DAB Performance of different makes?

In article , Nobody
Here wrote:
Jim Lesurf wrote:
There was a time when the audio mags would do a thorough examination
of new FM tuners, and show a great deal about their noise levels,
interference rejection ability, etc. Yet almost nothing functionally
equivalent seems to be done with DAB RXs. I find this quite baffling,
and unsatisfactory since it fails to provide some potential users with
info that they might find very helpful.

I wonder if that's because of the perception that digital (DAB, TV
whatever) either works of doesn't work, and that there's no middle
ground?

I suspect that is one of the main reasons. i.e. That a lot of the public
have been led to think "digital works or it doesn't", when that is an
over-simplification which may be misleading in many cases.

Also, the mags, as has been pointed out many times before, have to keep
their advertisers happy.

Another part of the problem, I fear, is that this is also a consequence of
the growth of "subjective" reviews in audio mags during the last 20-odd
years. These are often done by people who make no measurements and have
limited understanding of anything like RF or comms, or even the basics of
digital systems. Thus they simply listen to a tuner and no-one seems to do
any measurements which test for sensitivity, rejection of interference,
etc, etc. I doubt many of them would know third-order intermod from a plate
of sardines... This then tends to feed the lack of awareness of the
possibility that RXs may vary in performance in real world situations.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Jim Lesurf wrote:
In article , DAB sounds
worse than FM wrote:
Jim Lesurf wrote:
[snip]

There will always be bit errors, and different DAB modules will
perform differently.

Yes! That is the kind of thing I have been asking about - with the
aim of identifing the *actual* differences between *specific* RXs in
various specific situations. For the reasons I have (twice)
explained.


The output BER is the all-important parameter, and two receivers
which have an identical BER should provide effectively identical
output audio quality (assuming, say, that the audio is routed via
S/PDIF to the same DAC).

I'd agree with the above, but with some qualifiers that are in accord
with what you wrote lower down in your posting.

One is that if different RXs have different sensitivities or level of
interference rejection, then in some reception conditions different
RXs will output different BERs from the same RF input.


Agreed.


This is why I
think info on this would be of interest as it may affect some user's
choice of RX.

The other is the question of the 'strategy' a given RX takes to deal
with a given sequence of uncorrectable errors when they arise. My
experience with CD players and DACs is that when presented with a
disc which produces a high enough level of uncorrectable errors the
results can vary quite noticably.


Yeah, Radioscape and Frontier-Silicon may well use different error
concealment techniques.


Thus my curiosity that this may
also occur with DAB RXs. Some make 'mask' the errors in ways that
make them less noticable than how other RXs handle the same sequence
of errors, or produce artefacts that some find more/less annoying
than others.


It's possible, but you won't know if it's due to different error
concealment techniques or there's a different number of errors in the
first place. You'd have to start digging around in very low level stuff
to know one way or another.


This may for some people also matter. I'd agree that
what they should do in improve reception and get down the level of
errors, but for some people this may not be practical. Hence the
usefulness of our finding out how RXs may vary in these respects.

However, even with an identical output BER (the BER after the Viterbi
decoder) there may be very slight differences between the
performance of different DAB chipsets/modules. The possible
differences could be caused by different implementations of the
Viterbi algorithm such that the distribution of uncorrectable errors
over the different parts of the audio frame are different.

I'll explain what I mean by that:

DAB uses UEP (unequal error protection) where different parts of the
audio frame are protected with different error correction code rates:
the audio frame header uses a low code rate for high protection,
whereas the audio samples themselves use a higher code rate and thus
offer lower protection.

Therefore, if different chipsets/modules have implemented the Viterbi
algorithm differently (e.g by using a different constraint length)
then it is possible that the different chipsets/modules output a
slightly different distritution of uncorrectable errors over the
different parts of the audio frame, but still have the same overall
output BER.

Thanks for the above explanation. Yes, the above implies that there
may be differences of the kind that I am curious about.


Personally, I think this is very insignificant compared to other
factors.


Personally, I think it's unlikely that it is very unlikely that this
would be significant, because the different code rate levels offer
markedly different protection levels to the different parts of the
audio frame, so I would say it is extremely likely that the
distribution of errors over the different protection levels will be
the same.

