Re: [time-nuts] Sun Outage
Just to put that in perspective, we're measuring a few degrees of phase shift in a 32 GHz signal on a path that is over a billion km long. Now this is fully qualified nuttiness :) Didier KO4BB On October 10, 2014 8:17:13 AM CDT, Jim Lux jim...@earthlink.net wrote: On 10/9/14, 10:16 PM, Andy wrote: Bob Stewart b...@evoria.net wrote: It occurred to me that one could use satellite signals as a meteorological instrument to measure the water density in the atmosphere above you. I wonder if the NWS does that. WHy yes they do: that's what weather radar is. It detects the reflections from the rain drops or ice crystals in the storms. These days, it's doppler radar, so not only do you get the density of the return but whether it is moving towards or away from the radar. If multiple radars in different places cover the same volume, you can get full X-Y motion. On a more time-nutty note, they also use the small variations in GPS signal propagation to do this kind of measurement. COSMIC (and soon to be launched COSMIC-2) measure GPS signals passing through the atmosphere from satellite to satellite- grazing the earth's surface, and by measuring the phase and amplitude variations (because you know the underlying GPS signal is locked to an atomic standard), you can infer the properties of the atmosphere at various elevations. Such radio occultation measurements are the 3rd or 4th most useful measurement in feeding the numerical models that are used for weather prediction. On an even more gnat's eyelash time measurement note: We use radiometers (basically a sensitive power meter) to measure water vapor content (and, incidentally, cloud cover) at the DSN stations, to remove some of the variation in the measurements of propagation delay to and from spacecraft. By carefully gnawing away at all sources of error, we can measure the round trip light time with accuracies of 1E-14 (1000 second tau), which is how we can measure range to something at Saturn to a few cm, and radial velocity (range rate) to a few mm/sec. Just to put that in perspective, we're measuring a few degrees of phase shift in a 32 GHz signal on a path that is over a billion km long. http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/18497/1/99-1986.pdf, page 7, shows some radiometer data from a 13.402 GHz radiometer I built installed in Las Cruces, NM. It was easy to tell when it was overcast or clear: clear is cold, because you're seeing sky; overcast is warm, because you're seeing the reflection of the ground, and the warm water in the clouds. ___ 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. -- Sent from my Motorola Droid Razr HD 4G LTE wireless tracker while I do other things. ___ 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] Sun Outage
Jim Lux wrote: WHy yes they do: that's what weather radar is. It detects the reflections from the rain drops or ice crystals in the storms. ... But radar is much different than passively receiving known radio signals that penetrate the atmosphere from above. Conceivably one could have hundreds of small receivers, scattered around within the range of one WX radar. Much less cost than the radar, and no emissions so no need to license it. I don't know if it matters but they measure transmission, not scattering and reflectivity, and they look at the droplets from below, not the side. With the proliferation of personal weather stations, it seems like another source of information that could be exploited cheaply. Andy ___ 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] Sun Outage
Bob Stewart b...@evoria.net wrote: ... Also, the cartoons I was recording for my granddaughter were unaffected, but the station I was watching had the outage. That doesn't all fit together unless it was the uplink that had the problem. I don't think the uplink itself can have this problem. But DirecTV uses multiple transponders per satellite, and in some cases more than one satellite, so all the channels are not affected equally. When I had DirecTV, we had two dishes. The installer boggled up the first install so they came back and put up another one several feet away, mounted on a more stable surface (not roof shingles). The first dish was one that could be used for multiple satellites. It had three 'focal' points with three little radomes that either had, or could have, LNAs in them. Each points to a different spot in the sky. The second dish had only one. Regardless, we received only one satellite. I don't recall ever being affected by a solar outage, but rain and ice were real killers! Yeah they say rain shouldn't cause an outage, but it does when the rain density is high enough. I could use that to predict when we were about to be hit by a downpour. There was about a 3 minute lag between losing all the channels, and the downpour starting. It occurred to me that one could use satellite signals as a meteorological instrument to measure the water density in the atmosphere above you. I wonder if the NWS does that. Andy ___ 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] Sun Outage
