|
What is the point of digital voice?
What is the point of digital voice when there are already AM, SSB
and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? |
What is the point of digital voice?
On 24/02/15 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Technical developments of new encoding techniques that reduce required bandwidth, just as SSB improved over AM. You can get CODEC2 down to way less than an SSB signal quite easily. Technical developments of new encoding techniques that decrease the S/N margin needed for successful communications. Ability to send voice and data at the same time, over the same channel. Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Undoubtedly some are introducing digital technologies in an attempt to increase market share (hence them not all being compatible with each other), but there are many other reasons. A lot of the next generation HF rigs will have some kind of SDR onboard anyway (even if they have nice butons and knobs to use that we are all used to) Not everyone is going to want to get their hands dirty and code their own transceiver, or even hook up PA's PTT Changeover relays, preamps etc, so it's not as if the big manufacturers are going to be wiped out by SDR. There will still be a market for "black boxes" 73s Iain |
What is the point of digital voice?
"gareth" wrote in news:mchrrq$n83$1@dont-
email.me: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Technical investigations for those with the requisite skill set. Isn't that what you're always banging on about, OM? Inane babble (i.e. 95% of all QSOs) is till inane babble regardless of whether it is transported by voice or Morse code. |
What is the point of digital voice?
On 24/02/2015 12:47, gareth wrote:
What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. Clarity. With duplex transmission it is possible to transmit clear speech over a noisy channel assuming you use an error correcting and retransmission protocol, self correcting codes techniques etc. Band sharing. Multiple users can transmit on the same band assuming adequate time-slicing and collision detection and traffic handling. or just for the fun of doing it. Andy |
What is the point of digital voice?
On 2/24/2015 7:47 AM, gareth wrote:
What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Because it's there! -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Quote:
If you are asking - what good is digital, in my opinion the reason for digital is only because public service went digital and the only reason why public service radio is going digital is because they ran out of bandwidth and they would like to simulcast voice and internet - 2 times the amount of bandwidth or more into the same allotted space as their analog allotments. Why would ham radio want to go digital when we have all kinds of bandwidth that no one uses? I think a lot of it has to do with technology so advanced that it sells more - new radios. There is such a small percentage of people buying actual ham radios today that the manufacturers needs gimmicks to keep the flow of radios and technology going. On the UHF / VHF side of things, the capture ratio is much better for digital vs analog, but analog has the ability to communicate in places where digital will not penetrate. In public service radio, when the ability to talk further is produced, the first thing they do is turn down the transmit power. Anyone that has worked Part 90 radio will tell you that when the transmitters were tube, even if the load was not a true 50 ohm load, even if the antenna fell down, the tube equipment would either keep going or it would blow the tube and it wasn't hard to fix. With solid state, when something happens, the equipment fails and it is very costly to repair or replace. On the amateur radio side of things, the people licensed today as amateurs are stupid compared to those licensed 50 years ago when an applicant had to draw circuits and had to know the difference between different types of tubes and had to have an electrical background just to pass the test. Today, you get 10 points just for spelling your name right on the application. We give amateur radio licenses to 5 year old kids with no knowledge of electricity. If we deploy stupid amateurs that can't do anything - once their smart phones quits working, we have to supply them with radios that can do simple tasks such as giving GPS coordinates and sending simple text messages. This is basically what the Yaesu System Fusion equipment does and D-Star - which is practically worthless, allows the users to link up digital repeaters - VOIP. Which doesn't really teach the users anything about real ham radio. Unless it is my antenna talking to your antenna, you might as well use Skype or a telephone... On the HF side of things, the only benefits I can see to using digital modes is that it allows you to send blocks of text and it allows you to work weak signals - below the signal noise floor that we can perceive. It is great for working moon bounce and other things like that.. That is another thing that degraded amateur radio, because you don't need to know CW to operate digital modes. What happens when the computer fails or there is a problem with the program? The people trying to use the digital modes cannot communicate with each other. While CW might be antiquated, it works! Or problem is the CB'rs that we now license to occupy our bands so we don't loose our bandwidth doesn't know how to operate CW and doesn't want to learn and is too stupid to learn it on their own. So the only alternative is to give them something that they can use that they don't have to learn how to do anything other then press some keys on a computer keyboard. So in my opinion, the architect of this program was very ingenious to come up with modes to allow people to communicate with each other digitally that prolongs our hobby at least for a little while. It doesn't make the people smarter, but it does reduce the idle chatter and the lack of identification that I have observed on the phone bands elsewhere. You don't normally see rag chewing on the digital portion of the bands. |
What is the point of digital voice?