In general, I am inclined to agree. My experience with other systems
like CD players and DAC is that - given good signals - the
differences tend to be slight for well made units. However what
worries me in this area is the apparent lack of measurements and
comparisons under a range of recpetion conditions. Hence we can
assume that the differences will, generally, be small.


Differences in what: audio quality or perceptibility of reception
problems? Again, your wording is ambiguous. You started talking about CD
players and DACs given good signals, which presumably means that the BER
is very low, so there's no perceptible "reception" problems.


But I dislike
basing this on an assumption, however reasonable. I'd prefer evidence
as my experince in engineering and science is that evidence sometimes
shows unexpected results. e.g. here it may show that *some* RXs
behave is a different way to others, and in a way that would have a
significant effect for some users.

Different receivers will have different RF performance, but this is
-- or should be -- pretty irrelevant if the output BERs are
equivalent, for the reason I've just given.

That would be so if the BERs are equivalent, etc. However the problem
is that if their RF sensitivities, etc, differ, then their BERs may
also differ in some conditions of use.


Obviously.


You would expect the MP2 audio decoders would all pass the strict
conformance requirements, but there probably will be very, very
slight differences in the output PCM audio bitstream produced even
for the same input data stream (but due to the strict conformance
requirements I don't think this should be significant to the output
audio quality).

Again, I'd agree with that in principle, but I tend to prefer
evidence from measurements on real RXs to see if any of them fall
short of what is assumed or have unexpected 'features' in their
behaviour.


Good luck testing the MP2 decoders...


No, I can't direct you to any evidence.

There's 2 chipset/module design companies: Radioscape and
Frontier-Silicon, and they account for probably 95% or more of all
DAB receivers sold in the UK. They may use different RF front ends,
but my impression is that receivers usually install full modules
provided by these companies. Having said that, from reading people's
experiences, there does seem variability of reception quality for
things like DAB personal radios, so there may be some model-specific
stuff as well.

FWIW I bought a cheap 'DAB adaptor' a few weeks ago and use it some
of the time for 'background listening' or for stations like BBC7. As
you would expect, the sound quality on a station like BBC7 or World
Service ahem isn't exactly perfect. This, I expected, of course.

However what I am curious about is the following:

One the main BBC stations the multiplex signal level is good enough
for the RX to display "signal error 0" (whatever that means is
undefined). But on, say, Classic FM, on its multiplex I get "signal
error 3" (or a number in the range 2-5).

Classic FM sounds worse to me that R3. This isn't surprising for
reasons which I think will be obvious. However I am curious to know:


Classic FM uses a bit rate of 160kbps. That's why it sounds poor.


A) Would it sound any better if I improved the signal until I got
"signal error 0"?

B) Would a different RX give better results for the Classic FM
multiplex in the same location?


So, after I was slagged off for questioning your ambiguous wording the
other day, now you're asking *precisely* what I suggested you were
asking: do small differences in BER affect the audio quality.




--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

DAB sounds worse than FM wrote:

A) Would it sound any better if I improved the signal until I got
"signal error 0"?

B) Would a different RX give better results for the Classic FM
multiplex in the same location?


So, after I was slagged off for questioning your ambiguous wording the
other day, now you're asking *precisely* what I suggested you were
asking: do small differences in BER affect the audio quality.


Caveat: I'm presuming that the difference in BER between "signal error
3" and "signal error 0" is small, but I don't know what it is either.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

In article , DAB sounds worse
than FM wrote:
Jim Lesurf wrote:
In article , DAB sounds
worse than FM wrote:



Thus my curiosity that this may also occur with DAB RXs. Some make
'mask' the errors in ways that make them less noticable than how other
RXs handle the same sequence of errors, or produce artefacts that some
find more/less annoying than others.


It's possible, but you won't know if it's due to different error
concealment techniques or there's a different number of errors in the
first place.

This is the kind of thing that might be revealed when someone (e.g. a
magazine) actually records the series of samples produced by two RXs used
in parallel to receive and decode the same input RF signal. (See the tests
I describe below as an example.)


You'd have to start digging around in very low level stuff to know one
way or another.

The test I've been hoping that a magazine would do is:

A) Feed two RXs via a variable attenuator and a splitter, then record the
outputs from, say, the two spdif outputs of the RXs as the atennuator is
used to vary the input RF level presented to the two RXs. Then compare the
series of values and look for differences. Doing this with two different
models of RX would help show any differences between them in terms of
dealing with poor RF input, or factors that affect the output.

