On 12/16/2009 10:12 AM, Mark wrote:
> On Dec 15, 9:14 pm, Eric Jacobsen<eric.jacob...@ieee.org>  wrote:
>> On 12/15/2009 6:45 PM, Mark wrote:
>>
>>
>>
>>
>>
>>> snip
>>>> When it comes down to analog voice and the ability of a human to pick
>>>> out information in a noisy or weak signal, though, it becomes too
>>>> subjective to compare.  The brain does have a really good decoder for
>>>> human speech (usually), and that may help a link work in some places
>>>> where a digital system might lose lock.
>>>> But for transporting bits, I don't there's much contest.
>>> yes, I'm talking about transmitting voice info, not data.. over a
>>> dedicated public safety channel..
>>> If you were trapped in a burning building and your life depended on
>>> contacting  your backup 25 feet away, would you want a simple analog
>>> FM radio or a complex encrypted digital device?
>>> Mark
>> The answer would depend on a lot more than just that difference.   I'd
>> want the one that got the most reliable signal, and in many (but not
>> all) cases that's the digital device.   With proper engineering it's
>> pretty much nearly always the digital device.
>>
>>
> my point is that the Eb/No performace of the modulation is only a very
> small factor in the overall reliability of getting the message through
>
> I'd say the number of SMT solder joints in the hardware is a more
> important factor...
>
> Mark

There are tons of factors, obviously.  I've not personally seen solder 
reliability problems, or even part count, dominating hardware 
reliability for well-engineered systems for a long time.  Consumer cell 
phones have a pretty high degree of integration and seem to have pretty 
reliable electronic hardware on the whole.

Simpler is certainly more reliable in general, but manufacturing 
technology these days is capable of putting those factors in the noise 
for even highly integrated systems.  A bad part selection or a rogue 
vendor (e.g., bad caps) seems more likely, and that can happen to analog 
as well as digital systems.

-- 
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com

On Dec 15, 9:14&#4294967295;pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
> On 12/15/2009 6:45 PM, Mark wrote:
>
>
>
>
>
> > snip
> >> When it comes down to analog voice and the ability of a human to pick
> >> out information in a noisy or weak signal, though, it becomes too
> >> subjective to compare. &#4294967295;The brain does have a really good decoder for
> >> human speech (usually), and that may help a link work in some places
> >> where a digital system might lose lock.
>
> >> But for transporting bits, I don't there's much contest.
>
> > yes, I'm talking about transmitting voice info, not data.. over a
> > dedicated public safety channel..
>
> > If you were trapped in a burning building and your life depended on
> > contacting &#4294967295;your backup 25 feet away, would you want a simple analog
> > FM radio or a complex encrypted digital device?
>
> > Mark
>
> The answer would depend on a lot more than just that difference. &#4294967295; I'd
> want the one that got the most reliable signal, and in many (but not
> all) cases that's the digital device. &#4294967295; With proper engineering it's
> pretty much nearly always the digital device.
>
>
my point is that the Eb/No performace of the modulation is only a very
small factor in the overall reliability of getting the message through

I'd say the number of SMT solder joints in the hardware is a more
important factor...

Mark

On 12/15/2009 6:45 PM, Mark wrote:
> snip
>> When it comes down to analog voice and the ability of a human to pick
>> out information in a noisy or weak signal, though, it becomes too
>> subjective to compare.  The brain does have a really good decoder for
>> human speech (usually), and that may help a link work in some places
>> where a digital system might lose lock.
>>
>> But for transporting bits, I don't there's much contest.
>>
>>
> yes, I'm talking about transmitting voice info, not data.. over a
> dedicated public safety channel..
>
> If you were trapped in a burning building and your life depended on
> contacting  your backup 25 feet away, would you want a simple analog
> FM radio or a complex encrypted digital device?
>
> Mark

The answer would depend on a lot more than just that difference.   I'd 
want the one that got the most reliable signal, and in many (but not 
all) cases that's the digital device.   With proper engineering it's 
pretty much nearly always the digital device.