"AndyW" wrote in message
... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? -- ;-) .. 73 de Frank Turner-Smith G3VKI - mine's a pint. .. http://turner-smith.co.uk |
What is the point of digital voice?
"Iain Young, G7III" wrote in message
... On 24/02/15 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Technical developments of new encoding techniques that reduce required bandwidth, just as SSB improved over AM. You can get CODEC2 down to way less than an SSB signal quite easily. Those who subscribe to these digital voice apparatuses lack a single clue about any underlying technical development |
What is the point of digital voice?
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
What is the point of digital voice?
"Brian Reay" wrote in message
... After all, if they haven't understood say, super regeneration, after 40 years, what hope is there for their understanding, say, DSP? Put your money where your (big) mouth is and explain to all why a super-regenerative receiver will not resolve CW or SSB, when the oscilation, although quenched, is effectively amplitude modulated by the quenching? |
What is the point of digital voice?
"Spike" wrote in message
... Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter, with the phasing notching out any nearby signal, and you realise that DSP just isn't necessary due to the quality of the 80-year-old technology employed. WHS. The Eddystone EA12 does not have a phasing control as that part of the cct is fixed-tuned, but it does have a tunable notch in the 100kHz IF to achieve the same effect. Mind you, there seems to be a diminishing band of people who know how to do this, so the simplistic approach of using someone else's ever-upgraded software to do something less effective is about as far as the tick-box Amateur seems to go. Heavens - they even buy ready-made wire aerials! And going from previous threads, there are even fewer who understand that setting up for single-signal reception means that the notional carrier frequency has to lie half-way between the peak of the Xtal and the notch of the phasing control. We should not forget that he who sneers loud and long about others' grasp of the mathematics of DSP maintains that changing the direction of a rotating vector (A Phasor, and not related to the weapons of Star Trek!) causes it to decrease in sixe. |
What is the point of digital voice?
On Tue, 24 Feb 2015 16:57:04 +0000, gareth wrote:
Those who subscribe to these digital voice apparatuses lack a single clue about any underlying technical development I've had this dream before. Oh wait a minute, that was about Single Side Band :-) Charlie. -- Hello Wisconsin! |
What is the point of digital voice?
En el artículo , FranK Turner-Smith
G3VKI escribió: That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. One word: compression. If we all took the same attitude as the OP we'd still be using Strowger exchanges for the phone system. Thankfully, some people understand the need for progress and aren't stuck in the past. Times have changed and left me behind, but I've still got me beer so who cares? Good man :) -- :: je suis Charlie :: yo soy Charlie :: ik ben Charlie :: |
What is the point of digital voice?
"Mike Tomlinson" wrote in message
... If we all took the same attitude as the OP we'd still be using Strowger exchanges for the phone system. Thankfully, some people understand the need for progress and aren't stuck in the past. There you go again with your one-sided infantile outbursts. |
What is the point of digital voice?
"gareth" wrote in message
... What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? A very well informed and authoratative response to this has been made by "Channel Jumper" over in rec.radio.amateur.equipment, although he did not elect to post it here as well. .. |
What is the point of digital voice?
"Jerry Stuckle" wrote in message
... On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). Thanks, Jerry, you've explained a lot to me, and in a manner that an old fart like me can understand. I appreciate that, and feel I owe you a pint, (not a compressed 1cc one). -- ;-) .. 73 de Frank Turner-Smith G3VKI - mine's a pint. .. http://turner-smith.co.uk |
What is the point of digital voice?
On 2/24/2015 12:00 PM, Jerry Stuckle wrote:
On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol A friend worked in sonar where the data was collected on ships and transmitted via satellite to shore for signal processing rather than doing any compression on the data and sending the useful info. As the signal was nearly all "noise" trying to do any compression on it, even the aspects that weren't "pure" white noise, would potentially have masked the signals. Sonar is all about pulling the signal out of the noise. -- Rick |
What is the point of digital voice?
