Re: [time-nuts] Possible HP 10811 instability clue C ont’d.
Hi The tempco gotcha' with the10811 relates to crystal yields. With a true SC, the operating point on the 10811 is very close to the middle of the crystal curve (inflection temperature). You can indeed have a crystal with no turning points (temperature zero TC points). All it has to do is to be slightly on the wrong side of one of the critical angles. The crystals that are slightly on the wrong side are very low tempco ( 1x10^-8/C) but never hit zero anywhere. Since the crystal is always the most expensive part of an OCXO, anything you do to improve yields is going to help the bottom line. If you have enough thermal gain (about 300 or so) a crystal with no zero will make a fine 10811. Bob On Oct 7, 2010, at 11:59 PM, Perry Sandeen wrote: List, Wrote Some on this list mentioned having had less-than-optimal performance with their HP 10811 series oscillators. James Miller G3RUH made a slight mention of optimizing performance by readjusting the set point temperature in one of his phase detector articles. He said though time consuming the results were worth the effort. Replied: Regardless of isolated anecdotal data on one oscillator, it is probably not advisable to change the set point. Answer: Agree. My comments were made about someone with a “wonky” oscillator that that this MIGHT be part of the problem. Replied: The majority of 10811 crystals do NOT have a turnover, only a region of low tempco around 82 degrees. Answer: I respectfully disagree. First isn’t a region of low tempco another way of saying turning point? Semantics aside, I believe that they do have a turning point that is selected. This is why. HP selects 41 separate resistance values to obtain 41 different oven temperatures between 80.0C to 84.0 C in .1 degree increments. Now if that isn’t finding a turning point I don’t know what is. I believe that is why they say if the oscillator fails it needs to be repaired at the factory. Wrote: Instead of that, change the circuit to B-mode and optimize the heat between the two heater resistors for maximum thermal gain (you should be able to get 1000). Then change the circuit back to normal. Answer: I have no idea B-mode is. Would you please expand on it and how to do it? It could be very useful. Regards, Perrier ___ 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] 60 KHz Receiver
Lester Veenstra-“No, Andover Maine.” The white Dacron fabric dome of the station in Andover, Maine, really stood out and could be seen by hikers on the tops of mountains miles away. Somewhere I have photos I took looking down at that white speck in the distance. On one of my hiking trips I stopped to check out the facility. The Dacron fabric dome that was held up only by air pressure (like a carnival funhouse) was still standing but was scheduled to be taken down in the near future. Below is a link to a video about Telstar that appeared on the History Channel and another link to still photos of the horn and the inside of the dome. The date given for removal in the second link was 1985 but I was thinking the dome was removed a few years later than that. http://www.youtube.com/watch?v=NyfGuSmSHWM http://users658.mainememory.net/slideshow/386/display%3Fformat=listprev_object_id=1050prev_object=pageslide_num=1.html -Arthur ___ 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 backup for the stationary time and frequencyuser
The other thing is that something like a quad helix or patch doesn't have the same cross-pol over the hemisphere. It could be real good in one direction and not so good in others. Just like isotropic antennas, you can't physically realize the same cp in all directions (cf hairy ball theorem) On Oct 8, 2010, at 1:48 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 10/08/2010 03:35 AM, jmfranke wrote: When I said the feed would work, I was meaning it would work if LHC. The illustrations and text imply you could just place a normal GPS receiver at the feed location, but the polarization would be wrong. Which was what I reacted on... I am by no means a practical antenna expert, and the EM-theory is a bit fuzzy on the edges, but I do distinctly recall that signal is RHC and reflections becomes LHC so an antenna with RHC orientation will provide some first-degree damping of the LHC reflections. For this antenna setup the intended RHC signal is reflected and should become LHC... just as the interference... so it relies on the antenna gain of the dish to out-perform the other reflections for the half-space receiver that a normal GPS antenna is. The choke ring for a dish head has a distinct different pattern (forming an inner cone rather than flat space). So, a normal antenna would kind of work since the antenna gain would overcome the poor LHC supression of a simple RHC antenna... yay. If an LHC antenna was used instead... now we are talking. 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.
