Re: [time-nuts] locate 6 digit digital clock
Lovely! My first exposure to TTL logic circuits was through building a Nixie Clock. It looked nice, and certainly impressed my college dorm-mates, but didn't keep very good time. Very sensitive to power-line noise and dropouts, and I never got the seconds and minutes counters to reset to zero reliably on the count of 60. Now I know better, but I'm not sure that I want to go back to using 1970s technology. Except, of course, if I could find a nice set of nixie tubes at a reasonable price, and a set of sockets and a transformer for the high-voltage supply ... ! The controller chip looks interesting, and certainly has a lot of desirable features. It may be easily adaptable to different display types. I agree on the lack of a 1 PPM input, and I would prefer a 10 MHz TCXO timebase over the standard 32.768 kHz oscillator. -- Flemming Larsen Fra: W2HX w...@w2hx.com Til: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sendt: 19:13 onsdag den 8. juni 2011 Emne: Re: [time-nuts] locate 6 digit digital clock [snip] regards 73 Eugene W2HX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] locate 6 digit digital clock
Now that is very high in the cool factor! This has been an interesting thread and got me to thinking about building something similar for myself. A quick search for Arduino and LED or LCD Clock returned many hits and lots of interesting ideas for rolling my own. For those not acquainted Arduino it is a simple development/learning platform based on an Atmel chip which has become very popular for hacking and playing around with. So popular in fact that you can now get PIC and a 75 MHz ARM based Arduino like compatible boards - same form factor and common IDE. You could for example take an Arduino board, plug on a LCD display shield, add a simple sketch (aka program) and have a functional clock, - add some software to sync to a gps 1 pps (etc, etc). The plug on boards with different functionalities are called shields and you can get pretty much whatever you would like - Ethernet, wireless, Bluetooth, etc. Do a quick general Google search or have a look on eBay; you might be surprised. Cheers, Graham ve3gtc -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: June 8, 2011 15:11 To: Flemming Larsen; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] locate 6 digit digital clock In message 985823.67392...@web24819.mail.ird.yahoo.com, Flemming Larsen write s: I recently turned a HP frequency counter into a style-fitting clock for our workshop in Danish Computer History Association: http://ing.dk/artikel/119043-ur-til-tiden (Google translate does a decent job) I used a PIC18mumble and a DS3231 RTC. Since the RTC also tracks day-month-year, it was trivial to let it run in UTC and program the pic18 to figure out timezone + DST. Even if you use a uP to count time, it would make good sense to include a RTC so you don't have to reset the clock after each power-glitch. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] locate 6 digit digital clock
Hi My only connection with BRG is finding them on a web search. Other than that, I can't say anything about them. Bob On Jun 8, 2011, at 11:23 PM, Robert Watzlavick wrote: I would avoid BRG clocks. I've used them in two different companies now and they're pretty much junk in my opinion. Both of the clocks I used had IRIG inputs and they only sort of work. They seem to randomly lose IRIG lock every few days and will easily get 1/2 second off, even when locked. The user interface is incomprehensible and takes me 20 minutes to figure out every time I have to adjust the UTC offset to display local time. Finally the instruction manuals are too complicated to be useful. It seems like they just keep tacking on features to firmware written 20 years ago, even with the new features don't fit the UI model. When IRIG time wouldn't sync up on one of the units, I took it apart and found the clock to be constructed of a metal picture frame with the circuit boards loosely laying inside some green crafting foam and wires running all over the place. Even my electronics projects when I was a kid looked more professional than these clocks. When I reassembled it, the IRIG feature mysteriously started working again, sort of. The prices look very appealing but trust me, stay away - they just don't work. -Bob On 06/08/2011 03:46 PM, Bob Camp wrote: Hi Found the GSA price list at: http://www.brgprecision.com/pdffiles/brg_gsa_contract.pdf Looks like you can get the basic no frills model for about $400 and they go up from there. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Wednesday, June 08, 2011 4:35 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] locate 6 digit digital clock Hi I suspect that something like: http://www.brgprecision.com/products/synchronized_clocks/poe6mega.php would do the trick. No idea what they cost. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of William H. Fite Sent: Wednesday, June 08, 2011 4:07 PM To: j...@quik.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] locate 6 digit digital clock I think he wants a clock that will actually tell time, rather than one that merely blinks *12:00...12:00...12:00...* [?][?] On Wed, Jun 8, 2011 at 3:10 PM, J. Forsterj...@quik.com wrote: Why not just buy or scrounge a small microwave oven or VCR? -John == Please add my me-too to this discussion. I would like to see a clock that simply tells time, reminiscent of the ones I put together in the 1970s, but with LED displays large enough to read from across a darkened room. I would prefer 24-hour format and I want a 6-digit display with seconds. For accuracy, I would want an internal TCXO, with the option of using a 10 MHz or 1 PPS external signal when available, but I want the clock to automatically switch to the internal timebase if the external signal is disconnected or lost With a PIC I would like to see a switch for PDT/PST, so I don't have to reset the clock twice a year. I would also like to see an option for having the clock be self-setting or self-synchronizing by adding an inexpensive GPS module. I don't need date and I don't need DOW or DOY as I already have other clocks and watches that give me that information. It might be useful to have a smaller second line that would show me those, and show me the time in UTC to keep track of what time it is back in the old country when I want to listen to Radio Denmark on the Internet, but this would add to the complexity and the number of solder points. And I would like all this to fit in a spare HP 2U half-width rack-mount case that I have saved for that purpose. This would be a companion to my Thunderbolt GPSDO which is housed in an identical case. One option would be to mount the clock in the same case as the Thunderbird, and have the second line display your choice of GPS signal. -- Flemming Larsen, KB6ADS/OZ6OI Fra:Brooke Clarkebro...@pacific.net Til:Discussion of precise time and frequency measurement time-nuts@febo.com Sendt:7:12 onsdag den 8. juni 2011 Emne:Re: [time-nuts] locate 6 digit digital clock By using a PIC you can do much more than just tell time, for example display the Day of the Week and because the calendar is good back to 1800 something you can set the clock back that far and know the DOW. The next step was going to be to install a table of leap seconds so that you could replay any of those events in history. See: http://en.wikipedia.org/wiki/Zeller%27s_congruence Have Fun, Brooke Clarke http://www.PRC68.comhttp://www.prc68.com/ ___ time-nuts mailing list --
Re: [time-nuts] locate 6 digit digital clock
Hi That's just an Atmel ATmega16 micro. There's nothing unusual about it. Bob On Jun 8, 2011, at 10:13 PM, W2HX wrote: I picked up this chip to create a nixie clock: http://www.allspectrum.com/store/6-digit-nixie-tube-clock-controller-chip-p- 501.html it has tons of features which you can read about here (condensed feature list): http://www.allspectrum.com/semiconductors/ics/Neonixie/6DIGIT-NIXIE-CLOCK-CH IP/Neonixie-6-digit-nixie-clock-controller-options-v1.0.pdf I picked up an old nixie time code reader display (systron donner) from a surplus place (in seattle): http://www.w2hx.com/x/nixie/IMG_2113.jpg it was great because it had the nixies, controller chips, power supply and everything. I just had to wire in the chip (prototype here): http://www.w2hx.com/x/nixie/IMG_2511.JPG final soldered version here: http://www.w2hx.com/x/nixie/IMG_2721.JPG and the final product here: http://www.w2hx.com/x/nixie/IMG_2516.JPG only problem is, it doesn't (yet) take a 1PPS input. I've contacted the folks who made the chip to see if they would consider creating a version with 1PPS. But it does have a super cap that will let it keep time for something like 8 hours. regards 73 Eugene W2HX - ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] locate 6 digit digital clock
