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Paul W. Schleck posted on Sun, 23 Mar 2008 12:03:58 EDT:
Many types of communications vary over many orders of magnitude of information rate, yet are considered useful and up-to-date. For example, the Casio WaveCeptor on my wrist: http://www.eham.net/reviews/detail/2497 receives a ~ 1 Baud Pulse Position Modulated (PPM) signal from radio station WWVB in Fort Collins, Colorado, which transmits on 60 kHz. It takes about a minute to send the complete time code to synchronize my watch. Slow? Yes. Useful? Yes, very much so, especially when considering the coverage and reliability that can be obtained from such a low-bandwidth, groundwave-propagated, Very Low Frequency (VLF) signal. The watch only needs to receive the time code at most once per day, which it does so automatically in the early hours of the morning sitting on my desk or dresser. A faster data rate would require something other than a VLF signal, and would not improve much on the quality or usability of the communications. It would definitely increase the price. Witness the much greater success in the marketplace of WWVB-based watches versus more advanced, higher bandwidth, but much more expensive, "Smart Personal Object Technology" (SPOT) watches: Good mention, Paul. Ummm...the data rate is rather exactly one bit per second and takes exactly 60 seconds to send one frame of time and date data. :-) ALL the details are given at www.nist.gov under the 'Time Frequency' page, including propagation charts at various times of the day and for various seasons. This southern California region can regularly receive enough signal to set radio clocks even if at an approximate distance of about 900 miles to Fort Collins. In 2005 my wife and I drove to southern Wisconsin and my La Crosse radio wris****ch never failed to set itself properly even though some of our overnight stays were in hotels having steel structures or in among other buildings. We have two radio wall clocks in our residence and those are exact enough to compare on-the-second with HF time ticks from WWV and WWVH. [I won't quibble about the PPM mode descriptor since the full details of modulation are given at NIST website... :-) ] According to this recent demonstration on the Tonight Show with Jay Leno: http://www.youtube.com/watch?v=AhsSgcsTMd4 Ahem...quibble mode on...that little bit on the Tonight Show was a 'setup' gig that employed two young local male actors as the (described) "text messaging experts" but the two hams (one of which would very soon become marketing director for Heil Sound) were real. That is the input I got directly from a reliable staffer on the Tonight Show. Took a few phone calls to get that information but it is an advantage of living inside the entertainment capital of the USA (aka Los Angeles, CA)...and the NBC western Hq is only about 5 miles south of my place, down Hollywood Way to Alameda and then east about a mile. That whole bit was really a send-up on the popular fad of text messaging done by teeners and young adults. That bit is about as 'real documentary' as Leno's send-ups on the 'street interviews' with ordinary (apparently clueless) younger folk on various kinds of knowledge. In short, ONLY for gag purposes. To even give you a Morse code example, consider the simplicity and effectiveness of the NCDXF beacons running on the HF bands: http://www.ncdxf.org/beacons.html HF beacons are neat for their purposes of checking on HF propagation paths, but they aren't 'communications' in the regular sense. Those were also designed for simplicity at the various receiving sites but require rather precise time-of-day at each receiver in order to get the start of each cycle. While I had not intended to restart some morse-vs-others kind of argument, I have to note where I began HF communications with the US military some 55 years ago. Not a single communications circuit used any form of morse coding to achieve a throughput of nearly a quarter of a million messages per month (average in 1955). The majority was teleprinter of the 5-level 'Baudot' format running at 60 WPM equivalent rates. 