Re: [time-nuts] GPS interference and history...
In message 4f0fc1aa.5070...@earthlink.net, Jim Lux writes: On 6/9/11 1:30 PM, Javier Herrero wrote: I don't think it is feasible... for a cooling reason :) Soviet had an entire series of spy-satellits powered by reactors, one of them is still leaking droplets/pellets of sodium from the cooling system creating quite a mess. -- 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. ___ 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 6/10/11 7:01 PM, Hal Murray wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? GPS is pretty ubiquitous as a time source for data loggers in the field, things like traffic signals, etc. There's real value in an inexpensive little box that makes sure you don't have to set the clock, even if the clock accuracy requirement is something like 1 minute. What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) A fortune, quite literally I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) Not necessarily. And it's not cheap. Don't forget that you can't run power and phone in the same conduit, cable, etc. So basically you're doubling the physical plant installation costs to bring in phone, just for the labor to bring it from the nearest point of presence. Especially in rural farm kinds of areas, power is more pervaisve than phone (gotta run irrigation pumps, etc.) Adding a $100-200 GPS receiver (we're not talking GPSDO with OCXO here..) is probably cheaper than running ANY length of phone wires: just for the termination costs. I suppose one could use some sort of GPRS cellular service and get time, but then you're on the hook for a monthly subscription fee, etc. cheap L1 only GPS is a great solution. Apply power, wait, you've got accurate time. No need to have someone visit periodically and check to see if the clock needs to be reset, etc. I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. You're right, they don't need milliseconds, nor do they need seconds, probably. There's really no other convenient way to get time to the nearest minute that is as reliable and cheap as GPS. Think about it... WWVB? WWV? Vertical pointing sun sensor? ___ 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...
Any large IT organization has multiple stratum 1 GPS based timing receivers. The public key for our internal routing updates is the time. No time and the routing would break. We route ~10+ Tb/hr in the 8am-5pm business day. That would be noticed by our users... On one building on our campus (College of Engineering ~1/4 mile long building ) I counted 14 mushroom antennas, I see other patch antennas on windows... Jim Cotton On 1/13/12 9:29 AM, Jim Lux wrote: On 6/10/11 7:01 PM, Hal Murray wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? GPS is pretty ubiquitous as a time source for data loggers in the field, things like traffic signals, etc. There's real value in an inexpensive little box that makes sure you don't have to set the clock, even if the clock accuracy requirement is something like 1 minute. What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) A fortune, quite literally I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) Not necessarily. And it's not cheap. Don't forget that you can't run power and phone in the same conduit, cable, etc. So basically you're doubling the physical plant installation costs to bring in phone, just for the labor to bring it from the nearest point of presence. Especially in rural farm kinds of areas, power is more pervaisve than phone (gotta run irrigation pumps, etc.) Adding a $100-200 GPS receiver (we're not talking GPSDO with OCXO here..) is probably cheaper than running ANY length of phone wires: just for the termination costs. I suppose one could use some sort of GPRS cellular service and get time, but then you're on the hook for a monthly subscription fee, etc. cheap L1 only GPS is a great solution. Apply power, wait, you've got accurate time. No need to have someone visit periodically and check to see if the clock needs to be reset, etc. I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. You're right, they don't need milliseconds, nor do they need seconds, probably. There's really no other convenient way to get time to the nearest minute that is as reliable and cheap as GPS. Think about it... WWVB? WWV? Vertical pointing sun sensor? ___ 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...