B) Feed two RXs of the same model/make, via a splitter, but with an
attenuator in front of one of them. Record and compare the spdif outputs as
above. This would indicate how the performance of a given model may be
affected by the input RF level altering the BER, etc, it can produce.

The performance could then be judged by the results since what I'm
interested in here is if/how performance varies from one model to another
and/or when the RF input level is altered. If there are no measured
differences, then any possible differences in the internal arrangements may
be irrelevant. But if differences show up, they may then cast a light on
the possibility that one RX might be preferred by some customers to
another. May also give an indication of the reasons in design terms.

If the testers have a DAB generator they could use one RX at a time,
as used to be stanadard for FM RXs. However in the absence of that,
a good strong signal from an antenna could be used for the above by
making the test signal 'common' to the two RXs being compared.

To me, as someone who has worked on RF and mm-wave RX design over the
years, tests like the above seem a fairly obvious and basic thing
for reviewers to have done. It therefore is coming to intrigue me
that I can't find the results of any such tests...



Therefore, if different chipsets/modules have implemented the Viterbi
algorithm differently (e.g by using a different constraint length)
then it is possible that the different chipsets/modules output a
slightly different distritution of uncorrectable errors over the
different parts of the audio frame, but still have the same overall
output BER.

Thanks for the above explanation. Yes, the above implies that there
may be differences of the kind that I am curious about.


Personally, I think this is very insignificant compared to other
factors.

It may well be. The problem is that I can't find any results for tests like
the ones I suggest above. Hence I can't find any actual objective data on
this.


Personally, I think it's unlikely that it is very unlikely that this
would be significant, because the different code rate levels offer
markedly different protection levels to the different parts of the
audio frame, so I would say it is extremely likely that the
distribution of errors over the different protection levels will be
the same.

In general, I am inclined to agree. My experience with other systems
like CD players and DAC is that - given good signals - the differences
tend to be slight for well made units. However what worries me in this
area is the apparent lack of measurements and comparisons under a
range of recpetion conditions. Hence we can assume that the
differences will, generally, be small.


Differences in what: audio quality or perceptibility of reception
problems? Again, your wording is ambiguous. You started talking about CD
players and DACs given good signals, which presumably means that the
BER is very low, so there's no perceptible "reception" problems.

The qualifier was "given good signals". The problem with RF reception is
that this can't be assumed in all cases. (Indeed, it may not be the case
with CDs, either, as some are faulty and hard for the player to read.)


FWIW I bought a cheap 'DAB adaptor' a few weeks ago and use it some of
the time for 'background listening' or for stations like BBC7. As you
would expect, the sound quality on a station like BBC7 or World
Service ahem isn't exactly perfect. This, I expected, of course.

However what I am curious about is the following:

One the main BBC stations the multiplex signal level is good enough
for the RX to display "signal error 0" (whatever that means is
undefined). But on, say, Classic FM, on its multiplex I get "signal
error 3" (or a number in the range 2-5).

Classic FM sounds worse to me that R3. This isn't surprising for
reasons which I think will be obvious. However I am curious to know:


Classic FM uses a bit rate of 160kbps. That's why it sounds poor.

But how would the user know if seeing a message like "Signal error n"
(where n != 0) indicated that a change might cause an audible improvement?
I am not talking about the result becoming without any problems due to the
chosen bitrate, but assessing any other problems.


A) Would it sound any better if I improved the signal until I got
"signal error 0"?

B) Would a different RX give better results for the Classic FM
multiplex in the same location?


So, after I was slagged off for questioning your ambiguous wording the
other day, now you're asking *precisely* what I suggested you were
asking: do small differences in BER affect the audio quality.

Not quite. I am asking about what may be *large* differences or BERs in
some cases as well as *small* ones in others. I am also asking how the BER
values and concealment behaviours of RXs compare over a wide range of RF
reception conditions. i.e. to reference this to the RF available to the
(various) users.

FWIW I have no idea what "signal error 2" actually means on the 'adaptor'
I'm using. Hence I can't tell if indicates what you/I would call a high
BER or a low BER. All I can surmise is that it seems probable that it
indicates a BER higher than for "signal error 0". However my interest
isn't confined to just that single adaptor, but extend to all the RXs
on sale, and the range of conditions of use that they may experience.

