Due to access problems, I run my Thunderbolt with a Symmetricom 58532A antenna placed indoor near a window facing South… can’t get much worse but most of the time it will be locked onto 3 or 4 satellites. I recently bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my SDR ham radio setup. I was very surprised to find that this minimalist GPSDO using a small patch antenna with internal LNA placed near my window had satellite & PPL lock within a few seconds. It requires 3-4 satellite locks for its PPL. However, when I attached the patch antenna to my Thunderbolt – satellite signal strength were zero or minus for all satellites. The specs for the patch antenna are listed below. I would appreciate any advice understanding this behavior. Jerry NY2KW Center Frequency 1575.42MHz±3 MHz V.S.W.R 1.5:1 Band Width ±5 MHz Impendence 50 ohm Peak Gain >3dBic Based on 7×7cm ground plane Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) Polarization RHCP LNA/Filter LNA Gain (Without cable) 28+/-3dB Noise Figure 1.5dB Typ. Filter Out Band Attenuation (f° =1575.42MHz) 7dB Min f0+/-20MHZ 20dB Min f0+/-50MHZ 30dB Min f0+/-100MHZ V.S.W.R <2.0 DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other DC Current 5mA /11mA/15mA Max

Hello Jerry, I think the problem is not at the antenna, I consider the 58532A to be a lot better than these smal patch antennas. But the point is that modern receivers have a significant better sensivity! In my opinion, indoor position of any kind of antenna is not a good solution if you want to get low jitter results. Indoor antennas do get mostly indirect reception via reflections oft the SAT-signals, so even the position indicated is not really precise. When possible, any antenna should be positioned to get a free view to the sky 360 deg and at least about 20 deg in elevation. My antenna is mounted on the top of the roof outside at the highest point with abt. 10m coax cable down to my good old thunderbolt providing best reception possible. I wish you good luck for your further investigations, 73 Arnold, DK2WT Am 31.07.2017 um 19:19 schrieb Jerry: > Due to access problems, I run my Thunderbolt with a Symmetricom 58532A > antenna placed indoor near a window facing South… can’t get much worse but > most of the time it will be locked onto 3 or 4 satellites. I recently > bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my SDR ham > radio setup. I was very surprised to find that this minimalist GPSDO using > a small patch antenna with internal LNA placed near my window had satellite > & PPL lock within a few seconds. It requires 3-4 satellite locks for its > PPL. However, when I attached the patch antenna to my Thunderbolt – > satellite signal strength were zero or minus for all satellites. The specs > for the patch antenna are listed below. > > > > I would appreciate any advice understanding this behavior. > > > > Jerry NY2KW > > > > Center Frequency 1575.42MHz±3 MHz > > V.S.W.R 1.5:1 > > Band Width ±5 MHz > > Impendence 50 ohm > > Peak Gain >3dBic Based on 7×7cm ground plane > > Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) > > Polarization RHCP > > LNA/Filter > > LNA Gain (Without cable) 28+/-3dB > > Noise Figure 1.5dB Typ. > > Filter Out Band Attenuation (f° =1575.42MHz) > > 7dB Min f0+/-20MHZ > > 20dB Min f0+/-50MHZ > > 30dB Min f0+/-100MHZ > > V.S.W.R <2.0 > > DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other > > DC Current 5mA /11mA/15mA Max > > > > > > > > _______________________________________________ > time-nuts mailing 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 Thunderbolt is well known for not having the best sensitivity among GPS receivers. It seems that timing receivers in general, particularly those of the same generation as the Thunderbolt are not as sensitive as navigation (possibly newer) GPS receivers. It may be because they are expected to run with amplified antennas? Based on the spec you wrote, it looks like your antenna has no gain, so definitely I would expect less than good performance. My 3 Thunderbolts have been running with inside antennas (2 pucks and one Trimble Bullet) but my ham shack is upstairs and other than the ceiling and the shingle roof, there are no other obstructions and they are doing OK not great (all 3 go on holdover somewhat regularly). I am now running one downstairs (while I work on the new software for the TB Monitor) with 50 feet of RG-58 going to a HP 58532A antenna somewhat in the clear but only 8 feet above ground with significant obstructions in pretty much all directions due to the low height and the Thunderbolt is happy as a clam in spite of the significant losses in the cable. The HP antenna