The Ten Myths of DAB

[Resurrection Man]

Rajar sample size doesn't look particularly large. 1000 here. A 1000 there.

They report on the number of people who have 'Access to a DAB radio'. But they don't say how many people have access to a DAB radio but don't use it because the DAB signal is too poor, for example.

EDIT: Actually from what I can see digging a little deeper into their methodology, the listening figures for any channel or station can be overstated by 3x. If a diary respondent listens to a station for more than 5 minutes then they are assumed to have listened for 15 minutes!

[Eine Alpensinfonie]

I often wonder why when propaganda stooges are planted on forums such as this, that they are not trained in diplomacy.

[Nick_G]

I often wonder why whether propaganda stooges are planted on forums such as this, that they are not trained in diplomacy.

Funnily enough I was wondering about him myself:

http://www.for3.org/forums/showthread.php?7161-The-Ten-Myths-of-DAB&p=244132#post244132

Regards,
Nick

[An_Inspector_Calls]

I often wonder why when propaganda stooges are planted on forums such as this, that they are not trained in diplomacy.

I sometimes wonder why even forum moderators seem to rely heavily on ad hominem insults to make their piffling reposts?

[teamsaint]

My Kitchen radio is set to R3 on DAB (which is OK but no better than FM), and Radio Solent for the footy on FM.
That is a pure convenience on my part, because the Saints are on Solent FM , portmouth are on DAB (make of THAT what you will, I know what I think !!), and I can toggle between the two stations I listen to with ease.

Anyway, most people still listen to FM radio , don't they, despite multiple digital platforms.
It would be SO nice if governments gave us what we want, not what they tell us we want or is good for us.

[David-G]

As is the way you've construed my meaning. #281 makes it clear that I am assuming RAJAR are counting majority listening habits. You obviously listen to analogue radio for the majority of the time, so you won't be counted in the digital pile. I'm the opposite, I listen to digital most of the time (but not DAB) and I want to be counted in the digital pile and not be disenfranchised as RM would have it.

You are worried about being disenfranchised. I am worried about having FM removed.

[An_Inspector_Calls]

You are worried about being disenfranchised. I am worried about having FM removed.

That's democracy for you.

[teamsaint]

That's democracy for you.

I agree. Our democracy and system of government does seem to be based on making people worry about things that they shouldn't have to, or don't really have to worry about.

[Bryn]

... As Gordon points out, with DAB (and Freeview) digital reception is such that you either fail or you get excellent sound. ...

No, Gordon does not so much "point out" such a thing as mistakenly assert it. If the signal is marginal the error correction cannot cope and you get that distinctive DAB 'boiling mud' accompanying the intended audio. I suppose this might be thought of an analogue[sic] of FM birdies.

[Dave2002]

No, Gordon does not so much "point out" such a thing as mistakenly assert it. If the signal is marginal the error correction cannot cope and you get that distinctive DAB 'boiling mud' accompanying the intended audio. I suppose this might be thought of an analogue[sic] of FM birdies.

Sorry, but I don't think Gordon even asserted anything mistakenly - or have I missed something - msgs 257 and 259.

Gordon did state what worked for him, and I don't actually think he was denying your own situation re wet brick walls.

However, AIC - msg 276 - seems determined to mis-report what others (e.g Gordon) have written.

[Resurrection Man]

I agree. Our democracy and system of government does seem to be based on making people worry about things that they shouldn't have to, or don't really have to worry about.

Or spending money when they (a) don't want to and (b) don't have to.

Wonder who is 'funding' AIC ?

[An_Inspector_Calls]

Sorry, but I don't think Gordon even asserted anything mistakenly - or have I missed something - msgs 257 and 259.

Gordon did state what worked for him, and I don't actually think he was denying your own situation re wet brick walls.

However, AIC - msg 276 - seems determined to mis-report what others (e.g Gordon) have written.

