FPGA Central

Well not much I suppose since we use it for Wi-Fi - but what about
commercial broadcast radio propagation? The UK has had digital radio
for some time but it has not really caught on. I heard it had problems
in moving vehicles though it is supposed to be immune to multipath.


Hardy

On Thu, 15 Jan 2009 20:41:08 -0600, Vladimir Vassilevsky
<ant[email protected]> wrote:

>
>
>Eric Jacobsen wrote:
>> On Thu, 15 Jan 2009 13:54:10 -0800 (PST), HardySpicer
>> <[email protected]> wrote:
>>
>>
>>>Well not much I suppose since we use it for Wi-Fi - but what about
>>>commercial broadcast radio propagation? The UK has had digital radio
>>>for some time but it has not really caught on. I heard it had problems
>>>in moving vehicles though it is supposed to be immune to multipath.
>>>
>>
>> There's more to a system than just the modulation method, so it's hard
>> to pin down where the problem was if something fails.
>>
>> That being said, multipath and mobility are two different things.
>> Often a system that can handle severe multipath can't do it well if
>> the channel changes rapidly, which it does in a moving vehicle.
>> Handling vehicular speeds in multipath is a pretty difficult
>> proposition for wideband signals.
>
>A mobile receiver has a kind of spatial diversity because it is moving.
>So, if the channel can handle error bursts of up to 10% of the total
>traffic, then the multipath effects are efficiently averaged out. The
>modulation scheme of GSM is designed keeping those effects in mind;
>their parameters are actually optimal or near optimal for urban environment.

GSM has a relatively narrow bandwidth compared to what a lot of folks
want to do (and compared to how OFDM is typically applied). Just
having a narrow bandwidth helps quite a bit in surviving mobility.

Take a GSM signal and crank the symbol rate up to 5-15MHz and it
doesn't work so well any more.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php

Eric Jacobsen wrote:

> On Thu, 15 Jan 2009 20:41:08 -0600, Vladimir Vassilevsky
> <[email protected]> wrote:
>
>
>>
>>Eric Jacobsen wrote:
>>
>>>On Thu, 15 Jan 2009 13:54:10 -0800 (PST), HardySpicer
>>><[email protected]> wrote:
>>>
>>>
>>>
>>>>Well not much I suppose since we use it for Wi-Fi - but what about
>>>>commercial broadcast radio propagation? The UK has had digital radio
>>>>for some time but it has not really caught on. I heard it had problems
>>>>in moving vehicles though it is supposed to be immune to multipath.
>>>>
>>>
>>>There's more to a system than just the modulation method, so it's hard
>>>to pin down where the problem was if something fails.
>>>
>>>That being said, multipath and mobility are two different things.
>>>Often a system that can handle severe multipath can't do it well if
>>>the channel changes rapidly, which it does in a moving vehicle.
>>>Handling vehicular speeds in multipath is a pretty difficult
>>>proposition for wideband signals.
>>
>>A mobile receiver has a kind of spatial diversity because it is moving.
>>So, if the channel can handle error bursts of up to 10% of the total
>>traffic, then the multipath effects are efficiently averaged out. The
>>modulation scheme of GSM is designed keeping those effects in mind;
>>their parameters are actually optimal or near optimal for urban environment.
>
>
> GSM has a relatively narrow bandwidth compared to what a lot of folks
> want to do (and compared to how OFDM is typically applied). Just
> having a narrow bandwidth helps quite a bit in surviving mobility.
>
> Take a GSM signal and crank the symbol rate up to 5-15MHz and it
> doesn't work so well any more.


The DAB physical layer doesn't make much sense. First, the OFDM will
require the power backoff. Simulcast is not a good idea either. Wideband
processing in the receiver is another bad one. Mobility is the huge
problem. Looks like the system designed by graduate students and their
professors.

