Re: [digitalradio] Re: Curious sound card modes question -
It will be spread spectrum if the tone frequencies are controlled by a code as explained in the ROS documentation: A system is defined to be a spread-spectrum system if it fulfills the following requirements: 1. The signal occupies a bandwidth much in excess of the minimum bandwidth necessary to send the information. 2. Spreading is accomplished by means of a spreading signal, often called a code signal, which is independent of the data. 3. At the receiver, despreading (recovering the original data) is accomplished by the correlation of the received spread signal with a synchronized replica of the spreading signal used to spread the information. Standard modulation schemes as frequency modulation and pulse code modulation also spread the spectrum of an information signal, but they do not qualify as spread-spectrum systems since they do not satisfy all the conditions outlined above. Note that all three conditions must be met to be considered spread spectrum. I don;t know if it would be possible to send the data in less bandwidth, but, for example, PSK31 accomplishes the same typing speed in a bandwidth of 31 Hz, instead of in 2000 Hz, so ROS is probably truly spread-spectrum. Remember that spread spectrum was conceived as a way of coding transmissions so they could not be intercepted and decoded. In fact actress Hedy Lamarr invented spread spectrum, and you can read that here: http://en.wikipedia.org/wiki/Hedy_Lamarr. The difference is the use of a code to spread the data and signals to avoid detection and monitoring by those without the same code. Download the documentation from www. rosmodem.wordpress.com and read about spread spectrum and the ROS implementation. That will make it clear I think. Remembering that a single tone creates a single RF carrier makes it easy to see how just about anything can be done with tones, including sending data over several tones at once so if one carrier is lost, others carry the same data, or using a psuedo-random code to determine the carrier frequencies, as I think is done in ROS. That documentation also explains the difference between FHSS and modes like MFSK16. However, a main point is that the data does not have to be scattered over such a wide bandwidth to achieve communication, but ROS does, so it qualifies as spread spectrum. If you have a receive bandwith of 10,000 Hz, and you spread over that bandwidth, you really are using way more bandwidth than necessary to send the same data at a given speed. MT63 uses 64 carriers with the data divided among the carriers for redundancy and about 40% of the signal can be obilterated by QRM and still produce good copy. I think the difference with ROS is that the carrier frequencies are varied according to a code, instead of being at a fixed position, but I am no expert on modes, so someone else can probably explain it better and with more accuracy. Generally it is qualifies as spread spectrum if a code is used for the spreading, and in military communications (and even cell phones, I think) the code prevents anyone else from reconstructing the signal so that the intelligence can be recovered if they do not possess the same code. 73 - Skip KH6TY John wrote: Thanks Skip, Unfortunately, this really does not get to the crux of my question(s). I understand how an SSB transmitter works, but that is not really what I am after. What I am driving at is if like this. If I use DM780 to run some version of digital mode via an SSB transceiver, it uses a tone or series of tone modulation/shifting to create the output of the transmitter, and not one single mode is called spread spectrum output, but is called FSK or PSK, etc. Now, we get into the aforementioned discussion regarding ROS, and suddenly, still via the microphone input of the same transmitter, those shifted frequencies are now called spread spectrum instead. I am having a great deal of difficulty understanding, other than the author happened to call his scheme spread spectrum in his technical documentation. Thanks John KE5HAM --- In digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com, KH6TY kh...@... wrote: John, Given sufficient carrier suppression, any tone inputed to the microphone makes the transmitter output a pure RF carrier at a frequency of the suppressed carrier frequency plus the tone frequency for USB, or minus the tone frequency for LSB. Whatever you do with the tones determines what RF carriers come out. You can key the tones, or shift the tone frequencies, etc., and the RF output will follow. The ARRL Handbook usually has an explanation of this. Hope that answers the question. 73 - Skip KH6TY John wrote: So as to not continue growing the ROS legality discussion even further, I would like to ask a fairly simple question. How will the modulation be determined from any SSB transmitter when the source of the modulation is via the
Re: [digitalradio] Re: Curious sound card modes question -