Very nicely done! John WA4WDL -- From: W2HX w...@w2hx.com Sent: Wednesday, June 08, 2011 10:13 PM To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: Re: [time-nuts] locate 6 digit digital clock I picked up this chip to create a nixie clock: http://www.allspectrum.com/store/6-digit-nixie-tube-clock-controller-chip-p- 501.html it has tons of features which you can read about here (condensed feature list): http://www.allspectrum.com/semiconductors/ics/Neonixie/6DIGIT-NIXIE-CLOCK-CH IP/Neonixie-6-digit-nixie-clock-controller-options-v1.0.pdf I picked up an old nixie time code reader display (systron donner) from a surplus place (in seattle): http://www.w2hx.com/x/nixie/IMG_2113.jpg it was great because it had the nixies, controller chips, power supply and everything. I just had to wire in the chip (prototype here): http://www.w2hx.com/x/nixie/IMG_2511.JPG final soldered version here: http://www.w2hx.com/x/nixie/IMG_2721.JPG and the final product here: http://www.w2hx.com/x/nixie/IMG_2516.JPG only problem is, it doesn't (yet) take a 1PPS input. I've contacted the folks who made the chip to see if they would consider creating a version with 1PPS. But it does have a super cap that will let it keep time for something like 8 hours. regards 73 Eugene W2HX - ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] locate 6 digit digital clock
I have a good supply of MM5314N chips so all my clocks are based on the chip. But I always wondered why as long as I have been on the list no one has developed a LCD or LED unit using a PIC or other controller chip along with a board. Is there no interest? Bert Kehren Miami In a message dated 6/9/2011 8:25:18 A.M. Eastern Daylight Time, jmfra...@cox.net writes: Very nicely done! John WA4WDL -- From: W2HX w...@w2hx.com Sent: Wednesday, June 08, 2011 10:13 PM To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: Re: [time-nuts] locate 6 digit digital clock I picked up this chip to create a nixie clock: http://www.allspectrum.com/store/6-digit-nixie-tube-clock-controller-chip-p- 501.html it has tons of features which you can read about here (condensed feature list): http://www.allspectrum.com/semiconductors/ics/Neonixie/6DIGIT-NIXIE-CLOCK-CH IP/Neonixie-6-digit-nixie-clock-controller-options-v1.0.pdf I picked up an old nixie time code reader display (systron donner) from a surplus place (in seattle): http://www.w2hx.com/x/nixie/IMG_2113.jpg it was great because it had the nixies, controller chips, power supply and everything. I just had to wire in the chip (prototype here): http://www.w2hx.com/x/nixie/IMG_2511.JPG final soldered version here: http://www.w2hx.com/x/nixie/IMG_2721.JPG and the final product here: http://www.w2hx.com/x/nixie/IMG_2516.JPG only problem is, it doesn't (yet) take a 1PPS input. I've contacted the folks who made the chip to see if they would consider creating a version with 1PPS. But it does have a super cap that will let it keep time for something like 8 hours. regards 73 Eugene W2HX - ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] locate 6 digit digital clock
I think that there is plently of interest. Trouble is everyone wants something different. Brooke's LCD one looks good, may be he will finish it off. Just the 16x2 LCD, 1 PPS input, 10Mhz clock. Then add IRIG in and out, GPS update, serial output to drive a sipo shift register to drive 7 seg LED's, NTP, Battery back up Some of the published micro based designs are a bit kludgy. Robert G8RPI. --- On Thu, 9/6/11, ewkeh...@aol.com ewkeh...@aol.com wrote: From: ewkeh...@aol.com ewkeh...@aol.com Subject: Re: [time-nuts] locate 6 digit digital clock To: time-nuts@febo.com Date: Thursday, 9 June, 2011, 15:26 I have a good supply of MM5314N chips so all my clocks are based on the chip. But I always wondered why as long as I have been on the list no one has developed a LCD or LED unit using a PIC or other controller chip along with a board. Is there no interest? Bert Kehren Miami In a message dated 6/9/2011 8:25:18 A.M. Eastern Daylight Time, jmfra...@cox.net writes: Very nicely done! John WA4WDL -- From: W2HX w...@w2hx.com Sent: Wednesday, June 08, 2011 10:13 PM To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: Re: [time-nuts] locate 6 digit digital clock I picked up this chip to create a nixie clock: http://www.allspectrum.com/store/6-digit-nixie-tube-clock-controller-chip-p- 501.html it has tons of features which you can read about here (condensed feature list): http://www.allspectrum.com/semiconductors/ics/Neonixie/6DIGIT-NIXIE-CLOCK-CH IP/Neonixie-6-digit-nixie-clock-controller-options-v1.0.pdf I picked up an old nixie time code reader display (systron donner) from a surplus place (in seattle): http://www.w2hx.com/x/nixie/IMG_2113.jpg it was great because it had the nixies, controller chips, power supply and everything. I just had to wire in the chip (prototype here): http://www.w2hx.com/x/nixie/IMG_2511.JPG final soldered version here: http://www.w2hx.com/x/nixie/IMG_2721.JPG and the final product here: http://www.w2hx.com/x/nixie/IMG_2516.JPG only problem is, it doesn't (yet) take a 1PPS input. I've contacted the folks who made the chip to see if they would consider creating a version with 1PPS. But it does have a super cap that will let it keep time for something like 8 hours. regards 73 Eugene W2HX - ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightsquared test in las vegas
On the other hand, what can be said about the wisdom of engineers that designed a product that cannot withstand any interference from adjoining spectrum holders? It has been known for at least the last 6 years that LightSquared's predecessor was going to occupy that spectrum with a land based system. Does the GPS world really have much to say about the interference if LightSquared keeps their transmitters clean and out of the GPS spectrum? -Chuck Harris Jason Rabel wrote: This is kind of in reference to other LightSquared articles that all seem to make mention of, LightSquared's proposal for a network of 40,000 ground transmitters... These 40k ground transmitters to be installed... Are they just going to be additional antennas on existing cell towers, or is LightSquared planning to construct their own towers in new locations? Reason I say... Cell towers are located for maximum coverage and the most dense population. Likewise, when traveling between cities they stick them close to the interstates so people can have reception while traveling. A blind man should be able to see that problem. rantI guess the rest of the world will be able to enjoy GPS, while the US pays for it (but can't use it) But hey, watching people do stupid things on youtube is infinitely more necessary for the US economy than a critical navigation system deployed in countless cars, boats, planes, and anything else that moves This should have been killed off a long time ago, and the frequency spectrum stripped away from LightSquared just for the mere mention of doing something as stupid as they are trying to do.../rant ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightsquared test in las vegas
Perhaps not in the abstract, but on-orbit power is severely limited, and you can't get more RF watts out of a transmitter than you put in as DC. Can you imagine the uproar if every GPS bird had a 10 KW transmitter on board, powered bu a nuclear reactor? The low received power is a direct consequence of engineering of satellites. -John On the other hand, what can be said about the wisdom of engineers that designed a product that cannot withstand any interference from adjoining spectrum holders? It has been known for at least the last 6 years that LightSquared's predecessor was going to occupy that spectrum with a land based system. Does the GPS world really have much to say about the interference if LightSquared keeps their transmitters clean and out of the GPS spectrum? -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightsquared test in las vegas