24/7 of course with TTY distributors to to automatically start another p-tape reader when the other reader was done. FSK 'spread' was then 850 cycles, not the narrower 170 Hz of today. Radio circuits (where I was assigned) spanned the northern Pacific from Saigon, Seoul, and Manila to Anchorage, Seattle, San Francisco, and Hawaii. In 1955 the Army tried an experiment on a few select radio circuits to push the Teletype Corporation's machines to 75 WPM equivalent. End result of that was a failure rate more than double that of the standard 60 WPM equivalent machines. Teletype seems to have achieved an optimized design for 60 WPM equivalent; their 100 WPM equivalent next-generation machines used a different electromechanical system, were quite reliable at that rate. very fast determination of the link budget to the beacon locations. If you can't remember what a "V" sounds like in Morse Code (". . . _" like the intro to Beethoven's Fifth Symphony), I suppose you could put that on the chart as well. After all, the use of similar charts are how pilots usually decode the Morse code identifications of aeronautical beacons. Quibble mode on again. The LF aeronautical beacoms are what you are writing about but they are NOT used much at all for aircraft radio- navigation now, nor were they a half century ago. Present-day (and in 1962) radionavigation over land is done mainly by VOR (Very high frequency Omnidirectional Radio range) using a unique 30 Hz antenna pattern rotation with a reference phase of 30 Hz sent on a 9.96 KHz subcarrier. Aircraft VOR receivers have used very simple (even for tube circuits) to determine their bearing to a ground station. These were simple enough (and low cost enough) for small private general aviation craft and the US VOR system was adopted internationally in 1955. For distance to a ground station the civil method emplyed a low L-band interrogator sending a (jittered) double pulse and measuring the return delay (plus 50 uSec) from the ground station responder. This DME (Distance Measuring Equipment) was compatible with military TACAN (TACtical Area Navigation) signal format and the FAA combined VOR-DME-TACAN equipments on the ground and those are identified by the contraction VORTAC. On aeronautical charts (from the government, usually reprinted by private companies) there is usually a magnetic bearing compass circle (VOR and civil-use-TACAN reference magnetic reference, not actual north reference)...the VHF frequencies (DME and TACAN frequencies have been paired with VOR), ICAO 3-letter ID, and the dot-dash pattern of that 3-letter ID. The elegant simplicity of VOR is that it will permit AM Voice IN the ground station transmitter without disturbing the antenna pattern modulation or the reference phase subcarrier. In congested urban areas where a lot of general aviation aircraft abound, FAA stations routinely use VOR voice transmissions to aid civil pilots, easing the pilots' workload by providing extra information such as WX, special conditions at an airport. My local airport (BUR) now known as Bob Hope Airport, the FAA used to send a repeating voice announcement of local WX conditions, airport info, etc., all identified by a letter, beginning with A or Alpha at midnight. The tag on the voice tape loop was "please tell the tower you have received 'information Foxtrot or whatever letter'" when requesting landing at that airport. Yes, some VORs transmit the ICAO 3-letter ID as a low-modulation on-off tone in slow morse but I have yet to find any civil pilot, beginner to experienced, who USES that code for radionavigation. Focusing simply on information rate disregards other aspects of the communications and the channel over which it is transmitted. These important aspects include the bandwidth and propagation characteristics of the available channel, the complexity of the required transmitting and receiving equipment, the amount of data that needs to be transmitted, and how quickly and often it needs to be conveyed. Martinez' PSK31 was rather precisely designed for low (500 Hz) bandwidth coincident with non-typists typing rate of about 30 WPM equivalent, all in congested Data slices of amateur radio band 'bandplans' on HF. With relatively simple electronic terminal equipment with microprocessor-aided operation, I/O memory space and programming is a minor addition to handle faster typists' input, even burst typing on a keyboard to 100 WPM or so equivalent. The OLD FSK bandwidths on HF (of a half century ago) took up about a whole KHz while using an 850 cycle shift. On the 3 KHz of an old commercial-format SSB channel (one of four), as many as 8 separate TTY circuits could be frequency-multiplexed. A more reasonable shift (to 170 Hz) occurred later with improvements in terminal equipment technology, is the norm now, even for 100 WPM equivalent teleprinter rates of those still using electromechanical terminals. BANDWIDTH occupancy seems to be the primary driver for modulation rates on HF. YMMV. There are more complex methods of modulation-demodulation that have been available for some time. DRM (Digital Radio Mondial) is one such as has been verified on HF for 'SW BC' (Broadcasting). That DRM has not spread well among