On 2/24/2015 12:10 PM, Brian Morrison wrote:
On Tue, 24 Feb 2015 16:32:21 -0000 FranK Turner-Smith G3VKI wrote: Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. Have a look at David Rowe's web site about Codec 2 and his work on it. http://rowetel.com Most of the codec development effort goes into voice modelling that allows redundant information to be thrown away without making the encoded speech sound too horrible when decoded. And on working out which bits in the encoded frame need to be better protected and which don't, this is especially important when considering what encodes voiced and non-voiced speech and ensuring it doesn't get mixed up. Other than uLaw/Alaw, voice for telephony is not compressed in the same ways that a zip file is. As you say, they model the vocal tract and send the parameters for the sounds that are to be produced along with error information to make it more intelligible. For sounds that aren't voice or voice like, they are reproduced poorly. This is why low bit rate compression on cell phones doesn't convey music very well and background noise messes up the intelligibility much more than with uLaw or ALaw compression which are just ways of compressing the waveform without knowing anything about the content. -- Rick |
What is the point of digital voice?
On 2/24/2015 1:28 PM, gareth wrote:
"Mike Tomlinson" wrote in message ... If we all took the same attitude as the OP we'd still be using Strowger exchanges for the phone system. Thankfully, some people understand the need for progress and aren't stuck in the past. There you go again with your one-sided infantile outbursts. lol! -- Rick |
What is the point of digital voice?
On 2/24/2015 12:37 PM, gareth wrote:
"Spike" wrote in message ... Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter, with the phasing notching out any nearby signal, and you realise that DSP just isn't necessary due to the quality of the 80-year-old technology employed. WHS. The Eddystone EA12 does not have a phasing control as that part of the cct is fixed-tuned, but it does have a tunable notch in the 100kHz IF to achieve the same effect. Mind you, there seems to be a diminishing band of people who know how to do this, so the simplistic approach of using someone else's ever-upgraded software to do something less effective is about as far as the tick-box Amateur seems to go. Heavens - they even buy ready-made wire aerials! And going from previous threads, there are even fewer who understand that setting up for single-signal reception means that the notional carrier frequency has to lie half-way between the peak of the Xtal and the notch of the phasing control. We should not forget that he who sneers loud and long about others' grasp of the mathematics of DSP maintains that changing the direction of a rotating vector (A Phasor, and not related to the weapons of Star Trek!) causes it to decrease in sixe. What is "sixe"??? -- Rick |
What is the point of digital voice?
"rickman" wrote in message
... On 2/24/2015 12:37 PM, gareth wrote: "Spike" wrote in message ... Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter, with the phasing notching out any nearby signal, and you realise that DSP just isn't necessary due to the quality of the 80-year-old technology employed. WHS. The Eddystone EA12 does not have a phasing control as that part of the cct is fixed-tuned, but it does have a tunable notch in the 100kHz IF to achieve the same effect. Mind you, there seems to be a diminishing band of people who know how to do this, so the simplistic approach of using someone else's ever-upgraded software to do something less effective is about as far as the tick-box Amateur seems to go. Heavens - they even buy ready-made wire aerials! And going from previous threads, there are even fewer who understand that setting up for single-signal reception means that the notional carrier frequency has to lie half-way between the peak of the Xtal and the notch of the phasing control. We should not forget that he who sneers loud and long about others' grasp of the mathematics of DSP maintains that changing the direction of a rotating vector (A Phasor, and not related to the weapons of Star Trek!) causes it to decrease in sixe. What is "sixe"??? Typo - adjacent key - size |
What is the point of digital voice?
On 2/24/2015 5:47 PM, rickman wrote:
On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. A friend worked in sonar where the data was collected on ships and transmitted via satellite to shore for signal processing rather than doing any compression on the data and sending the useful info. As the signal was nearly all "noise" trying to do any compression on it, even the aspects that weren't "pure" white noise, would potentially have masked the signals. Sonar is all about pulling the signal out of the noise. You mean the signal can't be compressed? No way. Any non-random signal can be compressed to some extent. How much depends on the signal and the amount of processing power required to compress it. However, in your example, the processing power to compress the signal would probably have been greater than that required to process the original signal. So if there wasn't enough power to process the signal on the ship, there wouldn't be enough power to compress the near-white noise signal, either. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
What is the point of digital voice?
