Interested parties may like to look at this:
DAB Report
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Originally posted by Gordon View Post
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Originally posted by Eine Alpensinfonie View PostSo presumably 7 years is long enough to ensure a decent digital broadcasting system can be set up.
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Bubbling mud returns - FM immune!
Tonight I put on the DAB set in the kitchen which we use most nights for a short while around meal times. Bubbling mud has come back with a vengeance - speech unintelligible. Nudging the set slightly and tweaking the aerial, which sometimes works, made no difference. Moving to another room I picked up an FM set (Sony, at least 20 years old I think) - no problem with speech. I then walked back to the kitchen carrying the FM set, which continued to function acceptably well even when placed in the same area as the DAB set. I wouldn't say the FM quality was superb - but acceptable compares quite favourably against unintelligible garbage.
There are still issues with DAB, which the providers and planners for the future perhaps don't really want us to know or talk about. Oh - re coverage - this is in the area marked in dark brown on the map associated with the Ofcom report, so should have the best DAB coverage.
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Resurrection Man
I had the same problem with a DAB radio (now gone back) in the kitchen. The advice from Digital Radio UK? Why, take the radio and try it upstairs
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RM
I don't know why we had the bubbling mud yesterday. Reception on DAB on portables in our kitchen has been marginal for quite a while, but I thought it had improved since the analogue TV switch off, and it has mostly been acceptably OK in recent months, certainly never with unintelligible speech as per last night. The DAB portable is set up for Radio 4, since Mrs D likes it that way, for the news etc., so it was a BBC multiplex issue, not the commercial ones. It was reading the Ofcom update which reminded me that we do use DAB most days, though quite often we use the TV (satellite) for sound, and the internet - but we still do a significant amount of listening on FM, and none of our cars have DAB.
FM sets in the kitchen just work - more or less anywhere, though perhaps with slight distortion such as sibilance on speech. The DAB set, when it works, has to be positioned carefully in only a few locations to avoid any suspicion of distortion and bubbling. Otherwise it just doesn't work well at all. That's why it normally lives on a window sill, and in fairness mostly we have been happy with it when it works.
It did rain last evening - maybe that had something to do with it, though it's rained before without this happening.
Love the story about the Digital Radio UK advice!
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Resurrection Man
I am grateful for the link to that Ofcom report as it confirmed what was always my understanding. Namely:
The Action Plan stated that a decision on setting a date for digital radio switchover will be made when the following criteria are met:
- when 50% of all radio listening is via digital platforms; and
- when national DAB coverage is comparable to FM, and local DAB reaches 90% of the population and all major roads.
As I mentioned elsewhere in the latest reply to me from Vaizey, he had dropped the second criteria. Quite how he can arbitrarily do this I am not sure.
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Originally posted by Resurrection Man View PostI am grateful for the link to that Ofcom report as it confirmed what was always my understanding. Namely:
The Action Plan stated that a decision on setting a date for digital radio switchover will be made when the following criteria are met:
- when 50% of all radio listening is via digital platforms; and
- when national DAB coverage is comparable to FM, and local DAB reaches 90% of the population and all major roads.
As I mentioned elsewhere in the latest reply to me from Vaizey, he had dropped the second criteria. Quite how he can arbitrarily do this I am not sure.
Most of my live listening to music via the radio is using FM, and a significant proportion of that is in cars.
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Resurrection Man
Originally posted by Dave2002 View Post..... I feel that using "digital platforms" as a criterion is really rather dishonest - surely it should be by DAB radio, ....
To compound the issue, there is a fundamental flaw in the way RAJAR collects their data on which the percentage of listening is measured. On the questionnaire there are columns as to the source of listening. One column is for "DAB radio"...another for "FM radio". So anyone (and there are quite a few if local straw polls are anything to go by) who uses their DAB radio to listen to FM ...ie not DAB...will still stick the time down in the DAB radio slot. In other words, DAB listening is overstated.