John wrote: Thanks Skip, Unfortunately, this really does not get to the crux of my question(s). I understand how an SSB transmitter works, but that is not really what I am after. What I am driving at is if like this. If I use DM780 to run some version of digital mode via an SSB transceiver, it uses a tone or series of tone modulation/shifting to create the output of the transmitter, and not one single mode is called spread spectrum output, but is called FSK or PSK, etc. Now, we get into the aforementioned discussion regarding ROS, and suddenly, still via the microphone input of the same transmitter, those shifted frequencies are now called spread spectrum instead. I am having a great deal of difficulty understanding, other than the author happened to call his scheme spread spectrum in his technical documentation. OFDM used in Pactor 3 is legal due to it's low symbol rates and SSB sized effective bandwidth. If prior to P3 someone asked if FDM was legal on HF most would say no. Traditional FDM (frequency division multiplexing) as practiced in the real world would not ever be legal on HF. So technically it's FDM, but practically, it's not, as it's much narrower bandwidth. Lumping ROS in with Spread spectrum is similar. You can use FDM or SS approaches on an audio modulated sideband signal and not meet practical definitions. quack test- walks like a duck, must be a duck. Regarding the perfect SSB transmitter sending a 1khz tone equaling CW at a 1khz beat frequency, we all know there is a big difference between theoretical and reality. But in theory, ROS, P3, whatever could be represented by multiple transmitter signals, so could technically fall into legal gray area. I'm sure if we tried hard enough we could find a way to decide it's illegal, and should be banned. And in reality, the FCC won't care, as it did not meet the quack test of spread spectrum. :-) I don't have a horse in this race, however. :-) Have fun, Alan KM4BA
Re: [digitalradio] Re: Curious sound card modes question -
The only entity competent to answer the question is the FCC, and the accepted procedure when one is not sure is to ask for a clarification. Unfortunately, it is everyone's legal responsibility to understand the law and obey it. Since most of use cannot do that, we have to turn to lawyers to do it. You may or may not like the answer given, but the FCC does try to protect the ham bands for everyone and seems to make interpretations on that basis. Digital users are a tiny minority of users of the bands, but the FCC is accountable to all hams, so they must try to do what is right for all hams, not just for a minority. If it were not for that approach, the HF bands today might be covered with automatic messaging systems and it would be hard to even find a place to play or have a QSO without interference from an automatic station that does not listen first, does not QRL, and does not share frequencies. We may not like the time it takes for the process to play out, but that gives everyone a chance to present their case before any rules are made - EVERYONE, not just a vocal minority. 73 - Skip KH6TY Alan Barrow wrote: John wrote: Thanks Skip, Unfortunately, this really does not get to the crux of my question(s). I understand how an SSB transmitter works, but that is not really what I am after. What I am driving at is if like this. If I use DM780 to run some version of digital mode via an SSB transceiver, it uses a tone or series of tone modulation/shifting to create the output of the transmitter, and not one single mode is called spread spectrum output, but is called FSK or PSK, etc. Now, we get into the aforementioned discussion regarding ROS, and suddenly, still via the microphone input of the same transmitter, those shifted frequencies are now called spread spectrum instead. I am having a great deal of difficulty understanding, other than the author happened to call his scheme spread spectrum in his technical documentation. OFDM used in Pactor 3 is legal due to it's low symbol rates and SSB sized effective bandwidth. If prior to P3 someone asked if FDM was legal on HF most would say no. Traditional FDM (frequency division multiplexing) as practiced in the real world would not ever be legal on HF. So technically it's FDM, but practically, it's not, as it's much narrower bandwidth. Lumping ROS in with Spread spectrum is similar. You can use FDM or SS approaches on an audio modulated sideband signal and not meet practical definitions. quack test- walks like a duck, must be a duck. Regarding the perfect SSB transmitter sending a 1khz tone equaling CW at a 1khz beat frequency, we all know there is a big difference between theoretical and reality. But in theory, ROS, P3, whatever could be represented by multiple transmitter signals, so could technically fall into legal gray area. I'm sure if we tried hard enough we could find a way to decide it's illegal, and should be banned. And in reality, the FCC won't care, as it did not meet the quack test of spread spectrum. :-) I don't have a horse in this race, however. :-) Have fun, Alan KM4BA
RE: [digitalradio] Re: Curious sound card modes question -
re PSK31 accomplishes the same typing speed in a bandwidth of 31 Hz, instead of in 2000 Hz, so ROS is probably truly spread-spectrum. Applying this logic to RTTY, which employs ~10X the bandwidth employed by PSK31, would lead us to conclude that RTTY is also spread spectrum. 73, Dave, AA6YQ -Original Message- From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com]on Behalf Of KH6TY Sent: Monday, February 22, 2010 8:30 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Re: Curious sound card modes question - It will be spread spectrum if the tone frequencies are controlled by a code as explained in the ROS documentation: A system is defined to be a spread-spectrum system if it fulfills the following requirements: 1. The signal occupies a bandwidth much in excess of the minimum bandwidth necessary to send the information. 