Good morning Brooke, Sorry, don't know the answer to that question. Interesting question though. I am aware of the Radio Rove project and have played around at listening for Jupiter on HF and LO VHF but not in a very serious way. cheers, Graham ve3gtc On 2014-10-09 19:26, Brooke Clarke wrote: Hi Graham: Do you know if anyone has used a Ku-band receiver, like described in the paper, to look at Jupiter? The Radio Jove project is looking between 18 and 40 MHz. http://radiojove.gsfc.nasa.gov/ Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Graham wrote: If you have an interest in trying to measure sun noise, you might like to have a look at the itty bitty radio telescope. (watch the line wrap) http://www.arrl.org/files/file/ETP/Radio%20Astronomy/Build%20a%20Homebrew%20Radio%20Telescope-QST-0609.pdf http://www.gb.nrao.edu/epo/ambassadors/ibtmanualshort.pdf http://www.stargazing.net/david/radio/itty_bitty_radio_telescope.html as a start. A google search will return more. cheers, Graham ve3gtc On 2014-10-09 14:23, paul swed wrote: Exactly geosyncs have sun outages as the sun aligns with the sat and your dish. GPS because the sats are distributed do not suffer from the effect. Regards Paul WB8TSL On Thu, Oct 9, 2014 at 2:04 PM, Mike Feher mfe...@eozinc.com wrote: Bob - I do not believe it has any effect. The DirecTV satellites are geostationary at about 22K miles. I used to experience the same phenomenon in the late 70's with my TVRO receiver at C band. GPS has some 36 or so satellites in a Medium Earth Orbit (MEO). Blockage, if it can even occur due to the nature of the receiving antenna, of a single one for a few minutes will have no discernible effect in my opinion. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart Sent: Thursday, October 09, 2014 1:40 PM To: Time Nuts Subject: [time-nuts] Sun Outage Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
Hi Bringing this back to GPS… The TV stuff is at about 8X the frequency of GPS. That makes a difference in terms of things like rain. That said, yes, there probably is some giant rainstorm that would impact GPS accuracy. Much more likely in a “I can only see a small patch of sky” situation. Bob On Oct 10, 2014, at 1:16 AM, Andy ai.egrps...@gmail.com wrote: Bob Stewart b...@evoria.net wrote: ... Also, the cartoons I was recording for my granddaughter were unaffected, but the station I was watching had the outage. That doesn't all fit together unless it was the uplink that had the problem. I don't think the uplink itself can have this problem. But DirecTV uses multiple transponders per satellite, and in some cases more than one satellite, so all the channels are not affected equally. When I had DirecTV, we had two dishes. The installer boggled up the first install so they came back and put up another one several feet away, mounted on a more stable surface (not roof shingles). The first dish was one that could be used for multiple satellites. It had three 'focal' points with three little radomes that either had, or could have, LNAs in them. Each points to a different spot in the sky. The second dish had only one. Regardless, we received only one satellite. I don't recall ever being affected by a solar outage, but rain and ice were real killers! Yeah they say rain shouldn't cause an outage, but it does when the rain density is high enough. I could use that to predict when we were about to be hit by a downpour. There was about a 3 minute lag between losing all the channels, and the downpour starting. It occurred to me that one could use satellite signals as a meteorological instrument to measure the water density in the atmosphere above you. I wonder if the NWS does that. Andy ___ 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] Sun Outage
On 10/9/14, 10:16 PM, Andy wrote: Bob Stewart b...@evoria.net wrote: It occurred to me that one could use satellite signals as a meteorological instrument to measure the water density in the atmosphere above you. I wonder if the NWS does that. WHy yes they do: that's what weather radar is. It detects the reflections from the rain drops or ice crystals in the storms. These days, it's doppler radar, so not only do you get the density of the return but whether it is moving towards or away from the radar. If multiple radars in different places cover the same volume, you can get full X-Y motion. On a more time-nutty note, they also use the small variations in GPS signal propagation to do this kind of measurement. COSMIC (and soon to be launched COSMIC-2) measure GPS signals passing through the atmosphere from satellite to satellite- grazing the earth's surface, and by measuring the phase and amplitude variations (because you know the underlying GPS signal is locked to an atomic standard), you can infer the properties of the atmosphere at various elevations. Such radio occultation measurements are the 3rd or 4th most useful measurement in feeding the numerical models that are used for weather prediction. On an even more gnat's eyelash time measurement note: We use radiometers (basically a sensitive power meter) to measure water vapor content (and, incidentally, cloud cover) at the DSN stations, to remove some of the variation in the measurements of propagation delay to and from spacecraft. By carefully gnawing away at all sources of error, we can measure the round trip light time with accuracies of 1E-14 (1000 second tau), which is how we can measure range to something at Saturn to a few cm, and radial velocity (range rate) to a few mm/sec. Just to put that in perspective, we're measuring a few degrees of phase shift in a 32 GHz signal on a path that is over a billion km long. http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/18497/1/99-1986.pdf, page 7, shows some radiometer data from a 13.402 GHz radiometer I built installed in Las Cruces, NM. It was easy to tell when it was overcast or clear: clear is cold, because you're seeing sky; overcast is warm, because you're seeing the reflection of the ground, and the warm water in the clouds. ___ 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] Sun Outage