When you are thinking about replacing GPS receivers, don't forget about every police car, ambulance, fire truck and most of the tractor trailer's in the US...The latter don't need timing down to the second, but the first three use it to well under a minute. One of the first things you learn when on an ambulance crew is what lump on the roof to wrap the aluminum foil over when you are going to park the rig after that run of 5 middle of the night calls and go to sleep. ;) Some day I'll get the laptops in the rigs to sync up with the GPS directly rather than using NTP. ;) We probably should be using it to drive the time code in the video recorders...H. Bob On Fri, Jan 13, 2012 at 9:29 AM, Jim Lux jim...@earthlink.net wrote: On 6/10/11 7:01 PM, Hal Murray wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? GPS is pretty ubiquitous as a time source for data loggers in the field, things like traffic signals, etc. There's real value in an inexpensive little box that makes sure you don't have to set the clock, even if the clock accuracy requirement is something like 1 minute. What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) A fortune, quite literally I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) Not necessarily. And it's not cheap. Don't forget that you can't run power and phone in the same conduit, cable, etc. So basically you're doubling the physical plant installation costs to bring in phone, just for the labor to bring it from the nearest point of presence. Especially in rural farm kinds of areas, power is more pervaisve than phone (gotta run irrigation pumps, etc.) Adding a $100-200 GPS receiver (we're not talking GPSDO with OCXO here..) is probably cheaper than running ANY length of phone wires: just for the termination costs. I suppose one could use some sort of GPRS cellular service and get time, but then you're on the hook for a monthly subscription fee, etc. cheap L1 only GPS is a great solution. Apply power, wait, you've got accurate time. No need to have someone visit periodically and check to see if the clock needs to be reset, etc. I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. You're right, they don't need milliseconds, nor do they need seconds, probably. There's really no other convenient way to get time to the nearest minute that is as reliable and cheap as GPS. Think about it... WWVB? WWV? Vertical pointing sun sensor? __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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 Fri, Jan 13, 2012 at 6:29 AM, Jim Lux jim...@earthlink.net wrote: I suppose one could use some sort of GPRS cellular service and get time, but then you're on the hook for a monthly subscription fee, etc. They sell such devices. They don't require a subscription because they are receive-only. You don't need to send data to get time.I don't know about GPRS, but there have been commercial CDMA time receivers on the market for years. People who don't have access to the sky but do get cell phone service buy them. For example you are on the 14th floor of a 50 floor office building and your window faces another building. That is the biggest problem with GPS, you need access to the sky. cheap L1 only GPS is a great solution. Apply power, wait, you've got accurate time. No need to have someone visit periodically and check to see if the clock needs to be reset, etc. I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. You're right, they don't need milliseconds, nor do they need seconds, probably. There's really no other convenient way to get time to the nearest minute that is as reliable and cheap as GPS. Think about it... WWVB? WWV? Vertical pointing sun sensor? ___ 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. -- Chris Albertson Redondo Beach, California ___ 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 1:06 PM, J. Forster 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. Hmm.. when I was working on Prometheus aka Jupiter Icy Moons Orbiter (JIMO) there was a guy from NASA HQ who gave a talk at the Lunar Planetary Institute about flying reactors. His basic idea was that there is a fraction of people who will object to ANY nuclear power in orbit, be they 1 ounce Radioactive Heating Units (RHUs.. pretty much in every Mars mission we've flown) or RTGs or full on nuclear reactors (JIMO was going to fly a 300kWthermal/100kW electrical reactor being developed by the folks who do submarine reactors) So therefore, the incremental pain from flying a reactor is small. 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. A bit more than 1 kW/sq m (thats more like earth surface).. I think 1.3 is more of a typical number above the atmosphere.. 30% is more like what we get with triple junction enhanced solar cells, I think, but there's a whole lot of factors that go into it. In any case, there are lots of commercial COMSATs in GEO with tens of kW of solar panels (yes, many, many square meters). The power available on those things (to those of us used to deep space scientific missions) is gargantuan.. They're running more than a hundred TWTAs with hundreds of watts each. And the L band ones (Sirius/XM) are BIG tubes. But, for instance, Juno, which is on it's way to Jupiter has solar panels that are enormous (since it's NOT nuclear powered). ABout 60 square meters which produce just under 500W at the orbit of Jupiter (5AU, so 1/25th what they generate at earth).. That would be about 200W/square meter in earth orbit (which I concede is about your 20%) -John ___ 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 1:30 PM, Javier Herrero wrote: I don't think it is feasible... for a cooling reason :) You've got cold space to radiate to: a few hundred watts/square meter at 300K as I recall. And if you run a reactor which is the heat source for a steam engine of some sort, and the condenser can run moderately hot, you can reject a lot of heat. that T^4 factor really helps if you run the condenser at 100-200C. Glowing red would even be better, if the materials hold up. There's a lot of interesting things you can do in space if you have tons of power. For instance, you can run mechanical refrigeration to pull the heat away from your electronics and radiate it (from a hot radiator, which can be small). The comsats with the dozens of TWTAs use radiation cooling: the collector end of the tube sticks outside the body. Usually, in space, your problem is keeping things warm enough, not keeping them cold. There's more square meters facing cold space than facing the sun. 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. ___ 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...
