2012 10:42 AM
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cloudserver

Posts: 3
Joined: 05 November 2012

yap. you can set only your favorite channel. It save your money also. here you only use a specific frequency range. A converter box is used to convert this digital to analog.
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