Why couldn't they chose a narrowband scheme similar to that of GSM? That
would allow for the gain ~ several dB over analog FM, frequency reuse
1:3 pattern, simple and efficient receivers, keeping the existent
frequency allocation plans. Coverage of the large areas better achieved
by automatic handover rather then by multicasting.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On Sat, 17 Jan 2009 11:14:41 -0600, Vladimir Vassilevsky
<[email protected]> wrote:

>
>
>Eric Jacobsen wrote:
>
>> On Thu, 15 Jan 2009 20:41:08 -0600, Vladimir Vassilevsky
>> <[email protected]> wrote:
>>
>>
>>>
>>>Eric Jacobsen wrote:
>>>
>>>>On Thu, 15 Jan 2009 13:54:10 -0800 (PST), HardySpicer
>>>><[email protected]> wrote:
>>>>
>>>>
>>>>
>>>>>Well not much I suppose since we use it for Wi-Fi - but what about
>>>>>commercial broadcast radio propagation? The UK has had digital radio
>>>>>for some time but it has not really caught on. I heard it had problems
>>>>>in moving vehicles though it is supposed to be immune to multipath.
>>>>>
>>>>
>>>>There's more to a system than just the modulation method, so it's hard
>>>>to pin down where the problem was if something fails.
>>>>
>>>>That being said, multipath and mobility are two different things.
>>>>Often a system that can handle severe multipath can't do it well if
>>>>the channel changes rapidly, which it does in a moving vehicle.
>>>>Handling vehicular speeds in multipath is a pretty difficult
>>>>proposition for wideband signals.
>>>
>>>A mobile receiver has a kind of spatial diversity because it is moving.
>>>So, if the channel can handle error bursts of up to 10% of the total
>>>traffic, then the multipath effects are efficiently averaged out. The
>>>modulation scheme of GSM is designed keeping those effects in mind;
>>>their parameters are actually optimal or near optimal for urban environment.
>>
>>
>> GSM has a relatively narrow bandwidth compared to what a lot of folks
>> want to do (and compared to how OFDM is typically applied). Just
>> having a narrow bandwidth helps quite a bit in surviving mobility.
>>
>> Take a GSM signal and crank the symbol rate up to 5-15MHz and it
>> doesn't work so well any more.
>
>
>The DAB physical layer doesn't make much sense. First, the OFDM will
>require the power backoff. Simulcast is not a good idea either. Wideband
> processing in the receiver is another bad one. Mobility is the huge
>problem. Looks like the system designed by graduate students and their
>professors.
>
>Why couldn't they chose a narrowband scheme similar to that of GSM? That
>would allow for the gain ~ several dB over analog FM, frequency reuse
>1:3 pattern, simple and efficient receivers, keeping the existent
>frequency allocation plans. Coverage of the large areas better achieved
>by automatic handover rather then by multicasting.
>
>
>Vladimir Vassilevsky
>DSP and Mixed Signal Design Consultant
>http://www.abvolt.com

Personally I think audio broadcast radio should stay analog. You're
not going to beat it for simplicity and low power consumption in the
receiver, which is something that's desirable for critical
infrastructure.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php

On Jan 18, 8:30*am, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
> On Sat, 17 Jan 2009 11:14:41 -0600, Vladimir Vassilevsky
>
>
>
> <antispam_bo...@hotmail.com> wrote:
>
> >Eric Jacobsen wrote:
>
> >> On Thu, 15 Jan 2009 20:41:08 -0600, Vladimir Vassilevsky
> >> <antispam_bo...@hotmail.com> wrote:
>
> >>>Eric Jacobsen wrote:
>
> >>>>On Thu, 15 Jan 2009 13:54:10 -0800 (PST), HardySpicer
> >>>><gyansor...@gmail.com> wrote:
>
> >>>>>Well not much I suppose since we use it for Wi-Fi - but what about
> >>>>>commercial broadcast radio propagation? The UK has had digital radio
> >>>>>for some time but it has not really caught on. I heard it had problems
> >>>>>in moving vehicles though it is supposed to be immune to multipath.
>
> >>>>There's more to a system than just the modulation method, so it's hard
> >>>>to pin down where the problem was if something fails.
>
> >>>>That being said, multipath and mobility are two different things.
> >>>>Often a system that can handle severe multipath can't do it well if
> >>>>the channel changes rapidly, which it does in a moving vehicle.
> >>>>Handling vehicular speeds in multipath is a pretty difficult
> >>>>proposition for wideband signals.
>
> >>>A mobile receiver has a kind of spatial diversity because it is moving..
> >>>So, if the channel can handle error bursts of up to 10% of the total
> >>>traffic, then the multipath effects are efficiently averaged out. The
> >>>modulation scheme of GSM is designed keeping those effects in mind;
> >>>their parameters are actually optimal or near optimal for urban environment.
>
> >> GSM has a relatively narrow bandwidth compared to what a lot of folks
> >> want to do (and compared to how OFDM is typically applied). * *Just
> >> having a narrow bandwidth helps quite a bit in surviving mobility.
>
> >> Take a GSM signal and crank the symbol rate up to 5-15MHz and it
> >> doesn't work so well any more.
>
> >The DAB physical layer doesn't make much sense. First, the OFDM will
> >require the power backoff. Simulcast is not a good idea either. Wideband
> > *processing in the receiver is another bad one. Mobility is the huge
> >problem. Looks like the system designed by graduate students and their
> >professors.
>
> >Why couldn't they chose a narrowband scheme similar to that of GSM? That
> >would allow for the gain ~ several dB over analog FM, frequency reuse
> >1:3 pattern, simple and efficient receivers, keeping the existent
> >frequency allocation plans. Coverage of the large areas better achieved
> >by automatic handover rather then by multicasting.
>
> >Vladimir Vassilevsky
> >DSP and Mixed Signal Design Consultant
> >http://www.abvolt.com
>
> Personally I think audio broadcast radio should stay analog. * You're
> not going to beat it for simplicity and low power consumption in the
> receiver, which is something that's desirable for critical
> infrastructure.