-- 
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com

snip
>
> When it comes down to analog voice and the ability of a human to pick
> out information in a noisy or weak signal, though, it becomes too
> subjective to compare. �The brain does have a really good decoder for
> human speech (usually), and that may help a link work in some places
> where a digital system might lose lock.
>
> But for transporting bits, I don't there's much contest.
>
>
yes, I'm talking about transmitting voice info, not data.. over a
dedicated public safety channel..

If you were trapped in a burning building and your life depended on
contacting  your backup 25 feet away, would you want a simple analog
FM radio or a complex encrypted digital device?

Mark

>On 12/12/2009 1:49 PM, Steve Pope wrote:
>> Eric Jacobsen<eric.jacobsen@ieee.org>  wrote:
>>
>>> On 12/12/2009 11:01 AM, Steve Pope wrote:
>>
>>>> Another artifact digital broadcast TV can exhibit is a long lag
>>>> between picture and audio -- sometimes five to ten seconds.
>>
>>> Having had to work with broadcast standards for quite a while, this is
a
>>> total travesty and a complete failing of the broadcast engineering
>>> groups that worked on this.  It is comical how badly it's been done,
>>> where extreme constraints on clock stability had to be maintained
>>> throughout the entire chain (at great expense) for no apparent reason
>>> (e.g., SMPTE-310), and still there's no reliable mechanism to assure
>>> registration between the video and audio.
>>
>> Interesting; I would have thought the artifact had more to do
>> with receiver implementations than the ATSC standard itself.
>> Or that at least, a clever enough receiver could mitigate this
>> problem.
>>
>> Steve
>
>It's not ATSC-specific, as the ATSC specs (like DVB-T) just handle the 
>air interface.  Cable systems have the same problem, and they're not 
>ATSC (for the most part). The transport is usually MPEG, and the video 
>and audio packets are independent.   There are mechanisms to synch them 
>up, clearly, but the problem can be anywhere in the stream, or an 
>accumulation of problems at various places in the stream.   The receiver

>can only do so much.

Its interesting how vehemently some people extol the separation of audio
and video as a huge virtue. I wonder if the extremists would like to
separate the left and right channels of a stereo signal, so they also need
to be synced up downstream. :-)

Steve

On 12/12/2009 1:49 PM, Steve Pope wrote:
> Eric Jacobsen<eric.jacobsen@ieee.org>  wrote:
>
>> On 12/12/2009 11:01 AM, Steve Pope wrote:
>
>>> Another artifact digital broadcast TV can exhibit is a long lag
>>> between picture and audio -- sometimes five to ten seconds.
>
>> Having had to work with broadcast standards for quite a while, this is a
>> total travesty and a complete failing of the broadcast engineering
>> groups that worked on this.  It is comical how badly it's been done,
>> where extreme constraints on clock stability had to be maintained
>> throughout the entire chain (at great expense) for no apparent reason
>> (e.g., SMPTE-310), and still there's no reliable mechanism to assure
>> registration between the video and audio.
>
> Interesting; I would have thought the artifact had more to do
> with receiver implementations than the ATSC standard itself.
> Or that at least, a clever enough receiver could mitigate this
> problem.
>
> Steve

It's not ATSC-specific, as the ATSC specs (like DVB-T) just handle the 
air interface.  Cable systems have the same problem, and they're not 
ATSC (for the most part). The transport is usually MPEG, and the video 
and audio packets are independent.   There are mechanisms to synch them 
up, clearly, but the problem can be anywhere in the stream, or an 
accumulation of problems at various places in the stream.   The receiver 
can only do so much.

-- 
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com

Eric Jacobsen  <eric.jacobsen@ieee.org> wrote:

>On 12/12/2009 11:01 AM, Steve Pope wrote:

>> Another artifact digital broadcast TV can exhibit is a long lag
>> between picture and audio -- sometimes five to ten seconds.