Was this message relayed through a probe out about 3 light-months? -John On 6/9/11 1:06 PM, J. Forster 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. Hmm.. when I was working on Prometheus aka Jupiter Icy Moons Orbiter (JIMO) there was a guy from NASA HQ who gave a talk at the Lunar Planetary Institute about flying reactors. His basic idea was that there is a fraction of people who will object to ANY nuclear power in orbit, be they 1 ounce Radioactive Heating Units (RHUs.. pretty much in every Mars mission we've flown) or RTGs or full on nuclear reactors (JIMO was going to fly a 300kWthermal/100kW electrical reactor being developed by the folks who do submarine reactors) So therefore, the incremental pain from flying a reactor is small. 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. A bit more than 1 kW/sq m (thats more like earth surface).. I think 1.3 is more of a typical number above the atmosphere.. 30% is more like what we get with triple junction enhanced solar cells, I think, but there's a whole lot of factors that go into it. In any case, there are lots of commercial COMSATs in GEO with tens of kW of solar panels (yes, many, many square meters). The power available on those things (to those of us used to deep space scientific missions) is gargantuan.. They're running more than a hundred TWTAs with hundreds of watts each. And the L band ones (Sirius/XM) are BIG tubes. But, for instance, Juno, which is on it's way to Jupiter has solar panels that are enormous (since it's NOT nuclear powered). ABout 60 square meters which produce just under 500W at the orbit of Jupiter (5AU, so 1/25th what they generate at earth).. That would be about 200W/square meter in earth orbit (which I concede is about your 20%) -John ___ 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...
Hi Best guess - a few million timing receivers are out there. Probably not over ten million. To replace them at new prices, figure $5000 each including the labor. Lots of variables, might be twenty billion dollars if you did a straight swap. Changing out antennas would be cheaper for the hardware and likely more for the labor if a tower is involved. Might be half the price of doing the receivers. Quick math: Take a tower count (say 250,000). Assume each system on the tower has doubly redundant GPS. Take a reasonable number of systems per tower (at least 1 likely 4). That gets you to a million pretty quick. Add to that the non-cell tower telcom stuff and you likely double or triple the number. Bob -Original Message- From: Hal Murray Sent: Friday, June 10, 2011 10:01 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS interference and history... li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. -- 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. ___ 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 6/10/11 7:01 PM, Hal Murray wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? GPS timing antennas are sprouting like mushrooms in a lawn all over JPL. (that's what they look like... you'll be walking around, and you'll notice that there's 2 or 3 new stalks sticking up with a little antenna on the top, and conduit running down the side of the building) While we have masers and cesium sources at JPL, they're not distributed everywhere. So, usually, the easy solution is to just get yourself a Symmetricom or Fluke box, have facilities install the antenna, and your lab is set. I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. GPS is easy, that's why. It's under YOUR control. You spend a few thousand bucks (including installation labor) and you have something that works now and for the foreseeable future that you don't have to worry about a comm line dropping, or resetting a clock or any of a multitude of things. Think about it.. what other totally off the shelf approach is there to get time to 1 second accuracy over a span of years and temperatures that does not require periodic setting the clock ___ 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...
bob- you coming to greylock? -Brian, WA1ZMS On Jun 11, 2011, at 12:13 AM, bownes bow...@gmail.com wrote: That small hemispherical antenna could also have been 900mhz. I have one here @ home that is a combined gps/900mhz antenna from an ambulance tracking system. On Jun 10, 2011, at 22:01, Hal Murray hmur...@megapathdsl.net wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. -- 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. ___ 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...
