Re: [digitalradio] What is here Spread Spectrum and why and what is not?
Rein, You can decide for yourself if ROS is spread spectrum or not, just be observing it with any audio spectrum analyzer, or program like fldigi or Digipan that has a waterfall. Just observe the behavior with data and without data at idle and you will see. You find that the carriers of the 16 baud and 1 baud variations bear no relationship to the imposed data, but hop around randomly - a sure sign of spread spectrum or frequency hopping. Instead in FSK and PSK, the carrier frequencies are fixed and modulated with the data. MFSK16 is a FSK mode and MT63 is a PSK mode (modulation applied to 64 fixed frequencies). Here is a comparison I made, similar to what you can make yourself: http://home.comcast.net/~hteller/SPECTRUM.JPG There is indisputable randomness to the ROS tone frequencies, even if you watch it for a long enough time. Applied to modulate a SSB transmitter, the resulting RF frequencies are also indisputably random. The FCC engineers have performed the same spectral analysis and informed the ARRL that the mode is truly spread spectrum. ROS now has some more narrow modes added, which I have not inspected, but maybe only the wide 1 baud and 16 baud varieties are spread spectrum, or frequency hopping, and the narrow ones are FSK - I don't know. Even if those narrow modes are not frequency-hopped, they are still grouped under the same umbrella, ROS, which means any approval of ROS for narrowband modes would wind up also approving the wide versions, which have all the appearance of being spread spectrum, or frequency hopped. For this reason, it did not work to include some narrow FSK modes to try to get overall approval by the FCC engineers. In fact it probably was an insult to their intelligence! The distinction of spread spectrum, or frequency-hopping, is simply that the carrier frequencies are determined independently of the data. Originally this was done in order to encrypt the signal unless you possessed the de-hopping code. It does not matter if the de-hopping code is sent along with the data, or the frequency spread is unusually narrow - frequency hopping is still frequency hopping - and that happens not to be allowed under 222 Mhz in FCC jurisdictions. A petition to modify the regulations can be submitted, but that has not been done, to my knowledge - just repeated attempts to fool the FCC with untruths. If a SSB transmitter is fed audio tones and the carrier is adequately suppressed, then the output is pure RF at the suppressed carrier frequency plus the individual tone frequency (for USB) and if the tones are frequency-hopped, it makes no difference if the RF generation is by frequency shift of an oscillator or by means of tones - the FCC is only interested in the emitted RF and its behavior. The advantage to frequency hopping, if you have the de-hopping code, is that the noise is random, but the signal has a known autocorrelation function, so integration by looking for the correlation can make the weak signal stand out from the random noise background - something I am sure you are aware of that has been long used in deep space communications. Splitting off the frequency-hopped modes from the same program that contains the narrow FSK modes might result in approval to use a separate program that has no frequency-hopped modes. The remaining program would only be allowed in the US above 222 Mhz. 73 - Skip KH6TY Rein A wrote: Hello All, http://www.youtube.com/watch?v=lOmrgJkFY40 http://www.youtube.com/watch?v=lOmrgJkFY40 I found this interesting YouTube video, interesting to me at least. It is going a to be a big help watching waterfalls at 14.103 kHz and other channels such as http://etgd2.ewi.utwente.nl:8901/ http://etgd2.ewi.utwente.nl:8901/ 73 Rein W6SZ
Re: [digitalradio] What is here Spread Spectrum and why and what is not?
Trevor, I was not privy to the names of the engineers - only told in confidence by one of the group that it was done. There is no report, and Dan Henderson is the ARRL spokesman who relayed the information to hams. That finding was also published on the ARRL website. This is all I can say and will say on this subject. Sorry, that I can say no more, but you can make the tests for yourself and see that ROS is indeed frequency hopped. As has been stated, hams are responsible for following the regulations. It is definitely unusual that the FCC would look at the emitted frequencies as they did in this case, but I guess it was because of so much disagreement. When the FCC decides to prosecute an wrong-doer, they definitely make an analysis on their own - just read the various charges filed against out of banders that are caught, transmitting more than the allowed power, blocking repeaters, using profanity, etc. They have in many cases gone to much trouble to determine without a doubt that a rule was being broken. In this case, any ham can make the same analysis - just run ROS into a soundcard and look at the resulting spectrum. ARRL only tries to provide guidance so individuals do have to do that, but the responsibility is up to the individual amateur to comply with the regulations. 73 - Skip KH6TY Trevor . wrote: --- On Wed, 2/6/10, KH6TY kh...@comcast.net mailto:kh6ty%40comcast.net wrote: The FCC engineers have performed the same spectral analysis and informed the ARRL that the mode is truly spread spectrum. That's interesting, the FCC have said they they did not give judgments on individual data modes, it's up to the operator to decide. Who were the FCC engineers you mention, where is their report and who in ARRL HQ did they communicate with. 73 Trevor M5AKA
Re: [digitalradio] What is here Spread Spectrum and why and what is not?
