Best way to get Radio 3?
 

"tony sayer" wrote in message
...
In
Nope, they have to keep to what the government decrees, they keep the
mod to where they have to via their encoder/processor the where they
think it ought be within that constraint....
--
Tony Sayer

I recognise that spec.......Still giving good service?

S.


Well its been off air for a while now and was replaced by an analogue
exciter as that was deemed to be LOUDER 'cos wossisnamme at Radica said
it would be, and Jimbo is a loudness freak.

It was in use the other week for an RSL for 209 Radio and one afternoon
there was a Jazz piece on there that was recorded by the guy presenting
the programme and the sound was superb in the car:), really was, sounded
like the guitar was out there on the pavement somewhere and the vocalist
was sitting on the bonnet!..

If they get a full time licence its going there and thats going to be a
really good station:))
--
Tony Sayer

I *hate* these guys who don't know their deviation from their sidebands. An
exciter doesn't have the ability to make anything louder. The processor does
that, so the guy from Radica is talking out of his ring modulator, as
usual......

S.

Best way to get Radio 3?
 

Hi,

"Dave Plowman (News)" wrote in message
...
In article ,
wrote:
I think the whole DAB disaster could have been avoided if they'd
picked a solid technology, but they go for something 20 years old. Its
inexplicably wrongheaded....

First demonstration I heard of DAB was about 20 years ago. The better data
compression algorithms weren't around then.

It's DAB Jim, but not as we know it... :-)

Was that demo Eureka 147 based, or something different? I was at Hitachi and
then
VideoLogic (which gave birth to Pure) around that time, and was working on
MPEG coder/decoder products for both companies. I didn't get to hear any
real DAB (of any form) until after 1986.

The first generation of Hitachi's MPEG Audio chips could only just manage
layer 2 @ 128 kbits/sec, and the chipset cost upwards of 30 dollars in large
quantities. As I recall, the only customer was Sega, for the Saturn console,
which was a disaster (in sales terms - it had some decent technology).

Regards,

Glenn.

Best way to get Radio 3?
 

In article , hwh
wrote:

"Jim Lesurf" schreef in bericht
...
FWIW I did analyses of various examples of concerts and the plots in
the article are fairly representitive. The analysis/article was
directed specifically at 'proms' on BBC4TV and R3 as this was a very
convenient set of examples for comparison analysis.

But as I understand the advantage of Freeview is mainly in the lesser
amount of processing used compared to FM. The low bitrate still gives
it a metallic sound.

Rather depends on the extent to which your last statement is a sweeping
generalisation. I don't find that the sound of R3 or BBC4TV on DTTV
generally have a "metallic sound". Nor do I generally find this to be the
case for R3 on DAB.

What I do generally notice is the relative absence of level compression and
peak/average compression. I also notice the lack of background noise.

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

Best way to get Radio 3?
 

In article , tony sayer

wrote:
[big snip]

However, as with radio, the actual quality for TV will vary a lot from
station to station and item to item.


Quite..

I actually meant what do you think of the picture!!!

Depends again on the station and the item.[1] But in general on BBC1/2/4/24
I prefer the DTTV picture to the 'analog' one. I get a better picture from
DTTV than I've had for any analog TV I have ever used.

Slainte,

Jim

[1] Also on reception conditions. The DTTV signal level here is low, so we
suffer from II artefacts at times. As well as clicks and dropouts on DTTV
sound as this seems to use less redundancy and interleaving than DAB.

--
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

Best way to get Radio 3?
 

In article , tony sayer

wrote:
In article , Jim Lesurf jcgl@st-
and.demon.co.uk writes


I've got a top notch FM exciter in my workshop at the moment here is the
spec sheet or some of it..
[snip]

Stereo Total Harmonic Distortion: 0.005% or less for any modulating
frequency from 10Hz to 15kHz; measured in DC to 22kHz bandwidth with
75#s de-emphasis.

Intermodulation Distortion (L or R): CCIF: 0.02% (14/15kHz 1:1),

SMPTE: 0.025% (60 and 7000Hz 1:1).

Transient Intermodulation Distortion (DIM) (L or R): 0.005% (2.96kHz
square wave/14kHz sine wave modulation).


The problem isn't the generator, it is the effect of a finite transmission
bandwidth on an FM signal. This means that no matter how good the generator
or RX, there will be a lower limit to the distortion for high levels of
distortion which will be way above the values you quote.

My recollection of this may be hazy as it is some years since I did this,
however it is that the levels of nonlinearity due to the finite transmission
bandwidth rise, and are particularly a problem for the L-R component due
to the subcarrier components at HF.