Cellular benefited greatly from going digital.
TV benefited greatly from going digital.
Why is audio broadcast radio such a special case?

I suspect that while the EU people who devised the TV standard were
pretty smart about it, the people doing DAB just messed up. Though
I've never looked at its details, it has some blatantly dumb
decisions. The codec was a stupid choice - choosing something that
already looked old and clunky at the launch date was hardly setting it
up for a long and happy future. It imposes a higher than necessary bit
rate on the radio channel. The way they do error handling must have
seemed clever and tricky to someone, but they obviously hadn't though
it through. It actually produces the artefacts people complain most
heavily about.

Regards,
Steve

Eric Jacobsen wrote:

> Personally I think audio broadcast radio should stay analog. You're
> not going to beat it for simplicity and low power consumption in the
> receiver, which is something that's desirable for critical
> infrastructure.

With analog, you can't sell the content. That's the main push for going
digital :-) Besides, there is no easy way to achieve the wide coverage.
Also, the incredible complication of the system is one of the ways for
keeping the small players away from the table.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On Sat, 17 Jan 2009 19:42:31 -0800 (PST), [email protected] wrote:

>On Jan 18, 8:30*am, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>> On Sat, 17 Jan 2009 11:14:41 -0600, Vladimir Vassilevsky
>>
>>
>>
>> <antispam_bo...@hotmail.com> wrote:
>>
>> >Eric Jacobsen wrote:
>>
>> >> On Thu, 15 Jan 2009 20:41:08 -0600, Vladimir Vassilevsky
>> >> <antispam_bo...@hotmail.com> wrote:
>>
>> >>>Eric Jacobsen wrote:
>>
>> >>>>On Thu, 15 Jan 2009 13:54:10 -0800 (PST), HardySpicer
>> >>>><gyansor...@gmail.com> wrote:
>>
>> >>>>>Well not much I suppose since we use it for Wi-Fi - but what about
>> >>>>>commercial broadcast radio propagation? The UK has had digital radio
>> >>>>>for some time but it has not really caught on. I heard it had problems
>> >>>>>in moving vehicles though it is supposed to be immune to multipath.
>>
>> >>>>There's more to a system than just the modulation method, so it's hard
>> >>>>to pin down where the problem was if something fails.
>>
>> >>>>That being said, multipath and mobility are two different things.
>> >>>>Often a system that can handle severe multipath can't do it well if
>> >>>>the channel changes rapidly, which it does in a moving vehicle.
>> >>>>Handling vehicular speeds in multipath is a pretty difficult
>> >>>>proposition for wideband signals.
>>
>> >>>A mobile receiver has a kind of spatial diversity because it is moving.
>> >>>So, if the channel can handle error bursts of up to 10% of the total
>> >>>traffic, then the multipath effects are efficiently averaged out. The
>> >>>modulation scheme of GSM is designed keeping those effects in mind;
>> >>>their parameters are actually optimal or near optimal for urban environment.
>>
>> >> GSM has a relatively narrow bandwidth compared to what a lot of folks
>> >> want to do (and compared to how OFDM is typically applied). * *Just
>> >> having a narrow bandwidth helps quite a bit in surviving mobility.
>>
>> >> Take a GSM signal and crank the symbol rate up to 5-15MHz and it
>> >> doesn't work so well any more.
>>
>> >The DAB physical layer doesn't make much sense. First, the OFDM will
>> >require the power backoff. Simulcast is not a good idea either. Wideband
>> > *processing in the receiver is another bad one. Mobility is the huge
>> >problem. Looks like the system designed by graduate students and their
>> >professors.
>>
>> >Why couldn't they chose a narrowband scheme similar to that of GSM? That
>> >would allow for the gain ~ several dB over analog FM, frequency reuse
>> >1:3 pattern, simple and efficient receivers, keeping the existent
>> >frequency allocation plans. Coverage of the large areas better achieved
>> >by automatic handover rather then by multicasting.
>>
>> >Vladimir Vassilevsky
>> >DSP and Mixed Signal Design Consultant
>> >http://www.abvolt.com
>>
>> Personally I think audio broadcast radio should stay analog. * You're
>> not going to beat it for simplicity and low power consumption in the
>> receiver, which is something that's desirable for critical
>> infrastructure.
>
>Cellular benefited greatly from going digital.
>TV benefited greatly from going digital.
>Why is audio broadcast radio such a special case?