>Having had to work with broadcast standards for quite a while, this is a 
>total travesty and a complete failing of the broadcast engineering 
>groups that worked on this.  It is comical how badly it's been done, 
>where extreme constraints on clock stability had to be maintained 
>throughout the entire chain (at great expense) for no apparent reason 
>(e.g., SMPTE-310), and still there's no reliable mechanism to assure 
>registration between the video and audio.

Interesting; I would have thought the artifact had more to do
with receiver implementations than the ATSC standard itself.
Or that at least, a clever enough receiver could mitigate this
problem.

Steve

On 12/12/2009 11:01 AM, Steve Pope wrote:
> Jerry Avins<jya@ieee.org>  wrote:
>
>> Digital comms may be too good. There's no gradual degradation; they're
>> either perfect or they quit, usually without warning. Low SNR digital TV
>> breaks up or freezes where analog TV would be full of snow but usable.
>
> Another artifact digital broadcast TV can exhibit is a long lag
> between picture and audio -- sometimes five to ten seconds.
>
> Steve

Having had to work with broadcast standards for quite a while, this is a 
total travesty and a complete failing of the broadcast engineering 
groups that worked on this.  It is comical how badly it's been done, 
where extreme constraints on clock stability had to be maintained 
throughout the entire chain (at great expense) for no apparent reason 
(e.g., SMPTE-310), and still there's no reliable mechanism to assure 
registration between the video and audio.

Total and utter crap.   I'm shocked people put up with it.

-- 
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com

On 12/12/2009 10:58 AM, Jerry Avins wrote:
> Eric Jacobsen wrote:
>> On 12/11/2009 10:59 PM, Vladimir Vassilevsky wrote:
>>>
>>>
>>> Eric Jacobsen wrote:
>>>
>>>> On 12/11/2009 7:17 PM, Mark wrote:
>>>>
>>>>>> BTW, AD makes DDS chips which can generate linear frequency ramps by
>>>>>> themselves. I often have a sad feeling that with the technology of
>>>>>> today
>>>>>> it is possible to do a lot of things finally in the right way; like,
>>>>>> say, optimal FM receivers. However, modern technologies are mainly
>>>>>> used
>>>>>> to breed idiotic monstrous solutions, like 8-VSB, Windows Vista, LTE,
>>>>>> DAB, etc. which are nothing but a waste of resources.
>>>>>>
>>>>>> Vladimir Vassilevsky
>>>>>
>>>>>
>>>>> This is so true in the 2 way radio field. With todays IC's we could
>>>>> make really reliable, small, low power, agile FM transcievers...but
>>>>> no instead the industry has adopted digital modulation and the result
>>>>> is bigger heavier much more complex radios that provide less reliable
>>>>> communications. Its all about the $
>>>>>
>>>>> Mark
>>>>
>>>>
>>>> I wouldn't go that far. There's a difference between understanding
>>>> different modulations and their capabilities and building some
>>>> monstrosity out of them. How does one transmit digital data without
>>>> using a digital modulation? PSK and QAM have better capacities than
>>>> comparable FSK modulations, or did you mean something different?
>>>
>>> I think it is about DMR vs conventional analog FM 2-way radio. Mark has
>>> a point. BTW, trivial 800MHz analog cordless phone works better and has
>>> several times of battery life compared to those spread spectrum things.
>>>
>>> Vladimir Vassilevsky
>>> DSP and Mixed Signal Design Consultant
>>> http://www.abvolt.com
>>
>> There's no question the electronics required to do analog FM are far
>> simpler and more power efficient than most digital systems. As far as
>> squeezing the most performance out of the signal for the transmitted
>> power level, though, you'll always be better off with a
>> well-engineered digital system than the most efficient FM system.
>>
>> When it comes down to analog voice and the ability of a human to pick
>> out information in a noisy or weak signal, though, it becomes too
>> subjective to compare. The brain does have a really good decoder for
>> human speech (usually), and that may help a link work in some places
>> where a digital system might lose lock.
>>
>> But for transporting bits, I don't there's much contest.
>
> Digital comms may be too good. There's no gradual degradation; they're
> either perfect or they quit, usually without warning. Low SNR digital TV
> breaks up or freezes where analog TV would be full of snow but usable.
> IIRC,at least one urban fire department went back to analog walkie-talkies.
>
> Jerry

