Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rutgers!ucla-cs!zen!ucbvax!SIMTEL20.ARPA!W8SDZ From: W8SDZ@SIMTEL20.ARPA (Keith Petersen) Newsgroups: comp.dcom.modems Subject: Public Digital Radio Service wireless modem proposal Message-ID: Date: Fri, 7-Aug-87 02:45:00 EDT Article-I.D.: SIMTEL20.KPETERSEN.12324511877.BABYL Posted: Fri Aug 7 02:45:00 1987 Date-Received: Sat, 8-Aug-87 18:08:24 EDT Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 408 The following file was uploaded to my bulletin board. I am NOT the author. Replies to the author, please, not me. --Keith Petersen Arpa: W8SDZ@SIMTEL20.ARPA Uucp: {bellcore,decwrl,harvard,lll-crg,ucbvax,uw-beaver}!simtel20.arpa!w8sdz GEnie: W8SDZ RCP/M Royal Oak: 313-759-6569 - 300, 1200, 2400 (V.22bis) or 9600 (USR HST) --cut-here--PDRS.TXT--cut-here-- [This article is NOT COPYRIGHTED and may be freely reproduced, however, it is requested that all credits remain intact.] This File is provided as a Public Service by: Business Information Xchange NETwork BIXNET - 300/1200/2400 8-N-1 616-361-7500 24 Hours 7 Days a week Thom Byxbe, SysOp David Stockdale, Co-SysOp Jack Decker, Co-SysOp, Administrator of PDRS & Wireless Modem SIG BIXNET is a public BBS operated by: Advanced Business Technologies, Incorporated 4191 Plainfield Avenue Suite # 217 Grand Rapids, Michigan 49505 VOICE 616-361-0200 A public SIG is avaliable on BIXNET to discuss the Topic of Wireless Modems and The Public Digital Radio Service. Your input and comments are invited and encouraged. Voice communications may be made VIA Advanced Business Technologies Contact Jack Decker or Thom Byxbe. WIRELESS MODEMS: THE NEXT CORDLESS TELEPHONE? by Jack Decker I'd like you to think, for a moment, about the cordless telephone. For nearly a hundred years, if you wanted to use a telephone, your freedom of movement was restricted to the length of the cord attached to the receiver. Then someone got the idea to remove the cord and use a short-range radio transmitter-receiver in the handset instead, and the cordless telephone was born. Early units were very primitive by today's standards - they generally had no way to dial (you had to return to the base unit to do that), their range was limited to about 100 feet, and the sound quality was reminiscent of tin cans and string. In spite of all that, the idea of cutting the cord caught on with the public, and the cordless telephone is now a multimillion dollar industry. What is particularly worth noting, however, is that the cordless telephone is a "Part 15" device. This means that it operates under "Part 15" of the Federal Communications Commission rules and regulations, which specifically pertain to the operation of low-power transmitters for which no license is required. Keep in mind that originally there were no frequencies specifically allocated for cordless telephones, so the designers of the first cordless units had to find a suitable band on which low power, unlicensed operation was permitted. Originally, frequencies just above the AM broadcast band and frequencies in the 46-49 MHz band were used, but the AM frequencies were later dropped in favor of 46-49 MHz use only. The 46-49 MHz band was not originally set aside for cordless telephones, but low power operation was authorized in that band for the use of things like children's walkie-talkies and remote control models. However, as the cordless telephone became more and more popular, and there were more and more reports of interference between units, the F.C.C. realized that something needed to be done to bring order out of the chaos. So, they then set standards for cordless telephone operation, assigning cordless phones to certain frequencies and specifying permissible transmitter power levels. Part of the F.C.C. action was to allocate new frequencies for cordless phones in the 46-49 MHz range, while eliminating the use of the low-fidelity AM frequencies that were responsible for the poor audio quality of early cordless phones. When you stop and think about it, the cordless telephone would hardly fall into the category of a "necessity of life" for most people, but nevertheless they have made a big impact on the consumer market. Ten years ago, if you had asked people to name a needed product that had not yet been invented, I doubt that anyone would have said "I need a phone handset with no connecting cord." But, as is the case with so many consumer products, the availability of the product created the demand. People saw the product, realized that it could be of use to them, and bought - in big numbers! CAN HISTORY REPEAT ITSELF? Computer hobbyists are in a similar situation right now. Many computer users have discovered the pleasures and benefits of connecting their computer to other computers via telephone lines, using modems. However, the dependence on phone lines creates some problems