Re: [time-nuts] GPS active antenna delay ?
j...@febo.com said: > OK, so I had an HP 58535A two-port GPS splitter handy and put it on the > VNA. It clearly has a filter of some sort, as shown by the S21 frequency > response. The delay at the center of the passband is about 21ns, and it > increases to about 26ns at the edges. Thanks. It seems a bit strange that HP didn't mention the delay. That part seems likely to be used with their GPS gear that is setup to compensate for cable delays. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS active antenna delay ?
OK, so I had an HP 58535A two-port GPS splitter handy and put it on the VNA. It clearly has a filter of some sort, as shown by the S21 frequency response. The delay at the center of the passband is about 21ns, and it increases to about 26ns at the edges. That delay consists of the physical length of the signal path in the splitter, plus the effects of a 6dB amplifier, SAW filter, and a hybrid 2-way splitter. The noise in the delay plot is because I had to avoid overdriving the splitter amp, so the input signal was 40dB lower than normal for the VNA. Thus the analyzer receivers had pretty weak signals to work with (and I didn't do anything heroic to compensate, other than use a large averaging factor plus smoothing). I don't know how applicable this would be to the circuit in an antenna. I suspect the biggest difference might be due to the higher gain amp in the antenna vs. 6dB in the splitter. On 02/08/2015 08:29 AM, John Ackermann N8UR wrote: I think that the surplus HP/Agilent GPS splitters may have an SAW filter. If so, measuring the delay of one of those could yield at least an approximation. I may have that data laying around; I'll do some digging. John On 02/08/2015 05:11 AM, Attila Kinali wrote: On Sat, 7 Feb 2015 10:07:44 -0800 Tom McDermott wrote: While compensating for cable delay is relatively straight forward by measuring the length and compensating for the velocity factor, a question is: how much amplifier / filter group delay is to be expected within the antenna itself? The usual way is to calibrate the whole setup, including antenna, LNA, cable and receiver. Ie. you drive to the national lab, set up your whole system, then measure the timing difference of your GPS receiver to the one of the lab, drive back home, and apply the correction. Looking through GPS SAW filter datasheets seems to show none with group delay specifications. Not surprising. Group delay is not considered of any importance in most RF designs. googling leads to some research papers with delays of about: L1 - 20 MHz wide SAW filter has about 15 nsec of group delay L1 - 2 MHz wide SAW filter has about 65 nsec of group delay L1 - LC filter - can't find anything, but suspect it's probably just a few nanoseconds. I would be very much interested in those papers. Could you list their titles and authors at least? I'm not sure a consumer grade antenna even has a SAW filter, it may simply be an LC filter. Unlikely. LC filters are not sharp enough and difficult to build reliably at those frequencies. I would rather assume that there are no filters at all (beside the antenna characteristics). Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS active antenna delay ?
Hi all. The papers are: 1) "SAW Filter Modeling in MATLAB for GNSS Receivers", S.H. Abbas, et al., IJECE Oct 2013, ISSN: 2088-2078 The authors de-embed the group delay using FFT and MATLAB. Eyeball about 15-20 nsec. for a pretty wide filter. 2) "The Effects of SAW Group Delay Ripple on GPS and Glonass Signals", Simon Adams, Novatel, Inc., Calgary AB The author computes a group delay ripple of 38 nsec for a specific SAW filter due to triple-transit reflections. 3) "GPS + Modernized GPS + Gallileo Signal Timing Biases", Chris Hegerty, Ed Powers, Blair Fonville, all of USNO, GPS World, March 2006 pp 49-54. Figure 2 shows group delay minima of about 65 nsec. for the RF/IF filtering. 4) Arbiter Systems Datasheet for AS0087800 active timing antenna, the datasheet is numbered PD0050600A. Arbiter systems, Paso Robles, CA. They specify (or measured?) the antenna delay exclusive of any cable as 43 nsec. In reading through the various SAW filter specifications on the web, I've found a few that specify the group delay ripple, but none that specify the group delay itself. -- Tom, N5EG On Sun, Feb 8, 2015 at 2:11 AM, Attila Kinali wrote: > On Sat, 7 Feb 2015 10:07:44 -0800 > Tom McDermott wrote: > > > While compensating for cable delay is relatively straight forward by > > measuring the length and compensating for > > the velocity factor, a question is: how much amplifier / filter group > delay > > is to be expected within the antenna itself? > > The usual way is to calibrate the whole setup, including antenna, LNA, > cable and receiver. Ie. you drive to the national lab, set up your whole > system, then measure the timing difference of your GPS receiver to the > one of the lab, drive back home, and apply the correction. > > > Looking through GPS SAW filter datasheets seems to show none with group > > delay specifications. > > Not surprising. Group delay is not considered of any importance in most > RF designs. > > > googling leads to some research papers with delays of about: > > > > L1 - 20 MHz wide SAW filter has about 15 nsec of group delay > > L1 - 2 MHz wide SAW filter has about 65 nsec of group delay > > L1 - LC filter - can't find anything, but suspect it's probably just a > few > > nanoseconds. > > I would be very much interested in those papers. Could you list their > titles > and authors at least? > > > > I'm not sure a consumer grade antenna even has a SAW filter, it may > simply > > be an LC filter. > > Unlikely. LC filters are not sharp enough and difficult to build reliably > at those frequencies. I would rather assume that there are no filters > at all (beside the antenna characteristics). > > > Attila Kinali > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > ___ > 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] MSF Scheduled Maintenance Periods
MSF Scheduled Maintenance Periods The MSF 60 kHz standard-frequency and time signal, broadcast by Babcock on behalf of NPL, is occasionally taken off-air to allow maintenance work on the masts and antennas at Anthorn Radio Station to be carried out in safety. This means that your radio-controlled clock will not be picking up the MSF signal, so may not be working correctly. The dates and times of the forthcoming scheduled maintenance periods are as follows: Main scheduled 2015 MSF outage: 2 - 19 March 2015 from approximately 08:00 UTC to 18:00 UTC each weekday (normal transmission should be resumed overnight and at weekends) See: http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-outages Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS active antenna delay ?