Any enterprise large enough to have an IT deparment needs precise timing. The cheapest stratum one source is GPS. I work at a Research II university and have several in our network. The time is the public key for our routers that send encrypted routing table updates to each other. There are several mushrooms over the EE wing of the College of Engineering, and at least one over the ME neighborhood for some laser measurement equipment... One EE lab that is doing some GPS signal analysis has at least one 16 way splitter... Jim Cotton n8qoh - Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Saturday, June 11, 2011 10:08:18 AM Subject: Re: [time-nuts] GPS interference and history... On 6/10/11 7:01 PM, Hal Murray wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? GPS timing antennas are sprouting like mushrooms in a lawn all over JPL. (that's what they look like... you'll be walking around, and you'll notice that there's 2 or 3 new stalks sticking up with a little antenna on the top, and conduit running down the side of the building) While we have masers and cesium sources at JPL, they're not distributed everywhere. So, usually, the easy solution is to just get yourself a Symmetricom or Fluke box, have facilities install the antenna, and your lab is set. I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. GPS is easy, that's why. It's under YOUR control. You spend a few thousand bucks (including installation labor) and you have something that works now and for the foreseeable future that you don't have to worry about a comm line dropping, or resetting a clock or any of a multitude of things. Think about it.. what other totally off the shelf approach is there to get time to 1 second accuracy over a span of years and temperatures that does not require periodic setting the clock ___ 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 remember a professor at the University of Wisconsin Madison who postulated the advancement of Man could be measured by man's advancing technology of measuring time. We have come a long way to get down to nanoseconds, LigutSquared notwithstanding. I suppose the next advance will be to some soft of star date system. -- 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 10:36 PM, Henry Hallam wrote: On Thu, Jun 9, 2011 at 2:42 PM, Jim Luxjim...@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. I think this is an interesting thing, especially from a time-nuts perspective.. In order to transfer time from one place to another, you need to know where those two places are, very accurately (i.e. 3ns accuracy implies 1 m position uncertainty) Transit and GPS both make use of the dual curse and blessing of having a moving satellite so it has doppler (a pain for acq and track) but it also means that visibility is good. you can cover the sky with moving satellites, so pretty much anywhere you are, at some point you'll get enough visibility to make it work. The Doppler actually makes it easier to determine the accurate position of the satellites, too. In GEO, the positions of the satellites aren't known to anywhere near 1 m accuracy (10s-100s of meters, if they're using GPSgrin). And, as pointed out, you don't have anywhere near the flexibility of orbits. The MEO height of GPS was a deliberate choice (again, that GPSWorld series is a fascinating history of how it came about). Don't forget that one of the original reasons for GPS was for doing midcourse correction on ICBMs. The Japanese have a satellite with Nav signals up that is in a not quite GEO height orbit that is inclined so its ground track sort of appears to make a big figure 8 stretched N/S over Japan. ___ 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...
Jim Lux schrieb: The MEO height of GPS was a deliberate choice (again, that GPSWorld series is a fascinating history of how it came about). Don't forget that one of the original reasons for GPS was for doing midcourse correction on ICBMs. Where is this GPSWorld history located? regard - Henry -- ehydra.dyndns.info ___ 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 6/10/11 6:55 AM, ehydra wrote: Jim Lux schrieb: The MEO height of GPS was a deliberate choice (again, that GPSWorld series is a fascinating history of how it came about). Don't forget that one of the original reasons for GPS was for doing midcourse correction on ICBMs. Where is this GPSWorld history located? regard - Henry may 2010 and june 2010 http://www.gpsworld.com/content/issue-list http://www.gpsworld.com/gps-world-issue/may-1-2010-9875 http://www.gpsworld.com/gnss-system/gps-modernization/the-origins-gps-part-1-9890 ___ 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 problem is that many FM receivers leak LO signal, so if 2 receivers are next to each others and set 10.7 MHz apart, one will be receiving the LO of the oter. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Chuck Forsberg WA7KGX N2469R c...@omen.com Sender: time-nuts-boun...@febo.com Date: Thu, 09 Jun 2011 12:16:48 To: ehy...@arcor.de; Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com 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...