for the average user. For one thing, the family's telephone line is tied up while the computer is online, and for another, toll charges or measured service telephone charges may be imposed even though the computer being called is only a relatively short distance away. Also, since only two users at a time can be connected via a telephone connection, it is impossible to have local area "computer conferences" involving more than two users (unless there is a sophisticated, multi-user BBS in the area, to which all the potential participants have access). One obvious solution to these problems is packet radio, as widely used by amateur ("ham") radio operators. But, there are a couple of restrictions to the use of ham radio. The first is that all potential users of amateur radio must first learn the antiquated Morse Code, plus some electronic theory. While these requirements may not be burdensome for some computer hobbyists, others (who have little interest in electronics or no desire to learn the Morse Code) may see them as formidable obstacles. The other restriction is that no messages of a commercial nature may be sent via amateur radio. Since most BBS's contain advertising of one form or another (if only messages offering no-longer-needed computer equipment for sale or trade), the use of amateur radio might tend to limit the free exchange of messages that could remotely be considered "commercial". Besides, amateur radio operators and computers hobbyists may have totally different interests. While there are many people who are interested in both amateur radio and computers, there are also many people who are interested in one hobby but not the other. Amateur radio operators, who have suffered a decline in the number of people joining their fraternity in recent years, have sometimes looked at computer users as a source of potential "new blood" for their organizations. However, I believe it is a disservice to both the amateur radio community and to the computer user community to induce computer hobbyists who have no actual interest in amateur radio into becoming "hams". The computer hobbyists will have little interest in the majority of the activities enjoyed by amateurs (such as building radio transmitters and antennas, or talking to people on the other side of the world via Morse Code) while many of the amateurs may not be interested in discussions of bits and bytes, which DOS is best, or the differences between Basic, Pascal and C. While the ability to use packet radio may induce a number of computer hobbyists to join the ranks of the amateur radio operators, I believe this would be a "marriage of convenience" and not really satisfying to either group in the long run. A short analogy might be in order. Suppose we have a stamp collectors' club that, as a benefit to its members, offers a free trip to a philately convention in some major city of the world every year. Now, lets further suppose that club membership is declining, so some of the members, in an effort to boost membership, start selling the club as a good way to travel to various places at low cost. A number of people who like to travel might thus be attracted, and while a few of those might actually become interested in stamp collecting as a byproduct, most are going to become very bored and irritated with club meetings where the only discussion is about First Day Covers and commemoratives. By the same token, if these new members vote to change the format of the meetings so that travelogue films are shown during the meetings, the original members would quite rightly protest that the purpose of the club is being abandoned. Ultimately, neither group would be fully satisfied. And I suspect the same will be true when computer hobbyists, many of whom have no desire to ever pick up a soldering iron, become amateur radio hobbyists simply to gain the benefit of being able to operate packet radio stations. So, what is really needed is a way for computer users to be able to enjoy the benefits of packet radio operation, without the need to become amateur radio operators. Mr. Donald L. Stoner of Mercer Island, Washington proposed this very thing before the F.C.C., with a proposal to establish a computer hobbyist radio service, to be known as the "Public Digital Radio Service" (PDRS). This service would have operated on the 52-54 MHz band. However, the proposal was opposed by the American Radio Relay League (a national amateur radio organization) and a few other organizations and individuals, and the F.C.C. denied it (but said that they might consider allowing a similar service on a different frequency). Obviously, the formal implementation of this service is not a high priority for the F.C.C. But, under current F.C.C. regulations, it would be quite feasible to start a "bargain basement" version of PDRS and, once the need and desire for such