Hi Jason: For more than a decade the best internet connection I could get was 2-way satellite. The major problem with that is the ping time which approaches one second and no amount of technology will change it one iota (i.e. it's determined by two round trips up and back to the satellite and the speed of light). Now that I've got DSL the ping time is in the 25 ms area, see: http://www.prc68.com/I/attDSL.shtml With DSL I can now get Netflix streaming video. This means watching movies, some in HD. Crackle and others offer a similar service. This takes much more bandwidth than YouTube. Note that YouTube has a 10 minute time limit and used to have a file size limit, but the file size limit has been removed to encourage HD and/or 3D format uploads. I've heard the movies over the internet are driving internet bandwidth. Have Fun, Brooke Clarke http://www.PRC68.com Jason Rabel wrote: This is kind of in reference to other LightSquared articles that all seem to make mention of, LightSquared's proposal for a network of 40,000 ground transmitters... These 40k ground transmitters to be installed... Are they just going to be additional antennas on existing cell towers, or is LightSquared planning to construct their own towers in new locations? Reason I say... Cell towers are located for maximum coverage and the most dense population. Likewise, when traveling between cities they stick them close to the interstates so people can have reception while traveling. A blind man should be able to see that problem. rantI guess the rest of the world will be able to enjoy GPS, while the US pays for it (but can't use it) But hey, watching people do stupid things on youtube is infinitely more necessary for the US economy than a critical navigation system deployed in countless cars, boats, planes, and anything else that moves This should have been killed off a long time ago, and the frequency spectrum stripped away from LightSquared just for the mere mention of doing something as stupid as they are trying to do.../rant ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightsquared test in las vegas
Hi John: It's my understanding the the GPS system was designed by the military so that the received signal is below the thermal noise. That means that if you look for it with a spectrum analyzer you will see noise. It wasn't untill the KAL007 shoot down that the goverment disclosed it's existence to prevent a similar thing from happening. The new GPS L5 Safety of Life signal is to make aviation safer. So it appears that the focus has changed from military to aviation. http://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007#Aftermath http://www.prc68.com/I/DAGR.shtml#GPSs Have Fun, Brooke Clarke http://www.PRC68.com J. Forster wrote: Perhaps not in the abstract, but on-orbit power is severely limited, and you can't get more RF watts out of a transmitter than you put in as DC. Can you imagine the uproar if every GPS bird had a 10 KW transmitter on board, powered bu a nuclear reactor? The low received power is a direct consequence of engineering of satellites. -John On the other hand, what can be said about the wisdom of engineers that designed a product that cannot withstand any interference from adjoining spectrum holders? It has been known for at least the last 6 years that LightSquared's predecessor was going to occupy that spectrum with a land based system. Does the GPS world really have much to say about the interference if LightSquared keeps their transmitters clean and out of the GPS spectrum? -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPS interference and history...
For many years the FCC has not allowed FM broadcast stations within certain distances of each other where a 10.7 MHz frequency difference existed. Not exactly the same thing, but did show an understanding of what can go wrong as a result of good receiver front end selectivity. In AM and FM broadcasting there has also been required distances between 1st and 2nd adjacent channels, only partially because of overload issues but more so because of occupied bandwidth and overlapping. I'm not sure how much more it would cost to build GPS receivers with better front ends, but I'm sure it would've priced GPS devices out of the hands of many consumer level users. The FCC under the direction of Congress has made (allowed) some pretty stupid moves in the past bunch of years. In my opinion, the FCC has forgotten what their purpose is, and being run by attorneys has made the situation that much worse as there are very few attorneys that understand the un-revocable physics of the electromagnetic spectrum. Burt, K6OQK At 10:07 AM 6/9/2011, time-nuts-requ...@febo.com wrote On the other hand, what can be said about the wisdom of engineers that designed a product that cannot withstand any interference from adjoining spectrum holders? It has been known for at least the last 6 years that LightSquared's predecessor was going to occupy that spectrum with a land based system. Does the GPS world really have much to say about the interference if LightSquared keeps their transmitters clean and out of the GPS spectrum? -Chuck Harris Burt I. Weiner Associates Broadcast Technical Services Glendale, California U.S.A. b...@att.net www.biwa.cc K6OQK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Fluke PM6681 triggering
Hi Rex, You could try asking the guys at Pendulum. A couple of them came down a gave a talk at the UK's National Physical Laboratory Time Frequency Club meeting a few years ago and were very interesting and approachable. It looks like they might have been swallowed by Spectracom now - see: http://www.spectracomcorp.com/ProductsServices/TestandMeasurement/tabid/1244/Default.aspx Peter On 5 June 2011 05:05, Rex r...@sonic.net wrote: I recently picked up a Fluke PM6681 counter (same as a Pendulum CNT-81). Looks like a sweet device. ... I'm wondering if anyone has experience with this counter and can tell me if I have mis-understood the Hold-Off function. Or maybe it has something to do with me using Total A-B mode. The Op Manual covers a lot of ground, but it isn't the easiest to follow the finesse stuff unless you happen to need to do exactly what they are showing in an example. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Railroad clock
I had indeed seen this show a while ago. Pretty nice clocks On Thu, Jun 9, 2011 at 12:09 PM, Joseph Gray jg...@zianet.com wrote: I don't know if anyone has seen this yet, but the show History Detectives had an interesting episode about a railroad regulator clock. http://video.pbs.org/video/1579336059 Joe Gray W5JG ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightsquared test in las vegas
Hi Brooke, Could well be, but I know the system was severely constrained by satellite design considerations. 30+ years ago, high power was simply not available on orbit for long periods of time. The only real option is solar cells, then as now. -John == Hi John: It's my understanding the the GPS system was designed by the military so that the received signal is below the thermal noise. That means that if you look for it with a spectrum analyzer you will see noise. It wasn't untill the KAL007 shoot down that the goverment disclosed it's existence to prevent a similar thing from happening. The new GPS L5 Safety of Life signal is to make aviation safer. So it appears that the focus has changed from military to aviation. http://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007#Aftermath http://www.prc68.com/I/DAGR.shtml#GPSs Have Fun, Brooke Clarke http://www.PRC68.com J. Forster wrote: Perhaps not in the abstract, but on-orbit power is severely limited, and you can't get more RF watts out of a transmitter than you put in as DC. Can you imagine the uproar if every GPS bird had a 10 KW transmitter on board, powered bu a nuclear reactor? The low received power is a direct consequence of engineering of satellites. -John On the other hand, what can be said about the wisdom of engineers that designed a product that cannot withstand any interference from adjoining spectrum holders? It has been known for at least the last 6 years that LightSquared's predecessor was going to occupy that spectrum with a land based system. Does the GPS world really have much to say about the interference if LightSquared keeps their transmitters clean and out of the GPS spectrum? -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
I think it comes down to politicians that delude themselves into thinking they can legislate the laws of the natural world, and that laws that are generally applicable to the rest of the world do not apply to them. -John === [snip] The FCC under the direction of Congress has made (allowed) some pretty stupid moves in the past bunch of years. In my opinion, the FCC has forgotten what their purpose is, and being run by attorneys has made the situation that much worse as there are very few attorneys that understand the un-revocable physics of the electromagnetic spectrum. Burt, K6OQK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