On 10/10/14, 4:21 AM, Bob Camp wrote: Hi Bringing this back to GPS… The TV stuff is at about 8X the frequency of GPS. That makes a difference in terms of things like rain. That said, yes, there probably is some giant rainstorm that would impact GPS accuracy. Much more likely in a “I can only see a small patch of sky” situation. It's a huge difference.. The rain fading is typically represented by an equation like gamma = a * Rate^b (dB/km) (Rate is the rainfall rate in mm/hr) at 1 GHz, a = 0.387 and b=0.912 at 10 GHz, a=0.0101 and b = 1.276 at 30 GHz, a = 0.187 and b=1.021 The a term mostly has to do with the size of the raindrops vs the wavelength. Very few raindrops are close to 20cm in diameter (1500 MHz). the b term is mostly how many drops are in a given volume For lower frequencies (wavelength longer than drop size), it's mostly a Rayleigh scattering problem. For TV, the other factor that is important is that the rain depolarizes the signal, so you could lose half your signal power because of cross pol, and have an interfering signal become equal to the desired signal (because they use polarization diversity to double up channels) ___ 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] Sun Outage
Andy... On DirecTV and Dish, in order to get channels beyond the basic package, Dish and Direct both use additional satelites at different orbital locations. If you have only the basic package, you get one antenna and possibly only one feed horn. Dish for example can use a two antenna setup. The main antenna could have a dual feed horn that looks at two different satellites at 110 degrees W and 119 degrees W. Then the second antenna would have a single feed horn looking at either the satellite at 61.5 degrees W or 148 degrees W. The 110 and 119 satellites can be viewed from the east coast to Hawaii. The 61.5 satellite can be seen from the east coast to west Texas. The 148 satellite can be seen from west Texas to Hawaii. It would not be uncommon to have rain fade on one satellite and not on the others! Here is a list of some of the DishNetwork channels with their channel number and satellite assignment(s) http://www.alanthompson.com/dish-network-satellite-tv-channel-listings.asp Note that other than the ABC/CBS/NBC/Fox stations on channels 241-248, the local stations that you would normally watch, unless they are in SF or NYC, are not listed, but they are being carried on spot beams from one of the satellites. It is quite a shell game to fit all the feeds into the bandwidth available, and then instruct the receiver as to the frequency, polarization and satellite location for a particular channel. 73 Don W4WJ In a message dated 10/10/2014 1:34:34 A.M. Central Daylight Time, ai.egrps...@gmail.com writes: Bob Stewart b...@evoria.net wrote: ... Also, the cartoons I was recording for my granddaughter were unaffected, but the station I was watching had the outage. That doesn't all fit together unless it was the uplink that had the problem. I don't think the uplink itself can have this problem. But DirecTV uses multiple transponders per satellite, and in some cases more than one satellite, so all the channels are not affected equally. When I had DirecTV, we had two dishes. The installer boggled up the first install so they came back and put up another one several feet away, mounted on a more stable surface (not roof shingles). The first dish was one that could be used for multiple satellites. It had three 'focal' points with three little radomes that either had, or could have, LNAs in them. Each points to a different spot in the sky. The second dish had only one. Regardless, we received only one satellite. I don't recall ever being affected by a solar outage, but rain and ice were real killers! Yeah they say rain shouldn't cause an outage, but it does when the rain density is high enough. I could use that to predict when we were about to be hit by a downpour. There was about a 3 minute lag between losing all the channels, and the downpour starting. It occurred to me that one could use satellite signals as a meteorological instrument to measure the water density in the atmosphere above you. I wonder if the NWS does that. Andy ___ 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] Sun Outage
Jupiter emissions are MHz. Ku band is GHz. David On 10/10/14 5:17 AM, Graham wrote: Good morning Brooke, Sorry, don't know the answer to that question. Interesting question though. I am aware of the Radio Rove project and have played around at listening for Jupiter on HF and LO VHF but not in a very serious way. cheers, Graham ve3gtc On 2014-10-09 19:26, Brooke Clarke wrote: Hi Graham: Do you know if anyone has used a Ku-band receiver, like described in the paper, to look at Jupiter? The Radio Jove project is looking between 18 and 40 MHz. http://radiojove.gsfc.nasa.gov/ Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Graham wrote: If you have an interest in trying to measure sun noise, you might like to have a look at the itty bitty radio telescope. (watch the line wrap) http://www.arrl.org/files/file/ETP/Radio%20Astronomy/Build%20a%20Homebrew%20Radio%20Telescope-QST-0609.pdf http://www.gb.nrao.edu/epo/ambassadors/ibtmanualshort.pdf http://www.stargazing.net/david/radio/itty_bitty_radio_telescope.html as a start. A google search will return more. cheers, Graham ve3gtc On 2014-10-09 14:23, paul swed wrote: Exactly geosyncs have sun outages as the sun aligns with the sat and your dish. GPS because the sats are distributed do not suffer from the effect. Regards Paul WB8TSL On Thu, Oct 9, 2014 at 2:04 PM, Mike Feher mfe...