I think that the surplus HP/Agilent GPS splitters may have an SAW filter. If so, measuring the delay of one of those could yield at least an approximation. I may have that data laying around; I'll do some digging. John On 02/08/2015 05:11 AM, Attila Kinali wrote: On Sat, 7 Feb 2015 10:07:44 -0800 Tom McDermott wrote: While compensating for cable delay is relatively straight forward by measuring the length and compensating for the velocity factor, a question is: how much amplifier / filter group delay is to be expected within the antenna itself? The usual way is to calibrate the whole setup, including antenna, LNA, cable and receiver. Ie. you drive to the national lab, set up your whole system, then measure the timing difference of your GPS receiver to the one of the lab, drive back home, and apply the correction. Looking through GPS SAW filter datasheets seems to show none with group delay specifications. Not surprising. Group delay is not considered of any importance in most RF designs. googling leads to some research papers with delays of about: L1 - 20 MHz wide SAW filter has about 15 nsec of group delay L1 - 2 MHz wide SAW filter has about 65 nsec of group delay L1 - LC filter - can't find anything, but suspect it's probably just a few nanoseconds. I would be very much interested in those papers. Could you list their titles and authors at least? I'm not sure a consumer grade antenna even has a SAW filter, it may simply be an LC filter. Unlikely. LC filters are not sharp enough and difficult to build reliably at those frequencies. I would rather assume that there are no filters at all (beside the antenna characteristics). Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS active antenna delay ?
Attila, On 02/08/2015 11:11 AM, Attila Kinali wrote: On Sat, 7 Feb 2015 10:07:44 -0800 Tom McDermott wrote: While compensating for cable delay is relatively straight forward by measuring the length and compensating for the velocity factor, a question is: how much amplifier / filter group delay is to be expected within the antenna itself? The usual way is to calibrate the whole setup, including antenna, LNA, cable and receiver. Ie. you drive to the national lab, set up your whole system, then measure the timing difference of your GPS receiver to the one of the lab, drive back home, and apply the correction. I've seen a few different approaches. Looking through GPS SAW filter datasheets seems to show none with group delay specifications. Not surprising. Group delay is not considered of any importance in most RF designs. googling leads to some research papers with delays of about: L1 - 20 MHz wide SAW filter has about 15 nsec of group delay L1 - 2 MHz wide SAW filter has about 65 nsec of group delay L1 - LC filter - can't find anything, but suspect it's probably just a few nanoseconds. I would be very much interested in those papers. Could you list their titles and authors at least? Indeed. LC filters should avoid too high Q in pass-band, but should have a bunch of zeros a bit further out to punch out the stop-bands properly. SAW-filters should similarly avoid high Q notches, but there it is easy to achieve higher degree systems such that you achieve the filtering without going to high-Q systems. I'm not sure a consumer grade antenna even has a SAW filter, it may simply be an LC filter. Unlikely. LC filters are not sharp enough and difficult to build reliably at those frequencies. I would rather assume that there are no filters at all (beside the antenna characteristics). Works great unless you have a radio amateur doing L-band (23 cm) transmissions. Here in Sweden you can transmit 1 kW in that band, just a handfull of MHz from L2. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS active antenna delay ?