On 06/09/2011 07:29 PM, Burt I. Weiner wrote: For many years the FCC has not allowed FM broadcast stations within certain distances of each other where a 10.7 MHz frequency difference existed. Not exactly the same thing, but did show an understanding of what can go wrong as a result of good receiver front end selectivity. In AM and FM broadcasting there has also been required distances between 1st and 2nd adjacent channels, only partially because of overload issues but more so because of occupied bandwidth and overlapping. I'm not sure how much more it would cost to build GPS receivers with better front ends, but I'm sure it would've priced GPS devices out of the hands of many consumer level users. The FCC under the direction of Congress has made (allowed) some pretty stupid moves in the past bunch of years. In my opinion, the FCC has forgotten what their purpose is, and being run by attorneys has made the situation that much worse as there are very few attorneys that understand the un-revocable physics of the electromagnetic spectrum. Regarding GPS receivers there today exist many different front-end approaches. In particular have single-bit and 1.5 bit samplers and direct samplers been used for many customer GPSes. The GPS receivers needed in E911 compatible phones is hardly done with lots of money, space and power-budget. Bringing too quick shift of requirements onto the GPS receiver market would... well kill it. Some degradation would be tolerated. Look forward to L2C and L5 capabilities to show up alongside Glonass L1... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
The image frequency for an FM receiver with a 10.7 mHz IF is 21.4 mHz above or below. Perhaps they were worried about receivers with IFs in the 5 mHz range? -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
According to the John Deere article, the higher performance GPS receivers, such as those used for agricultural application and IFR navigation have wider front ends to obtain more precise information from GPS signals. The LightSquared transmitters wouldn't pose such a problem if they were in orbit. Regarding GPS receivers there today exist many different front-end approaches. In particular have single-bit and 1.5 bit samplers and direct samplers been used for many customer GPSes. The GPS receivers needed in E911 compatible phones is hardly done with lots of money, space and power-budget. Bringing too quick shift of requirements onto the GPS receiver market would... well kill it. Some degradation would be tolerated. Look forward to L2C and L5 capabilities to show up alongside Glonass L1... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
On 6/9/11 12:22 PM, Chuck Forsberg WA7KGX N2469R wrote: According to the John Deere article, the higher performance GPS receivers, such as those used for agricultural application and IFR navigation have wider front ends to obtain more precise information from GPS signals. The LightSquared transmitters wouldn't pose such a problem if they were in orbit. Exactly.. Deere (and others) designed based on the general understanding of what the spectrum would look like. Mostly satellite radiated (where, as others have noted, you're limited to a few kW) and a few fill-in transmitters to handle urban canyons and the like.. low power in general, and not in the middle of a farm field in any case. The L^2 scheme turned that on its head.. lots of high powered terrestrial transmitters, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
Actually Chuck it was intermod in the front end creating 10.7 directly. Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Forsberg WA7KGX N2469R Sent: Thursday, June 09, 2011 8:17 PM To: ehy...@arcor.de; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS interference and history... The image frequency for an FM receiver with a 10.7 mHz IF is 21.4 mHz above or below. Perhaps they were worried about receivers with IFs in the 5 mHz range? -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
I seem to recall that some of the high precision users also need to receive a satellite delivered differential GPS signal outside of the GPS band. - Original Message From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Thu, June 9, 2011 12:32:42 PM Subject: Re: [time-nuts] GPS interference and history... On 6/9/11 12:22 PM, Chuck Forsberg WA7KGX N2469R wrote: According to the John Deere article, the higher performance GPS receivers, such as those used for agricultural application and IFR navigation have wider front ends to obtain more precise information from GPS signals. The LightSquared transmitters wouldn't pose such a problem if they were in orbit. Exactly.. Deere (and others) designed based on the general understanding of what the spectrum would look like. Mostly satellite radiated (where, as others have noted, you're limited to a few kW) and a few fill-in transmitters to handle urban canyons and the like.. low power in general, and not in the middle of a farm field in any case. The L^2 scheme turned that on its head.. lots of high powered terrestrial transmitters, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
Correction: WAAS is a special transponder that is on the GPS freq, with a GPS like signal transponded from the C-Band uplink. Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: Lester Veenstra [mailto:les...@veenstras.com] Sent: Thursday, June 09, 2011 8:55 PM To: 'Discussion of precise time and frequency measurement' Subject: RE: [time-nuts] GPS interference and history... Yes, for instance the aviation industry, WAAS, which is in the L-Bans mobile satellite assignment, (INMARSAT etc), that L^2 reuses and thus kills. Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Thursday, June 09, 2011 8:42 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS interference and history... I seem to recall that some of the high precision users also need to receive a satellite delivered differential GPS signal outside of the GPS band. - Original Message From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Thu, June 9, 2011 12:32:42 PM Subject: Re: [time-nuts] GPS interference and history... On 6/9/11 12:22 PM, Chuck Forsberg WA7KGX N2469R wrote: According to the John Deere article, the higher performance GPS receivers, such as those used for agricultural application and IFR navigation have wider front ends to obtain more precise information from GPS signals. The LightSquared transmitters wouldn't pose such a problem if they were in orbit. Exactly.. Deere (and others) designed based on the general understanding of what the spectrum would look like. Mostly satellite radiated (where, as others have noted, you're limited to a few kW) and a few fill-in transmitters to handle urban canyons and the like.. low power in general, and not in the middle of a farm field in any case. The L^2 scheme turned that on its head.. lots of high powered terrestrial transmitters, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
Ha! Nuclear power in space is poltically utterly impossible in the US. There is huge opposition to RTGs, never mind even the thought of reactors. Solar is not really practical either. The sun puts out about 1 KW/Sq.M in EO, and solar cell efficiency is 20%; so 10 KW needs 50 Sq.M of stabilized pointing cells. -John = Perhaps in the longer term (ie. next the several decades) moving away from the current wide band spread spectrum scheme to a higher power narrow band scheme might make more sense for GPS. A previous poster mentioned the use of nuclear powered satellites to achieve higher transmit powers, given the benefits of GPS that option should not be entirely discoutned in my oppinion. - Original Message From: Magnus Danielson mag...@rubidium.dyndns.org To: time-nuts@febo.com Sent: Thu, June 9, 2011 12:03:45 PM Subject: Re: [time-nuts] GPS interference and history... On 06/09/2011 07:29 PM, Burt I. Weiner wrote: For many years the FCC has not allowed FM broadcast stations within certain distances of each other where a 10.7 MHz frequency difference existed. Not exactly the same thing, but did show an understanding of what can go wrong as a result of good receiver front end selectivity. In AM and FM broadcasting there has also been required distances between 1st and 2nd adjacent channels, only partially because of overload issues but more so because of occupied bandwidth and overlapping. I'm not sure how much more it would cost to build GPS receivers with better front ends, but I'm sure it would've priced GPS devices out of the hands of many consumer level users. The FCC under the direction of Congress has made (allowed) some pretty stupid moves in the past bunch of years. In my opinion, the FCC has forgotten what their purpose is, and being run by attorneys has made the situation that much worse as there are very few attorneys that understand the un-revocable physics of the electromagnetic spectrum. Regarding GPS receivers there today exist many different front-end approaches. In particular have single-bit and 1.5 bit samplers and direct samplers been used for many customer GPSes. The GPS receivers needed in E911 compatible phones is hardly done with lots of money, space and power-budget. Bringing too quick shift of requirements onto the GPS receiver market would... well kill it. Some degradation would be tolerated. Look forward to L2C and L5 capabilities to show up alongside Glonass L1... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightsquared test in las vegas
