daveb@comspec.uucp (dave berman) (07/05/90)
Dear new friends - I am very new to news in general, and have almost ZERO knowledge of LORAN-C, except that a close friend of mine spent an entire year trying to repair a defective STS (brand) Loran receiver. From my reading the manual that accompanies the receiver, I learned that the LORAN-C waves are extremely identical and sent in a predictable pattern at a standard time from 3 or 4 locations at a standard, very low radio frequency (? 8940? 8490? Hz for my part of North America). This can be used to determine (among other things) your exact location within a few hundred meters. This may not be accurate, but this summarizes what I know. I think I understand the postings here are kinda personal for you all who use this stuff in your labs. But I am interested in following the cross talk anyway. (I hope you don't mind). To this end, these are the terms which I could not understand from 3 postings. I have included the postings at the end for your information. Could you or someone define (or loosely define) these terms, please? I have included the few I know, just to show you how *little* definition would do the trick. To Mills, Dave or Richard, or whoever answers this posting: Thank you in advance. Maybe others have wanted to know about this stuff too - I hope I also thank you on their behalf. - Dave Glossary of Unknown Terms apple (in context) chimer, chimers clepsydra ECO, ECOs fuzz, fuzzball fuzzball hardware GPS JvNC JvNC fuzzy LORAN-C: an international time and location low frequency standard? MIT: Mass. Inst. of Technology? NEARNET net 128.175 friskers net 128.4 rascals norad (in context): ? a ____ site NSFNET NSS NTP ntpdc ntpdc billboards oxide plow: informal description of disk head collecting disk scrape stuff pelt, pelting primary server (in this context) Selective Availability umd1 UDP/TIME USCG: United States Coast Guard USNO The above list was gleaned from these messages: From: Mills@udel.edu Newsgroups: comp.protocols.time.ntp Subject: SDSC spins harder Folks, The legions of chimers now pelting primary server fuzz.sdsc.edu will be happy to learn that fuzzball has abandoned pelt of floppy disk in favor of the hard stuff, a 30-megabyte disk and controller kindly furnished courtesy the DEC folk. This should result in some improvement in accuracy, since the silly kernel loop necessary to hack the floppy-disk controller no longer spins. Similar equipment has been installed at ncarfuzz.ucar.edu and truechimer.cso.uiuc.edu, but so far has not been coaxed to life, due ECOs, cables or whatnot. The goal is a general upgrade of fuzzball hardware and removing the potential for the floppy drives to become oxide plows. Meanwhile, the JvNC fuzzy arrived here for temporary storage. We are hoping to find a home at MIT, assuming the NSFNET NSS is installed there and NEARNET agrees to house the critter. Dave From: Mills@udel.edu Newsgroups: comp.protocols.time.ntp Subject: Re: GPS News from CANSPACE Richard, According to the latest USCG newsletter, LORAN-C time-transfer accuracy is expected to be inproved to the order of 100 ns; at least, that's what the USCG has interpreted Congress to mandate. This is about three times more accurate that available with GPS Selective Availability as verified by published USNO weekly corrections. Accordingly, I have abandoned efforts to pursue GPS in favor of LORAN-C, which is potentially much cheaper and yields better accuracy, at least within groundwave range (which most of us are). Yes, I know LORAN-C groundwave is vulnerable to weather, season, etc., but not to the extent, as verified by measurements in my lab, to change my conclusion. Dave P.S. When the GPS community gets its hat on right and kills the Selective Availability nonsens, my conclusion may well change. DLM From: Mills@udel.edu Newsgroups: comp.protocols.time.ntp Subject: Re: New clock in the world Dave, Your chimer remains elusive to my net 128.4 rascals, but at least responds to ntpdc from net 128.175 friskers. Your ntpdc billboards show you have chime only from the radio and not from anybody else, including clepsydra (down at the moment), apple and norad (both up). Did we ever resolve this problem? Not that I would care a lot, but two of the NSFNET bunch are broken at the moment and the fuzzballs are groaning under the load of well over 120 chimers per machine, so any little help is spreading the load is much appreciated. Just for giggles, I see that umd1 is under pelt from misguided UDP/TIME chimers, some of which give pelt every couple of minutes and then machine- gun the victim several times in one second. This results in a packet flux six times the rate permitted by NTP. Most destructive. I suggest nobody use umd1, whose time is now degraded to the point my servers never select it. Kick those UPD/TIME brokons off the machine and maybe it would return to the useful. Dave -- Dave Berman 436 Perth Av #U-907 daveb@comspec.UUCP Computer at work Toronto Ontario uunet!mnetor!becker!comspec!daveb Canada M6P 3Y7 416-785-3668 Fax at work