On 2/24/2015 6:35 PM, gareth wrote:
"rickman" wrote in message ... On 2/24/2015 12:37 PM, gareth wrote: "Spike" wrote in message ... Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter, with the phasing notching out any nearby signal, and you realise that DSP just isn't necessary due to the quality of the 80-year-old technology employed. WHS. The Eddystone EA12 does not have a phasing control as that part of the cct is fixed-tuned, but it does have a tunable notch in the 100kHz IF to achieve the same effect. Mind you, there seems to be a diminishing band of people who know how to do this, so the simplistic approach of using someone else's ever-upgraded software to do something less effective is about as far as the tick-box Amateur seems to go. Heavens - they even buy ready-made wire aerials! And going from previous threads, there are even fewer who understand that setting up for single-signal reception means that the notional carrier frequency has to lie half-way between the peak of the Xtal and the notch of the phasing control. We should not forget that he who sneers loud and long about others' grasp of the mathematics of DSP maintains that changing the direction of a rotating vector (A Phasor, and not related to the weapons of Star Trek!) causes it to decrease in sixe. What is "sixe"??? Typo - adjacent key - size I thought it might be that, but it still makes no sense to me. Who or how does changing the direction of rotation of a rotating vector change its "size". Are you defining size as the rotation so that going from a + to a - is like reversing the direction of a vector? I think most people would consider the "size" of a vector to be the magnitude which is independent of phase angle and so rotation, no? Perhaps you can explain this with a little math? -- Rick |
What is the point of digital voice?
On 2/24/2015 6:37 PM, Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. Why does it not "exist"? That is not at all clear. You don't understand compression. Compression is a means of removing the part of a signal that is unimportant and sending only the part that is important. In most cases of "pure" noise, you can just send a statement that the signal is "noise" without caring about the exact voltages over time. So, yes, even noise can be compressed depending on your requirements. A friend worked in sonar where the data was collected on ships and transmitted via satellite to shore for signal processing rather than doing any compression on the data and sending the useful info. As the signal was nearly all "noise" trying to do any compression on it, even the aspects that weren't "pure" white noise, would potentially have masked the signals. Sonar is all about pulling the signal out of the noise. You mean the signal can't be compressed? No way. Any non-random signal can be compressed to some extent. How much depends on the signal and the amount of processing power required to compress it. However, in your example, the processing power to compress the signal would probably have been greater than that required to process the original signal. So if there wasn't enough power to process the signal on the ship, there wouldn't be enough power to compress the near-white noise signal, either. You really like your all encompassing assumptions. No, all signals can not be compressed, even non-noise signals can't be compressed if the signal is not appropriate for the compressor. This is really a very large topic and I think you are used to dealing with the special cases without understanding the general case. Try visiting comp.compression and offering them your opinions. There are many there who are happy to explain the details to you. -- Rick |
What is the point of digital voice?
On 2/24/2015 6:37 PM, Jerry Stuckle wrote:
On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. Here is a white noise signal... 4. That number was chosen at random, courtesy of XKCD.com. http://xkcd.com/221/ -- Rick |
What is the point of digital voice?
On 2/24/2015 7:03 PM, rickman wrote:
On 2/24/2015 6:37 PM, Jerry Stuckle wrote: On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. Why does it not "exist"? That is not at all clear. You don't understand compression. Compression is a means of removing the part of a signal that is unimportant and sending only the part that is important. In most cases of "pure" noise, you can just send a statement that the signal is "noise" without caring about the exact voltages over time. So, yes, even noise can be compressed depending on your requirements. Pure white noise is a concept only. There is no perfect white noise source, just as there is no pure resistor or capacitor. And yes, I do understand compression. One of the things it depends on is predictability and repeatability of the incoming signal. That does not exist with white noise. The fact you don't understand that pure white noise is only a concept and cannot exist in the real world shows your lack of understanding. Some compression algorithms (i.e. mp3) remove what they consider is "unimportant". However, the result after decompressing is a poor recreation of the original signal. But for perfect recreation, nothing is "unimportant". Voice/video compression is no different than file compression on a computer. Can you imaging what would happen if your favorite program was not perfectly recreated? A friend worked in sonar where the data was collected on ships and transmitted via satellite to shore for signal processing rather than doing any compression on the data and sending the useful info. As the signal was nearly all "noise" trying to do any compression on it, even the aspects that weren't "pure" white noise, would potentially have masked the signals. Sonar is all about pulling the signal out of the noise. You mean the signal can't be compressed? No way. Any non-random signal can be compressed to some extent. How much depends on the signal and the amount of processing power required to compress it. However, in your example, the processing power to compress the signal would probably have been greater than that required to process the original signal. So if there wasn't enough power to process the signal on the ship, there wouldn't be enough power to compress the near-white noise signal, either. You really like your all encompassing assumptions. No, all signals can not be compressed, even non-noise signals can't be compressed if the signal is not appropriate for the compressor. This is really a very large topic and I think you are used to dealing with the special cases without understanding the general case. Which is just the opposite of what you claimed above. Please make up your mind. Try visiting comp.compression and offering them your opinions. There are many there who are happy to explain the details to you. I understand the details, thank you. Much better than you do, obviously. But that's not surprising, either. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
What is the point of digital voice?