2. Spreading is accomplished by means of a spreading signal, often called a code signal, which is independent of the data. 3. At the receiver, despreading (recovering the original data) is accomplished by the correlation of the received spread signal with a synchronized replica of the spreading signal used to spread the information. Standard modulation schemes as frequency modulation and pulse code modulation also spread the spectrum of an information signal, but they do not qualify as spread-spectrum systems since they do not satisfy all the conditions outlined above. Note that all three conditions must be met to be considered spread spectrum. I don;t know if it would be possible to send the data in less bandwidth, but, for example, PSK31 accomplishes the same typing speed in a bandwidth of 31 Hz, instead of in 2000 Hz, so ROS is probably truly spread-spectrum. Remember that spread spectrum was conceived as a way of coding transmissions so they could not be intercepted and decoded. In fact actress Hedy Lamarr invented spread spectrum, and you can read that here: http://en.wikipedia.org/wiki/Hedy_Lamarr. The difference is the use of a code to spread the data and signals to avoid detection and monitoring by those without the same code. Download the documentation from www. rosmodem.wordpress.com and read about spread spectrum and the ROS implementation. That will make it clear I think. Remembering that a single tone creates a single RF carrier makes it easy to see how just about anything can be done with tones, including sending data over several tones at once so if one carrier is lost, others carry the same data, or using a psuedo-random code to determine the carrier frequencies, as I think is done in ROS. That documentation also explains the difference between FHSS and modes like MFSK16. However, a main point is that the data does not have to be scattered over such a wide bandwidth to achieve communication, but ROS does, so it qualifies as spread spectrum. If you have a receive bandwith of 10,000 Hz, and you spread over that bandwidth, you really are using way more bandwidth than necessary to send the same data at a given speed. MT63 uses 64 carriers with the data divided among the carriers for redundancy and about 40% of the signal can be obilterated by QRM and still produce good copy. I think the difference with ROS is that the carrier frequencies are varied according to a code, instead of being at a fixed position, but I am no expert on modes, so someone else can probably explain it better and with more accuracy. Generally it is qualifies as spread spectrum if a code is used for the spreading, and in military communications (and even cell phones, I think) the code prevents anyone else from reconstructing the signal so that the intelligence can be recovered if they do not possess the same code. 73 - Skip KH6TY John wrote: Thanks Skip, Unfortunately, this really does not get to the crux of my question(s). I understand how an SSB transmitter works, but that is not really what I am after. What I am driving at is if like this. If I use DM780 to run some version of digital mode via an SSB transceiver, it uses a tone or series of tone modulation/shifting to create the output of the transmitter, and not one single mode is called spread spectrum output, but is called FSK or PSK, etc. Now, we get into the aforementioned discussion regarding ROS, and suddenly, still via the microphone input of the same transmitter, those shifted frequencies are now called spread spectrum instead. I am having a great deal of difficulty understanding, other than the author happened to call his scheme spread spectrum in his technical documentation. Thanks John KE5HAM --- In digitalradio@yahoogroups.com, KH6TY kh...@... wrote: John, Given sufficient carrier suppression, any tone inputed to the microphone makes the transmitter output a pure RF carrier at a frequency of the suppressed carrier frequency plus the tone frequency for USB, or minus the tone frequency for LSB. Whatever you do with the tones
Re: [digitalradio] Re: Curious sound card modes question -
That is only ONE of the three conditions outlined by Jose. I thought I did not need to repeat the other two. 73 - Skip KH6TY Dave AA6YQ wrote: re PSK31 accomplishes the same typing speed in a bandwidth of 31 Hz, instead of in 2000 Hz, so ROS is probably truly spread-spectrum. Applying this logic to RTTY, which employs ~10X the bandwidth employed by PSK31, would lead us to conclude that RTTY is also spread spectrum. 73, Dave, AA6YQ -Original Message- *From:* digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com]*on Behalf Of *KH6TY *Sent:* Monday, February 22, 2010 8:30 PM *To:* digitalradio@yahoogroups.com *Subject:* Re: [digitalradio] Re: Curious sound card modes question - It will be spread spectrum if the tone frequencies are controlled by a code as explained in the ROS documentation: A system is defined to be a spread-spectrum system if it fulfills the following requirements: 1. The signal occupies a bandwidth much in excess of the minimum bandwidth necessary to send the information. 