Thanks Jim! Sorry for posting on time-nuts list with time-offset +1 ;-) corrected. - Henry -- ehydra.dyndns.info Jim Lux schrieb: On 6/10/11 6:55 AM, ehydra wrote: Jim Lux schrieb: The MEO height of GPS was a deliberate choice (again, that GPSWorld series is a fascinating history of how it came about). Don't forget that one of the original reasons for GPS was for doing midcourse correction on ICBMs. Where is this GPSWorld history located? ___ 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 The FCC (like most US agencies) has a mission to promote as well as regulate. The promotion side is what drives them to allocate frequencies in a way that you can reasonably produce gear. They have always come back years later and tried to change things around. Every time, the same issues get hashed over. Sometimes a change actually gets made, sometimes not. What's surprising with the GPS impact here is that the usual conversations are taking place a bit late in the process. The impact on legacy timing gear is one part of a much larger issue here. Hopefully it does not get lost in the back and forth. There's an enormous amount of gear out there that gets timing off of GPS. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of William H. Fite Sent: Friday, June 10, 2011 9:47 AM To: shali...@gmail.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS interference and history... You folks are all far more knowledgeable than I on these issues so I have a question: To what extent, from both an engineering perspective and from the standpoint of public policy, should it be the obligation of transmitter and receiver manufacturers to design and build devices with sufficient filtering, et alia, to avoid or at least vastly minimize problems such as those described below by Didier? I suppose from an engineering standpoint the issue is one of do-ability and from the public policy perspective, how much it is reasonable to expect both those who transmit and those who receive to pay for equipment that will minimize interference problems, given that we are running out of spectrum and demands for chunks of it will continue to pour in. Both technical information and philosophical ramblings will be appreciated. Bill On Fri, Jun 10, 2011 at 9:16 AM, shali...@gmail.com wrote: The problem is that many FM receivers leak LO signal, so if 2 receivers are next to each others and set 10.7 MHz apart, one will be receiving the LO of the oter. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Chuck Forsberg WA7KGX N2469R c...@omen.com Sender: time-nuts-boun...@febo.com Date: Thu, 09 Jun 2011 12:16:48 To: ehy...@arcor.de; Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com 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. ___ 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...
Also given that Galileo is subtantially delayed due to European budget constraints http://www.engadget.com/2010/10/07/eus-galileo-satnav-system-orbiting-way-past-budget-delayed-unt/ it does not seem like it can be expected to mitigate the issue for navigation purpose, aside political implications and the fact that every aircraft might not have combined receivers. Chris On Fri, Jun 10, 2011 at 12:42, Bob Camp li...@rtty.us wrote: Hi The FCC (like most US agencies) has a mission to promote as well as regulate. The promotion side is what drives them to allocate frequencies in a way that you can reasonably produce gear. They have always come back years later and tried to change things around. Every time, the same issues get hashed over. Sometimes a change actually gets made, sometimes not. What's surprising with the GPS impact here is that the usual conversations are taking place a bit late in the process. The impact on legacy timing gear is one part of a much larger issue here. Hopefully it does not get lost in the back and forth. There's an enormous amount of gear out there that gets timing off of GPS. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of William H. Fite Sent: Friday, June 10, 2011 9:47 AM To: shali...@gmail.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS interference and history... You folks are all far more knowledgeable than I on these issues so I have a question: To what extent, from both an engineering perspective and from the standpoint of public policy, should it be the obligation of transmitter and receiver manufacturers to design and build devices with sufficient filtering, et alia, to avoid or at least vastly minimize problems such as those described below by Didier? I suppose from an engineering standpoint the issue is one of do-ability and from the public policy perspective, how much it is reasonable to expect both those who transmit and those who receive to pay for equipment that will minimize interference problems, given that we are running out of spectrum and demands for chunks of it will continue to pour in. Both technical information and philosophical ramblings will be appreciated. Bill On Fri, Jun 10, 2011 at 9:16 AM, shali...@gmail.com wrote: The problem is that many FM receivers leak LO signal, so if 2 receivers are next to each others and set 10.7 MHz apart, one will be receiving the LO of the oter. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Chuck Forsberg WA7KGX N2469R c...@omen.com Sender: time-nuts-boun...@febo.com Date: Thu, 09 Jun 2011 12:16:48 To: ehy...