@eozinc.com wrote: Bob - I do not believe it has any effect. The DirecTV satellites are geostationary at about 22K miles. I used to experience the same phenomenon in the late 70's with my TVRO receiver at C band. GPS has some 36 or so satellites in a Medium Earth Orbit (MEO). Blockage, if it can even occur due to the nature of the receiving antenna, of a single one for a few minutes will have no discernible effect in my opinion. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart Sent: Thursday, October 09, 2014 1:40 PM To: Time Nuts Subject: [time-nuts] Sun Outage Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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. ___ 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] Sun Outage
Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
Bob - I do not believe it has any effect. The DirecTV satellites are geostationary at about 22K miles. I used to experience the same phenomenon in the late 70's with my TVRO receiver at C band. GPS has some 36 or so satellites in a Medium Earth Orbit (MEO). Blockage, if it can even occur due to the nature of the receiving antenna, of a single one for a few minutes will have no discernible effect in my opinion. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart Sent: Thursday, October 09, 2014 1:40 PM To: Time Nuts Subject: [time-nuts] Sun Outage Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
If you had an exact timing for the outage, would that have told you the beam-width of your antenna? -- project for next spring :-) On 10/9/2014 1:04 PM, Mike Feher wrote: Bob - I do not believe it has any effect. The DirecTV satellites are geostationary at about 22K miles. I used to experience the same phenomenon in the late 70's with my TVRO receiver at C band. GPS has some 36 or so satellites in a Medium Earth Orbit (MEO). Blockage, if it can even occur due to the nature of the receiving antenna, of a single one for a few minutes will have no discernible effect in my opinion. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart Sent: Thursday, October 09, 2014 1:40 PM To: Time Nuts Subject: [time-nuts] Sun Outage Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
b...@evoria.net said: Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Is there any easy way to get a signal/noise reading out of the receiver? It would be interesting to see a daily/weekly plot as well as the zoomed in area around things like sun events. What's the beam width of the DirectTV antennas? Does it agree with the 3 or 4 minutes at the back-of-envelope level? -- These are my opinions. 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] Sun Outage
Henry, I have more information and you may have explained it. The outages occurred at about 3:10PM, and with an azimuth here of about 180 degrees (which I just looked up), that makes no sense. Also, the cartoons I was recording for my granddaughter were unaffected, but the station I was watching had the outage. That doesn't all fit together unless it was the uplink that had the problem. I guess I should have checked all that before posting. Bob From: Henry Hallam he...@pericynthion.org To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: Bob Stewart b...@evoria.net; hmur...@megapathdsl.net Sent: Thursday, October 9, 2014 2:27 PM Subject: Re: [time-nuts] Sun Outage On Thu, Oct 9, 2014 at 11:18 AM, Hal Murray hmur...@megapathdsl.net wrote: What's the beam width of the DirectTV antennas? Does it agree with the 3 or 4 minutes at the back-of-envelope level? DirecTV is a Ku/Ka-band system operating with a 460mm dish antenna. At Ka-band, the 3dB full-width of the beam is 2.4 degrees. The earth rotates at 0.25 degrees per minute, giving approx 10 minutes for the sun to cross the beam assuming it crosses directly through the center of the beam. However, a little googling[1] suggests that in fact the DirecTV satellite signal usually has enough margin to overcome the sun noise, but that the C-band feed[2] that DirecTV uses at their uplink station to receive programs from their providers may itself suffer from solar conjunctions. Henry [1] http://www.dbstalk.com/topic/202779-sun-interference-message/ [2] http://www.prss.org/solar-outage-rules ___ 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] Sun Outage
On Thu, Oct 9, 2014 at 11:18 AM, Hal Murray hmur...@megapathdsl.net wrote: What's the beam width of the DirectTV antennas? Does it agree with the 3 or 4 minutes at the back-of-envelope level? DirecTV is a Ku/Ka-band system operating with a 460mm dish antenna. At Ka-band, the 3dB full-width of the beam is 2.4 degrees. The earth rotates at 0.25 degrees per minute, giving approx 10 minutes for the sun to cross the beam assuming it crosses directly through the center of the beam. However, a little googling[1] suggests that in fact the DirecTV satellite signal usually has enough margin to overcome the sun noise, but that the C-band feed[2] that DirecTV uses at their uplink station to receive programs from their providers may itself suffer from solar conjunctions. Henry [1] http://www.dbstalk.com/topic/202779-sun-interference-message/ [2] http://www.prss.org/solar-outage-rules ___ 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] Sun Outage