Re: [time-nuts] GPS backup for the stationary time and frequencyuser
Magnus Danielson wrote: On 10/08/2010 03:35 AM, jmfranke wrote: When I said the feed would work, I was meaning it would work if LHC. The illustrations and text imply you could just place a normal GPS receiver at the feed location, but the polarization would be wrong. Which was what I reacted on... I am by no means a practical antenna expert, and the EM-theory is a bit fuzzy on the edges, but I do distinctly recall that signal is RHC and reflections becomes LHC so an antenna with RHC orientation will provide some first-degree damping of the LHC reflections. For this antenna setup the intended RHC signal is reflected and should become LHC... just as the interference... so it relies on the antenna gain of the dish to out-perform the other reflections for the half-space receiver that a normal GPS antenna is. The choke ring for a dish head has a distinct different pattern (forming an inner cone rather than flat space). So, a normal antenna would kind of work since the antenna gain would overcome the poor LHC supression of a simple RHC antenna... yay. If an LHC antenna was used instead... now we are talking. Cheers, Magnus So a dish reflector and a sub reflector and the GPS receiver at the dish would work? What is that configuration called? I can't remember at this early hour. Bill K7NOM ___ 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 backup for the stationary time and frequencyuser
Yep, a Cassegrain antenna would work. John WA4WDL -- From: Bill Janssen bi...@ieee.org Sent: Friday, October 08, 2010 11:52 AM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPS backup for the stationary time and frequencyuser Magnus Danielson wrote: On 10/08/2010 03:35 AM, jmfranke wrote: When I said the feed would work, I was meaning it would work if LHC. The illustrations and text imply you could just place a normal GPS receiver at the feed location, but the polarization would be wrong. Which was what I reacted on... I am by no means a practical antenna expert, and the EM-theory is a bit fuzzy on the edges, but I do distinctly recall that signal is RHC and reflections becomes LHC so an antenna with RHC orientation will provide some first-degree damping of the LHC reflections. For this antenna setup the intended RHC signal is reflected and should become LHC... just as the interference... so it relies on the antenna gain of the dish to out-perform the other reflections for the half-space receiver that a normal GPS antenna is. The choke ring for a dish head has a distinct different pattern (forming an inner cone rather than flat space). So, a normal antenna would kind of work since the antenna gain would overcome the poor LHC supression of a simple RHC antenna... yay. If an LHC antenna was used instead... now we are talking. Cheers, Magnus So a dish reflector and a sub reflector and the GPS receiver at the dish would work? What is that configuration called? I can't remember at this early hour. Bill K7NOM ___ 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 backup for the stationary time and frequencyuser
Bill Janssen wrote: Magnus Danielson wrote: On 10/08/2010 03:35 AM, jmfranke wrote: When I said the feed would work, I was meaning it would work if LHC. The illustrations and text imply you could just place a normal GPS receiver at the feed location, but the polarization would be wrong. Which was what I reacted on... I am by no means a practical antenna expert, and the EM-theory is a bit fuzzy on the edges, but I do distinctly recall that signal is RHC and reflections becomes LHC so an antenna with RHC orientation will provide some first-degree damping of the LHC reflections. For this antenna setup the intended RHC signal is reflected and should become LHC... just as the interference... so it relies on the antenna gain of the dish to out-perform the other reflections for the half-space receiver that a normal GPS antenna is. The choke ring for a dish head has a distinct different pattern (forming an inner cone rather than flat space). So, a normal antenna would kind of work since the antenna gain would overcome the poor LHC supression of a simple RHC antenna... yay. If an LHC antenna was used instead... now we are talking. Cheers, Magnus So a dish reflector and a sub reflector and the GPS receiver at the dish would work? What is that configuration called? I can't remember at this early hour. Depends on the relative curvatures and focal points: Cassegrain if the subreflector convex. Gregorian if the subreflector is concave parabolic. Dragonian if the subreflector is concave hyperbolic IEEE Ant and Prop Magazine a few years back had a series of articles on designing them all. All of them can be done offset or coaxial Any would conceivably work.. It's all about what your pattern looks like, what sort of efficiency you need, any mechanical constraints, 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 backup for the stationary time and frequencyuser
