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GM7HUD > TECH 04.03.05 20:44l 87 Lines 3795 Bytes #999 (0) @ WW
BID : 1C2233GM7HUD
Read: GUEST
Subj: Re: FM Stereo Radio Principles 1/2
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0RES<ON0AR<IW8PGT<ON4HU<GB7YFS<GB7YKS<
GB7LGS<GB7ESX
Sent: 050304/1800z 23454@GB7ESX.#31.GBR.EU $:1C2233GM7HUD [Witham, Esx]NNA V3.1
GM0CSZ wrote:-
> What is the audio spectrum range of Digital Radio (DAB) as now available
> in the UK ?
IIRC the sample rate is 44.1kHZ as in CD. But the data is heavily
compressed using MPEG 1 layer 3 (aka MP3).
The BBC quote the following bitrates for DAB:
Radio 1 - 128 JS
Radio 2 - 128 JS
Radio 3 - 192 S *
Radio 4 - 128 JS **
Radio Five Live - 80 M
1Xtra - 128 JS
6 Music - 128 JS
BBC7 - 80 M
BBC Asian Network - 64 M
BBC World Service - 64 M
BBC Data services - 24
JS = joint stereo, M = mono, all speeds in kbps
* = When BBC Five Live Sports Extra is on air either Radio 4 drops to 80
kbits/s mono or Radio 3 drops to 160 kbits/s joint stereo.
**Radio 4 split for Yesterday in Parliament and Daily Service:
Station 0800 - 0900 0944 - 1000
Radio 4 80 M 80 M
Radio 4 (secondary services) 64 M 64 M
Data services 24 M 24 M
128kbps MP3 is certainly an easily perceived lower quality signal than
15kHz (b/w) FM stereo. In particular, rock music with a lot of "aggressive"
drumming and cymbals will sound wrong. Of course DAB will sound good when
analogue FM stereo is suffering from analogue propagation problems such as
multipath. In addition, many peoples experience of FM stereo is often with
a simple 300ohm ribbon dipole which gives insufficient signal for noise
free stereo reception. IIRC stereo FM requires 23dB greater SNR than mono
FM. So compared to the dire rubbish that the uninformed public associate
with FM from their nasty micro hifi, DAB is superior. To those with a good
antenna and a tuner capable of reproducing music (Quad FM3/4, Marantz ST-7,
McIntosh, Linn etc) then DAB sounds like a poor cassette tape player of the
mid70s.
Of course in the UK there is only one broadcast HiFi source and that is
Radio 3 (for non-UK readers, a classical music station run by the BBC).
Most of their programming is not my choice. BBC Radio 2 is mid-fi and BBC
Radio 1 has the classic "if 3db compression is good 300dB must be
excellent" overprocessed OptiMod sound. Most commercial FM radio in the UK
is so dire, repetitive and poorly setup that it hardly compares well with
AM :-(
So DAB gives better results than FM for those using a bit of wet spaghetti
as an antenna, yet sounds dire compared to well setup FM gear. Remarkably
similar to the arguments about DVB in the UK where a good analogue set
thumps the pants off low bitrate MPEG2 and its artefacted pictures. In
addition there is a greater choice of programming. But as my 22year old
Sony Walkman tape player sounds considerably better (with 22years of wear
on the heads) than most DAB stations, I wont be upgrading until FM is
shutdown or the bitrate is comparable with FM.
When the plug is pulled on FM radio, I'll invest in a cheap DAB receiver
and rebroadcast Radio 4 signal back where it should be on 94.8MHz so the FM
gear chez HUD is still usable. I guess I wont be the only person doing the
same.
The sad thing is that both DVB and DAB have the capability to produce
really outstanding results than would be a step improvement for all. But in
the UK commercial avarice and greed results in far too many signals being
broadcast. More choice is the motto. But more garbage quality is the
reality. Those who think that the vast amounts of spectrum freed when
analogue TV is closed down will allow an increase in bitrates are living in
a world viewed through rose-tinted spectacles. There is no commercial
incentive to increase bitrates when the great unwashed, uneducated masses
have their appetites satisfied for Soap and Reality TV now and aren't
complaining.
Hey it's digital, so it must be better :-(
73 de Andy GM7HUD
p.s. For anyone who thinks DAB sounds good, visit your nearest pharmacy and
enquire about the availabilty of over-the-counter remedies for the removal
of accumulated ear wax :-)
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