On 2/8/15 2:11 AM, Attila Kinali wrote: On Sat, 7 Feb 2015 10:07:44 -0800 Tom McDermott wrote: While compensating for cable delay is relatively straight forward by measuring the length and compensating for the velocity factor, a question is: how much amplifier / filter group delay is to be expected within the antenna itself? The usual way is to calibrate the whole setup, including antenna, LNA, cable and receiver. Ie. you drive to the national lab, set up your whole system, then measure the timing difference of your GPS receiver to the one of the lab, drive back home, and apply the correction. Looking through GPS SAW filter datasheets seems to show none with group delay specifications. Not surprising. Group delay is not considered of any importance in most RF designs. googling leads to some research papers with delays of about: L1 - 20 MHz wide SAW filter has about 15 nsec of group delay L1 - 2 MHz wide SAW filter has about 65 nsec of group delay L1 - LC filter - can't find anything, but suspect it's probably just a few nanoseconds. One has to be "very" careful about reading group delay specs on wideband devices. Sometimes, the group delay (or its flatness/deviations from a straight line) is measured ONLY over the frequency band of interest, which might not be the filter passband. You could have wild fluctuations of phase vs frequency somewhere, but as long as dphase/dfreq is constant in the desired area, the filter/amplifier meets spec. I'm not sure a consumer grade antenna even has a SAW filter, it may simply be an LC filter. Unlikely. LC filters are not sharp enough and difficult to build reliably at those frequencies. I would rather assume that there are no filters at all (beside the antenna characteristics). There might be a wideband (500MHz) filter in front of the LNA, and then separate narrow band filters for each of the three frequencies. The wideband filter could be LC or coupled microstripline equivalents. ___ 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] Datum PRS-45A Operating Data
Hi Eugene, A quick look, it looks healthy. About 2 years of tube operation, you should be good for quite some time. Cheers, Magnus On 02/08/2015 06:45 AM, W2HX wrote: Hello all, I got the monitor program working and connected to the PRS-45A Cs. Attached is the screenshot of the data I got. Can anyone translate the data into something meaningful for me as a newbie? Is this thing healthy? Thanks all Eugene ___ 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] Datum PRS-45A Operating Data
Hello all, I got the monitor program working and connected to the PRS-45A Cs. Attached is the screenshot of the data I got. Can anyone translate the data into something meaningful for me as a newbie? Is this thing healthy? Thanks all Eugene ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS active antenna delay ?
On Sat, 7 Feb 2015 10:07:44 -0800 Tom McDermott wrote: > While compensating for cable delay is relatively straight forward by > measuring the length and compensating for > the velocity factor, a question is: how much amplifier / filter group delay > is to be expected within the antenna itself? The usual way is to calibrate the whole setup, including antenna, LNA, cable and receiver. Ie. you drive to the national lab, set up your whole system, then measure the timing difference of your GPS receiver to the one of the lab, drive back home, and apply the correction. > Looking through GPS SAW filter datasheets seems to show none with group > delay specifications. Not surprising. Group delay is not considered of any importance in most RF designs. > googling leads to some research papers with delays of about: > > L1 - 20 MHz wide SAW filter has about 15 nsec of group delay > L1 - 2 MHz wide SAW filter has about 65 nsec of group delay > L1 - LC filter - can't find anything, but suspect it's probably just a few > nanoseconds. I would be very much interested in those papers. Could you list their titles and authors at least? > I'm not sure a consumer grade antenna even has a SAW filter, it may simply > be an LC filter. Unlikely. LC filters are not sharp enough and difficult to build reliably at those frequencies. I would rather assume that there are no filters at all (beside the antenna characteristics). Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] TimeLab with Wine: No RS232 interface available
Don't remove the serial mouse, just disable it. If you remove it, it will return on the next reboot. On 2/7/2015 9:11 AM, Jim Lux wrote: There's also the whole "microsoft serial mouse device" problem. A typical Windows 7 install (and other versions as well) will have a MS serial mouse device in the device manager, and when booting, the device driver goes out and looks for the mouse on COM1 (and maybe other COM devices) If the wrong characters come back from the device at the wrong time (e.g. something from the GPS receiver), the mouse driver takes over the device (and randomly moves the cursor around the screen, sometimes). You need to explicitly disable the device (and/or remove it) in Device Manager. ___ 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] question Alan deviation measured with Timelab and counters
Hej Attila, On 02/06/2015 01:22 PM, Attila Kinali wrote: Moin Magnus, On Wed, 21 Jan 2015 07:07:54 +0100 Magnus Danielson wrote: For oscillators, they should have been turned on long enough such that any drift is negligible. Alternatively you process out the quadratic trend out of it. The later should be accompanied by some quality measure of how much remaining systematics there is (see Jim Barnes PTTI paper on Drift Estimators). Do you mean "The measurement of linear frequency drift in oscillators", http://tf.nist.gov/timefreq/general/tn1337/Tn264.pdf ? Yes. I use the PTTI link http://tycho.usno.navy.mil/ptti/1983papers/Vol%2015_29.pdf I was just lazy to dig the link up when I wrote that. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