On 2/24/2015 7:07 PM, rickman wrote:
On 2/24/2015 6:37 PM, Jerry Stuckle wrote: On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. Here is a white noise signal... 4. That number was chosen at random, courtesy of XKCD.com. http://xkcd.com/221/ No, that is not a white noise signal. And the number, by definition, being computer generated, is only pseudo-random. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
What is the point of digital voice?
On 2/24/2015 7:32 PM, Brian Reay wrote:
Jerry Stuckle wrote: On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. To be more accurate, it has an infinite bandwidth and constant power density/Hz. As you say, it doesn't really exist. In practice, lab noise sources are specified over a bandwidth and to be within a given limit of power variation across that. Darn useful devices to have around. Brian, Thank you - you are much more accurate in describing it than I was able to. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
What is the point of digital voice?
On Tue, 24 Feb 2015, gareth wrote:
What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Because it's something new, at least to amateur radio. The phasing method of sideband was common in the early days of amateur SSB (I recall reading the first rigs were filter type, but with really low IFs, then phasing, then crystal and mechanical filters took over from phasing). It offered up a lot on transmit and receive, though not perfection. But now phasing is used a lot, because digital circuitry has made it viable. I remember seeing some of the potential when phasing was still analog, but I also remember reading articles where it was clear others didn't see the potential. Sometimes ideas become lost when something becomes commonplace. Who knows what would come from digital voice. But I remember 30 years ago one local ham being interested in it, not to the extent of putting something on the air, but as information from the computer world started flowing in, the potential started being there. YOu can't resist new things and say "they have no use", you have to embrace the new and see what can be done with it. Maybe not as initially seen, but maybe it fits in somewhere else. Amateur radio has never done much with envelope elimination and restoration (was that what it was called? I now forget). It's in one of the sideband books, and Karl Meinzer of AMSAT fame wrote about it in QST about 1970. Break the SSB signal into two components, so you can multiply it up to a higher frequency, then modulate the output stage. If you have an efficient modulator, you can do away with linear amplifiers (which is why it was in that SSB book). I gather he used the scheme in at least one of the amateur satellites after Oscar 6. But what happens in the digital age? Can you generate the two streems, in essence but not so simple an FM component and an AM component, without needing to generate SSB and then extract the two streams? I don't know, but so much digital processing is being done now, it may be something to look into. With solid state devices and class D amplifiers, modulating high level class C amplifiers can't be as much trouble as in the old days. Maybe it amounts to nothing, but maybe it overall becomes more efficient, if it can be done. Maybe there's no value to digital voice, except that in the process of learnign about it, and implementing it, one can learn something. Maybe something merely new to the person learning, but maybe something completely new. No advances are made without learning, the learning triggers new advances. Michael |
What is the point of digital voice?
On 2/24/2015 7:12 PM, Jerry Stuckle wrote:
On 2/24/2015 7:03 PM, rickman wrote: On 2/24/2015 6:37 PM, Jerry Stuckle wrote: On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. Why does it not "exist"? That is not at all clear. You don't understand compression. Compression is a means of removing the part of a signal that is unimportant and sending only the part that is important. In most cases of "pure" noise, you can just send a statement that the signal is "noise" without caring about the exact voltages over time. So, yes, even noise can be compressed depending on your requirements. Pure white noise is a concept only. There is no perfect white noise source, just as there is no pure resistor or capacitor. And yes, I do understand compression. One of the things it depends on is predictability and repeatability of the incoming signal. That does not exist with white noise. The fact you don't understand that pure white noise is only a concept and cannot exist in the real world shows your lack of understanding. This is not very productive. You make an assertion and the fact that I don't agree means I am wrong. Ok, you have an idea in your mind and can't explain it. I get that. The fact that you don't have a white noise source in your lab doesn't mean it doesn't exist other than in the same way that 100.1 doesn't exist. No one has ever made anything that was *exactly* 100.1. This is a pointless abstraction so I won't continue to debate it. Some compression algorithms (i.e. mp3) remove what they consider is "unimportant". However, the result after decompressing is a poor recreation of the original signal. That is a value judgement which most would disagree with not to mention that your example is not valid. MP3 does not *remove* anything from the signal. It is a form of compression that simply can't reproduce the signal exactly. The use of the term "poor" is your value judgement. Most people would say an MP3 audio sounds very much like the original. But for perfect recreation, nothing is "unimportant". Voice/video compression is no different than file compression on a computer. Can you imaging what would happen if your favorite program was not perfectly recreated? A friend worked in sonar where the data was collected on ships and