Standard GPS receiving antennas have a large beam width in order to cover most of the sky. Even in the Oregon Rainforest the sun is in view most of the day. Some satellite transponders have more power and are less prone to interference as they pass in front of the sun. Typical home TVROs have a number of feedhorns to receive more than one satellite. Different satellites will be affected at different times. On 10/09/2014 10:40 AM, Bob Stewart wrote: Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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 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] Sun Outage
Exactly geosyncs have sun outages as the sun aligns with the sat and your dish. GPS because the sats are distributed do not suffer from the effect. Regards Paul WB8TSL On Thu, Oct 9, 2014 at 2:04 PM, Mike Feher mfe...@eozinc.com wrote: Bob - I do not believe it has any effect. The DirecTV satellites are geostationary at about 22K miles. I used to experience the same phenomenon in the late 70's with my TVRO receiver at C band. GPS has some 36 or so satellites in a Medium Earth Orbit (MEO). Blockage, if it can even occur due to the nature of the receiving antenna, of a single one for a few minutes will have no discernible effect in my opinion. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart Sent: Thursday, October 09, 2014 1:40 PM To: Time Nuts Subject: [time-nuts] Sun Outage Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
The sun can have some effects on GPS signals, particularly when doing ultra-precisiony sorts of things. Version 4 of Lady Heather calculates the sun (and moon) positions (and moon phase) and can display them as part of the satellite position map (and analog watch display). This feature was added at the request of a few people that are/were investigating the effects of the sun on GPS signals. ___ 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] Sun Outage
Where is this Version 4 available? On 10/09/2014 01:28 PM, Mark Sims wrote: The sun can have some effects on GPS signals, particularly when doing ultra-precisiony sorts of things. Version 4 of Lady Heather calculates the sun (and moon) positions (and moon phase) and can display them as part of the satellite position map (and analog watch display). This feature was added at the request of a few people that are/were investigating the effects of the sun on GPS signals. ___ 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 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] Sun Outage
You pick up satellite TV with a parabolic dish that points at one spot in the sky where the geostationary satellite lives. A sun outage happens when the sun wanders into the focus and overloads the receiver with noise that drowns out the satellite signal (at least, it raises the noise floor enough that you can't receive the high bitrates needed for a TV picture). You pick up GPS with a whole-sky antenna that receives signals from the constantly-moving swarm of GPS satellites. It undoubtedly receives some noise from the sun, but the only factor in how much of that you get is the sun's elevation above the horizon. It's not really relevant whether the sun is aligned with a satellite or not. Even if it was, the satellite would be somewhere else a minute later. :) Andrew On Thu, Oct 9, 2014 at 1:40 PM, Bob Stewart b...@evoria.net wrote: Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
On 9 Oct 2014 22:17, Andrew Rodland and...@cleverdomain.org wrote: You pick up satellite TV with a parabolic dish that points at one spot in the sky where the geostationary satellite lives. A sun outage happens when the sun wanders into the focus and overloads the receiver with noise that drowns out the satellite signal (at least, it raises the noise floor enough that you can't receive the high bitrates needed for a TV picture). You pick up GPS with a whole-sky antenna that receives signals from the constantly-moving swarm of GPS satellites. It undoubtedly receives some noise from the sun, but the only factor in how much of that you get is the sun's elevation above the horizon. It's not really relevant whether the sun is aligned with a satellite or not. Even if it was, the satellite would be somewhere else a minute later. :) Andrew Also the much higher gain of the satellite antenna means if the Sun is in its beamwidth, a much larger increase in noise will occur. I would actually be concerned about the Sun heating (melting ??) the receiver, like I expect we have all done with a magnifying glass. The capture area of a dish is a lot more than any normal magnifying glass. 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] Sun Outage