A storm in a teacup. If there's an imagined transgression, then to save the reputation of Gordon, MY simplistic view of DAB and Freeview reception with a given aerial configuration is that you either get nothing or rubbish reception (and boiling mud falls firmly into the fail category: it is far worse than birdies and is quite unusable) or you get excellent sound. Now there'll be a blizzard of claims to the contrary, so yes, it's simplistic. A proper assessment of reception would require a lengthier study. But if the screwdriver in the aerial socket, or the manufacturer's humble bit of wire, works, unlike FM, there's unlikely to be any requirement to improve the signal strength because there'll be no audio improvement whatsoever. FM is completely different: increasing signal strength almost always implies better audfio quality.

[Bryn]

A storm in a teacup. If there's an imagined transgression, then to save the reputation of Gordon, MY simplistic view of DAB and Freeview reception with a given aerial configuration is that you either get nothing or rubbish reception (and boiling mud falls firmly into the fail category: it is far worse than birdies and is quite unusable) or you get excellent sound. Now there'll be a blizzard of claims to the contrary, so yes, it's simplistic. A proper assessment of reception would require a lengthier study. But if the screwdriver in the aerial socket, or the manufacturer's humble bit of wire, works, unlike FM, there's unlikely to be any requirement to improve the signal strength because there'll be no audio improvement whatsoever. FM is completely different: increasing signal strength almost always implies better audfio quality.

As thoroughly misleading as ever. The 'boiling mud' can vary from the occasional 'plop' to veritable Rotoruan intrusion, depending on just how challenged the error correction is.

Somewhat OT. I think I have discovered what is causing the repeats I get from my car's DAB/FM/CD/etc installation when passing close to mobile 'phone transmitter sites. I would appear that what is happening is that the device temporarily switches from DAB to the equivalent FM channel if the DAB is compromised. When it switches back, the delayed DAB repeats what was just heard via FM.

[Gordon]

Bryn said:

No, Gordon does not so much "point out" such a thing as mistakenly assert it. If the signal is marginal the error correction cannot cope and you get that distinctive DAB 'boiling mud' accompanying the intended audio.

In #259 I said:

….the point was that to get good audio S/N you need lots of RF, way above threshold. All you need with DAB is to get a few dB clear of the threshold and stay there.”

I don’t concede a mistake. In my book there is no question that “bubbling mud”, whether it is a plop or worse, is failure. The FEC has failed to deal adequately with errors for lack of signal strength [ie C/N] and/or simply inadequate receiver sensitivity [and measurements have shown this to be spectacularly the case in some receivers].

The dB margin between onset of failure [say a plop or click every 10 seconds] and total failure is small and that margin gets smaller the more sophisticated the FEC system. A typical rule is that about 1dB change in C/N leads to an order of magnitude change in probability of error, see ISBN 978-0-470-51037-7, page 47 for just one example:

http://www.amazon.co.uk/s/ref=nb_sb_noss/277-8118565-2108004?url=search-alias%3Dstripbooks&field-keywords=Hoeg%20%26%20Lauterbach

If you don’t want to spend £80 on a book [!] try the Figures in this free document:

http://www.rohde-schwarz.cz/file_1398/7BM03_4E.pdf. I’m sure if you google enough you’ll find more.

See Figure 11 and the Code Rate ½ for something close to DAB. “Failure” is usually defined as a BEP of 1 in 10,000 [ie BEP=0.0001] after the FEC has done its job. You’re looking primarily at the slope of these curves not necessarily the absolute values on the axes.

I stand by what I said in #259. In short posts in places like this brevity wins over precision. A full tutorial discussion of this issue and a comparison between the performance of FM [especially of you add stereo] and digital transmission [as used for broadcasting in both cases] is way beyond this place because as usual the devil is in the detail.

My #259 does have a chink in it, but wasn’t picked up!!

PS: I’m pleased that Bryn seems finally to have sussed that strange interference problem he reported some while ago.

[Bryn]

Apologies to Gordon for my taking AIC's attribution of 'all or nothing' to him at face value. I should have gone back to Gordon's messages to check the validity of that attribution.