Dave, The answer to your question is no for MT63, as it is nearly just as wide as ROS 16 baud, but will stop decoding at -8 dB S/N for the 50 wpm mode, Contestia 1000/64 at -13 dB S/N at 30 wpm, and Olivia slower at 15 wpm, but probably around -15 dB S/N. PSK31. PSK31 works down to -11.5 dB S/N at 50 wpm, as a comparison, but is only 31 Hz wide. The point is that for QSO's (which ROS does), not messaging (what WINMOR does), fast speed is not needed, because people usually cannot type more than around 50 wpm (the design goal for PSK31). For messaging however, you sacrifice minimum S/N for speed. You can get an idea by looking at the 1 baud mode of ROS, which is extremely slow, even for QSO's, but good just for exchanges, like in WSJT or moonbounce. This is where ROS has the greatest potential and where its wide width is not important because there is so much space at 70cm and 23cm. Otherwise, on HF, the same long-distance QSO's can be accomplished in much, much, less bandwidth, and probably just as effectively. I have often worked the South Pole, Japan, Australia, New Zealand with only 900 mw and PSK31 on 20m and the bandwidth was only 50 Hz maximum. If conditions are at all favorable, it does not take much power on the higher HF bands to go around the world. For UHF, and short exchanges, ROS is probably the best performer in a bandwidth of 2250 Hz, but the speed is very, very, slow. That is why the macros are like WSJT macros. It just takes too long to exchange much more. There is really no rationale for using ROS 16 baud on HF, as wide as it is, because our ham bands are shared, and spectrum hogs leave no room for others. However, on UHF, there is, and that is where ROS, with SS, is not counter-productive, but has the most promise. On UHF, we could use ROS, but it does not hold up well under Doppler Spreading, so we have settled on Contestia 1000/64 at 30 wpm as the best performing mode, decoding right down to the noise threshold, when even CW is hard to copy by ear. ROS simply failed to print when Contestia 1000/64 was printing 100%. Your point is well made, but there is a advantageous application for ROS, and that is on UHF for EME. Up there, it is legal for US hams to use also. 73 - Skip KH6TY Dave Sparks wrote: More importantly (to me, at least) is Spread Spectrum the most effective or efficient way of using a given amount of bandwidth to deliver a given data rate, from a weak signal point of view? IOW, would ROS work better than, let's say, MT-63, WINMOR, or Olivia if those three modes were adjusted to use the same bandwidth and data rate as ROS? If it were open source, I would have included Pactor-3 in that list, too. If not, then using SS is counter-productive as well as legally problematic. (I'm not implying that ROS is SS, BTW.) -- Dave Sparks AF6AS -- From: Trevor . m5...@yahoo.co.uk mailto:m5aka%40yahoo.co.uk Sent: Wednesday, June 02, 2010 2:29 PM To: digitalradio@yahoogroups.com mailto:digitalradio%40yahoogroups.com Subject: Re: [digitalradio] What is here Spread Spectrum and why and what is not? --- On Wed, 2/6/10, KH6TY kh...@comcast.net mailto:kh6ty%40comcast.net wrote: The FCC engineers have performed the same spectral analysis and informed the ARRL that the mode is truly spread spectrum. That's interesting, the FCC have said they they did not give judgments on individual data modes, it's up to the operator to decide. Who were the FCC engineers you mention, where is their report and who in ARRL HQ did they communicate with. 73 Trevor M5AKA http://www.obriensweb.com/digispotter.html Chat, Skeds, and Spots all in one (resize to suit) Facebook= http://www.facebook.com/pages/digitalradio/123270301037522 Yahoo! Groups Links
Re: [digitalradio] What is here Spread Spectrum and why and what is not?
Trevor, Just to clarify, the FCC defines modes by emission types and other things, such as if SS is allowed, and where. It is the operator who must follow the FCC regulations, and he has no legal right to decide whether or not HIS judgement is the one to follow, or if he follows the regulations or not. He MUST simply follow the regulations. If he cannot determine if he will legally emit with a certain mode, the ARRL is the one who has their technical experts provide guidance, but the ARRL does not make the rules! The FCC may or may not look at a particular mode's emissions - they usually only look at emissions on the air and determine if the operator is out of compliance or not. Probably similar to the enforcement vans that roam London looking for illegal TV and radio emissions, as I am told they did in the past, if they still do that. 73, Skip KH6TY That's interesting, the FCC have said they they did not give judgments on individual data modes, it's up to the operator to decide. 73 Trevor M5AKA