broadcasters has little to do with technical details of modulation-demodulation, but rather in the poor propagation conditions of this sunspot cycle limiting broadcasters' range. If a signal can't get through at all, NO modulation method is going to help. Besides, with the availability of satellite radio broadcasting, 'SW BC' has gradually shifted over to that method rather than using HF directly. I'm not sure that I understand your line of reasoning here. You are implying cause-and-effect. In other words, use and advocacy of Morse code somehow directly contributed to the obstruction of other technologies. Can you give direct evidence of specific examples? If you are implying that licensing requirements obstructed the development of advanced digital modes, that really doesn't appear to be the case. Witness the success of Tucson Amateur Packet Radio (TAPR): It is disingenuous to 'force' an argument by introduction of something not overtly stated by the originator. TAPR and its membership have done some excellent technical development and spread of such technology. Note also that its membership is made up of radio amateurs who've been licensed for a while and are NOT technical beginners in radio or electronics. In the view of the ENTIRE world of radio, not just amateur radio, the use of morse code modes to communicate has steadily decreased for over a half century. It has decreased so much so that some non- amateur radio services either stopped using that mode or never considered it for a new radio service introduced in the last half century. As a prime example, the changeover to GMDSS and replacement of the old 500 KHz international distress and safety frequency which used morse code exclusively. Even the USCG stopped monitoring that old 500 KHz frequency. GMDSS was designed and approved by the Maritime Community, not by amateurs. The decline, or perhaps more accurately, the failure to keep up with overall population increase (of USA) amateur licensees is (in my opinion) NOT due exclusively to 'USE' of morse code. US amateur radio license totals peaked 5 years ago. In general, by informal polling, newcomers are NOT embracing morse code modes...nor are they flocking to HF amateur bands. PART of that MAY be due to the insistence of the 'amateur radio community' to hang onto the morse code TEST forever. Part of that is due to the slow acceptance of international amateur radio to change the international amateur Radio Regulations away from old standards. WRC-03 of nearly 5 years ago allowed individual administrations to drop the morse code test for an amateur radio license. The USA did not follow through on that until more than 3 years later. [precisely, the end of July 2003 to 23 February 2007] [in response to 'Klystron'] If you are saying that someone *else* should have developed these technologies (other than you, of course), and that since they haven't, then someone *must* be to blame, well, you can't really dictate how the world should turn out without taking an active role to help make it that way. That's rather strong wording from a leading person of this newsgroup, isn't it? For a very long while, ever since I first began as a pro in HF radio communications, PART of the 'amateur radio community' had been very busy 'dictating' how the amateur radio world should be by the continuation of the morse code test for an amateur radio license. OTHERS, including those of us (like myself) who were NOT licensed in amateur radio have actively campaigned to remove that test from US amateur radio...even though other countries had already preceded the USA in abolishing that code test. I won't say that I've 'been responsible' for any USA changes but I was certainly 'active' in trying to do so. The FCC apparently agreed with some of my views as well as so many others supporting that test elimination. It came to pass. But, that coming might have been too late to change others' interests in US amateur radio. In my electronics work that began (professionally) in 1952, I've been involved in a lot of different electronics and modes and modulations of RF that were never allocated for US amateur radio use. Some of those just wouldn't apply to two-way communications but others would apply. There are still some US regulations that need altering but a very vocal PART of the 'amateur radio community' seems very adamant about NOT upsetting the status quo. The future of US amateur radio does NOT depend solely on them. 73, Len AF6AY First licensed in US amateur radio in March 2007 First licensed in US commercial radio in March 1956 First QSY of a 1 KW HF transmitter in February 1953 |
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