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 ----------------------

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-bounces@febo.com [mailto:time-nuts-bounces@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.

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" <mpb45@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.

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.melia@btinternet.com>wrote: > 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" <mpb45@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. >

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 Melia<alan.melia@btinternet.com>wrote: > >> 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"<mpb45@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.

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 >> Melia<alan.melia@btinternet.com>wrote: >> >>> 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"<mpb45@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.

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" <n1hac@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 >>> Melia<alan.melia@btinternet.com>wrote: >>> >>>> 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"<mpb45@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. >

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 >>> Melia<alan.melia@btinternet.com>wrote: >>> >>>> 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"<mpb45@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.

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 <n1hac@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 Melia<alan.melia@btinternet.com>wrote: >>> >>>> 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"<mpb45@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.

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 >>>> Melia<alan.melia@btinternet.com>wrote: >>>> >>>>> 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"<mpb45@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. >