2. Spreading is accomplished by means of a spreading signal, often called a code signal, which is independent of the data. 3. At the receiver, despreading (recovering the original data) is accomplished by the correlation of the received spread signal with a synchronized replica of the spreading signal used to spread the information. Standard modulation schemes as frequency modulation and pulse code modulation also spread the spectrum of an information signal, but they do not qualify as spread-spectrum systems since they do not satisfy all the conditions outlined above. Note that all three conditions must be met to be considered spread spectrum. I don;t know if it would be possible to send the data in less bandwidth, but, for example, PSK31 accomplishes the same typing speed in a bandwidth of 31 Hz, instead of in 2000 Hz, so ROS is probably truly spread-spectrum. Remember that spread spectrum was conceived as a way of coding transmissions so they could not be intercepted and decoded. In fact actress Hedy Lamarr invented spread spectrum, and you can read that here: http://en.wikipedia.org/wiki/Hedy_Lamarr. The difference is the use of a code to spread the data and signals to avoid detection and monitoring by those without the same code. Download the documentation from www. rosmodem.wordpress.com and read about spread spectrum and the ROS implementation. That will make it clear I think. Remembering that a single tone creates a single RF carrier makes it easy to see how just about anything can be done with tones, including sending data over several tones at once so if one carrier is lost, others carry the same data, or using a psuedo-random code to determine the carrier frequencies, as I think is done in ROS. That documentation also explains the difference between FHSS and modes like MFSK16. However, a main point is that the data does not have to be scattered over such a wide bandwidth to achieve communication, but ROS does, so it qualifies as spread spectrum. If you have a receive bandwith of 10,000 Hz, and you spread over that bandwidth, you really are using way more bandwidth than necessary to send the same data at a given speed. MT63 uses 64 carriers with the data divided among the carriers for redundancy and about 40% of the signal can be obilterated by QRM and still produce good copy. I think the difference with ROS is that the carrier frequencies are varied according to a code, instead of being at a fixed position, but I am no expert on modes, so someone else can probably explain it better and with more accuracy. Generally it is qualifies as spread spectrum if a code is used for the spreading, and in military communications (and even cell phones, I think) the code prevents anyone else from reconstructing the signal so that the intelligence can be recovered if they do not possess the same code. 73 - Skip KH6TY John wrote: Thanks Skip, Unfortunately, this really does not get to the crux of my question(s). I understand how an SSB transmitter works, but that is not really what I am after. What I am driving at is if like this. If I use DM780 to run some version of digital mode via an SSB transceiver, it uses a tone or series of tone modulation/shifting to create the output of the transmitter, and not one single mode is called spread spectrum output, but is called FSK or PSK, etc. Now, we get into the aforementioned discussion regarding ROS, and suddenly, still via the microphone input of the same transmitter, those shifted frequencies are now called spread spectrum instead. I am having a great deal of difficulty understanding, other than the author happened to call his scheme spread spectrum in his technical documentation. Thanks John KE5HAM --- In digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com, KH6TY kh...@... wrote: John, Given sufficient carrier
Re: [digitalradio] Re: Curious sound card modes question -
Gentlemen, I have spent way too much time with my limited knowledge trying to make some sense of this issue and answer questions. I am going to use ROS on UHF only anyway, and it is legal there no matter if it is FHSS or not, so I'll leave it to the rest of you to discuss the issue. Thanks for the bandwidth and I hope it can be used on HF! 73, Skip, KH6TY
Re: [digitalradio] Re: Curious sound card modes question -
KH6TY wrote: It will be spread spectrum if the tone frequencies are controlled by a code as explained in the ROS documentation: A system is defined to be a spread-spectrum system if it fulfills the following requirements: 1. The signal occupies a bandwidth much in excess of the minimum bandwidth necessary to send the information. 2. Spreading is accomplished by means of a spreading signal, often called a code signal, which is independent of the data. 3. At the receiver, despreading (recovering the original data) is accomplished by the correlation of the received spread signal with a synchronized replica of the spreading signal used to spread the information. Standard modulation schemes as frequency modulation and pulse code modulation also spread the spectrum of an information signal, but they do not qualify as spread-spectrum systems since they do not satisfy all the conditions outlined above. Note that all three conditions must be met to be considered spread spectrum. I don;t know if it would be possible to send the data in less bandwidth, but, for example, PSK31 accomplishes the same typing speed in a bandwidth of 31 Hz, instead of in 2000 Hz, so ROS is probably truly spread-spectrum. The key is the much in excess in item 1. If you were to use 31hz vs 2000, you'd be approaching the minimum bandwidth expansion factor in practical usage at 64:1. I'd have to go look at realistic bandwidth for psk, I was thinking it's a bit higher in the real world. Modern SS runs way higher, often 1000:1. But just like the fsk symbol rate anachronism in the regs, I suspect the spread spectrum restriction in the regs was targeted the very broad (50-100khz minimum) spread spectrum signals. Realistically, they did not anticipate that we'd