Mono Stereo

[Dave Plowman (News)]

It's obviously going to depend on which transmitters are where. It's not a public service where the whole country gets fair do's. Anymore than with anything else. So rather obviously centres of population are better covered. The real test is to do a comparison where signal strengths and expected coverage are about the same.

One thing I did discover, though. An aerial designed for FM doesn't work well with DAB. And even maker's systems factory installed ain't necessarily state of the art.

I have one car with a factory FM radio. Aerial in the screen. Noticeably poorer FM reception than the old car on FM with a roof aerial.

[Johnny B Good]

A match made in heaven as far as low bit rate DAB is concerned. DAB is basically a low quality broadcasting system designed to match the equally low quality listening environments it was optimised for.

The egregious aspect of DAB was in its marketing claims that it could replace the old and tried FM broadcasting system in all usage cases. Clearly, once the bean counters had taken advantage of the cost cutting low bandwidth options inherent to the system, this rapidly (and with obscene haste) became yet another "Lie by omission advertising claim" (which is at the heart of pretty well all commercial advertising - "The large print giveth, whilst the small print taketh away." principle).

[Jethro_uk]

Utter bollocks, of course. Particularly for battery powered tranny radios.

[Dave Plowman (News)]

No it is not. But like many digital systems, it's easy to alter the bitrate. Which costs the broadcaster less in rental.

That is a facility DAB offers. Up to the broadcaster and the listener if they would prefer to pay more for better quality.

But then FM reception in a car or portable is rarely perfect either. Multipath introduces distortion.

[Dave Plowman (News)]

Dunno about you, but I find FM reception on a portable radio less than perfect in this part of London. Same as it always has been.

[Jethro_uk]

It was OK when I lived in London. batteries lasted hours ...

[Johnny B Good]

To make it clear, this "AM modulation" is only referenced to the baseband audio signals that are frequency modulating the VHF carrier. Since it's (afaicr) some 20dB down on the primary baseband modulation, this stereo difference signal adds extra noise (an extra 3 or 6dB overall under ideal conditions afaicr).

Under less ideal conditions, it adds even more noise. Since it manifests itself as "hiss", a simple hf blending of the left and right channels can mitigate this noise at the expense of stereo separation. A receiver design which applies a graduated increase in reducing the effective stereo separation at the higher audio frequencies provides a more graceful degradation to pure mono with worsening reception conditions beyond a lower threshold limit of acceptability for full stereo separation operation.

[rmlaws54]

I think that DAB has three 'grades': mono, 'joint stereo' and 'full stereo'. AFAIK only radio 3 is in full stereo (at least some of the time).

In my expereice FM stereo is a only slightly more noisy than FM mono, provided the signal strength is good.

Robert

[The Natural Philosopher]

from memory when was designing said stuff about 5dB worse.

[Bill Wright]

1. Inadequate DAB aerial. Was it using the same aerial as the FM, or a windscreen thing, or whatever?
2. Insensitive tuner, or one that couldn't discriminate against strong adjacent muxes.

Bill

[harry]

Fiddle with the controls. If it has a balance control, it is stereo.

[Jethro_uk]

Whatever the car came with

Possible - and almost a certainty if it was designed to the same standard as the rest of the electronics. Which is not to say they are unreliable. Just the design is shit ... almost a collection of everything that's annoying in one system.

[Mark Carver]

The noise is as a result of FM's 'triangular noise spectrum'.

The stereo difference signals (which are between 23 and 53kHz are far more impacted by noise than the mono channel 0 to 15 kHz.

The 'extra' noise as a result of the difference channel is actually anti-phase L/R, you can remove it by simply summing L and R channels together, rather than disabling the stereo decoder within the tuner .

The SCA system that the US used as an additional independent audio channel around 67 kHz was servery impacted, and required a very strong signal to remain noise free.

[tony sayer]

In article [e-mail]>, Dave Plowman (News) [e-mail]> scribeth thus

Those on screen things are s**te squared we had Taxi drivers trying to use them for their Two-way radios and they were around a tenth as efficient as a roof mounted one either a mag base or hole in the roof mount...

[tony sayer]

That's more the problem, seems most all DAB radios the front end is wide open no tuned RF stages at all...

[Dave Plowman (News)]

Yup.

My only DAB car unit is an aftermarket Blaupunkt in the old Rover. Top of the range Blaupunkt - at the time. Since I don't change that car every couple of years wanted something good.

The DAB aerial input was separate to the FM/AM one. It came with a stick on windscreen DAB aerial. Pretty useless - as well as looking horrid. FM/AM using the original wing mounted telescopic aerial just fine.

It may well have been on here I got the heads up about a local (Wandsworth) aerial supplier that do all sorts of specialist aerials for mobile reception. And they had a roof one with twin amplifiers - one for DAB, one for the rest, and twin feeders. Cost more than many a car radio new. But works a treat. Cost even more to have a new nearside front wing fitted to get rid of the original aerial hole. ;-)

But it's no different from the best TV or posh FM tuner. Neither will work well without a decent aerial.

[Jethro_uk]

"Squariel" ?

[mm0fmf]

It's sounds so f****ng awful. The Archers on R4 DAB sounds lifeless and flat yet on FM (even if a bit poppy and noisy) has depth and life. And is in stereo.

2 cars with DAB and coverage about Scotland is dire. 1 DAB/FM radio in the kitchen (spends it's life on R4 FM) and I'm optical line of site to the most power DAB transmitter in Scotland and the DAB reception is s**te.

The proponents still pushing DAB now need to be castrated in public for forcing this bag of dated pish onto the public.

(I feel much better for that.)

[mm0fmf]

DAB doesn't work well even with a good antenna. It's a piss poor standard designed for 1995 level electronics with no upgrade potential. Having had it foisted on us, nobody in power is prepared to admit it's crap and should be ditched.

It offers no improved quality of reception over FM. My 1969 Roberts R707 FM portable radio sounds better than just about all modern portable radios, FM or DAB.

[charles]

It offers signifiacant immprovement for the motorist in heavily built up areas.