Yeah, it's hard to beat a genuine wet brain for voice or image decoding. 
  The "cliff effect" can be mitigated by channel adaptation, and I think 
eventually that'll take over in bi-directional channels that can support 
it.   Clearly broadcast can't do that, but things like walkie-talkies 
should be able to take advantage of it without too much trouble.

That does, of course, assume that bandwidth is also a constraint.   If 
there's enough bandwidth available to always support the most robust 
modulation at a low code rate, then the limit is the limit and the 
"cliff effect" is harder to avoid.

-- 
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com

Eric Jacobsen wrote:
> On 12/11/2009 10:59 PM, Vladimir Vassilevsky wrote:
> 
>>
>>
>> Eric Jacobsen wrote:
>>
>>> On 12/11/2009 7:17 PM, Mark wrote:
>>>
>>>>> BTW, AD makes DDS chips which can generate linear frequency ramps by
>>>>> themselves. I often have a sad feeling that with the technology of
>>>>> today
>>>>> it is possible to do a lot of things finally in the right way; like,
>>>>> say, optimal FM receivers. However, modern technologies are mainly 
>>>>> used
>>>>> to breed idiotic monstrous solutions, like 8-VSB, Windows Vista, LTE,
>>>>> DAB, etc. which are nothing but a waste of resources.
>>>>>
>>>>> Vladimir Vassilevsky
>>>>
>>>>
>>>>
>>>> This is so true in the 2 way radio field. With todays IC's we could
>>>> make really reliable, small, low power, agile FM transcievers...but
>>>> no instead the industry has adopted digital modulation and the result
>>>> is bigger heavier much more complex radios that provide less reliable
>>>> communications. Its all about the $
>>>>
>>>> Mark
>>>
>>>
>>>
>>> I wouldn't go that far. There's a difference between understanding
>>> different modulations and their capabilities and building some
>>> monstrosity out of them. How does one transmit digital data without
>>> using a digital modulation? PSK and QAM have better capacities than
>>> comparable FSK modulations, or did you mean something different?
>>
>>
>> I think it is about DMR vs conventional analog FM 2-way radio. Mark has
>> a point. BTW, trivial 800MHz analog cordless phone works better and has
>> several times of battery life compared to those spread spectrum things.

> 
> There's no question the electronics required to do analog FM are far 
> simpler and more power efficient than most digital systems.  As far as 
> squeezing the most performance out of the signal for the transmitted 
> power level, though, you'll always be better off with a well-engineered 
> digital system than the most efficient FM system.

A vocoder at ~1000 bps could be more robust then analog FM under extreme 
propagation conditions, however voice quality in good conditions would 
be much worse then that of FM. A digital system could have adaptive 
rate, however this is a significant complication. A friend of my tried 
to design voice encoding scheme which would behave like analog; i.e. 
exhibit gradual degradation of quality; but it appeared to perform worse 
    both in cases of low SNR and high SNR.

> When it comes down to analog voice and the ability of a human to pick 
> out information in a noisy or weak signal, though, it becomes too 
> subjective to compare.  The brain does have a really good decoder for 
> human speech (usually), and that may help a link work in some places 
> where a digital system might lose lock.
> 
> But for transporting bits, I don't there's much contest.

Digital can be made better then analog for any *given* channel. However 
digital will fail if the channel is worse then expected, and digital 
won't get any better if the channel improves.

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