Because the usage model is different than the others, as well as the
function. A lot of radio listeners are using very small,
battery-powered devices for which extreme battery life is very useful.
Keeping contact with the outside world while on a long backpack trip
or while hunkered down in a shelter (without power) waiting for big
storm cells (or tornados or a flood or whatever) to pass can be a
life-critical function. That's just a lot harder to do at low cost
with a long battery life with a digital receiver than it is with an
analog equivalent.

The effects of the full transition to digital for TV isn't yet known,
so I'm not sure just yet that I'd conclude it's benefitted from the
transition to digital. I suspect a lot of rural receivers are going
to lose coverage (I'm just about willing to bet our cabin will have no
TV after the transition, with the exception of the remaining analog
translators). The same issue holds true with radio when considering
the safety infrastructure function: range will likely be reduce with
digital as compared to analog for similar transmit power.

I think Vladimir's right that the real motivation is the additional
services that can be done with digital, e.g., station ID, song ID,
etc., etc. There'll be the possibility of adding services with
additional revenue streams (small display ads, whatever) that are
probably the main motivation. The tradeoff of reduced range and
reducing the scope of users (via requiring more expensive,
shorter-lived receivers) is yet to be experienced. I hope I'm wrong
and everything comes up roses, but I suspect not.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php

On Sun, 18 Jan 2009 09:37:48 -0600, Vladimir Vassilevsky
<[email protected]> wrote:

>
>
>Eric Jacobsen wrote:
>
>> Personally I think audio broadcast radio should stay analog. You're
>> not going to beat it for simplicity and low power consumption in the
>> receiver, which is something that's desirable for critical
>> infrastructure.

Modern digital circuitry for decoding the signal takes less power
than an audio amplifier to drive an earbud, so I don't see that part
as a valid argument, unless you're comparing digital to an (AM only)
crystal receiver.

On the other hand, the digital compression (psychoacoustic, just
like mp3) is lossy and has artifacts that are audible and annoying to
a significant number of people. Going digital just trades off some
types of classic analog distortion for Bold, New Distortions No Man
Has Ever Heard Before.

At least CD's use a straight, lossless PCM format, and that can be
losslessly compressed by about 2 to 1 as is done on DVD (or it CAN be
done, DVD has many audio and video formats, and some, probably the
best quality, are rarely used).

>
>With analog, you can't sell the content. That's the main push for going
>digital :-) Besides, there is no easy way to achieve the wide coverage.

What do you mean by not achieving wide coverage?

>Also, the incredible complication of the system is one of the ways for
>keeping the small players away from the table.

And of course those are advantages for large manufacturers, not
consumers.

>
>
>Vladimir Vassilevsky
>DSP and Mixed Signal Design Consultant
>http://www.abvolt.com

Ben Bradley wrote:


> Modern digital circuitry for decoding the signal takes less power
> than an audio amplifier to drive an earbud,

)))))

Even the simple MP3 decoder on the specialised chip drains about 10
times more power then the headphone amplifier. The OFDM receiver for DAB
is likely to drain more.


> On the other hand, the digital compression (psychoacoustic, just
> like mp3) is lossy and has artifacts that are audible and annoying to
> a significant number of people.

This is the matter of bit rate. MP3 at 192kb sounds very decent, and I
doubt if one can distinguish the original CD from MP3 at 256k.

> Going digital just trades off some
> types of classic analog distortion for Bold, New Distortions No Man
> Has Ever Heard Before.

Aha. People were quite happy about Edison's phonograph.

>>With analog, you can't sell the content. That's the main push for going
>>digital :-) Besides, there is no easy way to achieve the wide coverage.
>
> What do you mean by not achieving wide coverage?