@arcor.de; Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com 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. ___ 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 06/10/2011 06:42 PM, Bob Camp wrote: Hi The FCC (like most US agencies) has a mission to promote as well as regulate. The promotion side is what drives them to allocate frequencies in a way that you can reasonably produce gear. They have always come back years later and tried to change things around. Every time, the same issues get hashed over. Sometimes a change actually gets made, sometimes not. What's surprising with the GPS impact here is that the usual conversations are taking place a bit late in the process. The impact on legacy timing gear is one part of a much larger issue here. Hopefully it does not get lost in the back and forth. There's an enormous amount of gear out there that gets timing off of GPS. Blinding the receivers like that hurts both because antennas and front-end isn't prepared for quite that interference, and simple 1-bit receivers will be caught... so more dynamics will be needed for the 30 dB correlation gain to be of any use. Correlation gain could be increased... with a massive replacement of receivers as signal would change... oh and sats. Still the front-end would require much more interference tolerance... and to some degree this is against the military aspect, as they rely on being able to noise out un-keyed receivers when needed. So the counter-measure becomes less usefull when counter-counter measures is needed on a wide scale just to do normal civilian business. Raising the signal level in a band by, what was it? 70 dB suddenly might be a little too steep a change. Also, it would rule out many hardware approaches which have made GPS useful in so many places. 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...
li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. -- 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] GPS interference and history...
Some other users of gps timing that I have noted thru observation or have personal knowledge of: Timing for telecom providers (I have seen loran used in the past, but this option is more or less gone in North America now.) Timing for power companies Timing for industrial process control Timing and frequency control for long range high performance microwave radio links Timing and frequency control for private mobile radio systems Timing for computer systems Sent from my iPad On 2011-06-10, at 7:01 PM, Hal Murray hmur...@megapathdsl.net wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. -- 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. ___ 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...
Maybe the site has other sensors, like seizmographs or groundwater level that are not obvious. -John li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. -- 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. ___ 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...
That small hemispherical antenna could also have been 900mhz. I have one here @ home that is a combined gps/900mhz antenna from an ambulance tracking system. On Jun 10, 2011, at 22:01, Hal Murray hmur...@megapathdsl.net wrote: li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. -- 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. ___ 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 so called atomic clocks that used to be locked to WWVB have switched over to GPs for higher reliability. My WWVB clocks loose lock when ever there is a lightning storm within 50 miles but the GPS clocks stay locked. No one is going to get hurt or killed because of a disabled GPS clock but it's going to make a lot of people unhappy along with the manufacturers of the clocks. Regards. Max. K 4 O D S. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com - Original Message - From: Hal Murray hmur...@megapathdsl.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, June 10, 2011 9:01 PM Subject: Re: [time-nuts] GPS interference and history... li...@rtty.us said: There's an enormous amount of gear out there that gets timing off of GPS. That's an interesting claim. Does anybody have any data on the usage of GPS for timing? I assume there is one in every cell tower and one in every 911 call center. Are there other large categories of users? What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) I think I saw one last week. It was on a river level measuring station on the Sacramento River. It was a small block building. There was an antenna pointing up into the sky. I assume there is a satellite up there. There was also a small (~3 inch dia) hemisphere antenna. I assume it was GPS. (They had power going into the building (no solar panels) so it should have been simple to get a phone line too.) I'm not sure why they need GPS at the recording house. They know where it is so timing is the only use I can think of. But they could also get that at the receiving end. Millisecond accuracy isn't helpful. Second level accuracy might be interesting if something breaks and you want to know when the wave got to downstream stations. The risetime is probably over a second. -- 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. ___ 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...
Hal wrote: What would it cost to replace all of it? If you wanted to do something like that, what would it cover? How about people like us running old recycled gear? (Z3801A, ThunderBolt, ...) Not a chance. Probably not consumer navigation receivers, either. Maybe public safety users. 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.
[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] 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] 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.
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] 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] 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.