works much better than the Trimble Bullet antenna. On Mon, Jul 31, 2017 at 12:19 PM, Jerry <jsternmd@att.net> wrote: > Due to access problems, I run my Thunderbolt with a Symmetricom 58532A > antenna placed indoor near a window facing South… can’t get much worse but > most of the time it will be locked onto 3 or 4 satellites. I recently > bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my SDR > ham > radio setup. I was very surprised to find that this minimalist GPSDO using > a small patch antenna with internal LNA placed near my window had satellite > & PPL lock within a few seconds. It requires 3-4 satellite locks for its > PPL. However, when I attached the patch antenna to my Thunderbolt – > satellite signal strength were zero or minus for all satellites. The specs > for the patch antenna are listed below. > > > > I would appreciate any advice understanding this behavior. > > > > Jerry NY2KW > > > > Center Frequency 1575.42MHz±3 MHz > > V.S.W.R 1.5:1 > > Band Width ±5 MHz > > Impendence 50 ohm > > Peak Gain >3dBic Based on 7×7cm ground plane > > Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) > > Polarization RHCP > > LNA/Filter > > LNA Gain (Without cable) 28+/-3dB > > Noise Figure 1.5dB Typ. > > Filter Out Band Attenuation (f° =1575.42MHz) > > 7dB Min f0+/-20MHZ > > 20dB Min f0+/-50MHZ > > 30dB Min f0+/-100MHZ > > V.S.W.R <2.0 > > DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other > > DC Current 5mA /11mA/15mA Max > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >

Hi > On Jul 31, 2017, at 3:32 PM, Didier Juges <shalimr9@gmail.com> wrote: > > The Thunderbolt is well known for not having the best sensitivity among GPS > receivers. It seems that timing receivers in general, particularly those of > the same generation as the Thunderbolt are not as sensitive as navigation > (possibly newer) GPS receivers. It may be because they are expected to run > with amplified antennas? The newer the receiver, the more horsepower in the silicon. In the case of GPS, that gives you more correlators to do DSP. The sensitivity improvement is a direct result of that. If you take a look at the guts of a TBolt, they date to the late 1990’s. That’s a long time in silicon years …. Bob > > Based on the spec you wrote, it looks like your antenna has no gain, so > definitely I would expect less than good performance. > > My 3 Thunderbolts have been running with inside antennas (2 pucks and one > Trimble Bullet) but my ham shack is upstairs and other than the ceiling and > the shingle roof, there are no other obstructions and they are doing OK not > great (all 3 go on holdover somewhat regularly). I am now running one > downstairs (while I work on the new software for the TB Monitor) with 50 > feet of RG-58 going to a HP 58532A antenna somewhat in the clear but only 8 > feet above ground with significant obstructions in pretty much all > directions due to the low height and the Thunderbolt is happy as a clam in > spite of the significant losses in the cable. The HP antenna works much > better than the Trimble Bullet antenna. > > On Mon, Jul 31, 2017 at 12:19 PM, Jerry <jsternmd@att.net> wrote: > >> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A >> antenna placed indoor near a window facing South… can’t get much worse but >> most of the time it will be locked onto 3 or 4 satellites. I recently >> bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my SDR >> ham >> radio setup. I was very surprised to find that this minimalist GPSDO using >> a small patch antenna with internal LNA placed near my window had satellite >> & PPL lock within a few seconds. It requires 3-4 satellite locks for its >> PPL. However, when I attached the patch antenna to my Thunderbolt – >> satellite signal strength were zero or minus for all satellites. The specs >> for the patch antenna are listed below. >> >> >> >> I would appreciate any advice understanding this behavior. >> >> >> >> Jerry NY2KW >> >> >> >> Center Frequency 1575.42MHz±3 MHz >> >> V.S.W.R 1.5:1 >> >> Band Width ±5 MHz >> >> Impendence 50 ohm >> >> Peak Gain >3dBic Based on 7×7cm ground plane >> >> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) >> >> Polarization RHCP >> >> LNA/Filter >> >> LNA Gain (Without cable) 28+/-3dB >> >> Noise Figure 1.5dB Typ. >> >> Filter Out Band Attenuation (f° =1575.42MHz) >> >> 7dB Min f0+/-20MHZ >> >> 20dB Min f0+/-50MHZ >> >> 30dB Min f0+/-100MHZ >> >> V.S.W.R <2.0 >> >> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other >> >> DC Current 5mA /11mA/15mA Max >> >> >> >> >> >> >> >> _______________________________________________ >> time-nuts mailing 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.