The problem is that until someone does the relevant measurements this can't
be reliably assessed. It will be no surprise to discover that if we have
reasonably high level and clean RF inputs, the BERs will be low, and the
RXs may then tend to sound similar or indistinguishable. But what about
under poorer reception conditions?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Jim Lesurf wrote:

Classic FM sounds worse to me that R3. This isn't surprising for
reasons which I think will be obvious. However I am curious to know:

A) Would it sound any better if I improved the signal until I got
"signal error 0"?


Have you tried the obvious simple test?:

Increase the BER on the BBC mux to "signal error 3" and see if you can
perceive any difference.

Try scrunching up the wire aerial and/or move the receiver.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

In article , DAB sounds worse
than FM wrote:
DAB sounds worse than FM wrote:

A) Would it sound any better if I improved the signal until I got
"signal error 0"?

B) Would a different RX give better results for the Classic FM
multiplex in the same location?


So, after I was slagged off for questioning your ambiguous wording the
other day, now you're asking *precisely* what I suggested you were
asking: do small differences in BER affect the audio quality.


Caveat: I'm presuming that the difference in BER between "signal error
3" and "signal error 0" is small, but I don't know what it is either.

Yes, in this example case, we can't tell what it means as the makers give
no info on what the value is supposed to me. This is a part of what I think
is a more general problem due to a lack of measurements or performance
definitions.

For all I know Classic FM would sound the same if the value was "0" as it
does when the value is in the range 2-4. Or it might sound noticably
different. Can't be sure. I'm just using this as an example as I tend not
to listen to Classic FM anyway. But it illuminates the sort of problems I'm
curious about.

The makers do not provide the necessary info to interpret the numbers. Nor
do reviews seem to give any info on this - for the various RXs I've seen.
Hence if someone has poor reception conditions, how can they judge before
they buy what RXs might - for them - function worse than others? No data to
make comparisions and reach decisions.

If the reception conditions are good, then it may not really matter. But
the potential buyer/user may not know this in advance, and so if in a poor
location may chose the 'wrong' RX due to lack of relevant info.

This is why I am interested in discovering the relevant data I've been
asking about, and why I am now intrigued/puzzled by the apparent lack of
any tests by magazines, etc, to produce it for readers...

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Jim Lesurf wrote:
In article , DAB sounds
worse than FM wrote:
Jim Lesurf wrote:
In article , DAB sounds
worse than FM wrote:



Thus my curiosity that this may also occur with DAB RXs. Some make
'mask' the errors in ways that make them less noticable than how
other RXs handle the same sequence of errors, or produce artefacts
that some find more/less annoying than others.


It's possible, but you won't know if it's due to different error
concealment techniques or there's a different number of errors in the
first place.

This is the kind of thing that might be revealed when someone (e.g. a
magazine) actually records the series of samples produced by two RXs
used in parallel to receive and decode the same input RF signal. (See
the tests I describe below as an example.)


If you're talking about comparing audio samples then you have to bear in
mind that this is perceptually codec audio.


You'd have to start digging around in very low level stuff to know
one way or another.

The test I've been hoping that a magazine would do is:

A) Feed two RXs via a variable attenuator and a splitter, then record
the outputs from, say, the two spdif outputs of the RXs as the
atennuator is used to vary the input RF level presented to the two
RXs. Then compare the series of values and look for differences.
Doing this with two different models of RX would help show any
differences between them in terms of dealing with poor RF input, or
factors that affect the output.


Seeing as different make receivers are likely to differ significantly,
e.g. in their sensitivies, and considering that the audio is
perceptually codec, then I think such a comparison would be
near-meangingless. For example, how can you tell that a difference in
the waveform is actually perceptible?


B) Feed two RXs of the same model/make, via a splitter, but with an
attenuator in front of one of them. Record and compare the spdif
outputs as above. This would indicate how the performance of a given
model may be affected by the input RF level altering the BER, etc, it
can produce.


That's reasonable, but how are you going to access the true BER?


The performance could then be judged by the results since what I'm
interested in here is if/how performance varies from one model to
another and/or when the RF input level is altered. If there are no
measured differences, then any possible differences in the internal
arrangements may be irrelevant.