a service is established, I believe that the F.C.C. might then reconsider the PDRS proposal with a bit more urgency. PDRS NOW? You may be asking yourself, "Is it really true? Is there a way for computers to communicate with each other via packet radio, without the need to obtain a license, and with no restrictions on message content (other than, perhaps, the general restrictions on the use of obscenity and profanity on the airwaves)?" It sure is, but the only problem is that nobody's making the equipment yet, probably because nobody has given much thought to the particular frequency band involved. "But if the F.C.C. hasn't authorized packet radio for non-amateurs, how can I use it?" Easy. Under the provisions of good old Part 15, the same section of the F.C.C. rules that the cordless telephone manufacturers used to get their product started. "But cordless telephones only have a range of about 1000 feet. What good will that do me?" Well, we can stay within the scope of Part 15 regulations and still get a MUCH greater range than 1000 feet. You see, there is one major difference between a wireless modem and a cordless telephone handset. The cordless phone is intended to be portable, so ideally we want to be able to use the shortest possible antenna on it. It wouldn't be very practical to have a cordless handset with, for example, a ten foot antenna on it. The higher the transmit frequency used, the shorter the antenna you can get by with, and at the 46-49 MHz range the short antenna used with most cordless phones is adequate. But, at 46-49 Mhz, F.C.C. (Part 15) regulations only permit a transmitter output power of 1/10 watt, which severely limits the distance at which the handset and base can be separated before the signal fades out. But a modem generally remains in one place, and for that reason we can easily connect it to a larger, outdoor antenna if necessary. In the case of amateur packet radio stations, outside antennas are often used to increase range (even though they are not strictly necessary at the frequencies used by amateur radio operators). With no practical limitation on antenna length, we can use frequencies that might be unsuitable for portable operation. And, as it turns out, there is a small band of frequencies that can provide us with a much greater range under Part 15 rules and regulations, if we are willing to erect a good antenna. That frequency band is the 160-190 KHz band (sometimes known at the "1750 Meter band"), located well below the AM broadcast band. As I understand it, at these low frequencies you can use up to one watt of power and an antenna length of up to fifty feet, and still remain within F.C.C. regulations for unlicensed operation. Theoretically, a range of up to 30 miles is possible, although you may practically not be able to communicate that far. But please keep in mind that packet radio stations can act as repeaters (while still permitting normal local use of the packet station), so, for example, to send messages or data to someone as far as 100 miles away might be possible if there are enough conveniently-spaced repeater stations with good antennas in between. Low frequency equipment is very inexpensive to build and operate, but the antenna is very important. The best antenna would be a fifty foot vertical mast with lots of radials (ground plane wires) buried in the ground, but this is obviously impractical for most users (although, if this mode of operation ever catches on, it's quite possible that one or two companies may specialize in manufacturing "easy to install" low frequency antennas!). However, if you are willing to accept a reduction in range, shorter antennas can be used. Even a relatively small loop antenna may get you a five mile range (and, again, don't forget that repeaters can be used for greater distance). Transmission on the 1750 Meter band can be by AM, FM, SSB or any other mode you like, but it has been suggested to me (by Bill de Carle) that the optimum mode at 300 baud might be MSK (minimum-shift-key). Bill states that "at these low frequencies you can do everything digitally, even when it comes to directly synthesizing the RF waveforms." Another correspondent (Jay Coote) has suggested that it may be possible to use a High-Frequency amateur type packet (AMTOR) in the low frequency band. Some others are using BPSK [bi- phase shift keying], which for all I know, may be the same thing as MSK. I am convinced that if some individual or company would take the time to design and build a low-frequency Part 15 wireless packet radio unit (which could be a low-frequency transceiver intended to be connected to any of the commercially-available amateur packet radio Terminal Node Controllers), it could well be the turning point in getting PDRS "off the ground." Computer hobbyists would begin to see the desirability of having this kind