Hi Jerry: The Trimble is the oldest mass produced GPS receiver I know of and because the early receivers used high gain antennas it seems that Trimble kept that idea for the newer designs. They like about 41 dB gain between the antenna and the input to the receiver. http://www.prc68.com/I/Trimpack.shtml#Ant Newer designs probably place that gain in the front end rather than at the antenna. But having around 20 dB of gain at the antenna gretly decreases the effect of feed line loss on noise figure. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html -------- Original Message -------- > Due to access problems, I run my Thunderbolt with a Symmetricom 58532A > antenna placed indoor near a window facing South… can’t get much worse but > most of the time it will be locked onto 3 or 4 satellites. I recently > bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my SDR ham > radio setup. I was very surprised to find that this minimalist GPSDO using > a small patch antenna with internal LNA placed near my window had satellite > & PPL lock within a few seconds. It requires 3-4 satellite locks for its > PPL. However, when I attached the patch antenna to my Thunderbolt – > satellite signal strength were zero or minus for all satellites. The specs > for the patch antenna are listed below. > > > > I would appreciate any advice understanding this behavior. > > > > Jerry NY2KW > > > > Center Frequency 1575.42MHz±3 MHz > > V.S.W.R 1.5:1 > > Band Width ±5 MHz > > Impendence 50 ohm > > Peak Gain >3dBic Based on 7×7cm ground plane > > Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) > > Polarization RHCP > > LNA/Filter > > LNA Gain (Without cable) 28+/-3dB > > Noise Figure 1.5dB Typ. > > Filter Out Band Attenuation (f° =1575.42MHz) > > 7dB Min f0+/-20MHZ > > 20dB Min f0+/-50MHZ > > 30dB Min f0+/-100MHZ > > V.S.W.R <2.0 > > DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other > > DC Current 5mA /11mA/15mA Max > > > > > > > > _______________________________________________ > time-nuts mailing 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 newer the receiver, the more horsepower in the silicon. In the case of GPS, that gives you more correlators to do DSP. The sensitivity improvement is a direct result of that. If you take a look at the guts of a TBolt, they date to the late 1990’s. That’s a long time in silicon years …." It seems that more correlators would speed up the time to first fix, not necessarily the sensitivity, particularly I do not see how it would directly affect the capability to stay locked when signal strength fluctuates? On the other hand, more correlators may help when there is multipath and a whole bunch of extraneous signals are fed into the receiver, so maybe the apparent lack of sensitivity is really the inability to see the signal from the chaff, not necessarily sensitivity in terms of noise figure. On Mon, Jul 31, 2017 at 3:06 PM, Bob kb8tq <kb8tq@n1k.org> wrote: > Hi > > > On Jul 31, 2017, at 3:32 PM, Didier Juges <shalimr9@gmail.com> wrote: > > > > The Thunderbolt is well known for not having the best sensitivity among > GPS > > receivers. It seems that timing receivers in general, particularly those > of > > the same generation as the Thunderbolt are not as sensitive as navigation > > (possibly newer) GPS receivers. It may be because they are expected to > run > > with amplified antennas? > > The newer the receiver, the more horsepower in the silicon. In the case of > GPS, that > gives you more correlators to do DSP. The sensitivity improvement is a > direct result > of that. If you take a look at the guts of a TBolt, they date to the late > 1990’s. That’s > a long time in silicon years …. > > Bob > > > > > > Based on the spec you wrote, it looks like your antenna has no gain, so > > definitely I would expect less than good performance. > > > > My 3 Thunderbolts have been running with inside antennas (2 pucks and one > > Trimble Bullet) but my ham shack is upstairs and other than the ceiling > and > > the shingle roof, there are no other obstructions and they are doing OK > not > > great (all 3 go on holdover somewhat regularly). I am now running one > > downstairs (while I work on the new software for the TB Monitor) with 50 > > feet of RG-58 going to a HP 58532A antenna somewhat in the clear but > only 8 > > feet above ground