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Originally posted by Bryn View PostI am advised that while rain falling through the air should aid propagation of the DAB signal, wet brickwork tends to attenuate it. Perhaps Gordon could offer an explanation.
A plane surface like a wet brick wall or a roof of tiles/slates - at least if the undulations in the plane are small compared to the wavelength - will act like a barrier and mirror to a radio wave because water does conduct electricity. Then the incident wave will be reflected, almost coherently rather than pass through the barrier as would happen if that same surface was dry.
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Originally posted by Gordon View PostRadio waves travel freely in empty space. Any material that occupies that free space will impair transmission in some way, usually by attenuating the wave and marginally changing its speed. Air does that. More importantly a volume of damp air will attenuate a radio wave and absorb some of the power because the water is conductive. If the wavelength is very small and comparable to the rain drop size the wave will also diffract and will scatter and cause it to lose its coherence.
A plane surface like a wet brick wall or a roof of tiles/slates - at least if the undulations in the plane are small compared to the wavelength - will act like a barrier and mirror to a radio wave because water does conduct electricity. Then the incident wave will be reflected, almost coherently rather than pass through the barrier as would happen if that same surface was dry.
Are you suggesting that if my outside wall gets wet, that the wall will present a greater barrier to transmission than if it stays dry?
I'm not really convinced about the situation a few nights ago, as the rain had, I think, only just started.
However, despite all that, and with no resiting of the DAB set, it's back to working acceptably again this morning. Maybe the problem was weather induced, or perhaps there really was a fault or change of settings in the transmission system.
RM
Whether my sets are working or not, I still think that there is persuasive dishonesty amongst those wishing to promote DAB. I'm not against digital per se, but rather the current DAB system which was heralded as being the best thing since sliced bread more than a decade ago, but for various reasons is now not up to scratch. One reason is that the original DAB system envisaged a bit rate of 256 kbps, which arguably does give sufficiently high quality, but the "needs" of broadcasters to increase the number of channels, and to commercialise broadcasting, and the constraints which do not permit any significantly greater use of spectrum, have led to the rather poor situation we are now faced with. DAB+, DMB etc which are mostly digital relatives of DAB could offer better compromises permitting the broadcasters to do their commercial thing, while at the same time providing the possibility of better perceive audio quality where it might be appreciated. I have lost track of/not kept up with the latest state of Digital Radio Mondiale which is another digital system which can work using AM on other bands. Similarly, I have not recently followed the state of affairs in the USA, which has other digital systems.
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Originally posted by Dave2002 View PostGordon
Are you suggesting that if my outside wall gets wet, that the wall will present a greater barrier to transmission than if it stays dry?
I should add of course that there are forms of enhancement to radio transmissions eg "Sporadic E" where very large distances can be attained under special conditions but these will not affect DAB transmissions here. More local enhancements can occur if a quirk of terrain and buildings etc focus a wave at a particular location [usually short term] but this is at the expense of nearby locations that lose their power.
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The poor DAB reception that Dave2002 reports was probably due to tropospheric ducting bringing in another distant MUX on the same channel. There was a spectacular lift to southern Germany at the beginning of the week that only fizzled out on Wednesday evening. However, there is another very good one now towards NE France and as far as Germany tonight so it would be interesting to see if Dave has any drop-outs or bubbling mud tonight or tomorrow.
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Major DAB disruption here in Bracknell this morning. I have two feeds here, a chimney-mounted dipole for a couple of Pure Bugs, and a DAB yagi directed at the relatively low power Guildford relay. Both usually give good, consistent results. However, when I checked the tuners fed by each aerial at 04:00 today the dipole offered lots of boiling mud and broken up audio, while the yagi only gave the occasional burst of audio. Things have improved considerably now, but there is still some break-up from the dipole, and the yagi signal remains intermittent at best.
It occurs to me that should such poor DAB reception obtain during a national emergency, DAB would prove unfit for purpose.
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