Hi Jim: I've got a spare Ku band satellite dish and would like to use it for GPS. In an ideal application the GPS antenna would be mounted in the normal manner and above it would be a sub-reflector aimed at the Ku dish. That way the antenna might pickup sats near the horizon directly and from a narrow part of the sky by means of the dish. The dish might be aimed at a WAAS GPS sat. I've heard that you can just use the TV dish with a normal GPS antenna, and it gas gain even though the polarization is reversed. Have Fun, Brooke Clarke http://www.PRC68.com jimlux wrote: Bill Janssen wrote: Magnus Danielson wrote: On 10/08/2010 03:35 AM, jmfranke wrote: When I said the feed would work, I was meaning it would work if LHC. The illustrations and text imply you could just place a normal GPS receiver at the feed location, but the polarization would be wrong. Which was what I reacted on... I am by no means a practical antenna expert, and the EM-theory is a bit fuzzy on the edges, but I do distinctly recall that signal is RHC and reflections becomes LHC so an antenna with RHC orientation will provide some first-degree damping of the LHC reflections. For this antenna setup the intended RHC signal is reflected and should become LHC... just as the interference... so it relies on the antenna gain of the dish to out-perform the other reflections for the half-space receiver that a normal GPS antenna is. The choke ring for a dish head has a distinct different pattern (forming an inner cone rather than flat space). So, a normal antenna would kind of work since the antenna gain would overcome the poor LHC supression of a simple RHC antenna... yay. If an LHC antenna was used instead... now we are talking. Cheers, Magnus So a dish reflector and a sub reflector and the GPS receiver at the dish would work? What is that configuration called? I can't remember at this early hour. Depends on the relative curvatures and focal points: Cassegrain if the subreflector convex. Gregorian if the subreflector is concave parabolic. Dragonian if the subreflector is concave hyperbolic IEEE Ant and Prop Magazine a few years back had a series of articles on designing them all. All of them can be done offset or coaxial Any would conceivably work.. It's all about what your pattern looks like, what sort of efficiency you need, any mechanical constraints, 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. -- Have Fun, Brooke Clarke http://www.PRC68.com ___ 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 backup for the stationary time and frequencyuser
I've been half following this thread and can't make out the reason for a less than hemispheric antenna pattern. GPS needs several birds to lock up, and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. Best, -John = Hi Jim: I've got a spare Ku band satellite dish and would like to use it for GPS. In an ideal application the GPS antenna would be mounted in the normal manner and above it would be a sub-reflector aimed at the Ku dish. That way the antenna might pickup sats near the horizon directly and from a narrow part of the sky by means of the dish. The dish might be aimed at a WAAS GPS sat. I've heard that you can just use the TV dish with a normal GPS antenna, and it gas gain even though the polarization is reversed. Have Fun, Brooke Clarke http://www.PRC68.com jimlux wrote: Bill Janssen wrote: Magnus Danielson wrote: On 10/08/2010 03:35 AM, jmfranke wrote: When I said the feed would work, I was meaning it would work if LHC. The illustrations and text imply you could just place a normal GPS receiver at the feed location, but the polarization would be wrong. Which was what I reacted on... I am by no means a practical antenna expert, and the EM-theory is a bit fuzzy on the edges, but I do distinctly recall that signal is RHC and reflections becomes LHC so an antenna with RHC orientation will provide some first-degree damping of the LHC reflections. For this antenna setup the intended RHC signal is reflected and should become LHC... just as the interference... so it relies on the antenna gain of the dish to out-perform the other reflections for the half-space receiver that a normal GPS antenna is. The choke ring for a dish head has a distinct different pattern (forming an inner cone rather than flat space). So, a normal antenna would kind of work since the antenna gain would overcome the poor LHC supression of a simple RHC antenna... yay. If an LHC antenna was used instead... now we are talking. Cheers, Magnus So a dish reflector and a sub reflector and the GPS receiver at the dish would work? What is that configuration called? I can't remember at this early hour. Depends on the relative curvatures and focal points: Cassegrain if the subreflector convex. Gregorian if the subreflector is concave parabolic. Dragonian if the subreflector is concave hyperbolic IEEE Ant and Prop Magazine a few years back had a series of articles on designing them all. All of them can be done offset or coaxial Any would conceivably work.. It's all about what your pattern looks like, what sort of efficiency you need, any mechanical constraints, 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. -- Have Fun, Brooke Clarke http://www.PRC68.com ___ 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 backup for the stationary time and frequencyuser