with significant obstructions in pretty much all > > directions due to the low height and the Thunderbolt is happy as a clam > in > > spite of the significant losses in the cable. The HP antenna works much > > better than the Trimble Bullet antenna. > > > > On Mon, Jul 31, 2017 at 12:19 PM, Jerry <jsternmd@att.net> wrote: > > > >> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A > >> antenna placed indoor near a window facing South… can’t get much worse > but > >> most of the time it will be locked onto 3 or 4 satellites. I recently > >> bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my SDR > >> ham > >> radio setup. I was very surprised to find that this minimalist GPSDO > using > >> a small patch antenna with internal LNA placed near my window had > satellite > >> & PPL lock within a few seconds. It requires 3-4 satellite locks for > its > >> PPL. However, when I attached the patch antenna to my Thunderbolt – > >> satellite signal strength were zero or minus for all satellites. The > specs > >> for the patch antenna are listed below. > >> > >> > >> > >> I would appreciate any advice understanding this behavior. > >> > >> > >> > >> Jerry NY2KW > >> > >> > >> > >> Center Frequency 1575.42MHz±3 MHz > >> > >> V.S.W.R 1.5:1 > >> > >> Band Width ±5 MHz > >> > >> Impendence 50 ohm > >> > >> Peak Gain >3dBic Based on 7×7cm ground plane > >> > >> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) > >> > >> Polarization RHCP > >> > >> LNA/Filter > >> > >> LNA Gain (Without cable) 28+/-3dB > >> > >> Noise Figure 1.5dB Typ. > >> > >> Filter Out Band Attenuation (f° =1575.42MHz) > >> > >> 7dB Min f0+/-20MHZ > >> > >> 20dB Min f0+/-50MHZ > >> > >> 30dB Min f0+/-100MHZ > >> > >> V.S.W.R <2.0 > >> > >> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other > >> > >> DC Current 5mA /11mA/15mA Max > >> > >> > >> > >> > >> > >> > >> > >> _______________________________________________ > >> time-nuts mailing 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. >

" having around 20 dB of gain at the antenna greatly decreases the effect of feed line loss on noise figure." And that would be consistent with usage for a timing receiver which is expected to have a well exposed antenna and a significant line length, as opposed to navigation receivers where the antenna is expected to have a short feed line. On Mon, Jul 31, 2017 at 4:17 PM, Brooke Clarke <brooke@pacific.net> wrote: > Hi Jerry: > > The Trimble is the oldest mass produced GPS receiver I know of and because > the early receivers used high gain antennas it seems that Trimble kept that > idea for the newer designs. They like about 41 dB gain between the antenna > and the input to the receiver. > http://www.prc68.com/I/Trimpack.shtml#Ant > Newer designs probably place that gain in the front end rather than at the > antenna. But having around 20 dB of gain at the antenna gretly decreases > the effect of feed line loss on noise figure. > > -- > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.end2partygovernment.com/2012Issues.html > > > -------- Original Message -------- > >> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A >> antenna placed indoor near a window facing South… can’t get much worse but >> most of the time it will be locked onto 3 or 4 satellites. I recently >> bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my SDR >> ham >> radio setup. I was very surprised to find that this minimalist GPSDO >> using >> a small patch antenna with internal LNA placed near my window had >> satellite >> & PPL lock within a few seconds. It requires 3-4 satellite locks for its >> PPL. However, when I attached the patch antenna to my Thunderbolt – >> satellite signal strength were zero or minus for all satellites. The >> specs >> for the patch antenna are listed below. >> >> >> I would appreciate any advice understanding this behavior. >> >> >> Jerry NY2KW >> >> >> Center Frequency 1575.42MHz±3 MHz >> >> V.S.W.R 1.5:1 >> >> Band Width ±5 MHz >> >> Impendence 50 ohm >> >> Peak Gain >3dBic Based on 7×7cm ground plane >> >> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) >> >> Polarization RHCP >> >> LNA/Filter >> >> LNA Gain (Without cable) 28+/-3dB >> >> Noise Figure 1.5dB Typ. >> >> Filter Out Band Attenuation (f° =1575.42MHz) >> >> 7dB Min f0+/-20MHZ >> >> 20dB Min f0+/-50MHZ >> >> 30dB Min f0+/-100MHZ >> >> V.S.W.R <2.0 >> >> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other >> >> DC Current 5mA /11mA/15mA Max >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/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/m > ailman/listinfo/time-nuts > and follow the instructions there. >