You can certainly 'tweak' an FM RX to reduce one specific signal
distortion. So a maker might tweak the IF/RF alignment to get a lower mono
300Hz 30% mono THD. However if you do this, you find you have increased the
distortion for some other form of input modulation pattern. My perhaps
unreliable recollection is that trying to get a genuine (i.e. with a
band limited input) result much below 0.1 to 0.2 percent for mono was
misleading as real stereo TX modulations would end up being worse than
this, and you might make the stereo performance worse by tweaking to get
an apparent low distortion for a mono test signal.

[snip]

Must get round to measuring that through the Audiolab sometime, but I
tell you this, most people are hard pressed to tell the difference on
most source materiel with the CD on one input and the output of the
tuner on the another .

I would agree. I also find that FM can be similar to a CD, and may be
indistinguishable from it *given some conditions*. One being the absence of
any obvious addition of level compression, or background noise becoming
noticable on quiet passages. Provided the modulation levels are low,
the distortion for FM is too small to notice. Indeed, it can become
an unbobjectionable part of the 'sound' unless you have a comparison.

The problem here is that the R3 engineers have a more limited dyamamic
range for FM in reality than is available for CD. Thus the tendency to keep
the modulation well below peak to avoid noticable peak/HF distortion, and
then the temptation to level-compress to avoid noise or loss of audience.

I have been very happy with FM R3 for many years. I has delivered very
good results with a decent RX. However it seems to me that recent
comparisons lead me to the conclusions I have already reported - based
partly on a subjective assessment of the sound I now prefer, and partly
on measurements of the dynamic ranges which seem to confirm my feelings
about that preference. I will be investigating this further in the
future, though... :-)


Course this bears no resemblance to real world
conditions, but thats down to what the BBC decided to do with it before
it hits the air!..

These days, though, the makers and magazines have tended to 'solve'
this problem in the same was as they'd dealt with the similar issue of
nonlinearity in pickup cartridges for LP. Just ignore it and hope
no-one notices or cares... :-)

If you measure 'higher levels' - i.e. modulation depths up to 100
percent, and higher frequencies, and also L or R or L-R, or intermod,
the amount of distortion rises.

What depth do you mean in an FM system?..

Modulation depth. The tradition was to use 30% in magazine reviews (when
they bothered to actually measure tuners). Full mod (100%) would correspond
to 75kHz, nominally.


I suspect that. like myself, you have measured the distortion of more
than one FM RX whilst trying to align or tweak it, or just to see if it
was working as it should. it is easy enough to get THDs of the order of
0.2 percent for 300Hz 30 percent mod mono. But when you then measure
higher (signal) levels, etc, the results can be somewhat different.
Ditto for HF intermod or L+R and L-R intermod.

Haven't done that for quite somewhile but a Denon we're using as an RBR
receiver was down to .06% at 10 K at 50 K dev a while ago....

Erm... The second harmonic of 10k is 20k. What components were you
expecting to get through the MPX filtering? Or were you including intermod
with the pilot tone, etc?

If you wish to explore the effects of nonlinearity, you are better off
to use test modulation which includes a L-R component, and intermod
to probe HF effects. As with LP cartridges, the results of you do this
may well be significantly poorer than mono LF modulation at modest
levels.

You are reminding me of measurements on a tuner like the CT7000 which has
selectable IF widths. If you make bench measurements the 'wide' IF has
a lower distortion. Some of this is due to a lower ripple and dispersion
across the 200kHz band, but some is due to the acceptance of out-of-band
sidebands from a bench generator. I am afraid the BBC may be less
obliging as they may not be allowed to do this. :-)

Thus even though such tuners are indeed excellent ones, the performance
in real use is perhaps not as impressive as the bench measurements may
indicate.



The above occurs even for an 'ideal' RX and is due simply due to the
finite bandwidth and the removal of the higher terms of the modulation
by the bandwidth restriction. This, and avoiding modulation clipping is
why BBC R3 have always tended to err on the side of keeping down the
modulation.

Nope, they have to keep to what the government decrees, they keep the
mod to where they have to via their encoder/processor the where they
think it ought be within that constraint.... -


75kHz modulation depth does not mean that all the modulation sidebands will
be confined to a 200kHz transmission bandwidth unless you then filter the
signal. The higher the modulation depth and frequency, the more of the
signal pattern this filtering will exclude... Even with an otherwise
perfectly linear system, the removal of these sidebands introduces
nonlinearity. This situation is complicated by the use of the subcarrier
for the stereo difference signals - thus transferring modulation up
to the band around 38kHz.

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

Best way to get Radio 3?
 

In article , Jim Lesurf jcgl@st-
and.demon.co.uk writes
In article , hwh
wrote:

"Jim Lesurf" schreef in bericht
...
FWIW I did analyses of various examples of concerts and the plots in
the article are fairly representitive. The analysis/article was
directed specifically at 'proms' on BBC4TV and R3 as this was a very
convenient set of examples for comparison analysis.