The Doppler is dramatically reduced by looking only at the WAAS bird(s). John WA4WDL -- From: J. Forster j...@quik.com Sent: Friday, October 08, 2010 1:27 PM To: bro...@pacific.net; Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPS backup for the stationary time and frequencyuser I've been half following this thread and can't make out the reason for a less than hemispheric antenna pattern. GPS needs several birds to lock up, and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. Best, -John = Hi Jim: I've got a spare Ku band satellite dish and would like to use it for GPS. In an ideal application the GPS antenna would be mounted in the normal manner and above it would be a sub-reflector aimed at the Ku dish. That way the antenna might pickup sats near the horizon directly and from a narrow part of the sky by means of the dish. The dish might be aimed at a WAAS GPS sat. I've heard that you can just use the TV dish with a normal GPS antenna, and it gas gain even though the polarization is reversed. Have Fun, Brooke Clarke http://www.PRC68.com jimlux wrote: Bill Janssen wrote: Magnus Danielson wrote: On 10/08/2010 03:35 AM, jmfranke wrote: When I said the feed would work, I was meaning it would work if LHC. The illustrations and text imply you could just place a normal GPS receiver at the feed location, but the polarization would be wrong. Which was what I reacted on... I am by no means a practical antenna expert, and the EM-theory is a bit fuzzy on the edges, but I do distinctly recall that signal is RHC and reflections becomes LHC so an antenna with RHC orientation will provide some first-degree damping of the LHC reflections. For this antenna setup the intended RHC signal is reflected and should become LHC... just as the interference... so it relies on the antenna gain of the dish to out-perform the other reflections for the half-space receiver that a normal GPS antenna is. The choke ring for a dish head has a distinct different pattern (forming an inner cone rather than flat space). So, a normal antenna would kind of work since the antenna gain would overcome the poor LHC supression of a simple RHC antenna... yay. If an LHC antenna was used instead... now we are talking. Cheers, Magnus So a dish reflector and a sub reflector and the GPS receiver at the dish would work? What is that configuration called? I can't remember at this early hour. Depends on the relative curvatures and focal points: Cassegrain if the subreflector convex. Gregorian if the subreflector is concave parabolic. Dragonian if the subreflector is concave hyperbolic IEEE Ant and Prop Magazine a few years back had a series of articles on designing them all. All of them can be done offset or coaxial Any would conceivably work.. It's all about what your pattern looks like, what sort of efficiency you need, any mechanical constraints, 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. -- Have Fun, Brooke Clarke http://www.PRC68.com ___ 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 backup for the stationary time and frequencyuser
On Oct 8, 2010, at 10:27 AM, J. Forster wrote: GPS needs several birds to lock up, To get a position fix, this is true; 3 birds minimum for a 2D fix, 4 birds minimum for a 3D fix. and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. Only if you don't already know your position. Once your position has been determined accurately and you have the current ephemeris data for the bird you're listening to, you can factor out the predictable doppler and use a single bird for timing and frequency. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 backup for the stationary time and frequencyuser
KISS. This seems like a lot of work for not particularily good results. Among other things, you have no closure so no measure of how good your measuremwent is. FWIW, -John On Oct 8, 2010, at 10:27 AM, J. Forster wrote: GPS needs several birds to lock up, To get a position fix, this is true; 3 birds minimum for a 2D fix, 4 birds minimum for a 3D fix. and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. Only if you don't already know your position. Once your position has been determined accurately and you have the current ephemeris data for the bird you're listening to, you can factor out the predictable doppler and use a single bird for timing and frequency. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 backup for the stationary time and frequencyuser