transmitted via satellite to shore for signal processing rather than doing any compression on the data and sending the useful info. As the signal was nearly all "noise" trying to do any compression on it, even the aspects that weren't "pure" white noise, would potentially have masked the signals. Sonar is all about pulling the signal out of the noise. You mean the signal can't be compressed? No way. Any non-random signal can be compressed to some extent. How much depends on the signal and the amount of processing power required to compress it. However, in your example, the processing power to compress the signal would probably have been greater than that required to process the original signal. So if there wasn't enough power to process the signal on the ship, there wouldn't be enough power to compress the near-white noise signal, either. You really like your all encompassing assumptions. No, all signals can not be compressed, even non-noise signals can't be compressed if the signal is not appropriate for the compressor. This is really a very large topic and I think you are used to dealing with the special cases without understanding the general case. Which is just the opposite of what you claimed above. Please make up your mind. This is the sort of stuff that makes discussions with you unenjoyable. You clearly don't understand compression or you would understand this statement. Compression maps a combination of bits into a smaller number of bits. By the counting theorem it is impossible for any compression algorithm to compress all possible input sets. Whether it can be compressed depends on a match between the input bits and the compression algorithm. Even white noise (which can exist if you define "white noise" adequately) can be compressed by the appropriate algorithm. That algorithm won't compress much else though. Try visiting comp.compression and offering them your opinions. There are many there who are happy to explain the details to you. I understand the details, thank you. Much better than you do, obviously. But that's not surprising, either. Ok, you have reverted into snarky mode. I'm done. -- Rick |
What is the point of digital voice?
On 2/24/2015 7:22 PM, Jerry Stuckle wrote:
On 2/24/2015 7:07 PM, rickman wrote: On 2/24/2015 6:37 PM, Jerry Stuckle wrote: On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. Here is a white noise signal... 4. That number was chosen at random, courtesy of XKCD.com. http://xkcd.com/221/ No, that is not a white noise signal. And the number, by definition, being computer generated, is only pseudo-random. You didn't even read the damn reference. The number was *not* computer generated. -- Rick |
What is the point of digital voice?
On 2/24/2015 7:32 PM, Brian Reay wrote:
Jerry Stuckle wrote: On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. To be more accurate, it has an infinite bandwidth and constant power density/Hz. As you say, it doesn't really exist. In practice, lab noise sources are specified over a bandwidth and to be within a given limit of power variation across that. Darn useful devices to have around. So if I have a string of random numbers they can not represent a white noise source of infinite bandwidth and constant power density? -- Rick |
What is the point of digital voice?
On 2/24/2015 7:32 PM, Brian Reay wrote:
rickman wrote: On 2/24/2015 6:35 PM, gareth wrote: "rickman" wrote in message ... On 2/24/2015 12:37 PM, gareth wrote: "Spike" wrote in message ... Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter, with the phasing notching out any nearby signal, and you realise that DSP just isn't necessary due to the quality of the 80-year-old technology employed. WHS. The Eddystone EA12 does not have a phasing control as that part of the cct is fixed-tuned, but it does have a tunable notch in the 100kHz IF to achieve the same effect. Mind you, there seems to be a diminishing band of people who know how to do this, so the simplistic approach of using someone else's ever-upgraded software to do something less effective is about as far as the tick-box Amateur seems to go. Heavens - they even buy ready-made wire aerials! And going from previous threads, there are even fewer who understand that setting up for single-signal reception means that the notional carrier frequency has to lie half-way between the peak of the Xtal and the notch of the phasing control. We should not forget that he who sneers loud and long about others' grasp of the mathematics of DSP maintains that changing the direction of a rotating vector (A Phasor, and not related to the weapons of Star Trek!) causes it to decrease in sixe. What is "sixe"??? Typo - adjacent key - size I thought it might be that, but it still makes no sense to me. Who or how does changing the direction of rotation of a rotating vector change its "size". Are you defining size as the rotation so that going from a + to a - is like reversing the direction of a vector? I think most people would consider the "size" of a vector to be the magnitude which is independent of phase angle and so rotation, no? Perhaps you can explain this with a little math? He is (deliberately) misrepresenting the discussion. The point was made that the phasor was rotating clockwise, thus the angle decreasing, ie becoming negative. This has been repeatedly explained to him but he continues to churn out his bilge. His maths (or math) isn't up to it, it is too complex for him (pun intended). If you look in the archives you will see him referring to 'negative frequency', not to mention questioning basic DSP theory, the use of the Dirac Delta, ..... Best just to ignore him, he is simply trying to start a row. Maybe I don't understand the issue. Isn't that a valid example of a negative frequency? There are some DSP experts in comp.dsp who talk about negative frequency often. -- Rick |
What is the point of digital voice?
