[time-nuts] Re-radiating a GPS signal...??
Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
Hi The re-radiators are active devices. They are every bit as much a lightning attractor as the GPS it's self. They also cost more than a TBolt (even at current prices). Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Michael Baker Sent: Thursday, April 12, 2012 9:06 AM To: time-nuts@febo.com Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Baker mp...@clanbaker.org To: time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Melia alan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Baker mp...@clanbaker.org To: time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
David's comment on the direct and retransmitted signals is right on point. You are creating a multipath environment with increased signal strength and matching polarization. Even with no amplification between the antennas, you are generating multipath signals for you and your neighbors. Advocating signal repeaters is very dangerous. With out proper bandpass filtering and path isolation you are inviting trouble from feedback oscillation, both in-band and out of band. You may not even be aware of out of band effects. If not done properly, including taking in account seasonal variation of vegetation, possible effects of someone moving lawn furniture around or even vehicular motion changing the feedback path, the results could be disastrous. You could be the owner of an intermittent jammer, interfere with GPS and/or other signals, and possibly receive a visit from the authorities. Look at the problems that where caused by oscillating TV peamplifiers radiating from a marina on the west coast. Retransmitting with a different output frequency is a different issue and may be a better approach. John WA4WDL -- From: David McGaw n1...@alum.dartmouth.org Sent: Thursday, April 12, 2012 11:11 AM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Re-radiating a GPS signal...?? The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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
Re: [time-nuts] Re-radiating a GPS signal...??
Not quite, the delay of the antenna cable is affecting less the horizontal position (it depends also on the current received constellation geometry), but mostly the height ASL of the fix point, prolonging simultaneously all the paths from the satellites with a fixed value. Also, the propagation speed in a cable is significantly lower than in free space - the perceived delay increase is ~1.5 times for usual cables (~.67 velocity factor), and the computed fix point would have a lower height ASL than the real one. Those relaying systems are merely good for an approximate location fix, mostly for not loosing the GPS signal in covered areas so that the reacquire of the real signal is faster, with almost no perceived discontinuity. On 4/12/2012 6:11 PM, David McGaw wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
David, That is correct, the signal is delayed by at least the run length as well. We had to tweak the ublox parameters on our GPSDOs for a particular data center application that used a re-radiator to make it work as the default ublox parameters would get the unit confused due to residual multipath etc. This is the type of obscure real-world firmware fine-tuning that separates the boys from the men... One may never need it, but it's good to know its there. Bye, Said On Apr 12, 2012, at 8:11, David McGaw n1...@alum.dartmouth.org wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
Not at all! The (first) receiving antenna defines the position you get out of a long antenna cable or a reradiating system. The delays in LNA, filters, cables, rerad antenna, free air between rerad antenna and final receiving antenna ALL goed into the receiver clock error. This is clear both from a theoretical point, from most standard GPS texts and from practical experience from multiple installations I have used over the years. If you disagree, please provide evidence. -- Björn Not quite, the delay of the antenna cable is affecting less the horizontal position (it depends also on the current received constellation geometry), but mostly the height ASL of the fix point, prolonging simultaneously all the paths from the satellites with a fixed value. Also, the propagation speed in a cable is significantly lower than in free space - the perceived delay increase is ~1.5 times for usual cables (~.67 velocity factor), and the computed fix point would have a lower height ASL than the real one. Those relaying systems are merely good for an approximate location fix, mostly for not loosing the GPS signal in covered areas so that the reacquire of the real signal is faster, with almost no perceived discontinuity. On 4/12/2012 6:11 PM, David McGaw wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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
Re: [time-nuts] Re-radiating a GPS signal...??
Delay of the complete ensemble of signals results in a time shift much like the addition of cable between the antenna and receiver. The position solution will be the location of the first receiving antenna. John WA4WDL -- From: MailLists li...@medesign.ro Sent: Thursday, April 12, 2012 10:17 AM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Re-radiating a GPS signal...?? GPS being extremely time-dependent, any delay introduced will affect positioning precision. ___ time-nuts mailing 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] Re-radiating a GPS signal...??