If you have an interest in trying to measure sun noise, you might like to have a look at the itty bitty radio telescope. (watch the line wrap) http://www.arrl.org/files/file/ETP/Radio%20Astronomy/Build%20a%20Homebrew%20Radio%20Telescope-QST-0609.pdf http://www.gb.nrao.edu/epo/ambassadors/ibtmanualshort.pdf http://www.stargazing.net/david/radio/itty_bitty_radio_telescope.html as a start. A google search will return more. cheers, Graham ve3gtc On 2014-10-09 14:23, paul swed wrote: Exactly geosyncs have sun outages as the sun aligns with the sat and your dish. GPS because the sats are distributed do not suffer from the effect. Regards Paul WB8TSL On Thu, Oct 9, 2014 at 2:04 PM, Mike Feher mfe...@eozinc.com wrote: Bob - I do not believe it has any effect. The DirecTV satellites are geostationary at about 22K miles. I used to experience the same phenomenon in the late 70's with my TVRO receiver at C band. GPS has some 36 or so satellites in a Medium Earth Orbit (MEO). Blockage, if it can even occur due to the nature of the receiving antenna, of a single one for a few minutes will have no discernible effect in my opinion. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart Sent: Thursday, October 09, 2014 1:40 PM To: Time Nuts Subject: [time-nuts] Sun Outage Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
Hi Bob: The geostationary sats are in a 24 hour orbit. The orbit is also in the plane of the Earth's equator. Because of these two facts they appear stationary. Also because of that twice a year near equinox the Sun will be directly behind the sat and the C/N goes to pot so no signal. I have a mirror with masking tape reducing it's size to about 5/8 on a window sill that gets light at equinox and all through winter. I've marked the ceiling so I can just look up to see if the Sun is anywhere near the satellite. http://www.prc68.com/I/Sundial.shtml#SSB I can also tell when it's noon local time from this ceiling sundial. The orbit time for GPS sats is 12.0 sidereal hours and the plane of their orbits is angled 55 degrees from the equator so the Sun at most can be behind only one sat and then not for long, so you will not see any solar blockage, unless you are in a single satellite time only mode of operation and even they it would be a science experiment to detect the effect of the Sun. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Stewart wrote: Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
Hi Dave: The small size of the Ku-band TV dish and that it's surface is covered with a flat type paint means there's little or no thermal heating of the receiver or feed. There were cases with the early C-band TVRO systems where they did melt the receiver. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Dr. David Kirkby (Kirkby Microwave Ltd) wrote: On 9 Oct 2014 22:17, Andrew Rodland and...@cleverdomain.org wrote: You pick up satellite TV with a parabolic dish that points at one spot in the sky where the geostationary satellite lives. A sun outage happens when the sun wanders into the focus and overloads the receiver with noise that drowns out the satellite signal (at least, it raises the noise floor enough that you can't receive the high bitrates needed for a TV picture). You pick up GPS with a whole-sky antenna that receives signals from the constantly-moving swarm of GPS satellites. It undoubtedly receives some noise from the sun, but the only factor in how much of that you get is the sun's elevation above the horizon. It's not really relevant whether the sun is aligned with a satellite or not. Even if it was, the satellite would be somewhere else a minute later. :) Andrew Also the much higher gain of the satellite antenna means if the Sun is in its beamwidth, a much larger increase in noise will occur. I would actually be concerned about the Sun heating (melting ??) the receiver, like I expect we have all done with a magnifying glass. The capture area of a dish is a lot more than any normal magnifying glass. 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. ___ 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] Sun Outage
On 9 Oct 2014 23:28, Brooke Clarke bro...@pacific.net wrote: Hi Dave: The small size of the Ku-band TV dish and that it's surface is covered with a flat type paint means there's little or no thermal heating of the receiver or feed. There were cases with the early C-band TVRO systems where they did melt the receiver. Reminds me of some idiot who designed a building in London. It had curved mirrors on it, angled towards the road. The result was the road, vehicles and shops were being burnt by the sun. It was all in the news here a year or two ago. ___ 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] Sun Outage
Hi Graham: Do you know if anyone has used a Ku-band receiver, like described in the paper, to look at Jupiter? The Radio Jove project is looking between 18 and 40 MHz. http://radiojove.gsfc.nasa.gov/ Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Graham wrote: If you have an interest in trying to measure sun noise, you might like to have a look at the itty bitty radio telescope. (watch the line wrap) http://www.arrl.org/files/file/ETP/Radio%20Astronomy/Build%20a%20Homebrew%20Radio%20Telescope-QST-0609.pdf http://www.gb.nrao.edu/epo/ambassadors/ibtmanualshort.pdf http://www.stargazing.net/david/radio/itty_bitty_radio_telescope.html as a start. A google search will return more. cheers, Graham ve3gtc On 2014-10-09 14:23, paul swed wrote: Exactly geosyncs have sun outages as the sun aligns with the sat and your dish. GPS because the sats are distributed do not suffer from the effect. Regards Paul WB8TSL On Thu, Oct 9, 2014 at 2:04 PM, Mike Feher mfe...@eozinc.com wrote: Bob - I do not believe it has any effect. The DirecTV satellites are geostationary at about 22K miles. I used to experience the same phenomenon in the late 70's with my TVRO receiver at C band. GPS has some 36 or so satellites in a Medium Earth Orbit (MEO). Blockage, if it can even occur due to the nature of the receiving antenna, of a single one for a few minutes will have no discernible effect in my opinion. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart Sent: Thursday, October 09, 2014 1:40 PM To: Time Nuts Subject: [time-nuts] Sun Outage Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