But as I understand the advantage of Freeview is mainly in the lesser
amount of processing used compared to FM. The low bitrate still gives
it a metallic sound.

Rather depends on the extent to which your last statement is a sweeping
generalisation. I don't find that the sound of R3 or BBC4TV on DTTV

AFAIK TV sound on DTV is at 256 K which is quite acceptable, R3 isn't at
160/192....

generally have a "metallic sound". Nor do I generally find this to be the
case for R3 on DAB.

What I do generally notice is the relative absence of level compression and
peak/average compression. I also notice the lack of background noise.

Slainte,

Jim


--
Tony Sayer

Best way to get Radio 3?
 

"Dave Plowman (News)" schreef in bericht
...
Few units had been sold because those who wanted 'quality' sound didn't
buy it - although at the high bit rates then on offer it was fine.

But very expensive.

Now it has taken off due to offering a wide choice of stations at low
quality on most it's rather too late to complain.

It is. More capacity is the only thing that helps.

gr, hwh

Best way to get Radio 3?
 

In article , Jim Lesurf jcgl@st-
and.demon.co.uk writes
In article , tony sayer

wrote:
In article , Jim Lesurf jcgl@st-
and.demon.co.uk writes


I've got a top notch FM exciter in my workshop at the moment here is the
spec sheet or some of it..
[snip]

Stereo Total Harmonic Distortion: 0.005% or less for any modulating
frequency from 10Hz to 15kHz; measured in DC to 22kHz bandwidth with
75#s de-emphasis.

Intermodulation Distortion (L or R): CCIF: 0.02% (14/15kHz 1:1),

SMPTE: 0.025% (60 and 7000Hz 1:1).

Transient Intermodulation Distortion (DIM) (L or R): 0.005% (2.96kHz
square wave/14kHz sine wave modulation).


The problem isn't the generator, it is the effect of a finite transmission
bandwidth on an FM signal. This means that no matter how good the generator
or RX, there will be a lower limit to the distortion for high levels of
distortion which will be way above the values you quote.

My recollection of this may be hazy as it is some years since I did this,
however it is that the levels of nonlinearity due to the finite transmission
bandwidth rise, and are particularly a problem for the L-R component due
to the subcarrier components at HF.

Yes so it is, but its to a degree. No of course FM isn't perfect by any
means but I think it puts up a very good performance against the current
implementation of DAB in the UK..

You can certainly 'tweak' an FM RX to reduce one specific signal
distortion. So a maker might tweak the IF/RF alignment to get a lower mono


*300Hz 30% mono THD. However if you do this, you find you have
increased the
distortion for some other form of input modulation pattern. My perhaps
unreliable recollection is that trying to get a genuine (i.e. with a
band limited input) result much below 0.1 to 0.2 percent for mono was
misleading as real stereo TX modulations would end up being worse than
this, and you might make the stereo performance worse by tweaking to
get
an apparent low distortion for a mono test signal.

I think receivers may have come along a bit since that!..

[snip]

Must get round to measuring that through the Audiolab sometime, but I
tell you this, most people are hard pressed to tell the difference on
most source materiel with the CD on one input and the output of the
tuner on the another .

I would agree. I also find that FM can be similar to a CD, and may be
indistinguishable from it *given some conditions*. One being the absence of
any obvious addition of level compression, or background noise becoming
noticable on quiet passages. Provided the modulation levels are low,
the distortion for FM is too small to notice. Indeed, it can become
an unbobjectionable part of the 'sound' unless you have a comparison.

The problem here is that the R3 engineers have a more limited dyamamic
range for FM in reality than is available for CD. Thus the tendency to keep
the modulation well below peak to avoid noticable peak/HF distortion, and
then the temptation to level-compress to avoid noise or loss of audience.

I don't think its done for that reason, its done for people in cars and
other compromised listening environments..


I have been very happy with FM R3 for many years. I has delivered very
good results with a decent RX. However it seems to me that recent
comparisons lead me to the conclusions I have already reported - based
partly on a subjective assessment of the sound I now prefer, and partly
on measurements of the dynamic ranges which seem to confirm my feelings
about that preference. I will be investigating this further in the
future, though... :-)


Course this bears no resemblance to real world
conditions, but thats down to what the BBC decided to do with it before
it hits the air!..

These days, though, the makers and magazines have tended to 'solve'
this problem in the same was as they'd dealt with the similar issue of
nonlinearity in pickup cartridges for LP. Just ignore it and hope
no-one notices or cares... :-)

If you measure 'higher levels' - i.e. modulation depths up to 100
percent, and higher frequencies, and also L or R or L-R, or intermod,
the amount of distortion rises.