Hi Ummm, errr ... not so much. KAL007 went down September 7th 1983. NIST was publishing papers on two way time transfer in 1980: http://tf.nist.gov/general/pdf/192.pdf Much of the early GPS timing and design work was made quite public in various FCS papers in the 1970's. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Brooke Clarke Sent: Thursday, June 09, 2011 1:28 PM To: j...@quik.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] lightsquared test in las vegas Hi John: It's my understanding the the GPS system was designed by the military so that the received signal is below the thermal noise. That means that if you look for it with a spectrum analyzer you will see noise. It wasn't untill the KAL007 shoot down that the goverment disclosed it's existence to prevent a similar thing from happening. The new GPS L5 Safety of Life signal is to make aviation safer. So it appears that the focus has changed from military to aviation. http://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007#Aftermath http://www.prc68.com/I/DAGR.shtml#GPSs Have Fun, Brooke Clarke http://www.PRC68.com J. Forster wrote: Perhaps not in the abstract, but on-orbit power is severely limited, and you can't get more RF watts out of a transmitter than you put in as DC. Can you imagine the uproar if every GPS bird had a 10 KW transmitter on board, powered bu a nuclear reactor? The low received power is a direct consequence of engineering of satellites. -John On the other hand, what can be said about the wisdom of engineers that designed a product that cannot withstand any interference from adjoining spectrum holders? It has been known for at least the last 6 years that LightSquared's predecessor was going to occupy that spectrum with a land based system. Does the GPS world really have much to say about the interference if LightSquared keeps their transmitters clean and out of the GPS spectrum? -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
I well recall the furor over Cassini-Huygens in 1997 but approval was ultimately granted and, of course, the launch was without incident. Since then, New Horizons, Galileo, and Ulysses have been launched with far less public outcry, despite the fact that all are powered by RTGs. Arguably, well-designed reactors could be even safer. While I appreciate that sensitivity to nuclear power for earth orbit satellites could be greater than for deep space vehicles, we may have to agree to disagree on the feasibility of nuclear powered satellites. On Thu, Jun 9, 2011 at 4:06 PM, J. Forster j...@quik.com wrote: Ha! Nuclear power in space is poltically utterly impossible in the US. There is huge opposition to RTGs, never mind even the thought of reactors. Solar is not really practical either. The sun puts out about 1 KW/Sq.M in EO, and solar cell efficiency is 20%; so 10 KW needs 50 Sq.M of stabilized pointing cells. -John = Perhaps in the longer term (ie. next the several decades) moving away from the current wide band spread spectrum scheme to a higher power narrow band scheme might make more sense for GPS.A previous poster mentioned the use of nuclear powered satellites to achieve higher transmit powers, given the benefits of GPS that option should not be entirely discoutned in my oppinion. - Original Message From: Magnus Danielson mag...@rubidium.dyndns.org To: time-nuts@febo.com Sent: Thu, June 9, 2011 12:03:45 PM Subject: Re: [time-nuts] GPS interference and history... On 06/09/2011 07:29 PM, Burt I. Weiner wrote: For many years the FCC has not allowed FM broadcast stations within certain distances of each other where a 10.7 MHz frequency difference existed. Not exactly the same thing, but did show an understanding of what can go wrong as a result of good receiver front end selectivity. In AM and FM broadcasting there has also been required distances between 1st and 2nd adjacent channels, only partially because of overload issues but more so because of occupied bandwidth and overlapping. I'm not sure how much more it would cost to build GPS receivers with better front ends, but I'm sure it would've priced GPS devices out of the hands of many consumer level users. The FCC under the direction of Congress has made (allowed) some pretty stupid moves in the past bunch of years. In my opinion, the FCC has forgotten what their purpose is, and being run by attorneys has made the situation that much worse as there are very few attorneys that understand the un-revocable physics of the electromagnetic spectrum. Regarding GPS receivers there today exist many different front-end approaches. In particular have single-bit and 1.5 bit samplers and direct samplers been used for many customer GPSes. The GPS receivers needed in E911 compatible phones is hardly done with lots of money, space and power-budget. Bringing too quick shift of requirements onto the GPS receiver market would... well kill it. Some degradation would be tolerated. Look forward to L2C and L5 capabilities to show up alongside Glonass L1... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
I don't think it is feasible... for a cooling reason :) Regards, Javier El 09/06/2011 22:18, William H. Fite escribió: I well recall the furor over Cassini-Huygens in 1997 but approval was ultimately granted and, of course, the launch was without incident. Since then, New Horizons, Galileo, and Ulysses have been launched with far less public outcry, despite the fact that all are powered by RTGs. Arguably, well-designed reactors could be even safer. While I appreciate that sensitivity to nuclear power for earth orbit satellites could be greater than for deep space vehicles, we may have to agree to disagree on the feasibility of nuclear powered satellites. On Thu, Jun 9, 2011 at 4:06 PM, J. Forsterj...@quik.com wrote: Ha! Nuclear power in space is poltically utterly impossible in the US. There is huge opposition to RTGs, never mind even the thought of reactors. Solar is not really practical either. The sun puts out about 1 KW/Sq.M in EO, and solar cell efficiency is20%; so 10 KW needs 50 Sq.M of stabilized pointing cells. -John = Perhaps in the longer term (ie. next the several decades) moving away from the current wide band spread spectrum scheme to a higher power narrow band scheme might make more sense for GPS.A previous poster mentioned the use of nuclear powered satellites to achieve higher transmit powers, given the benefits of GPS that option should not be entirely discoutned in my oppinion. - Original Message From: Magnus Danielsonmag...@rubidium.dyndns.org To: time-nuts@febo.com Sent: Thu, June 9, 2011 12:03:45 PM Subject: Re: [time-nuts] GPS interference and history... On 06/09/2011 07:29 PM, Burt I. Weiner wrote: For many years the FCC has not allowed FM broadcast stations within certain distances of each other where a 10.7 MHz frequency difference existed. Not exactly the same thing, but did show an understanding of what can go wrong as a result of good receiver front end selectivity. In AM and FM broadcasting there has also been required distances between 1st and 2nd adjacent channels, only partially because of overload issues but more so because of occupied bandwidth and overlapping. I'm not sure how much more it would cost to build GPS receivers with better front ends, but I'm sure it would've priced GPS devices out of the hands of many consumer level users. The FCC under the direction of Congress has made (allowed) some pretty stupid moves in the past bunch of years. In my opinion, the FCC has forgotten what their purpose is, and being run by attorneys has made the situation that much worse as there are very few attorneys that understand the un-revocable physics of the electromagnetic spectrum. Regarding GPS receivers there today exist many different front-end approaches. In particular have single-bit and 1.5 bit samplers and direct samplers been used for many customer GPSes. The GPS receivers needed in E911 compatible phones is hardly done with lots of money, space and power-budget. Bringing too quick shift of requirements onto the GPS receiver market would... well kill it. Some degradation would be tolerated. Look forward to L2C and L5 capabilities to show up alongside Glonass L1... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