Hello all... Not all satellite TV antennas are parabolic. A typical C-Band antenna is parabolic and aligned for one satellite. But, that could change if the feed was modified to receive multi-satellites, while the shape of the reflector remained parabolic. Or the antenna could be an off-center fed elliptical version. Satellite antennas for Dish and DirecTV are not parabolic, but they are off-center fed and either circular or elliptical. The elliptical version usually supports a feed that will cover multiple satellites. C-Band satellites in the U.S. Domestic arc are normally spaced two degrees apart, with some at 4 degrees spacing. DBS (Direct Broadcast Service) i.e. Dish and DirecTV, satellites are spaced 9 degrees apart. Clusters of satellites can be parked at one location to supply additional capacity for spot beam coverage. DBS service is located in the Ku-Band. More info at: https://docs.google.com/presentation/d/1eNMYmcNIxRFpK1PY0GqbvOfvNfzRra4fHxs8 A4hSy7o/preview#slide=id.p18 73 Don W4WJ In a message dated 10/9/2014 4:17:20 P.M. Central Daylight Time, and...@cleverdomain.org writes: You pick up satellite TV with a parabolic dish that points at one spot in the sky where the geostationary satellite lives. A sun outage happens when the sun wanders into the focus and overloads the receiver with noise that drowns out the satellite signal (at least, it raises the noise floor enough that you can't receive the high bitrates needed for a TV picture). You pick up GPS with a whole-sky antenna that receives signals from the constantly-moving swarm of GPS satellites. It undoubtedly receives some noise from the sun, but the only factor in how much of that you get is the sun's elevation above the horizon. It's not really relevant whether the sun is aligned with a satellite or not. Even if it was, the satellite would be somewhere else a minute later. :) Andrew On Thu, Oct 9, 2014 at 1:40 PM, Bob Stewart b...@evoria.net wrote: Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
Hi Don: It's my understanding that all satellite dishes have a parabolic curve which focuses the signal on the feed. The C-band dish has a round outline and the feed is located along the dish center line. Most commercial Ku-band antennas have a parabolic curve, but have a elliptical or orange peal outline. These are off center fed so that the feed does not shadow the antenna like it did on the C-band dishes. This is the same problem that the vast majority of reflecting astronomical telescopes have, i.e. the secondary mirror area needs to be subtracted from the primary mirror area to get the effective primary mirror area. A very practical result of that difference is that a C-band dish has it's main beam along the dish center line, but a Ku-band dish does not. http://www.prc68.com/I/Images/SB_angw.jpg - showing the beam realtive to the dish and beam hitting gutter. Better when dish mounted on roof: http://www.prc68.com/I/SBvsat.shtml But the construction of the older dish was better than the newer/cheaper dish. The Free To Air (FTA) Ku-band dishes also have a parabolic curve round outline, but they are offset fed, see: http://www.prc68.com/I/FTA.shtml Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Don Murray via time-nuts wrote: Hello all... Not all satellite TV antennas are parabolic. A typical C-Band antenna is parabolic and aligned for one satellite. But, that could change if the feed was modified to receive multi-satellites, while the shape of the reflector remained parabolic. Or the antenna could be an off-center fed elliptical version. Satellite antennas for Dish and DirecTV are not parabolic, but they are off-center fed and either circular or elliptical. The elliptical version usually supports a feed that will cover multiple satellites. C-Band satellites in the U.S. Domestic arc are normally spaced two degrees apart, with some at 4 degrees spacing. DBS (Direct Broadcast Service) i.e. Dish and DirecTV, satellites are spaced 9 degrees apart. Clusters of satellites can be parked at one location to supply additional capacity for spot beam coverage. DBS service is located in the Ku-Band. More info at: https://docs.google.com/presentation/d/1eNMYmcNIxRFpK1PY0GqbvOfvNfzRra4fHxs8 A4hSy7o/preview#slide=id.p18 73 Don W4WJ In a message dated 10/9/2014 4:17:20 P.M. Central Daylight Time, and...@cleverdomain.org writes: You pick up satellite TV with a parabolic dish that points at one spot in the sky where the geostationary satellite lives. A sun outage happens when the sun wanders into the focus and overloads the receiver with noise that drowns out the satellite signal (at least, it raises the noise floor enough that you can't receive the high bitrates needed for a TV picture). You pick up GPS with a whole-sky antenna that receives signals from the constantly-moving swarm of GPS satellites. It undoubtedly receives some noise from the sun, but the only factor in how much of that you get is the sun's elevation above the horizon. It's not really relevant whether the sun is aligned with a satellite or not. Even if it was, the satellite would be somewhere else a minute later. :) Andrew On Thu, Oct 9, 2014 at 1:40 PM, Bob Stewart b...@evoria.net wrote: Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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] Sun Outage