What depth do you mean in an FM system?..

Modulation depth. The tradition was to use 30% in magazine reviews (when
they bothered to actually measure tuners). Full mod (100%) would correspond
to 75kHz, nominally.

It have a measure up with a good exciter and couple or three tuners just
to see what is the current standard.



I suspect that. like myself, you have measured the distortion of more
than one FM RX whilst trying to align or tweak it, or just to see if it
was working as it should. it is easy enough to get THDs of the order of
0.2 percent for 300Hz 30 percent mod mono. But when you then measure
higher (signal) levels, etc, the results can be somewhat different.
Ditto for HF intermod or L+R and L-R intermod.

Haven't done that for quite somewhile but a Denon we're using as an RBR
receiver was down to .06% at 10 K at 50 K dev a while ago....

Erm... The second harmonic of 10k is 20k. What components were you
expecting to get through the MPX filtering? Or were you including intermod
with the pilot tone, etc?

Well the residual was in the noise in that instance..

If you wish to explore the effects of nonlinearity, you are better off
to use test modulation which includes a L-R component, and intermod
to probe HF effects. As with LP cartridges, the results of you do this
may well be significantly poorer than mono LF modulation at modest
levels.

You are reminding me of measurements on a tuner like the CT7000 which has
selectable IF widths. If you make bench measurements the 'wide' IF has
a lower distortion. Some of this is due to a lower ripple and dispersion
across the 200kHz band, but some is due to the acceptance of out-of-band
sidebands from a bench generator. I am afraid the BBC may be less
obliging as they may not be allowed to do this. :-)

Thus even though such tuners are indeed excellent ones, the performance
in real use is perhaps not as impressive as the bench measurements may
indicate.

I think that tuner design has come some what I recent years. One does
wonder about the sideband issue and the practical effect it has compared
to the encoding of DAB...



The above occurs even for an 'ideal' RX and is due simply due to the
finite bandwidth and the removal of the higher terms of the modulation
by the bandwidth restriction. This, and avoiding modulation clipping is
why BBC R3 have always tended to err on the side of keeping down the
modulation.

Nope, they have to keep to what the government decrees, they keep the
mod to where they have to via their encoder/processor the where they
think it ought be within that constraint.... -


75kHz modulation depth does not mean that all the modulation sidebands will
be confined to a 200kHz transmission bandwidth unless you then filter the
signal. The higher the modulation depth and frequency, the more of the
signal pattern this filtering will exclude... Even with an otherwise
perfectly linear system, the removal of these sidebands introduces
nonlinearity. This situation is complicated by the use of the subcarrier
for the stereo difference signals - thus transferring modulation up
to the band around 38kHz.

Slainte,

Jim


--
Tony Sayer

Best way to get Radio 3?
 

"Jim Lesurf" schreef in bericht
...
In article , hwh
Rather depends on the extent to which your last statement is a sweeping
generalisation. I don't find that the sound of R3 or BBC4TV on DTTV
generally have a "metallic sound". Nor do I generally find this to be the
case for R3 on DAB.

Well, at 192 kbps (including overhead) MP2 does not really sound very
natural to me.

What I do generally notice is the relative absence of level compression
and
peak/average compression. I also notice the lack of background noise.

It is either compression and perhaps some noise versus (too) low bitrate
digital audio. The best compromise must be high bitrate audio :-)
In the evenings compression on FM is not as heavy, so then it is perhaps
some noise against (too) low bitrate digital audio.

gr, hwh

Best way to get Radio 3?
 

In article , Jim Lesurf jcgl@st-
and.demon.co.uk writes
In article , tony sayer

wrote:
[big snip]

However, as with radio, the actual quality for TV will vary a lot from
station to station and item to item.


Quite..

I actually meant what do you think of the picture!!!

Depends again on the station and the item.[1] But in general on BBC1/2/4/24
I prefer the DTTV picture to the 'analog' one. I get a better picture from
DTTV than I've had for any analog TV I have ever used.

Now this is quite a significant thing. On the TV's we have here and an 8
odd year old B&O is used for main viewing, the piccy on analogue knocks
spots off the digital one. The analogue picture is far more believable
and lifelike, and I'm not talking about HF ringing effects etc to make
it sharper. Do you not notice the lack of colour graduation and
pixelation especially on rapid moving objects etc?. That effect of
appearing like a CCTV system where its going down an ISDN line?...

Slainte,

Jim

[1] Also on reception conditions. The DTTV signal level here is low, so we
suffer from II artefacts at times. As well as clicks and dropouts on DTTV
sound as this seems to use less redundancy and interleaving than DAB.

I'm not talking about those their just symptomatic of low RF power
levels.


--
Tony Sayer