On 10/8/2010 10:44 AM, J. Forster wrote: KISS. This seems like a lot of work for not particularily good results. I think the point is that the results are amazingly better than the alternative if the medium-orbit GPS sats are all destroyed and/or there's jamming coming from all over the sky. What bothers me is that I haven't figured out yet how the WAAS satellite configuration itself isn't usable as a wide-area GPS jammer. It is just a bent-pipe transponder down from 6 GHz or so to L1, so if you can overpower the uplink with spoofed data that interferes with reception of the other satellites *and* jam the CC channels that would be used to shut the transponder off, you're able to jam a whole continent at once. I'm sure this must have been considered before deployment, but I can't find any references to the countermeasure(s). Matthew Kaufman ___ 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 backup for the stationary time and frequencyuser
Brooke Clarke wrote: Hi Jim: I've got a spare Ku band satellite dish and would like to use it for GPS. In an ideal application the GPS antenna would be mounted in the normal manner and above it would be a sub-reflector aimed at the Ku dish. That way the antenna might pickup sats near the horizon directly and from a narrow part of the sky by means of the dish. The dish might be aimed at a WAAS GPS sat. I've heard that you can just use the TV dish with a normal GPS antenna, and it gas gain even though the polarization is reversed. Give it a shot. The other thing is that if you have your GPS antenna facing straight up, at the focus of the dish, you're looking at the side of the gps antenna, where the polarization might be less circular. But one thing to think about here... a standard Ku dish isn't very big.. At GPS frequencies, you're looking at 20 cm wavelength. The dish is perhaps 2, maybe 3 wavelengths across. That's not a huge amount of gain. You might do just as well with a flat cookie sheet. ___ 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 backup for the stationary time and frequencyuser
J. Forster wrote: I've been half following this thread and can't make out the reason for a less than hemispheric antenna pattern. GPS needs several birds to lock up, and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. If you're looking at boosting the level of the WAAS signal, it's broadcast from a Clarke Orbit satellite, and has no doppler. ___ 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 backup for the stationary time and frequencyuser
Matthew Kaufman wrote: On 10/8/2010 10:44 AM, J. Forster wrote: KISS. This seems like a lot of work for not particularily good results. I think the point is that the results are amazingly better than the alternative if the medium-orbit GPS sats are all destroyed and/or there's jamming coming from all over the sky. What bothers me is that I haven't figured out yet how the WAAS satellite configuration itself isn't usable as a wide-area GPS jammer. It is just a bent-pipe transponder down from 6 GHz or so to L1, so if you can overpower the uplink with spoofed data that interferes with reception of the other satellites *and* jam the CC channels that would be used to shut the transponder off, you're able to jam a whole continent at once. Most spacecraft have a command loss timer that would shut off the transmitter in the event that a valid command isn't received every so often, in case the transmitter is malfunctioning and jamming the uplink. I'm sure this must have been considered before deployment, but I can't find any references to the countermeasure(s). Maybe because WAAS is basically a civilian use system to do precision approaches? ___ 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 backup for the stationary time and frequencyuser
On Oct 8, 2010, at 10:44 AM, J. Forster wrote: KISS. This seems like a lot of work for not particularily good results. Among other things, you have no closure so no measure of how good your measuremwent is. Single-satellite timing mode is already commonly implemented in timing receivers; there's no work to be done other than turning it on. Closure is only lacking if all of the USAF ground stations are taken out such that the ephemeris and health information can no longer be updated on any intact birds; otherwise you know where every existing bird is at any instant in time, and each bird indicates whether it should be trusted. Bottom line: If there's still one intact bird and one intact ground station to control it, you can get accurate time and frequency whenever it's visible (assuming no local jamming/spoofing) if you've already surveyed your position, using off-the-shelf hardware like a TBolt. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 backup for the stationary time and frequencyuser
