digital radios

[The Natural Philosopher]

Radio 5 live.

World service.

Er...thats IT.

[tony sayer]

In practice I doubt anyone would notice NP...

But I sure do notice that bloody horrible MP 2 coder noise grating away;(..

[tony sayer]

All Dab sets in the same room..

Might be fractional differences in decoding delays but nothing that anyone would notice..

[Dave Liquorice]

What he said. The "time bubble" would have to be at least the maximum evisaged transmission chain delay in any part of the system. This could be considerable with satellite distribution (live or standbys), and possibly two hops of that then digital code/decode delays... I don't think 2 seconds would be enough, I think you would be looking at 5 seconds.

Now think it through. Studio presenter hands "live" to remote reporter who is taking his cue off air. He doesn't hear that cue until 5 seconds later then starts speaking, now you can't feed the reporter direct to distribution as that removes the whole point of the time bubble in the first place (sync at receivers) so the reporter doesn't come out of the system until 5 seconds after he started speaking. So you know have a 10 second gap from the hand over to the reporter picking up...

Watch any live news report these days that is satellite linked and you get that pregnant pause when handing to the remote. That's the delay in the two hops of satellite, one of the cue going and the other coming back. That delay is only about 3/4 of a second.

They did think about it but it really does become an horrendous mine field extremely quickly.

[Mike Barnes]

Thanks, v. interesting.

[Dave Plowman (News)]

Oh no they're not. FreeView either.

That bit is so.

[Dave Plowman (News)]

No - I have two identical tuners that have different delays. Much less than the difference between FM and DAB, but noticeable. The 'ear' can detect pretty small differences.

[Mike Barnes]

No problem there AFAICS - I did say two seconds "for the sake of argument".

That makes sense but it comes as something of a surprise to me that that's the way they do it. The stations I listen to don't do much, if any, live reporting during the news. What's the point? It seems simpler for the reporter to file the report when they're ready and the studio to replay it when required.

From what you say the time bubble is impractical with the current ways of working, but that way isn't the only way. From what you say it's clear that nothing is going to change within the immediate future so I'll stick with FM, thank you.

I don't watch TV. I was talking about radio.

[Dave Plowman (News)]

Right. I have a separate clock. The system has an on off switch, the normal volume tone and balance controls, and a selector for which service you want. All ultra low voltage - and nowhere near a source of water, etc. I'm not sure what the sleep timer would be used for...

Fairy nuff. I tend to use headphones if I want to listen outdoors.

[Dave Plowman (News)]

Then there's no one forcing you to buy one.

Advantages are easier tuning and programme information. Possibly better reception. Some progs only on DAB.

[Dave Plowman (News)]

R7 - worth it for just that alone.

[geoff]

In message , tony sayer writes

I haven't even worn a watch for 10 years

[Mike Barnes]

That seems so obvious I wonder you bother stating it.

All I can say is I've bought three DAB radios and none of those advantages have even begun to make up for the disadvantages of sound delays, poor battery life, and poor sound quality[1]. One radio broke and the other two are unused. Other people's priorities are clearly different, but I'm used to that.

I was hoping that DAB+ would address all those problems, but apparently not. That makes it easy for me to dismiss it altogether.

[1] Poor sound quality admittedly not inherent in the technology, but a fact of life.

[Dave Liquorice]

Reverse lines are expensive compared to a portable radio... If the outside broadcast is linked via ISDN then the reverse come "free" with that so could be feed pre-transmission chain delay.

A very good question and another thread...

True enough but the system that is time coherant at point of delivery across multiple platforms would be a nightmare in itself. You could probably do it for a static and simple system for a single regional station but one dealing with 7 national networks, only 4 of which are available on all platforms with the reserve arrangements (which may have differing delays to the main feed) is just horrendous for basicaly no gain.

You and me both as BBC Local radio isn't on DAB. World Service would be nice but is that the real World Service of WS for Europe?

That was just to illustrate how even a short delay breaks up the flow of a "conversation". Personally the few tens of milliseconds delay in mobile phones drives me up the wall, that and the poor quality.

[Mike Barnes]

SWMBO isn't a great switcher-offer, so I've got her into the habit of using the sleep button rather than the on button. Rarely is the bathroom radio wanted for more than about half an hour, so it's convenient to have it turn itself off after that time if no-one has switched it off (and easy to turn it on again if it does catch you out). I even use the sleep button myself now, if I'm popping in and out and I'm not sure which is my last visit. Same goes for the bedroom radios.

The problems I see with a fixed installation are selecting a place that's conveniently within reach of the bog and the bath, and hiding the wires. But I've not given it serious consideration because a cheap FM portable does everything I want without fuss.

[Mike Barnes]

OK, I see that, so I guess the pips being wrong is a problem that's not going to go away anytime soon. But I've heard no objection to imposing a standardised interval between reception and output, which would get round the "echo from the other room" problem when one goes to the trouble and expense of replacing all the FM radios in the house with digital (DAB/Freeview) receivers.

And given a standardised delay, creative ways could be found to present time signals correctly. I'm still baffled by the meek acceptance of time signals (Big Ben, pips) that someone has taken trouble to ensure are accurate being significantly delayed in transit and therefore rendered pretty-much useless, or worse than useless.

[Rod]

And I have been on the phone and heard both radio and television out of step with the same program where I am. Had it been behind, I would just put it down to delay on the phone. But when it is ahead, I was forced to think about how the program is distributed, local booster transmitters and so on. (And that seems to be so for some things regardless of the actual technology of the receiver.)

We can actually get 'radio' via FM, internet, cable and DAB. I would not like to be in a room with all four in (near-)simultaneous use on the same station.

PS Don't we need to rethink the word 'radio'?

[Dave Liquorice]

Actually radio use off air cueing far more than TV. They don't have the budget for the reverse line, always assuming that there is spare capacity for that line to be installed. This is particularly so for local stations.

These days of mobiles you need coverage and there is no guarantee of that or being able to establish and maintain a call over a mobile network reliably. Not something you want to be a critical part of an OB...

[Dave Liquorice]

That's not quite the same thing, your "orgination time" moves about in relation to "transmission time". They are quite clever these days with automatic build up of the delay in the feed, so the operator doesn't have to manually switch from direct to delayed feed or indeed remember to get back to the delayed feed after use.

[Dave Plowman (News)]

Just added to emphasis that FM isn't being switched off like analogue TV.

I'm afraid as has been said delays are part of all digital systems. Perhaps not so great as on DAB - but there nevertheless. And variable between receivers.

As regards battery life every new generation of portable seems to have got worse in this respect - I have an ancient AM only one (quite large with a decent sized speaker) where a PP9 gives many months of daily use. The only other one I have - more recent - which covers FM and SW bands, consumes 8 C sells in far less time. But it can be used on mains, as I'd guess most would round the house except in bathrooms.

I've a feeling you're right in that. Despite all the bile from some about poor DAB quality, I don't think DAB+ will result in any more sales. And that plus perhaps better battery life is its only real advantages.

With perhaps the majority of portables actual sound quality seems to come far down the list after styling and facilities. It's not impossible to get a decent sound out of a 4" loudspeaker.