of equipment, would most likely pressure the F.C.C. for better frequencies, and the industry would take off. And, of course, the first company to produce such a unit would likely wind up being a major player in this industry (how would you like to be the next Hayes or Microsoft?). You may ask why, if I think this is such a great idea, I don't keep it to myself and build a prototype unit. The answer is very simple: I'm not a hardware hacker! I don't have the technical knowledge required to make such a unit, and don't personally know anyone who has the expertise or initiative to produce such a unit. Also, I do not have the financial resources to participate in this endeavor, being one of the underemployed at present. So, although I would love to get a piece of the action on this industry, there really is no way for me to actively participate. And keeping the idea to myself would accomplish nothing, since then the units would never be built and no one would benefit. I only hope that, if anyone gets filthy rich in this industry, they will remember me and, if nothing else, at least send me a couple of free samples of each new model of wireless modem that they create. Personally, I could put a pair of wireless modems to good use. The SYSOP of an area BBS lives approximately five miles away from me, but it is a toll charge for me to call his BBS. Conversely, people in my phone exchange have access to cheap long distance (good for calling other BBS's) while people in his exchange do not. So, we could both make use of a radio link to connect our two sites. At present, the only workable solution we can find are the wireless modems manufactured by a company called Electronic Systems Technology (1031 N. Kellogg Street, Kennewick, Washington 99336). They manufacture a device called the "ESTeem Wireless Modem" that transmits on 24 channels in the frequency range of 72.040 to 72.960 MHz. It is licensed using "F.C.C. form 574" (under "Part 90" of the F.C.C. regulations, I believe), and appears to be intended for business applications only. Therefore, it probably would not be possible to license this unit for what would basically be considered "hobbyist" use, and the units are certainly not priced with the hobbyist in mind - each wireless modem costs over $1,000! I can't imagine why the cost is so high when an amateur Terminal Node Controller/Transceiver combination can be purchased for under $400, but we can't afford one, let alone the two we'd need to establish communications between us. In conclusion, I am firmly convinced that if computer hobbyists understood the benefits of PDRS, they would be solidly behind efforts to get a decent frequency allocation for this service. However, until they have actually had the opportunity to sample such a service and see what it can do for them, they will remain apathetic toward it, and will not put any pressure upon the F.C.C. to formally recognize this type to service. By providing low-cost equipment to operate this service on 160-190 KHz, computer hobbyists would be able to utilize the service now (instead of waiting for the F.C.C. to act, which may take years) and would have practical knowledge of the benefits of this type of service and more incentive to lobby the F.C.C. for a better frequency allocation. I would suggest that any individuals or groups that attempt to create a working low-frequency packet radio standard try to keep in touch with each other, so that incompatible standards don't develop between different groups. A public SIG is avaliable on the BIXNET BBS at (616) 361-7500 (300/1200/2400 8-N-1) to discuss the topic of Wireless Modems and The Public Digital Radio Service, and I would suggest that this would be a good place for people who are interested in this subject to exchange information and keep in contact with others who have similar interests. One final technical suggestion: Although this may exceed the scope of the basic system described above, if you do decide to design a low-frequency packet radio system "from scratch" and you give it any amount of intelligence, please give it the capability to require a fairly complex (say 10 or 14 character) password for access (and even possibly the ability to be able to vary passwords according to time of day, or to use passwords from a pre- created list) and/or the ability to accept incoming calls from only one other packet system; and also give it the ability to be connected "back to back" with a conventional smart modem (in addition to the "standard" conection to a computer). Why? Because then a low-frequency packet radio system and conventional modem could be placed at a friend's or neighbor's home, or at an office location, and used to gain access to the telephone line there without necessarily giving everyone else with a similar system the same access. The big advantage of doing this would be