I meant moving from one zone of reception to another. With the analog
radio, you have to switch the channels. With digital, it can be done
seemlessly.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On 18 Jan, 19:18, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
wrote:
> Ben Bradley wrote:

> > * *What do you mean by not achieving wide coverage?
>
> I meant moving from one zone of reception to another. With the analog
> radio, you have to switch the channels. With digital, it can be done
> seemlessly.

I've used RDS FM radio for more than ten years. Very useful in cars.
Once you select a station the reciever sticks with that station,
seamlessly tuning on to the best transmitter available, until you
turn it off, select a different station, or leave the area covered
by the local station (*not* transmitter). If you choose one of the
nation-wide stations you can drive all around the country listening
to it without ever touching the reciever.

Rune

Rune Allnor wrote:

> On 18 Jan, 19:18, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
> wrote:
>
>>I meant moving from one zone of reception to another. With the analog
>>radio, you have to switch the channels. With digital, it can be done
>>seemlessly.
>
>
> I've used RDS FM radio for more than ten years. Very useful in cars.

I am aware of RDS/RBDS and I've been involved with car audio for about
the same time. Never seen that RDS thing working or anyone who actually
used it. Satellite radio broadcasts like "Sirius" or "XM" are very popular.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On 18 Jan, 21:45, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
wrote:
> Rune Allnor wrote:
> > On 18 Jan, 19:18, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
> > wrote:
>
> >>I meant moving from one zone of reception to another. With the analog
> >>radio, you have to switch the channels. With digital, it can be done
> >>seemlessly.
>
> > I've used RDS FM radio for more than ten years. Very useful in cars.
>
> I am aware of RDS/RBDS and I've been involved with car audio for about
> the same time. Never seen that RDS thing working or anyone who actually
> used it. Satellite radio broadcasts like "Sirius" or "XM" are very popular.

We discussed sattelite radio here a couple of years ago, and as I
recall,
we found it's a north American thing. Has something to do with cost
per
audience and covered area to do. In Europe (and maybe elsewhere),
where
the audience and/or geographical area to be covered is smaller, RDS
FM
is big.

Rune

On Sun, 18 Jan 2009 12:56:04 -0500, Ben Bradley
<[email protected]> wrote:

>On Sun, 18 Jan 2009 09:37:48 -0600, Vladimir Vassilevsky
><[email protected]> wrote:
>
>>
>>
>>Eric Jacobsen wrote:
>>
>>> Personally I think audio broadcast radio should stay analog. You're
>>> not going to beat it for simplicity and low power consumption in the
>>> receiver, which is something that's desirable for critical
>>> infrastructure.
>
> Modern digital circuitry for decoding the signal takes less power
>than an audio amplifier to drive an earbud, so I don't see that part
>as a valid argument, unless you're comparing digital to an (AM only)
>crystal receiver.

You have to have the amp for the earbud or speakers in either case. In
the digital case you need a digital demodulator, including a FEC
decoder and a decompressor. In the analog case you need a handful of
transistors (even for FM).

It's very hard to beat a modern analog FM receiver for cost and power
consumption when compared to anything digital.

> On the other hand, the digital compression (psychoacoustic, just
>like mp3) is lossy and has artifacts that are audible and annoying to
>a significant number of people. Going digital just trades off some
>types of classic analog distortion for Bold, New Distortions No Man
>Has Ever Heard Before.

Right, so I don't think the audio quality is a huge argument, although
I do think it's valid. Even a high SNR FM station doesn't sound that
great compared to a good digital stream. So it's a tradeoff, I just
don't think the tradeoff is a slam-dunk in favor of digital, or even
close.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php

Eric Jacobsen <[email protected]> wrote:

>Right, so I don't think the audio quality is a huge argument, although
>I do think it's valid. Even a high SNR FM station doesn't sound that
>great compared to a good digital stream.

I'm wondering how universally true this is. An FM station doesn't
sound as good as a high-quality digital stream (CD or SACD quality),
but it sounds better than a 128 kbps mp3 stream. (Speaking
in rough terms.) They're probably roughly equivalent at intermediate
bit rates for AAC or AC3.

I am in the broadcast range of some FM stations that also stream
live, notably KALX, and the broadcast signal usually sounds
somewhat better than even the fastest net-feed.