The cold side can be cooled by radiation. It's been done. The View Factor to the 3 K of space is nearly 1.0, and the heat transfer rate goes up as the radiator temp EXP 4. -John I don't think it is feasible... for a cooling reason :) Regards, Javier El 09/06/2011 22:18, William H. Fite escribió: I well recall the furor over Cassini-Huygens in 1997 but approval was ultimately granted and, of course, the launch was without incident. Since then, New Horizons, Galileo, and Ulysses have been launched with far less public outcry, despite the fact that all are powered by RTGs. Arguably, well-designed reactors could be even safer. While I appreciate that sensitivity to nuclear power for earth orbit satellites could be greater than for deep space vehicles, we may have to agree to disagree on the feasibility of nuclear powered satellites. On Thu, Jun 9, 2011 at 4:06 PM, J. Forsterj...@quik.com wrote: Ha! Nuclear power in space is poltically utterly impossible in the US. There is huge opposition to RTGs, never mind even the thought of reactors. Solar is not really practical either. The sun puts out about 1 KW/Sq.M in EO, and solar cell efficiency is20%; so 10 KW needs 50 Sq.M of stabilized pointing cells. -John = Perhaps in the longer term (ie. next the several decades) moving away from the current wide band spread spectrum scheme to a higher power narrow band scheme might make more sense for GPS.A previous poster mentioned the use of nuclear powered satellites to achieve higher transmit powers, given the benefits of GPS that option should not be entirely discoutned in my oppinion. - Original Message From: Magnus Danielsonmag...@rubidium.dyndns.org To: time-nuts@febo.com Sent: Thu, June 9, 2011 12:03:45 PM Subject: Re: [time-nuts] GPS interference and history... On 06/09/2011 07:29 PM, Burt I. Weiner wrote: For many years the FCC has not allowed FM broadcast stations within certain distances of each other where a 10.7 MHz frequency difference existed. Not exactly the same thing, but did show an understanding of what can go wrong as a result of good receiver front end selectivity. In AM and FM broadcasting there has also been required distances between 1st and 2nd adjacent channels, only partially because of overload issues but more so because of occupied bandwidth and overlapping. I'm not sure how much more it would cost to build GPS receivers with better front ends, but I'm sure it would've priced GPS devices out of the hands of many consumer level users. The FCC under the direction of Congress has made (allowed) some pretty stupid moves in the past bunch of years. In my opinion, the FCC has forgotten what their purpose is, and being run by attorneys has made the situation that much worse as there are very few attorneys that understand the un-revocable physics of the electromagnetic spectrum. Regarding GPS receivers there today exist many different front-end approaches. In particular have single-bit and 1.5 bit samplers and direct samplers been used for many customer GPSes. The GPS receivers needed in E911 compatible phones is hardly done with lots of money, space and power-budget. Bringing too quick shift of requirements onto the GPS receiver market would... well kill it. Some degradation would be tolerated. Look forward to L2C and L5 capabilities to show up alongside Glonass L1... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
On Thu, 2011-06-09 at 22:30 +0200, Javier Herrero wrote: I don't think it is feasible... for a cooling reason :) You would think the cooling would be a critical issue (It usually is in spacecraft), but the Russians flew a few surveillance birds with reactors on board (and had at least one more such fail to make orbit). Cosmos 954 also failed to eject its core to a safe orbit before reentry and radioactive components were recovered from the impact site in Canada. So yes, a nuclear powered bird is possible, I suspect by running the entire thermodynamic cycle very hot and thereby increasing the radiative cooling efficiency on the 'cold' side. Regards, Dan. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Light Squared, etc.
Yes, what about L5? I thought that was going to be the new civilian frequency that was going to revolutionize GPS. If the FCC is hellbent on approving Light Squared's request, L5 might be our only option. Of course the transition would be very nasty and expensive. Regarding nuclear powered satellites, I suspect that spy satellites are nuclear powered but since they are classified, who knows. Perhaps future GPS satellites with higher powered transmitters could be nuclear powered and classified. Perhaps some surveillance equipment could ride aboard getting them under the secret umbrella. Or, the FCC could use some common sense for a change and deny Light Squared. If I had to choose between a functional GPS system and wireless internet, GPS would win hands down. This kind of reminds me of the whole IDEN fiasco where the FCC took Motorola's word that the emission mask for IDEN would allow adjacent channel operation without interference. Nextel ended up paying Billions to move all the other 800 MHz licensees to the other end of the band to get rid of interference they caused. I can't see Light Squared buying me a new, improved Z3801. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
Hi There are similar protections built into the TV station licensing process. In the case of TV it's a whole raft of issues that all boil down to how good the receiver needs to be. IMD, RF selectivity, IF selectivity, all figured in. I suspect there were other things I've forgotten about. About every 10 years or so, the FCC used to sponsor a study done by one company or the other of how much things could be improved. Each and every study came to the conclusion that you could make a better TV and have more channels on the air. As far as I know, nothing ever changed as a result. They were interesting papers though. Frequency allocation and large scale receiver design have always gone hand in hand. It's been that way at least since WWII and likely before that as well. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Lester Veenstra Sent: Thursday, June 09, 2011 3:32 PM To: 'Discussion of precise time and frequency measurement'; ehy...@arcor.de Subject: Re: [time-nuts] GPS interference and history... Actually Chuck it was intermod in the front end creating 10.7 directly. Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Forsberg WA7KGX N2469R Sent: Thursday, June 09, 2011 8:17 PM To: ehy...@arcor.de; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS interference and history... The image frequency for an FM receiver with a 10.7 mHz IF is 21.4 mHz above or below. Perhaps they were worried about receivers with IFs in the 5 mHz range? -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
I was also thinking of the John Deer Starfire system that works in L band IIRC http://stellarsupport.deere.com/en_GB/pdfs/starfire_frequency_change_en.pdf - Original Message From: Lester Veenstra les...@veenstras.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thu, June 9, 2011 12:55:16 PM Subject: Re: [time-nuts] GPS interference and history... Yes, for instance the aviation industry, WAAS, which is in the L-Bans mobile satellite assignment, (INMARSAT etc), that L^2 reuses and thus kills. Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Thursday, June 09, 2011 8:42 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS interference and history... I seem to recall that some of the high precision users also need to receive a satellite delivered differential GPS signal outside of the GPS band. - Original Message From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Thu, June 9, 2011 12:32:42 PM Subject: Re: [time-nuts] GPS interference and history... On 6/9/11 12:22 PM, Chuck Forsberg WA7KGX N2469R wrote: According to the John Deere article, the higher performance GPS receivers, such as those used for agricultural application and IFR navigation have wider front ends to obtain more precise information from GPS signals. The LightSquared transmitters wouldn't pose such a problem if they were in orbit. Exactly.. Deere (and others) designed based on the general understanding of what the spectrum would look like. Mostly satellite radiated (where, as others have noted, you're limited to a few kW) and a few fill-in transmitters to handle urban canyons and the like.. low power in general, and not in the middle of a farm field in any case. The L^2 scheme turned that on its head.. lots of high powered terrestrial transmitters, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Light Squared, etc.