On 10/08/2010 07:27 PM, J. Forster wrote: I've been half following this thread and can't make out the reason for a less than hemispheric antenna pattern. GPS needs several birds to lock up, and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. If you target the WAAS, EGNOS or SBAS birds you have significant less doppler since they sit on geostationary orbit. However, since these orbits is not perfect circular but slightly elliptic, so a 24 h pattern evolves. Just squaring up, as proposed earlier in the thread, will suffer from these shifts. Also, ionospheric and tropospheric delays also plays in, but the point of these birds is to provide improved predictions so a good receiver should be able to handle it. You also rely on the time of the base-station, but that is obvious I hope. 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 backup for the stationary time and frequencyuser
On 10/08/2010 08:07 PM, Matthew Kaufman wrote: On 10/8/2010 10:44 AM, J. Forster wrote: KISS. This seems like a lot of work for not particularily good results. I think the point is that the results are amazingly better than the alternative if the medium-orbit GPS sats are all destroyed and/or there's jamming coming from all over the sky. What bothers me is that I haven't figured out yet how the WAAS satellite configuration itself isn't usable as a wide-area GPS jammer. It is just a bent-pipe transponder down from 6 GHz or so to L1, so if you can overpower the uplink with spoofed data that interferes with reception of the other satellites *and* jam the CC channels that would be used to shut the transponder off, you're able to jam a whole continent at once. I'm sure this must have been considered before deployment, but I can't find any references to the countermeasure(s). I would not be supprised if they had not considered such a threat. This is a common threat for all bent-pipe birds. They have been jammed before and we can expect them to be jammed again. However, I do not think the WAAS or any similar is highest up on the target list as for most uses it is a support-function rather than main function system. Birds which has been jammed is typically TV signal relays. 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 backup for the stationary time and frequencyuser
On 10/08/2010 08:22 PM, jimlux wrote: Brooke Clarke wrote: Hi Jim: I've got a spare Ku band satellite dish and would like to use it for GPS. In an ideal application the GPS antenna would be mounted in the normal manner and above it would be a sub-reflector aimed at the Ku dish. That way the antenna might pickup sats near the horizon directly and from a narrow part of the sky by means of the dish. The dish might be aimed at a WAAS GPS sat. I've heard that you can just use the TV dish with a normal GPS antenna, and it gas gain even though the polarization is reversed. Give it a shot. The other thing is that if you have your GPS antenna facing straight up, at the focus of the dish, you're looking at the side of the gps antenna, where the polarization might be less circular. But one thing to think about here... a standard Ku dish isn't very big.. At GPS frequencies, you're looking at 20 cm wavelength. The dish is perhaps 2, maybe 3 wavelengths across. That's not a huge amount of gain. You might do just as well with a flat cookie sheet. Well, a 1 m dish gives you 48 dB gain at L1 if I calculate correctly. The normal antenna is at 6 db of antenna gain? Even if less than perfect, not too big size is needed to get meaningful antenna gain. 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] 60 KHz Receiver
We had similar dome in Sunnyvale (Ca) until the late 80's, but I can't remember who owned it, maybe GE?; it's all housing now. Dave - Original Message - From: Arthur Dent golgarfrinc...@yahoo.com To: time-nuts@febo.com Sent: Friday, October 8, 2010 5:06:34 AM Subject: [time-nuts] 60 KHz Receiver Lester Veenstra-“No, Andover Maine.” The white Dacron fabric dome of the station in Andover, Maine, really stood out and could be seen by hikers on the tops of mountains miles away. Somewhere I have photos I took looking down at that white speck in the distance. On one of my hiking trips I stopped to check out the facility. The Dacron fabric dome that was held up only by air pressure (like a carnival funhouse) was still standing but was scheduled to be taken down in the near future. Below is a link to a video about Telstar that appeared on the History Channel and another link to still photos of the horn and the inside of the dome. The date given for removal in the second link was 1985 but I was thinking the dome was removed a few years later than that. http://www.youtube.com/watch?v=NyfGuSmSHWM http://users658.mainememory.net/slideshow/386/display%3Fformat=listprev_object_id=1050prev_object=pageslide_num=1.html -Arthur ___ 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] 60 KHz Receiver