There will be measured differences, but what do these measured
differences prove?? Are the errors below or above the psychoacoustic
masking curves in the frequency domain? If they're below then you
shouldn't be able to perceive them. But how are you going to access the
psychoacoustic masking curves that are only accessible internal to the
chip/software?

All your traditional tests go out of the window with perceptually coded
audio, I'm afraid.


But if differences show up, they may
then cast a light on the possibility that one RX might be preferred
by some customers to another.


So, you WERE talking about audio quality ALL ALONG, which is what I said
in the first place. But oh no, I get accused of mis-interpreting your
ambiguously worded paragraph.


May also give an indication of the
reasons in design terms.

If the testers have a DAB generator they could use one RX at a time,
as used to be stanadard for FM RXs. However in the absence of that,
a good strong signal from an antenna could be used for the above by
making the test signal 'common' to the two RXs being compared.

To me, as someone who has worked on RF and mm-wave RX design over the
years, tests like the above seem a fairly obvious and basic thing
for reviewers to have done.


They're meaningless.


In general, I am inclined to agree. My experience with other systems
like CD players and DAC is that - given good signals - the
differences tend to be slight for well made units. However what
worries me in this area is the apparent lack of measurements and
comparisons under a range of recpetion conditions. Hence we can
assume that the differences will, generally, be small.


Differences in what: audio quality or perceptibility of reception
problems? Again, your wording is ambiguous. You started talking
about CD players and DACs given good signals, which presumably means
that the BER is very low, so there's no perceptible "reception"
problems.

The qualifier was "given good signals". The problem with RF reception
is that this can't be assumed in all cases. (Indeed, it may not be
the case with CDs, either, as some are faulty and hard for the player
to read.)


But are you talking about audio quality differences? If so, then why TF
was I accused of jumping to the wrong conclusions????


FWIW I bought a cheap 'DAB adaptor' a few weeks ago and use it some
of the time for 'background listening' or for stations like BBC7.
As you would expect, the sound quality on a station like BBC7 or
World Service ahem isn't exactly perfect. This, I expected, of
course.

However what I am curious about is the following:

One the main BBC stations the multiplex signal level is good enough
for the RX to display "signal error 0" (whatever that means is
undefined). But on, say, Classic FM, on its multiplex I get "signal
error 3" (or a number in the range 2-5).

Classic FM sounds worse to me that R3. This isn't surprising for
reasons which I think will be obvious. However I am curious to know:


Classic FM uses a bit rate of 160kbps. That's why it sounds poor.

But how would the user know if seeing a message like "Signal error n"
(where n != 0) indicated that a change might cause an audible
improvement?


They wouldn't know.


I am not talking about the result becoming without any
problems due to the chosen bitrate, but assessing any other problems.


A) Would it sound any better if I improved the signal until I got
"signal error 0"?

B) Would a different RX give better results for the Classic FM
multiplex in the same location?


So, after I was slagged off for questioning your ambiguous wording
the other day, now you're asking *precisely* what I suggested you
were asking: do small differences in BER affect the audio quality.

Not quite. I am asking about what may be *large* differences or BERs
in some cases as well as *small* ones in others.


That sentence doesn't make sense.


I am also asking how
the BER values and concealment behaviours of RXs compare over a wide
range of RF reception conditions. i.e. to reference this to the RF
available to the (various) users.

FWIW I have no idea what "signal error 2" actually means on the
'adaptor' I'm using. Hence I can't tell if indicates what you/I would
call a high BER or a low BER. All I can surmise is that it seems
probable that it indicates a BER higher than for "signal error 0".


Obviously.


However my interest isn't confined to just that single adaptor, but
extend to all the RXs
on sale, and the range of conditions of use that they may experience.

The problem is that until someone does the relevant measurements this
can't be reliably assessed. It will be no surprise to discover that
if we have reasonably high level and clean RF inputs, the BERs will
be low, and the RXs may then tend to sound similar or
indistinguishable. But what about under poorer reception conditions?


Under poor reception conditions you get bubbling mud. The audio quality
probably degrades just before the onset of bubbling mud, but so long as
the BER is lower than some given value then I'd bet you wouldn't be able
to perceive any difference (assuming they're using the same DAC) between
receivers. I don't know exactly what that BER is (and this BER is for
the audio samples, because the BER of the header and scale factors will
be diffferent due to different code rates being used for them), but
basically so long as you have reasonable reception and the same DAC is
being used then I say the differences will be imperceptible. Will there
be measurable differences? Yeah, but they'd be meaningless if you can't
hear any difference, becauase it's perceptually coded audio.