Spy satellites either image in the optical, listen in to RF, or use RADAR. Only the RADAR satellites require high power. Sensors, even if cryogenically cooled, are relatively low power. -John = [snip} Regarding nuclear powered satellites, I suspect that spy satellites are nuclear powered but since they are classified, who knows. Perhaps future GPS satellites with higher powered transmitters could be nuclear powered and classified. [snip] ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
So back to my original question (I didn't mean to spark such a debate)... These 40,000 transmitter towers... Are they merely talking about attaching their antennas on existing cell towers or totally new deployment? FWIW, perhaps there wouldn't be as much of a fiasco if every other navigation and timing technology didn't get phased out in favor of GPS... There literally is no backup sans a fold-out map or sun-dial... To say it is 'key' or 'critical' is an understatement. Likewise, I don't like the idea of existing L1 devices becoming scrap to merely support someone's cell phone / broadband addiction. There's too much hardware out there to make replacement impractical short of a decade long transition period. Even then during that transition period lord only knows how many millions (billions?) of dollars it will cost to replace / retrofit existing hardware. Who's going to pay for all that? If I can put a $5 filter on my incoming antenna line to make it reduce most interference from L^2 and I loose maybe one satellite out of eight visible, I'll be content with that... If I have to put a $100 filter to pray I can get signal for an hour a day... Well... L^2 is going to have mysterious constant hardware failures in this area. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
I would expect Lightsquared would attempt to acquire space on existing towers rather than build their own but I have no insight into what Lightsquared is planning to do. The US has a relatively mature tower industry that caters to cellular type providers. . - Original Message From: Jason Rabel ja...@extremeoverclocking.com To: time-nuts@febo.com Sent: Thu, June 9, 2011 2:18:01 PM Subject: Re: [time-nuts] GPS interference and history... So back to my original question (I didn't mean to spark such a debate)... These 40,000 transmitter towers... Are they merely talking about attaching their antennas on existing cell towers or totally new deployment? FWIW, perhaps there wouldn't be as much of a fiasco if every other navigation and timing technology didn't get phased out in favor of GPS... There literally is no backup sans a fold-out map or sun-dial... To say it is 'key' or 'critical' is an understatement. Likewise, I don't like the idea of existing L1 devices becoming scrap to merely support someone's cell phone / broadband addiction. There's too much hardware out there to make replacement impractical short of a decade long transition period. Even then during that transition period lord only knows how many millions (billions?) of dollars it will cost to replace / retrofit existing hardware. Who's going to pay for all that? If I can put a $5 filter on my incoming antenna line to make it reduce most interference from L^2 and I loose maybe one satellite out of eight visible, I'll be content with that... If I have to put a $100 filter to pray I can get signal for an hour a day... Well... L^2 is going to have mysterious constant hardware failures in this area. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightsquared test in las vegas
Does the GPS world really have much to say about the interference if LightSquared keeps their transmitters clean and out of the GPS spectrum? I think the key idea is that the receiver can't build a brick-wall filter. Even if the transmitter stays within their assigned band, a strong enough signal near enough to the receiver channel will leak through the filters. At the FCC level, there has to be coordination between the frequency allocations, the signal power the receiver is expected to work with, and the expected signal power at the receiver from the transmitters on nearby channels. If the Lightsquared frequency assignment were farther away from the GPS frequency we wouldn't be having this discussion. Some other users might be complaining, but if their application used stronger signal levels at the receiver it might be easier to find a workable solution. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Fluke PM6681 triggering
Magnus, Thanks for the detailed reply and history. The counter (just got it recently) came with the Fluke CD which had an op manual on it. I also found the CNT-81 manual on a Pendulum site. They seem to have identical content except for name changes. One note, if anyone else has one of these counters, one difference is that the CNT-81 pdf is searchable where the PM6681 pdf is image based, so isn't searchable. Reading the manual is where I got the impression that hold off could solve my triggering issue. I just looked at the manual again and found there is a performance test setup described for verifying the hold off function (pge 9-16 in the CNT-81 manual). Using that with a 3314A generator I verified hold off working as expected. One difference: the 3314A couldn't make a two-cycle pulse as fast as the test described, but allowing for that with slightly longer hold off period, it worked as expected seeing freq measured at 20K or 10K with hold off. That was just as I expected it to work and seemed I should have been able to use hold off in my problematic measurement to mask out a glitch from causing a second trigger on the leading edge of the signal. So, today I used that 3314A test setup to compare in the mode of the counter I was using. I was using the counter to total the number of random pulses over a preset interval of several minutes. I set the counter into TOT A-B mode with the measuring interval set by Aux configuration of 21.12 as described on page 4-18. Today I put the counter in this mode and fed it the same 3314A 2-cycle bursts with 100 uS interval. The count was what I should expect for the measurement interval I used. I turned on hold off with the delay time as set in the verification test above. The expected result would be the count dropping by 1/2. It did not change. So my idea the hold off could solve my measurement issue, bypassing the glitch, was ok in principle, but for some reason the hold off function doesn't seem to work in this Totalize mode. Just closing out with a verification of why it didn't seem to work as I thought it should. Thanks for getting me to think about this again and finding a verification of my results with less random test equipment. On 6/9/2011 11:43 AM, Magnus Danielson wrote: On 06/09/2011 07:30 PM, Peter Vince wrote: Hi Rex, You could try asking the guys at Pendulum. A couple of them came down a gave a talk at the UK's National Physical Laboratory Time Frequency Club meeting a few years ago and were very interesting and approachable. It looks like they might have been swallowed by Spectracom now - see: http://www.spectracomcorp.com/ProductsServices/TestandMeasurement/tabid/1244/Default.aspx They are part of Spectracom now, but the people is still there. The CNT-81 production stopped only due to lack of key components. The CNT-81 has a full custom chip in it for the time counter stuff. I had one for a while but swapped gear with a fellow time-nut. The manuals is downloadable from Fluke if you follow the PM-6681 search. The Fluke connection goes back to they days when Philip Industries in Järfälla designed and manufactured a lot of the Philips stuff. Then Fluke came into the picture and after number of years Philips killed of that branch of the buissness, but Harald took over the remains and formed Pendulum. Pendulum itself has swallowed XL in the US and a result of that was the development of the CNT-90XL which brings the CNT-90 base into higher frequencies, using the base functionality of the CNT-90 with the key technology of the XL stuff. The CNT-81 is a nice box, but the CNT-90 is much more versatile. Still, there is room for improvements! If there is any specifics, let me know and I'll try to find out. To the best of my knowledge regarding this thread, the most specific issue related to triggering on that specific signal. I've often found good use for a good scope along-side counters, because you need to do the reality check to know what your actual signal is, and then be able to trigger properly on it. For more expensive counters, I also want to check the signal range. That way I can see if I have any runt pulses to avoid or possibly filter out Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Light Squared, etc.