On 24/02/2015 16:32, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. But then you add compression on top. As technology increases and the ability to process data quickly advances you can real-time encode and decode data at a frightening rate. Back when I started playing about with digital sound we had enough speed to run-length encode in real time, now with dedicated number cruncher chips you can carry out very complex lossless sound compression in real time and for lo-fi sound you can use lossy compression and have a lot of the band left over for a time-slice share. One of my final dissertation for university was on digital compression techniques (lossy and lossless) and I get a bit geeky about it all :-) Surprised I still remember it all.... Andy |
What is the point of digital voice?
On 24/02/2015 16:57, gareth wrote:
"Iain Young, G7III" wrote in message ... On 24/02/15 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Technical developments of new encoding techniques that reduce required bandwidth, just as SSB improved over AM. You can get CODEC2 down to way less than an SSB signal quite easily. Those who subscribe to these digital voice apparatuses lack a single clue about any underlying technical development Sweeping statement. I have used digital voice and I have built my own kit (non-ham but basically the same as a digital voice front end) and wrote my own codecs (both fractal lossy and various lossless codecs). If you have trouble sleeping at night I am sure I can dig out my dissertation and forward it. The technology is dated (I built my first one using thick-film technology - that dates it a little) but the underlying work is still valid. Andy |
What is the point of digital voice?
On 24/02/2015 17:00, Jerry Stuckle wrote:
But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? Which is why, on cheaper televisions, the picture tesselates when showing random images such as rain, fire, waterfalls etc. The true test of a quality television is to watch a waterfall or flames and see it pin-sharp. Cheaper TVs use cheap lower-powered decoding systems and for complex images they do not have enough time to fully decode the image before the next frame arrives. Andy |
What is the point of digital voice?
Thank you - you are much more accurate in describing it than I was able to. don't say that....he can barely get his head through a door as it is....... |
What is the point of digital voice?
On 25/02/15 06:43, rickman wrote:
On 2/24/2015 7:32 PM, Brian Reay wrote: Jerry Stuckle wrote: On 2/24/2015 5:47 PM, rickman wrote: On 2/24/2015 12:00 PM, Jerry Stuckle wrote: On 2/24/2015 11:32 AM, FranK Turner-Smith G3VKI wrote: "AndyW" wrote in message ... On 24/02/2015 12:47, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Bandwidth reduction for one. If you can encode and compress speech sufficiently then you can use less bandwidth in transmission. That's the bit I have trouble getting my head around. Back in the 1970s and 1980s digital transmissions used a much greater bandwidth than their analogue equivalents. Sampling at 2.2 x max frequency x number of bits plus housekeeping bits etc. etc. A UK standard 625 line PAL video transmission would have used a bandwidth of over 400MHz! Times have changed and left me behind, but I've still got me beer so who cares? But you forget compression. For instance, unless there is a scene change, the vast majority of a television picture does not change from frame to frame. Even if the camera moves, the picture shifts but doesn't change all that much. Why waste all of that bandwidth resending information the receiver already has? And voice isn't continuous; it has lots of pauses. Some are very noticeable, while others are so short we don't consciously hear them, but they are there. And once you've compressed everything you can out of the original signal, you can do bit compression, similar to zipping a file for sending. There are lots of ways to compress a signal before sending it digitally. About the only one which can't be compressed is pure white noise - which, of course, is only a concept (nothing is "pure"). I think that depends on what you mean by "pure". Sounds very non-technical to me. Even noise can be compressed since if it is truly noise, you don't need to send the data, just send the one bit that says there is no signal, just noise. lol Pure white noise is a random distribution of signal across the entire spectrum, with an equal distribution of frequencies over time. Like a pure resistor or capacitor, it doesn't exist. But the noise IS the signal. To recreate the noise, you have to sample the signal and transmit it. However, since it is completely random, by definition no compression is possible. To be more accurate, it has an infinite bandwidth and constant power density/Hz. As you say, it doesn't really exist. In practice, lab noise sources are specified over a bandwidth and to be within a given limit of power variation across that. Darn useful devices to have around. So if I have a string of random numbers they can not represent a white noise source of infinite bandwidth and constant power density? Not perfectly. The string would need to be infinitely long and truly random. That is why the term Pseudo Random is generally used for strings used in such applications. |
What is the point of digital voice?