I have a section of the radome material, and the aluminum reflector surface (honeycomb backing structure) at home. 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: +1-671-929-8141 UK Cell: +44-(0)7716-298-224 US Cell: +1-240-425-7335 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 d.sei...@comcast.net Sent: 09 October 2010 10:42 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 60 KHz Receiver We had similar dome in Sunnyvale (Ca) until the late 80's, but I can't remember who owned it, maybe GE?; it's all housing now. Dave - Original Message - From: Arthur Dent golgarfrinc...@yahoo.com To: time-nuts@febo.com Sent: Friday, October 8, 2010 5:06:34 AM Subject: [time-nuts] 60 KHz Receiver Lester Veenstra-No, Andover Maine. The white Dacron fabric dome of the station in Andover, Maine, really stood out and could be seen by hikers on the tops of mountains miles away. Somewhere I have photos I took looking down at that white speck in the distance. On one of my hiking trips I stopped to check out the facility. The Dacron fabric dome that was held up only by air pressure (like a carnival funhouse) was still standing but was scheduled to be taken down in the near future. Below is a link to a video about Telstar that appeared on the History Channel and another link to still photos of the horn and the inside of the dome. The date given for removal in the second link was 1985 but I was thinking the dome was removed a few years later than that. http://www.youtube.com/watch?v=NyfGuSmSHWM http://users658.mainememory.net/slideshow/386/display%3Fformat=listprev_obj ect_id=1050prev_object=pageslide_num=1.html -Arthur ___ 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] 60 KHz Receiver
Where? Off 401 near the Blue Cube? -John = We had similar dome in Sunnyvale (Ca) until the late 80's, but I can't remember who owned it, maybe GE?; it's all housing now. Dave - Original Message - From: Arthur Dent golgarfrinc...@yahoo.com To: time-nuts@febo.com Sent: Friday, October 8, 2010 5:06:34 AM Subject: [time-nuts] 60 KHz Receiver Lester Veenstra-âNo, Andover Maine.â The white Dacron fabric dome of the station in Andover, Maine, really stood out and could be seen by hikers on the tops of mountains miles away. Somewhere I have photos I took looking down at that white speck in the distance. On one of my hiking trips I stopped to check out the facility. The Dacron fabric dome that was held up only by air pressure (like a carnival funhouse) was still standing but was scheduled to be taken down in the near future. Below is a link to a video about Telstar that appeared on the History Channel and another link to still photos of the horn and the inside of the dome. The date given for removal in the second link was 1985 but I was thinking the dome was removed a few years later than that.  http://www.youtube.com/watch?v=NyfGuSmSHWM http://users658.mainememory.net/slideshow/386/display%3Fformat=listprev_object_id=1050prev_object=pageslide_num=1.html -Arthur          ___ 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 backup for the stationary time and frequencyuser
Magnus Danielson wrote: On 10/08/2010 08:22 PM, jimlux wrote: B You might do just as well with a flat cookie sheet. Well, a 1 m dish gives you 48 dB gain at L1 if I calculate correctly. I don't think so..48dBi would be huge...A numerical gain of 48 I can believe: let's say we have an antenna that is 2x3 wavelengths (40x60cm, 1.5 GHz = 20 cm) or 6 square wavelengths. the gain is 4 pi * A, or about 75. But in reality, the efficiency is typically no better than 50% (because of sidelobes, illumination, etc.)... Call 66% to be sporty, and you've got a numerical gain of 50, or 17dBi. The normal antenna is at 6 db of antenna gain? Even if less than perfect, not too big size is needed to get meaningful antenna gain. Cheers, M ___ 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 backup for the stationary time and frequencyuser
48dBi is way way too big 18 I might go for Look at aperture. Say it's six square wavelengths(40x60 cm). A dipole is about 1/8th square wave lengths..so the gain is 48 times that of a dipole. Say about 17dB +2dB or 19 dBi On Oct 8, 2010, at 3:05 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 10/08/2010 08:22 PM, jimlux wrote: Brooke Clarke wrote: Hi Jim: I've got a spare Ku band satellite dish and would like to use it for GPS. In an ideal application the GPS antenna would be mounted in the normal manner and above it would be a sub-reflector aimed at the Ku dish. That way the antenna might pickup sats near the horizon directly and from a narrow part of the sky by means of the dish. The dish might be aimed at a WAAS GPS sat. I've heard that you can just use the TV dish with a normal GPS antenna, and it gas gain even though the polarization is reversed. Give it a shot. The other thing is that if you have your GPS antenna facing straight up, at the focus of the dish, you're looking at the side of the gps antenna, where the polarization might be less circular. But one thing to think about here... a standard Ku dish isn't very big.. At GPS frequencies, you're looking at 20 cm wavelength. The dish is perhaps 2, maybe 3 wavelengths across. That's not a huge amount of gain. You might do just as well with a flat cookie sheet. Well, a 1 m dish gives you 48 dB gain at L1 if I calculate correctly. The normal antenna is at 6 db of antenna gain? Even if less than perfect, not too big size is needed to get meaningful antenna gain. 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.
