Here are some comments from Ad Hoc HF Digital Committee Chairman Vic Poor, W5SMM. 73, Dave K1ZZ -----Original Message----- From: Victor Poor [mailto:vpoor@cfl.rr.com] Sent: Thursday, October 14, 2004 9:48 AM To: Sumner, Dave, K1ZZ Cc: Butler, Frank (Dir, SE) Subject: Bandwidth Proposal Dave... Several people have asked me to "respond" to Skip Teller's email of October 11 to the members of the board and to his various WEB pages. I hope this email will serve that purpose. I leave it to you to decide what distribution should be made. First of all, the digital committee recommendations were the result of looking at all possible future digital modes and were not focused on just Winlink. Like so many technologies Winlink will blossom and fade as other more attractive methodologies emerge. The whole philosophy behind the recommendations was to provide a future framework for development and experimentation without being unduly confined to rules. This does not mean there shouldn't be segmentation by modes of operations as well and by bandwidth but the point was to avoid hardening modes of operations into law. Who can say what communication modes the amateur community will find attractive in the future. Skip purports offers a "simple" solution. H. L. Mencken once said for every complex problem, there is a solution that is simple, neat, that everyone understands, and is wrong. Skip's solution fits that description exactly. In a nutshell, Skip claims that Winlink causes harmful interference and should be confined to narrow sub-bands and that Pactor III is not efficient and should not be allowed. Winlink operation is no different than any other amateur mode of operation. An operator is expected to listen first and make sure the frequency is clear before transmitting. This, in fact, is the practice and Winlink itself would not be a viable mode if this were not the practice. By mutual agreement by Winlink operators around the world Pactor III is currently ONLY being used in the U.S. automatic sub-bands (remember this restriction only applies to U.S. operators) and could not possibly be causing interference with operations outside of those sub-bands. Narrow band Winlink operations take place outside those sub-bands and are legal in all countries, U.S. included. Again, by mutual agreement, all Winlink operators have agreed to remain clear of the popular 14070-14072 kHz sub-band that is widely used by PSK31 operators. Yet much of the complaints about interference come from operators in that sub-band. This is due to poor operating practice on the part of users of the very popular Digipan software (written and promoted by Skip Teller). This scheme of operation encourages running receivers at wide bandwidths to receive signals of less than 100 Hz bandwidth. Anytime a signal (ANY signal) that falls within the receiver bandwidth that is strong enough to pump the received AGC there will be "interference". The digital committee was fully aware of this phenomenon and was in full agreement (except by Skip Teller) that this was not good amateur operating practice and that other modes should not be penalized because of it. The interference argument against Winlink specifically is bogus. Skip makes a claim that Pactor III is only 30% faster than Pactor II and therefore 3-kHz data modes should not be permitted BY LAW from semi-automatic operation on the HF bands. This is nonsense on at least two counts. Even if the assertion that Pactor III wasn't efficient was true that should not prevent any future 3-kHz mode from being used. Isn't this the very kind of rule we are trying to avoid? However, Pactor III is very efficient. Rick Muething, KN6KB, has made an apples-to-apples comparison of many of the popular HF digital modes that was presented in a paper presented at the latest DCC. He did this using a very sophisticated HF channel simulator developed by Johan Forrer, KC7WW, that implements the "Watterson Gaussian-scatter HF ionospheric channel model" (see http://www.johanforrer.net/SIMULR/ for a complete description of the simulator). Rick found that of all the modes tested Pactor III has the very smallest footprint on the HF spectrum based on the bandwidth used, the amount of data transmitted, and the time takes to do it (The bandwidth/data rate/time product). For any use other than simple keyboard-to-keyboard operation Pactor III has the highest throughput and the least possible impact on the HF spectrum of any mode tested. It is also very robust, maintaining a data flow under the very poorest conditions. These comments are not intended as simply a defense of Pactor III but to point out the fallacy of Skip's argument and the need to have rules that permit the use and development of more advanced modes of communications. Skip somehow seems to argue that Winlink is different that other digital modes. There are two kinds of digital operation, keyboard-to-keyboard where two operators converse, holding a channel open during the entire QSO and higher speed modes where data is sent at as high a speed as possible and then the channel is left free. Both modes have been in use since the earliest days of RTTY operation and to enact a rule now that limits the get-on-and-get-off type of operation to legislated narrow subbands does not pass a test of reasonableness. This was the digital committee's view. Skip also claims to be speaking for 99% of the amateur operators. There is no basis for a claim like that. There are thousands of amateur operators using non-keyboard digital modes. I doubt if anyone can tell who uses what or how often but I don't believe anyone is in a position to speak for more than themselves. One final comment: Should there be HF subbands for different modes? Yes, but not in the FCC rules. This is something that needs to remain flexible as operating practices and operating needs change. Recommended sub-bands drawn by mutual agreement by the regional societies can keep modes that are truly mutually conflicting separated. The FCC rules, after all, only apply to U.S. operators and there is a whole world of operators that are not subject to those rules. Using the regional societies for band planning makes the best possible sense in the end. Vic Poor, W5SMM