when the remote conventional modem is connected to a different telephone exchange (with a different local calling area) than yours, and making a connection through the remote packet system/conventional modem combination saves you outgoing toll charges. In this type of situation, it would be ideal if the packet system could contain enough intelligence to reject unauthorized usage and/or to reject the sending of outdialing commands to the conventional modem that would place a long distance call (i.e. "ATD" commands where the first digit is a "1", or the second digit is a "1" or "0"). RESOURCES:The following is a list of various resources on the subject of low- frequency radio, including a few people who seem to be knowledgeable on the subject. If I have omitted anyone from this list, I apologize. The Longwave Club of America, 45 Wildflower Road, Levittown, Pennsylvania 19057. Has a publication called the "LOWDOWN" which apparently is widely circulated among low-frequency enthusiasts (although I have yet to see a copy!). Radio Computing Digest, c/o Paul Louden Christensen, P.O. Box 916, Oroville, Washington 98844-0916, telephone (509) 476-2600. Send $3.00 to receive issue number one, the only issue published so far. It has a wealth of information on radio computing, including a much more complete list of resources than what is being provided here. Panaxis Products, P.O. Box 130, Paradise, California 95969, telephone (916) 534-0417. These folks produced an 1750 Meter FM transmitter-receiver kit a couple of years ago but recently stated they only have three (3) printed circuit board sets left. A plans and circuit board set goes for $28.50 while a complete kit is $134.95 (antenna not included). Panaxis also sells other types of kits and equipment, including transmitters for (unlicensed) low-power AM and FM (including stereo FM) broadcasting. Dave Riley (Broadcast Technical Services), 11 Walnut Street Marshfield, Massachusetts 02050, telephone (617) 837-3521. Radio Computing Digest states that Dave has lots of experience in RF communications and Radio Computing and has published a small book on the subject ($10). He also operates a BBS at (617) 837-2880. Kevin B. Haywood, another correspondent, states that Mr. Riley's booklet is called "Computer Communications Study" and contains information on F.C.C. rules governing no-license broadcasting, addresses of radio manufacturers, and hints and ideas on how to convert ham radio gear to the license-free bands. Donald L. Stoner, 6014 East Mercer Way, Mercer Island, Washington 98040. Original author of the Public Digital Radio Service proposal, now said to be working on a revised proposal. His time is quite limited but he may appreciate hearing any PDRS suggestions you may have, even if he is unable to respond. Bill de Carle, 235 Baythorn Drive # 301, Thornhill, Ontario, Canada L3T 3V6. Bill has done some work with low frequencies, including running "some experiments with a low-frequency beacon transmitter sending FSK data on 180.2 KHz" in one direction from his apartment to his office, a distance of about five miles. He states that his transmissions "can be copied reliably at this distance even with inefficient antennas, but I use computerized signal processing to enhance data recovery." Mel Carter, 46 14th Street, Wheatland, New York 82201. Bill de Carle states that Mr. Carter "has designed a simple BPSK [bi-phase shift keying] transmitter/receiver using only CMOS chips." Jay Coote, 808 North Avenue 66, Los Angeles, California 90042. Another low- frequency beacon operator who may be able to offer information on the peculiarities of LF operation. Jack Decker, 1804 West 18th Street # 155, Sault Ste. Marie, Michigan 49783- 1268, telephone (906) 632-3248. I will be more than happy to field-test any prototypes of low-frequency radio modems or packet radio systems. As a computer user who has had some experience in telecommunicating with conventional modems but virtually no experience with packet radio, I can easily discover any difficulties that the average computer user might have with your product, and would be more than willing to offer suggestions for product improvement! This File is provided as a Public Service by: Business Information Xchange NETwork BIXNET - 300/1200/2400 8-N-1 616-361-7500 24 Hours 7 Days a week Thom Byxbe, SysOp David Stockdale, Co-SysOp Jack Decker, Co-SysOp, Administrator of PDRS & Wireless Modem SIG BIXNET is a public BBS operated by: Advanced Business Technologies, Incorporated 4191 Plainfield Avenue Suite # 217 Grand Rapids, Michigan 49505 VOICE 616-361-0200 A public SIG is avaliable on BIXNET to discuss the Topic of Wireless Modems and The Public Digital Radio Service. Your input and comments are invited and encouraged. Voice communications may be made VIA Advanced Business Technologies Contact Jack Decker or Thom Byxbe.