Brian Reay wrote:
rickman wrote: On 2/24/2015 6:35 PM, gareth wrote: "rickman" wrote in message ... On 2/24/2015 12:37 PM, gareth wrote: "Spike" wrote in message ... Get a CW signal peaked on the 20 c/s nose of the HRO crystal filter, with the phasing notching out any nearby signal, and you realise that DSP just isn't necessary due to the quality of the 80-year-old technology employed. WHS. The Eddystone EA12 does not have a phasing control as that part of the cct is fixed-tuned, but it does have a tunable notch in the 100kHz IF to achieve the same effect. Mind you, there seems to be a diminishing band of people who know how to do this, so the simplistic approach of using someone else's ever-upgraded software to do something less effective is about as far as the tick-box Amateur seems to go. Heavens - they even buy ready-made wire aerials! And going from previous threads, there are even fewer who understand that setting up for single-signal reception means that the notional carrier frequency has to lie half-way between the peak of the Xtal and the notch of the phasing control. We should not forget that he who sneers loud and long about others' grasp of the mathematics of DSP maintains that changing the direction of a rotating vector (A Phasor, and not related to the weapons of Star Trek!) causes it to decrease in sixe. What is "sixe"??? Typo - adjacent key - size I thought it might be that, but it still makes no sense to me. Who or how does changing the direction of rotation of a rotating vector change its "size". Are you defining size as the rotation so that going from a + to a - is like reversing the direction of a vector? I think most people would consider the "size" of a vector to be the magnitude which is independent of phase angle and so rotation, no? Perhaps you can explain this with a little math? He is (deliberately) misrepresenting the discussion. The point was made that the phasor was rotating clockwise, thus the angle decreasing, ie becoming negative. This has been repeatedly explained to him but he continues to churn out his bilge. His maths (or math) isn't up to it, it is too complex for him (pun intended). If you look in the archives you will see him referring to 'negative frequency', not to mention questioning basic DSP theory, the use of the Dirac Delta, ..... Best just to ignore him, he is simply trying to start a row. Or seek attention. He's bean almost universally ignored over in ukra for some considerable time now, and is flailing around desperately trying to get the spotlight on him. Our American friends will soon realise shunning him is the wisest path. -- STC // M0TEY // twitter.com/ukradioamateur |
What is the point of digital voice?
Michael Black wrote:
On Tue, 24 Feb 2015, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Because it's something new, at least to amateur radio. The phasing method of sideband was common in the early days of amateur SSB (I recall reading the first rigs were filter type, but with really low IFs, then phasing, then crystal and mechanical filters took over from phasing). It offered up a lot on transmit and receive, though not perfection. But now phasing is used a lot, because digital circuitry has made it viable. I remember seeing some of the potential when phasing was still analog, but I also remember reading articles where it was clear others didn't see the potential. Sometimes ideas become lost when something becomes commonplace. Who knows what would come from digital voice. But I remember 30 years ago one local ham being interested in it, not to the extent of putting something on the air, but as information from the computer world started flowing in, the potential started being there. YOu can't resist new things and say "they have no use", you have to embrace the new and see what can be done with it. Maybe not as initially seen, but maybe it fits in somewhere else. Amateur radio has never done much with envelope elimination and restoration (was that what it was called? I now forget). It's in one of the sideband books, and Karl Meinzer of AMSAT fame wrote about it in QST about 1970. Break the SSB signal into two components, so you can multiply it up to a higher frequency, then modulate the output stage. If you have an efficient modulator, you can do away with linear amplifiers (which is why it was in that SSB book). I gather he used the scheme in at least one of the amateur satellites after Oscar 6. But what happens in the digital age? Can you generate the two streems, in essence but not so simple an FM component and an AM component, without needing to generate SSB and then extract the two streams? I don't know, but so much digital processing is being done now, it may be something to look into. With solid state devices and class D amplifiers, modulating high level class C amplifiers can't be as much trouble as in the old days. Maybe it amounts to nothing, but maybe it overall becomes more efficient, if it can be done. Maybe there's no value to digital voice, except that in the process of learnign about it, and implementing it, one can learn something. Maybe something merely new to the person learning, but maybe something completely new. No advances are made without learning, the learning triggers new advances. Michael You do realise that you're responding to a troll post, right? -- STC // M0TEY // twitter.com/ukradioamateur |
| All times are GMT +1. The time now is 05:38 PM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com