On 8/1/17 11:11 AM, Didier Juges wrote: > "The newer the receiver, the more horsepower in the silicon. In the case of > GPS, that > gives you more correlators to do DSP. The sensitivity improvement is a > direct result > of that. If you take a look at the guts of a TBolt, they date to the late > 1990’s. That’s > a long time in silicon years …." > > It seems that more correlators would speed up the time to first fix, not > necessarily the sensitivity, particularly I do not see how it would > directly affect the capability to stay locked when signal strength > fluctuates? > On the other hand, more correlators may help when there is multipath and a > whole bunch of extraneous signals are fed into the receiver, so maybe the > apparent lack of sensitivity is really the inability to see the signal from > the chaff, not necessarily sensitivity in terms of noise figure. > > There's also "more sophisticated correlators" and "more sophisticated tracking loops" that are enabled by more computational horsepower. The days of "independent" PN tracking loops for each signal are probably long gone, and there's clever "aiding" of the loops by estimating the on-the-fly variations.

Dider: This is a CDMA signal. (With a 'chip' rate that far exceeds the information rate.) If you put a different correlator on every multipath signal, which are each differently delayed in time, then they can be independently demodulated. (Or time shifted and added back together with some quality indicator for weighting.) So, in CDMA, multipath is used as a form of (time) diversity reception and will improve the signal to noise of the combined signal. By definition, the signal with the least time delay either is, or is closest to, the most direct path. You don't have to necessarily fully demodulate this early signal by itself, just know what its timing is. (And remember where it was, if fading in and out.) Since multi-path is a destructive mechanism in most narrow band radio systems, the above may not be intuitive to people not familiar with CDMA and "rake receiver" based systems. Multipath helps, not hurts, these systems, as long as the multipath delays are most of one chip apart, or more. --- Graham On Tue, Aug 1, 2017 at 1:11 PM, Didier Juges <shalimr9@gmail.com> wrote: > "The newer the receiver, the more horsepower in the silicon. In the case of > GPS, that > gives you more correlators to do DSP. The sensitivity improvement is a > direct result > of that. If you take a look at the guts of a TBolt, they date to the late > 1990’s. That’s > a long time in silicon years …." > > It seems that more correlators would speed up the time to first fix, not > necessarily the sensitivity, particularly I do not see how it would > directly affect the capability to stay locked when signal strength > fluctuates? > On the other hand, more correlators may help when there is multipath and a > whole bunch of extraneous signals are fed into the receiver, so maybe the > apparent lack of sensitivity is really the inability to see the signal from > the chaff, not necessarily sensitivity in terms of noise figure. > > > On Mon, Jul 31, 2017 at 3:06 PM, Bob kb8tq <kb8tq@n1k.org> wrote: > > > Hi > > > > > On Jul 31, 2017, at 3:32 PM, Didier Juges <shalimr9@gmail.com> wrote: > > > > > > The Thunderbolt is well known for not having the best sensitivity among > > GPS > > > receivers. It seems that timing receivers in general, particularly > those > > of > > > the same generation as the Thunderbolt are not as sensitive as > navigation > > > (possibly newer) GPS receivers. It may be because they are expected to > > run > > > with amplified antennas? > > > > The newer the receiver, the more horsepower in the silicon. In the case > of > > GPS, that > > gives you more correlators to do DSP. The sensitivity improvement is a > > direct result > > of that. If you take a look at the guts of a TBolt, they date to the late > > 1990’s. That’s > > a long time in silicon years …. > > > > Bob > > > > > > > > > > Based on the spec