Yes, what about L5? I thought that was going to be the new civilian frequency that was going to revolutionize GPS. If the FCC is hellbent on approving Light Squared's request, L5 might be our only option. IOC level (18) of L5 sending satellites probably available in the 2016-2019 range. FOC (min 24) between 2018 and 2022. We are now used to 30+ working GPS satellites. http://www.gpsworld.com/gnss-system/gps-modernization/future-wave-11401?page_id=7 Of course the transition would be very nasty and expensive. Regarding nuclear powered satellites, I suspect that spy satellites are nuclear powered but since they are classified, who knows. Perhaps future GPS satellites with higher powered transmitters could be nuclear powered and classified. When did GPSIII studies start? ca 2000? First launch now predicted 2014-15. Lesson: It takes a lot of time to get new shining features up in space. Also consider the new military M-code. The M-code is a binary-offset-carrier (BOC) signal a split spectrum signal that places most of its power near the edges of the allocated GPS frequency bands, thereby having negligible impact on the legacy signals. http://www.gpsworld.com/gnss-system/gps-modernization/innovation-mboc-signal-options-11721 Looking at the picture in a L1C article http://www.gpsworld.com/files/gpsworld/nodes/2011/11401/L1C-3.jpg You will see the M-code lower band making a nice shield against the evil L^2 for the narrow band civil GPS signal(s). -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
The main issue with nuclear power in space is that there is a serious worldwide shortage of Plutonium 238 used in RTG's. This is a different isotope than the Pu 239 used in nuclear weapons and breeder reactors. Pu 238 is produced by bombarding Neptunium 237 with neutrons in a reactor, the Np 237 itself has to be chemically extracted from spent nuclear fuel rods. Neither of these processes is easy or cheap. The USA does not currently have the capacity to produce Pu 238, the Department of Energy was able to purchase enough from Russia to fuel the Cassini and New Horizons missions but there is barely enough Pu 238 in the world to supply NASA's proposed outer planet missions. The government is debating the possibility of restarting the reactor that would produce more Pu 238 but that won't be cheap either. The Wikipedia article contains links to articles describing the problem: http://en.wikipedia.org/wiki/Plutonium_238 Dan Schultz N8FGV I well recall the furor over Cassini-Huygens in 1997 but approval was ultimately granted and, of course, the launch was without incident. Since then, New Horizons, Galileo, and Ulysses have been launched with far less public outcry, despite the fact that all are powered by RTGs. Arguably, well-designed reactors could be even safer. While I appreciate that sensitivity to nuclear power for earth orbit satellites could be greater than for deep space vehicles, we may have to agree to disagree on the feasibility of nuclear powered satellites. Nuclear power in space is poltically utterly impossible in the US. There is huge opposition to RTGs, never mind even the thought of reactors. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
On 6/9/11 1:00 PM, Mark Spencer wrote: Perhaps in the longer term (ie. next the several decades) moving away from the current wide band spread spectrum scheme to a higher power narrow band scheme might make more sense for GPS.A previous poster mentioned the use of nuclear powered satellites to achieve higher transmit powers, given the benefits of GPS that option should not be entirely discoutned in my oppinion. I suspect that there are no new nuclear powered satellites being created, at least by the US. There was a fair amount of analysis to choose the formats and powers used by GPS (e.g. Transit was narrow band). GPS World had a great series a couple months ago about the history of GPS and how it got where it is. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
On 6/9/11 1:18 PM, William H. Fite wrote: I well recall the furor over Cassini-Huygens in 1997 but approval was ultimately granted and, of course, the launch was without incident. Since then, New Horizons, Galileo, and Ulysses have been launched with far less public outcry, despite the fact that all are powered by RTGs. Arguably, well-designed reactors could be even safer. Galileo was launched before Cassini. MSL is carrying RTGs and launches Nov-Dec this year. The problem isn't so much political as practical. Limited fuel availability, and you don't get kilowatts from an RTG. Kilowatts from solar panels are very doable, but expensive. A typical GEO comsat will probably have 10 or more kW of power available, but it's a billion dollar plus thing. GPS is smaller, lighter, etc. Juno is going to Jupiter in a couple months, and is solar powered... quite the challenge at 5 AU.. it has monster solar arrays. GPS orbits are tough from a radiation standpoint too. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
New antenna sites are extremely hard to get in the populated US areas, so I would have to say that given the power levels, and the quantity they will be piggybacking off of any structure that can hold them. -Chuck Harris Jason Rabel wrote: So back to my original question (I didn't mean to spark such a debate)... These 40,000 transmitter towers... Are they merely talking about attaching their antennas on existing cell towers or totally new deployment? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
Jason wrote: So back to my original question (I didn't mean to spark such a debate)... These 40,000 transmitter towers... Are they merely talking about attaching their antennas on existing cell towers or totally new deployment? What difference does it make? They will certainly want to cover the country by descending population density, just like all the other carriers. Thus, whether they use existing towers or build new ones, their signals will be distributed the same as all the others. To answer your question, they will almost certainly do both -- lease space on existing towers/buildings/etc. as they can, and build where they must. Building takes longer because of the land use issues (zoning, permitting, etc.), and LS is under the gun to get the network deployed fast because of commitments they made to the FCC to get their waivers. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
On Thu, Jun 9, 2011 at 2:42 PM, Jim Lux jim...@earthlink.net wrote: GPS orbits are tough from a radiation standpoint too. In particular, the orbits are considerably worse for radiation than GEO, and photovoltaic panels are quite susceptible to radiation. Of course you could put a GNSS in GSO but I think it's not as favorable from a constellation design point of view, and the launches are more expensive. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