Hi Brooke... You are correct. My semantics were confusing! The offset feed certainly has an advantage because of no shadowing, but a lot of commercial Ku-Band antennas are complete parabolic reflectors with a sub-reflector and cassegrain feed. There obviously is some loss because of the sub reflector, but these are larger antennas and the loss is acceptable. TNX for you feedback Brooke! 73 Don W4WJ In a message dated 10/9/2014 7:26:55 P.M. Central Daylight Time, bro...@pacific.net writes: Hi Don: It's my understanding that all satellite dishes have a parabolic curve which focuses the signal on the feed. The C-band dish has a round outline and the feed is located along the dish center line. Most commercial Ku-band antennas have a parabolic curve, but have a elliptical or orange peal outline. These are off center fed so that the feed does not shadow the antenna like it did on the C-band dishes. This is the same problem that the vast majority of reflecting astronomical telescopes have, i.e. the secondary mirror area needs to be subtracted from the primary mirror area to get the effective primary mirror area. A very practical result of that difference is that a C-band dish has it's main beam along the dish center line, but a Ku-band dish does not. http://www.prc68.com/I/Images/SB_angw.jpg - showing the beam realtive to the dish and beam hitting gutter. Better when dish mounted on roof: http://www.prc68.com/I/SBvsat.shtml But the construction of the older dish was better than the newer/cheaper dish. The Free To Air (FTA) Ku-band dishes also have a parabolic curve round outline, but they are offset fed, see: http://www.prc68.com/I/FTA.shtml Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Don Murray via time-nuts wrote: Hello all... Not all satellite TV antennas are parabolic. A typical C-Band antenna is parabolic and aligned for one satellite. But, that could change if the feed was modified to receive multi-satellites, while the shape of the reflector remained parabolic. Or the antenna could be an off-center fed elliptical version. Satellite antennas for Dish and DirecTV are not parabolic, but they are off-center fed and either circular or elliptical. The elliptical version usually supports a feed that will cover multiple satellites. C-Band satellites in the U.S. Domestic arc are normally spaced two degrees apart, with some at 4 degrees spacing. DBS (Direct Broadcast Service) i.e. Dish and DirecTV, satellites are spaced 9 degrees apart. Clusters of satellites can be parked at one location to supply additional capacity for spot beam coverage. DBS service is located in the Ku-Band. More info at: https://docs.google.com/presentation/d/1eNMYmcNIxRFpK1PY0GqbvOfvNfzRra4fHxs8 A4hSy7o/preview#slide=id.p18 73 Don W4WJ In a message dated 10/9/2014 4:17:20 P.M. Central Daylight Time, and...@cleverdomain.org writes: You pick up satellite TV with a parabolic dish that points at one spot in the sky where the geostationary satellite lives. A sun outage happens when the sun wanders into the focus and overloads the receiver with noise that drowns out the satellite signal (at least, it raises the noise floor enough that you can't receive the high bitrates needed for a TV picture). You pick up GPS with a whole-sky antenna that receives signals from the constantly-moving swarm of GPS satellites. It undoubtedly receives some noise from the sun, but the only factor in how much of that you get is the sun's elevation above the horizon. It's not really relevant whether the sun is aligned with a satellite or not. Even if it was, the satellite would be somewhere else a minute later. :) Andrew On Thu, Oct 9, 2014 at 1:40 PM, Bob Stewart b...@evoria.net wrote: Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish. So I was wondering what kind of effect this has on the GPS system and especially timing receivers. Bob - AE6RV ___ 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 --
Re: [time-nuts] Sun Outage
On Thu, 09 Oct 2014 18:14:55 -0400 Graham planoph...@aei.ca wrote: If you have an interest in trying to measure sun noise, you might like to have a look at the itty bitty radio telescope. (watch the line wrap) http://www.arrl.org/files/file/ETP/Radio%20Astronomy/Build%20a%20Homebrew%20Radio%20Telescope-QST-0609.pdf http://www.gb.nrao.edu/epo/ambassadors/ibtmanualshort.pdf http://www.stargazing.net/david/radio/itty_bitty_radio_telescope.html as a start. A google search will return more. cheers, Graham ve3gtc As an alternative, you might consider the Drake commercial satellite receivers. I've bought a few of these off of Ebay for about $20 each. These show up at recyclers. Every one I got worked. They have just been sitting in rack until I suppose the service wasn't needed. These commercial receivers have analog meters that you could tap. I've bough the ESR 1255. I have manuals for the 1245, 1252, 1255, 1260, and 1450 if you can't find them online. But probably the 1252 or 1255 is what would work best in this application. ___ 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.