you wrote, it looks like your antenna has no gain, so > > > definitely I would expect less than good performance. > > > > > > My 3 Thunderbolts have been running with inside antennas (2 pucks and > one > > > Trimble Bullet) but my ham shack is upstairs and other than the ceiling > > and > > > the shingle roof, there are no other obstructions and they are doing OK > > not > > > great (all 3 go on holdover somewhat regularly). I am now running one > > > downstairs (while I work on the new software for the TB Monitor) with > 50 > > > feet of RG-58 going to a HP 58532A antenna somewhat in the clear but > > only 8 > > > feet above ground with significant obstructions in pretty much all > > > directions due to the low height and the Thunderbolt is happy as a clam > > in > > > spite of the significant losses in the cable. The HP antenna works much > > > better than the Trimble Bullet antenna. > > > > > > On Mon, Jul 31, 2017 at 12:19 PM, Jerry <jsternmd@att.net> wrote: > > > > > >> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A > > >> antenna placed indoor near a window facing South… can’t get much worse > > but > > >> most of the time it will be locked onto 3 or 4 satellites. I > recently > > >> bought a www.leobodnar.com <http://www.leobodnar.com> GPSDO for my > SDR > > >> ham > > >> radio setup. I was very surprised to find that this minimalist GPSDO > > using > > >> a small patch antenna with internal LNA placed near my window had > > satellite > > >> & PPL lock within a few seconds. It requires 3-4 satellite locks for > > its > > >> PPL. However, when I attached the patch antenna to my Thunderbolt – > > >> satellite signal strength were zero or minus for all satellites. The > > specs > > >> for the patch antenna are listed below. > > >> > > >> > > >> > > >> I would appreciate any advice understanding this behavior. > > >> > > >> > > >> > > >> Jerry NY2KW > > >> > > >> > > >> > > >> Center Frequency 1575.42MHz±3 MHz > > >> > > >> V.S.W.R 1.5:1 > > >> > > >> Band Width ±5 MHz > > >> > > >> Impendence 50 ohm > > >> > > >> Peak Gain >3dBic Based on 7×7cm ground plane > > >> > > >> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume) > > >> > > >> Polarization RHCP > > >> > > >> LNA/Filter > > >> > > >> LNA Gain (Without cable) 28+/-3dB > > >> > > >> Noise Figure 1.5dB Typ. > > >> > > >> Filter Out Band Attenuation (f° =1575.42MHz) > > >> > > >> 7dB Min f0+/-20MHZ > > >> > > >> 20dB Min f0+/-50MHZ > > >> > > >> 30dB Min f0+/-100MHZ > > >> > > >> V.S.W.R <2.0 > > >> > > >> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other > > >> > > >> DC Current 5mA /11mA/15mA Max > > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> _______________________________________________ > > >> time-nuts mailing 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. >

On 8/1/17 12:11 PM, Graham / KE9H wrote: > Dider: > > This is a CDMA signal. (With a 'chip' rate that far exceeds the information > rate.) > > If you put a different correlator on every multipath signal, which are each > differently delayed in time, then they can be independently demodulated. > (Or time shifted and added back together with some quality indicator for > weighting.) > So, in CDMA, multipath is used as a form of (time) diversity reception and > will improve the signal to noise of the combined signal. > > By definition, the signal with the least time delay either is, or is > closest to, the most direct path. > > You don't have to necessarily fully demodulate this early signal by itself, > just know what its timing is. (And remember where it was, if fading in and > out.) > > Since multi-path is a destructive mechanism in most narrow band radio > systems, the above may not be intuitive to people not familiar with CDMA > and "rake receiver" based systems. > > Multipath helps, not hurts, these systems, as long as the multipath delays > are most of one chip apart, or more. > For GPS raw (off the air), when they post process at JPL, they use a fairly sophisticated correlation process, incorporating an estimator of the underlying time delay trajectory: you can use a later "big peak" to help recover the early "first peak", for instance. Rake receivers (under the name "adaptive equalizers") are also why digital TV works fairly well in high multipath environments - with modern receivers that do this.