You must read: http://transition.fcc.gov/eb/Orders/2005/DA-05-2998A1.html Which discusses a FCC complaint with Navtech for selling GPS repeaters. An exert is presented below: ``Please note: re-radiation kits are currently only available for purchase to International Customers and in cases where the U.S. Government is the end user.'' Pursuant to Section 15.201(b) of the Rules, 47 C.F.R. § 15.201(b), intentional radiators must be authorized in accordance with the FCC's certification procedures prior to the initiation of marketing in the United States. However, GPS re-radiators operate within the restricted frequency bands listed in Section 15.205(a) of the Rules, 47 C.F.R. § 15.205(a).4 Thus, GPS re- radiators cannot comply with the FCC's technical standards and therefore cannot be certificated or marketed for use by the general public or non-federal government entities. Accordingly, it appears that Navtech has violated Section 302(b) of the Act and Sections 2.803 and 15.205(a) of the Rules by marketing in the United States radio frequency devices that are not eligible to receive a grant of certification. You should be aware that the Commission has recently addressed a Petition for Rulemaking and a Request for Waiver seeking amendment of FCC regulations to permit the marketing of GPS re-radiation kits.5 By Order released July 6, 2005, the FCC's Office of Engineering and Technology (OET) denied the Petition for Rulemaking and Request for Waiver.6 OET noted that the Petition raised significant issues that needed further study and therefore did not warrant consideration at the time. Accordingly, Navtech is reminded that at this time GPS re- radiating devices are not permitted to be sold to the general public or to state or local governments. John WA4WDL ___ time-nuts mailing 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] Re-radiating a GPS signal...??
Purely geometrically, the fix solution is computed as the intersection point of spheres with the radii determined by the propagation time, and the centers by the positions of the satellites (practically not all spheres intersect in the same geometrical point, so an average is computed). If the GPS Rx would receive simultaneously all satellites, considered evenly distributed on a sphere, then the added path delays would mostly cancel out - but if only the visible satellites are accounted for, we will have an unbalanced system, approximated to an hemispehere, in which the horizontal error will be low, as the longer paths cancel mostly out, but for the vertical one it's not the case. Any GPS receiver will exhibit lower vertical precision than the horizontal one. The same phenomenon, of low precision, and biasing of position is evident if just a part of the constellation is used (an obstacle obscures a large part of the sky). The internal delays of the Rx are mostly fixed and known, so they can be accounted for, and compensated in the firmware fix solution, but the cable length is a variable (depending on the installation) factor, not accounted for. On 4/12/2012 7:15 PM, b...@lysator.liu.se wrote: Not at all! The (first) receiving antenna defines the position you get out of a long antenna cable or a reradiating system. The delays in LNA, filters, cables, rerad antenna, free air between rerad antenna and final receiving antenna ALL goed into the receiver clock error. This is clear both from a theoretical point, from most standard GPS texts and from practical experience from multiple installations I have used over the years. If you disagree, please provide evidence. -- Björn Not quite, the delay of the antenna cable is affecting less the horizontal position (it depends also on the current received constellation geometry), but mostly the height ASL of the fix point, prolonging simultaneously all the paths from the satellites with a fixed value. Also, the propagation speed in a cable is significantly lower than in free space - the perceived delay increase is ~1.5 times for usual cables (~.67 velocity factor), and the computed fix point would have a lower height ASL than the real one. Those relaying systems are merely good for an approximate location fix, mostly for not loosing the GPS signal in covered areas so that the reacquire of the real signal is faster, with almost no perceived discontinuity. On 4/12/2012 6:11 PM, David McGaw wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes
Re: [time-nuts] Re-radiating a GPS signal...??
Since I am used to figuring the cable (and additional propagation) delays, I did forget to mention that for timing. :-) On the other hand, I would not be using a repeater except for just functional testing of a payload system. David On 4/12/12 12:15 PM, b...@lysator.liu.se wrote: Not at all! The (first) receiving antenna defines the position you get out of a long antenna cable or a reradiating system. The delays in LNA, filters, cables, rerad antenna, free air between rerad antenna and final receiving antenna ALL goed into the receiver clock error. This is clear both from a theoretical point, from most standard GPS texts and from practical experience from multiple installations I have used over the years. If you disagree, please provide evidence. -- Björn Not quite, the delay of the antenna cable is affecting less the horizontal position (it depends also on the current received constellation geometry), but mostly the height ASL of the fix point, prolonging simultaneously all the paths from the satellites with a fixed value. Also, the propagation speed in a cable is significantly lower than in free space - the perceived delay increase is ~1.5 times for usual cables (~.67 velocity factor), and the computed fix point would have a lower height ASL than the real one. Those relaying systems are merely good for an approximate location fix, mostly for not loosing the GPS signal in covered areas so that the reacquire of the real signal is faster, with almost no perceived discontinuity. On 4/12/2012 6:11 PM, David McGaw wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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
Re: [time-nuts] Re-radiating a GPS signal...??