Steve

On Jan 18, 8:04*pm, spop...@speedymail.org (Steve Pope) wrote:
> Eric Jacobsen *<eric.jacob...@delete.ieee.org> wrote:
>
> >Right, so I don't think the audio quality is a huge argument, although
> >I do think it's valid. * Even a high SNR FM station doesn't sound that
> >great compared to a good digital stream. *
>
> I'm wondering how universally true this is. *An FM station doesn't
> sound as good as a high-quality digital stream (CD or SACD quality),
> but it sounds better than a 128 kbps mp3 stream. *(Speaking
> in rough terms.) *They're probably roughly equivalent at intermediate
> bit rates for AAC or AC3.
>
> I am in the broadcast range of some FM stations that also stream
> live, notably KALX, and the broadcast signal usually sounds
> somewhat better than even the fastest net-feed.
>
> Steve

the reason many FM stations sound bad has nothing to do with
limitations of the analog FM system, but rather with often extreame
dynamic range compression applied to the audio to make it sound LOUD.
There is a belief in the broadcast industry that people will tune into
the loudest signal on the dial or that the louder signal can carry
further. There was some truth to this in the old days of AM with
static but is is no longer true for FM today. But many radio stations
still engage in the loudness war.
Mark

On Mon, 19 Jan 2009 01:04:39 +0000 (UTC), [email protected]
(Steve Pope) wrote:

>Eric Jacobsen <[email protected]> wrote:
>
>>Right, so I don't think the audio quality is a huge argument, although
>>I do think it's valid. Even a high SNR FM station doesn't sound that
>>great compared to a good digital stream.
>
>I'm wondering how universally true this is. An FM station doesn't
>sound as good as a high-quality digital stream (CD or SACD quality),
>but it sounds better than a 128 kbps mp3 stream. (Speaking
>in rough terms.) They're probably roughly equivalent at intermediate
>bit rates for AAC or AC3.
>
>I am in the broadcast range of some FM stations that also stream
>live, notably KALX, and the broadcast signal usually sounds
>somewhat better than even the fastest net-feed.
>
>Steve

Yes, I guess the bottom line is that the audio quality doesn't seem to
be a clear argument for ditching analog FM and going all-digital.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org

Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php

>
>
>Rune Allnor wrote:
>
>> On 18 Jan, 19:18, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
>> wrote:
>>
>>>I meant moving from one zone of reception to another. With the analog
>>>radio, you have to switch the channels. With digital, it can be done
>>>seemlessly.
>>
>>
>> I've used RDS FM radio for more than ten years. Very useful in cars.
>
>I am aware of RDS/RBDS and I've been involved with car audio for about
>the same time. Never seen that RDS thing working or anyone who actually
>used it. Satellite radio broadcasts like "Sirius" or "XM" are ver
popular.

Sirius and XM are US only things. Outside the US RDS FM radio is extremel
popular in cars, and works well. Where have you seen it not work?

RDS has even been used to broadcast paging messages to pocket pagers
though the pagers were a bit clumsy compared to a POCSAG or FLEX pager. RD
doesn't provide for the same level of battery savings as a purpose designe
paging code.

Regards,
Steve

On 18 Jan, 23:44, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
> On Sun, 18 Jan 2009 12:56:04 -0500, Ben Bradley

> > * On the other hand, the digital compression (psychoacoustic, just
> >like mp3) is lossy and has artifacts that are audible and annoying to
> >a significant number of people. Going digital just trades off some
> >types of classic analog distortion for Bold, New Distortions No Man
> >Has Ever Heard Before.
>
> Right, so I don't think the audio quality is a huge argument, although
> I do think it's valid. * Even a high SNR FM station doesn't sound that
> great compared to a good digital stream. *So it's a tradeoff, I just
> don't think the tradeoff is a slam-dunk in favor of digital, or even
> close.

The arguments I remember hearing in favour of digital, was based
on the (possibly unique) geography and demography of Norway: We
are very few people (approacing 5 million), and the average
population density is very sparse ( < 1 person ber sq. km).
So outside population centra there are just a few radio transitters,
which are pushed to the limit to save costs. Add in the mountanous
topography, where you get all sorts of shadows or multipaths,
and it used to be a mess to obtain good analog radio coverage.

The arguments in favour of digital radio was that it could achieve
better signal quality with weaker signals and in multipath
situations. It used to make a lot of sense, but something
has changed over the past couple of decades. It might be that
RDS FM has masked the problems of finding good signals
while on the road, or the recievers have become better.
Whatever the reason, I remember FM radio being far more itchy
in the past than it is now.

Rune