brian@ucsd.Edu (Brian Kantor) (07/06/90)
There is a nice NBS monograph #129 in many libraries (ours here at ucsd had it) that describes Loran-C in a LOT of detail and will explain many of the technical terms you were curious about. Much of the rest of the terms you were questioning were simply Dr. Mills being excessively cute; although fun to read, it can take some effort to decrypt. Let me assure you, it's usually worth the effort. (Sorry, Dave, but it does get a bit thick at times.) A shorthand and only somewhat-accurate explanation of Loran-C: Loran-C is transmitted on a radio frequency of 100kHz in the form of pulses. There are "chains" of stations sending pulses at the same rate within a chain and differing rates between chains; by observing the repetition rate and delays between pulses it is possible to derive the distance between yourself and the transmitting stations. Since the stations are at known locations, hyperbolic geometry can be used to figure out the location of the receiving station to some small degree of error. The timing of the Loran-C transmissions is quite precise. Although Loran pulses do not encode time in the sense of you being able to read hours minutes and seconds from the pulse train directly, they do represent a nice reasonably-stable timebase - and it's quite easy to receive them. Thus it may be possible for time freaks such as myself to cobble up something that uses the received Loran signal as a timebase to keep a clock ticking at precise intervals, with the actual setting of the clock being done by other means, such as a WWV receiver. That's not a terribly accurate explanation, but it may help. - Brian
lars@spectrum.CMC.COM (Lars Poulsen) (07/07/90)
In article <1990Jul5.044200.3261@comspec.uucp> daveb@comspec.uucp (dave berman) writes: >To this end, these are the terms which I could not understand from 3 postings. >apple (in context) The site APPLE.COM (Apple Computers, in Cupertino (?)) >chimer, chimers An informal term for someone that speaks clock protocol (NTP). >clepsydra Another host site; don't know who or where. >ECO, ECOs Engineering Change Order. A hardware bugfix (published by the manufacturers field service organization). >fuzz, fuzzball >fuzzball hardware The Fuzzball was an experimental TCP/IP package that ran on LSI-11's. Developed and maintained for the public good by Dave Mills for several years. The first NSFnet was built out of Fuzzballs. >GPS Global positioning System. A US military navigation satellite system; I think it contains about 27 satellites. Missiles can get their position to about 50 feet; but commercial customers can not get nearly as good accuracy: We did not want the Soviet missiles to benefit from our system !! The equivalent Soviet system is called Glonass. >JvNC >JvNC fuzzy John von Neumann Center for supercomputing. A fuzzball at that location. >LORAN-C: an international time and location low frequency standard? A ground-based navigation system, similar to DECCA. Used by commercial aircraft and ships. >MIT: Mass. Inst. of Technology? You got it. >NEARNET New England Academic Research NETwork. >net 128.175 friskers >net 128.4 rascals Machines located on the networks with these addresses. >norad (in context): ? a ____ site NORth American Air Defense. The command center of the USAF Strategic Air Command. An early pioneer in research of synchronizing distributed clocks. >NSFNET NSS National Science Foundation Network Network Support System. A soon-to-be-built central monitoring site for NSFNET. I was surprised to hear that NSF might move their network operations away from Michigan. >NTP Network Time Protocol. >ntpdc >ntpdc billboards A remote monitoring tool for NTP time server programs. >oxide plow: informal description of disk head collecting disk scrape stuff >pelt, pelting To beat on. To access/utilize a resource. >primary server (in this context) The NTP synchronization mechanism allows for a primary peer group, to which other timers align themselves, in a manner similar to the tiered control of the network name service. >Selective Availability The deliberate distortion of the commercial signal from the GPS satellites. >umd1 A host at University of MarylanD. >UDP/TIME User Datagram Protocol encapsulated time protocol information. >USCG: United States Coast Guard >USNO United States Naval Observatory. -- / Lars Poulsen, SMTS Software Engineer CMC Rockwell lars@CMC.COM
vixie@decwrl.dec.com (Paul A Vixie) (07/08/90)
>>clepsydra > Another host site; don't know who or where. That's clepsydra.dec.com, in Palo Alto, California. -- Paul Vixie DEC Western Research Lab <vixie@wrl.dec.com> Palo Alto, California ...!decwrl!vixie