have the capability to do SS in a 2khz signal. (and we probably could not have pre-sound card) But after reading the NTIA definition, and the one in the docs, I agree it's technically SS by a strict interpretation. Just like P3 is technically FDM. But since both live in a SSB signal bandwidth, they are not what the regs were trying to prevent. Based on the FCC ruling on P3 OFDM, my suspicion is they'd fall in favor of ROS. I don't see a practical reason for them to disallow it, it does not have expanded footprint, etc. But all this points out to me how out of date the US regs are! It would be easier if they had used the NTIA definition, and ideally put some practical measures around bandwidth expansion factor and overall bandwidth. No matter what, it's a neat idea, and thanks for taking the time to code it! have fun, Alan km4ba
Re: [digitalradio] Re: Curious sound card modes question -
No, the shift on RTTY and other soundcard modes is not determined by a pseudo random code but always known and predictable. Instead, the tones on ROS are driven by a code signal. To quote from the ROS documentation, 2. Spreading is accomplished by means of a spreading signal, often called a code signal, which is independent of the data. The original intent of spread spectrum was to make it impossible to monitor without possessing the despreading code, but ROS can be monitored. There is a good chance that the FCC will allow us to use ROS on HF - why not! But as the rules are written right now, ROS is FHSS - by design, and it does not matter if the description is changed or not, so it is necessary to get a waiver or other FCC agreement that we can use it on HF. ROS can be copied by third parties, and is no wider than a phone signal, so I cannot think of any reason the FCC would decline, but they have to give permission. That is just the way it works, because that is how the rules happen to have been written in the past. If the spreading is NOT actually accomplished by means of a spreading signal, often called a code signal, which is independent of the data then ROS is not spread spectrum and there is no problem. 73 - Skip KH6TY jhaynesatalumni wrote: --- In digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com, John ke5h...@... wrote: Thanks Skip, Unfortunately, this really does not get to the crux of my question(s). I understand how an SSB transmitter works, but that is not really what I am after. What I am driving at is if like this. If I use DM780 to run some version of digital mode via an SSB transceiver, it uses a tone or series of tone modulation/shifting to create the output of the transmitter, and not one single mode is called spread spectrum output, but is called FSK or PSK, etc. Now, we get into the aforementioned discussion regarding ROS, and suddenly, still via the microphone input of the same transmitter, those shifted frequencies are now called spread spectrum instead. I am having a great deal of difficulty understanding, other than the author happened to call his scheme spread spectrum in his technical documentation. That's a good question. If we run RTTY with 850 Hz shift like we did in the old days, has that turned into spread spectrum?
Re: [digitalradio] Re: Curious sound card modes question -
On Mon, Feb 22, 2010 at 08:30:29PM -0500, KH6TY wrote: It will be spread spectrum if the tone frequencies are controlled by a code as explained in the ROS documentation: A system is defined to be a spread-spectrum system if it fulfills the following requirements: 1. The signal occupies a bandwidth much in excess of the minimum bandwidth necessary to send the information. 2. Spreading is accomplished by means of a spreading signal, often called a code signal, which is independent of the data. 3. At the receiver, despreading (recovering the original data) is accomplished by the correlation of the received spread signal with a synchronized replica of the spreading signal used to spread the information. Standard modulation schemes as frequency modulation and pulse code modulation also spread the spectrum of an information signal, but they do not qualify as spread-spectrum systems since they do not satisfy all the conditions outlined above. Note that all three conditions must be met to be considered spread spectrum. I don;t know if it would be possible to send the data in less bandwidth, but, for example, PSK31 accomplishes the same typing speed in a bandwidth of 31 Hz, instead of in 2000 Hz, so ROS is probably truly spread-spectrum. Remember that spread spectrum was conceived as a way of coding transmissions so they could not be intercepted and decoded. In fact actress Hedy Lamarr invented spread spectrum, and you can read that here: http://en.wikipedia.org/wiki/Hedy_Lamarr. The difference is the use of a code to spread the data and signals to avoid detection and monitoring by those without the same code. She invented FHSS as a torpedo control technique; most folks don't know that she had an EE degree. DSSS came about later, as a classified technique called Phantom, to permit transmissions with a low probability of interception (LPI). With a typical 3 KHz bandwidth receiver, or even a 50 KHz wide panadaptor, you won't see all the spectrum from a wideband (say, 100 KHz spreading code) DSSS transmission. You may notice only a slightly raised noise floor. But that's only part of the deal with DSSS. The correlation and despreading produces a really nice gain in noise immunity, as well. -- Mike Andrews, W5EGO mi...@mikea.ath.cx Tired old sysadmin