--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

DAB sounds worse than FM wrote:
Jim Lesurf wrote:
In article , DAB sounds
worse than FM wrote:
Jim Lesurf wrote:
In article , DAB sounds
worse than FM wrote:



Thus my curiosity that this may also occur with DAB RXs. Some make
'mask' the errors in ways that make them less noticable than how
other RXs handle the same sequence of errors, or produce artefacts
that some find more/less annoying than others.


It's possible, but you won't know if it's due to different error
concealment techniques or there's a different number of errors in the
first place.

This is the kind of thing that might be revealed when someone (e.g. a
magazine) actually records the series of samples produced by two RXs
used in parallel to receive and decode the same input RF signal. (See
the tests I describe below as an example.)


If you're talking about comparing audio samples then you have to bear in
mind that this is perceptually codec audio.


You'd have to start digging around in very low level stuff to know
one way or another.

The test I've been hoping that a magazine would do is:

A) Feed two RXs via a variable attenuator and a splitter, then record
the outputs from, say, the two spdif outputs of the RXs as the
atennuator is used to vary the input RF level presented to the two
RXs. Then compare the series of values and look for differences.
Doing this with two different models of RX would help show any
differences between them in terms of dealing with poor RF input, or
factors that affect the output.


Seeing as different make receivers are likely to differ significantly,
e.g. in their sensitivies, and considering that the audio is
perceptually codec, then I think such a comparison would be
near-meangingless. For example, how can you tell that a difference in
the waveform is actually perceptible?

But is *exactly* the reason for performing the test in the first place.
The receivers *are* different, and the test might tell you how much
better one of them was compared with the other. If the difference is
*significant* then surely it's *important*, not *meaningless*.

Sigh.

Oh, I forgot, the dope's not listening to me any more.

--
Nobby

Jim Lesurf wrote:
In article , DAB sounds worse
than FM wrote:
DAB sounds worse than FM wrote:

A) Would it sound any better if I improved the signal until I got
"signal error 0"?

B) Would a different RX give better results for the Classic FM
multiplex in the same location?


So, after I was slagged off for questioning your ambiguous wording
the other day, now you're asking *precisely* what I suggested you
were asking: do small differences in BER affect the audio quality.


Caveat: I'm presuming that the difference in BER between "signal
error 3" and "signal error 0" is small, but I don't know what it is
either.

Yes, in this example case, we can't tell what it means as the makers
give no info on what the value is supposed to me. This is a part of
what I think is a more general problem due to a lack of measurements
or performance definitions.

For all I know Classic FM would sound the same if the value was "0"
as it does when the value is in the range 2-4. Or it might sound
noticably different.


Do you know what the "signal error" goes up to?

In my experience, there's no difference in audio quality from when
there's maximum signal quality down to when the bubbling mud actually
starts.


Can't be sure. I'm just using this as an example
as I tend not to listen to Classic FM anyway. But it illuminates the
sort of problems I'm curious about.

The makers do not provide the necessary info to interpret the
numbers. Nor do reviews seem to give any info on this - for the
various RXs I've seen. Hence if someone has poor reception
conditions, how can they judge before they buy what RXs might - for
them - function worse than others? No data to make comparisions and
reach decisions.


You seem to be flitting between talking about reception problems and
audio quality problems.



--
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Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
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In article , DAB sounds worse
than FM wrote:
Jim Lesurf wrote:

Classic FM sounds worse to me that R3. This isn't surprising for
reasons which I think will be obvious. However I am curious to know:

A) Would it sound any better if I improved the signal until I got
"signal error 0"?


Have you tried the obvious simple test?:

Increase the BER on the BBC mux to "signal error 3" and see if you can
perceive any difference.

Try scrunching up the wire aerial and/or move the receiver.

I've been meaning to do this. Also to take the system into the living room
and use it with the better audio system. However so far I haven't bothered
as I mainly use it for occasional 'background' listening to R7/WS. Most of
the time I listen to R3/4 on FM.

Slainte,

Jim

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