Timing GPS receivers have the cable delay parameter to account for the cable delay. added path delays would mostly cancel out How can delays cancel out? On Thu, Apr 12, 2012 at 7:33 PM, MailLists li...@medesign.ro wrote: Purely geometrically, the fix solution is computed as the intersection point of spheres with the radii determined by the propagation time, and the centers by the positions of the satellites (practically not all spheres intersect in the same geometrical point, so an average is computed). If the GPS Rx would receive simultaneously all satellites, considered evenly distributed on a sphere, then the added path delays would mostly cancel out - but if only the visible satellites are accounted for, we will have an unbalanced system, approximated to an hemispehere, in which the horizontal error will be low, as the longer paths cancel mostly out, but for the vertical one it's not the case. Any GPS receiver will exhibit lower vertical precision than the horizontal one. The same phenomenon, of low precision, and biasing of position is evident if just a part of the constellation is used (an obstacle obscures a large part of the sky). The internal delays of the Rx are mostly fixed and known, so they can be accounted for, and compensated in the firmware fix solution, but the cable length is a variable (depending on the installation) factor, not accounted for. On 4/12/2012 7:15 PM, b...@lysator.liu.se wrote: Not at all! The (first) receiving antenna defines the position you get out of a long antenna cable or a reradiating system. The delays in LNA, filters, cables, rerad antenna, free air between rerad antenna and final receiving antenna ALL goed into the receiver clock error. This is clear both from a theoretical point, from most standard GPS texts and from practical experience from multiple installations I have used over the years. If you disagree, please provide evidence. -- Björn Not quite, the delay of the antenna cable is affecting less the horizontal position (it depends also on the current received constellation geometry), but mostly the height ASL of the fix point, prolonging simultaneously all the paths from the satellites with a fixed value. Also, the propagation speed in a cable is significantly lower than in free space - the perceived delay increase is ~1.5 times for usual cables (~.67 velocity factor), and the computed fix point would have a lower height ASL than the real one. Those relaying systems are merely good for an approximate location fix, mostly for not loosing the GPS signal in covered areas so that the reacquire of the real signal is faster, with almost no perceived discontinuity. On 4/12/2012 6:11 PM, David McGaw wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might
Re: [time-nuts] Re-radiating a GPS signal...??
Yes, but the propagation times are the times from each satellite antenna phase center to the phase center of the receiving antenna. From that point forward, the relative time delays are unchanged. It is the same as if one was to record the RF signals at the back of the receiving antenna and then play the recording into a receiver a week later. The navigation solution would give the location of the receiving antenna when the recording was made and the displayed time would also correspond to when the signals were recorded and be off from the current time by a week. John WA4WDL -- From: MailLists li...@medesign.ro Sent: Thursday, April 12, 2012 1:33 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Re-radiating a GPS signal...?? Purely geometrically, the fix solution is computed as the intersection point of spheres with the radii determined by the propagation time, ___ time-nuts mailing 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] Re-radiating a GPS signal...??
li...@medesign.ro said: GPS being extremely time-dependent, any delay introduced will affect positioning precision. I think you will just get the position of the receiving antenna for the repeater. It will get the time when the signals arrived at that antenna. Consider what happens if you replace the air between the repeater's transmit antenna and the GPS receiver with a chunk of coax. The key idea is that the signals from each satellite are delayed the same amount with either a repeater or coax. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-radiating a GPS signal...??
It seems to me that the rebroadcast signal will need to be really low to avoid interference with the original signal, at that level multipath could be a big problem. From my experience fiber is the method of choice commercially for both lightning protection and long cable runs. But those systems are really expensive unless you are protecting some serious equipment. Thomas Knox To: time-nuts@febo.com From: hmur...@megapathdsl.net Date: Thu, 12 Apr 2012 12:44:19 -0700 Subject: Re: [time-nuts] Re-radiating a GPS signal...?? li...@medesign.ro said: GPS being extremely time-dependent, any delay introduced will affect positioning precision. I think you will just get the position of the receiving antenna for the repeater. It will get the time when the signals arrived at that antenna. Consider what happens if you replace the air between the repeater's transmit antenna and the GPS receiver with a chunk of coax. The key idea is that the signals from each satellite are delayed the same amount with either a repeater or coax. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-radiating a GPS signal...??
hmur...@megapathdsl.net said: I think you will just get the position of the receiving antenna for the repeater. It will get the time when the signals arrived at that antenna. Consider what happens if you replace the air between the repeater's transmit antenna and the GPS receiver with a chunk of coax. The key idea is that the signals from each satellite are delayed the same amount with either a repeater or coax. Argh. I hate it when I'm thinking one thing and type the opposite. The GPS-repeater receiver will see the time at the receiving antenna for the repeater as delayed by the propagation from repeater to GPS receiver. You get the right answer if you think of that air path as coax. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-radiating a GPS signal...??
-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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 mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