Re: [time-nuts] GPS backup for the stationary time and frequencyuser
20 log(base10) (diameter in meters) + 20log(frequency in ghz) +17.8 = dbi On 10/8/2010 8:39 PM, jimlux wrote: Magnus Danielson wrote: On 10/08/2010 08:22 PM, jimlux wrote: B You might do just as well with a flat cookie sheet. Well, a 1 m dish gives you 48 dB gain at L1 if I calculate correctly. I don't think so..48dBi would be huge...A numerical gain of 48 I can believe: let's say we have an antenna that is 2x3 wavelengths (40x60cm, 1.5 GHz = 20 cm) or 6 square wavelengths. the gain is 4 pi * A, or about 75. But in reality, the efficiency is typically no better than 50% (because of sidelobes, illumination, etc.)... Call 66% to be sporty, and you've got a numerical gain of 50, or 17dBi. The normal antenna is at 6 db of antenna gain? Even if less than perfect, not too big size is needed to get meaningful antenna gain. Cheers, M ___ 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 backup for the stationary time and frequencyuser
Hi John: The WAAS birds may be too weak to receive with an omni antenna, hence the desire to get some gain. The normal GPS sats will pass through the beam and the GPS antenna will pick up some sats directly so you do get some TRAIM. Doppler is not an issue in timing mode (i.e. position is known) and only one sat is required. Have Fun, Brooke Clarke http://www.PRC68.com J. Forster wrote: KISS. This seems like a lot of work for not particularily good results. Among other things, you have no closure so no measure of how good your measuremwent is. FWIW, -John On Oct 8, 2010, at 10:27 AM, J. Forster wrote: GPS needs several birds to lock up, To get a position fix, this is true; 3 birds minimum for a 2D fix, 4 birds minimum for a 3D fix. and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. Only if you don't already know your position. Once your position has been determined accurately and you have the current ephemeris data for the bird you're listening to, you can factor out the predictable doppler and use a single bird for timing and frequency. -- Mark J. Blair, NF6Xn...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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. -- Have Fun, Brooke Clarke http://www.PRC68.com ___ 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 backup for the stationary time and frequencyuser
Brian Kirby wrote: 20 log(base10) (diameter in meters) + 20log(frequency in ghz) +17.8 = dbi That assumes some nominal efficiency? I'll have to remember that one.. 17.8 It's like the 32.44 dB for free space loss between isotropes 1 km apart at 1 MHz (+20log10(dist in km) + 20log10(freq in MHz)) ___ 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] 60 KHz Receiver
You mean near the intersection of 401 and 537? Close to 385 also. (I took the liberty of keeping up the code and adding 300 to everything.) -Rex On 10/8/2010 6:26 PM, J. Forster wrote: Where? Off 401 near the Blue Cube? -John = We had similar dome in Sunnyvale (Ca)Â until the late 80's, but I can't remember who owned it, maybe GE?; it's all housing now. Dave ___ 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 backup for the stationary time and frequencyuser
The received WAAS signal strength is designed to be similar to that from regular GPS satellites. And, I find that to be true in practice. John -- From: Brooke Clarke brooke95...@att.net Sent: Friday, October 08, 2010 2:09 PM To: j...@quik.com; Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] GPS backup for the stationary time and frequencyuser Hi John: The WAAS birds may be too weak to receive with an omni antenna, hence the desire to get some gain. The normal GPS sats will pass through the beam and the GPS antenna will pick up some sats directly so you do get some TRAIM. Doppler is not an issue in timing mode (i.e. position is known) and only one sat is required. Have Fun, Brooke Clarke http://www.PRC68.com J. Forster wrote: KISS. This seems like a lot of work for not particularily good results. Among other things, you have no closure so no measure of how good your measuremwent is. FWIW, -John On Oct 8, 2010, at 10:27 AM, J. Forster wrote: GPS needs several birds to lock up, To get a position fix, this is true; 3 birds minimum for a 2D fix, 4 birds minimum for a 3D fix. and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. Only if you don't already know your position. Once your position has been determined accurately and you have the current ephemeris data for the bird you're listening to, you can factor out the predictable doppler and use a single bird for timing and frequency. -- Mark J. Blair, NF6Xn...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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. -- Have Fun, Brooke Clarke http://www.PRC68.com ___ 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 backup for the stationary time and frequencyuser
These were formulas I had written in my notes about 30 years ago, when I worked in Satcom for the military and NASA. I think they used an efficiency of 55 percent another was 20log D(feet) + 20log F(mhz) - 52.4 = dbi and the main formula of gain in db = k(pi*D/wave)squared showing k=0.55, d is diameter, wave is the operating frequency On 10/8/2010 9:47 PM, jimlux wrote: Brian Kirby wrote: 20 log(base10) (diameter in meters) + 20log(frequency in ghz) +17.8 = dbi That assumes some nominal efficiency? I'll have to remember that one.. 17.8 It's like the 32.44 dB for free space loss between isotropes 1 km apart at 1 MHz (+20log10(dist in km) + 20log10(freq in MHz)) ___ 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.
