[time-nuts] Fun with the Z3815
HI all, I posted a question recently here for a friend re a Z3815 not receiving, having formerly been perfect. Here's what he says now: I've done more testing with my HP3815A. Firstly I rewired the coax cable between the external antenna connector and the PCB - there was some evidence of snagging on the outside of the cable where it passes through the metal casing. However, no improvement in performance resulted. Also the blocking capacitor referred to turns out to be an inductor. DC is making it through to the antenna amp, and there is continuity along the whole route from N-connector to the Furuno GPS receiver input. The status screen on Hyperterminal shows that something is happening, however. The SYNCHRONIZATION section on the display showed outputs invalid, TFOM = 9 and FFOM = 3 (i.e. no sync). But the ACQUISITION section showed that although no satellites had been tracked, several had been detected - in fact 9 of them. Also, the correct date and time were displayed. The LAT and LONG data was incorrect, being the original northern hemisphere figures. Health monitor reads OK and there are no ALARMS. So the receiver appears to be picking up enough information to show the satellites' PRN, EL and AZ (and furthermore they change between readings) as well as the date and time. What's more the time displayed is local time! Any suggestions as to what's going on? Morris ___ 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] Fun with the Z3815
Have you tried commanding a survey to get the receive to ignore the old location? :PTIME:GPSYSTEM:POSITION:SURVEY ONCE John WA4WDL -- From: Morris Odell vilgo...@bigpond.net.au Sent: Saturday, August 11, 2012 7:27 AM To: time-nuts@febo.com Subject: [time-nuts] Fun with the Z3815 HI all, I posted a question recently here for a friend re a Z3815 not receiving, having formerly been perfect. Here's what he says now: I've done more testing with my HP3815A. Firstly I rewired the coax cable between the external antenna connector and the PCB - there was some evidence of snagging on the outside of the cable where it passes through the metal casing. However, no improvement in performance resulted. Also the blocking capacitor referred to turns out to be an inductor. DC is making it through to the antenna amp, and there is continuity along the whole route from N-connector to the Furuno GPS receiver input. The status screen on Hyperterminal shows that something is happening, however. The SYNCHRONIZATION section on the display showed outputs invalid, TFOM = 9 and FFOM = 3 (i.e. no sync). But the ACQUISITION section showed that although no satellites had been tracked, several had been detected - in fact 9 of them. Also, the correct date and time were displayed. The LAT and LONG data was incorrect, being the original northern hemisphere figures. Health monitor reads OK and there are no ALARMS. So the receiver appears to be picking up enough information to show the satellites' PRN, EL and AZ (and furthermore they change between readings) as well as the date and time. What's more the time displayed is local time! Any suggestions as to what's going on? Morris ___ 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] Fun with the Z3815
Try to preset the receiver too: :SYSTEM:PRESET But first you can read the system log to try to identify when the failure started: :DIAGNOSTIC:LOG:READ:ALL? Doing a SYSTEM:PRESET will clear the log, of course. Very strange the inductor on the antenna cable: my Z3815A has a capacitor also because there is a different power for the antenna and I suspect that you have a short between the Furuno antenna power and the Z3815A antenna power. On Sat, Aug 11, 2012 at 1:51 PM, jmfranke jmfra...@cox.net wrote: Have you tried commanding a survey to get the receive to ignore the old location? :PTIME:GPSYSTEM:POSITION:SURVEY ONCE John WA4WDL -- From: Morris Odell vilgo...@bigpond.net.au Sent: Saturday, August 11, 2012 7:27 AM To: time-nuts@febo.com Subject: [time-nuts] Fun with the Z3815 HI all, I posted a question recently here for a friend re a Z3815 not receiving, having formerly been perfect. Here's what he says now: I've done more testing with my HP3815A. Firstly I rewired the coax cable between the external antenna connector and the PCB - there was some evidence of snagging on the outside of the cable where it passes through the metal casing. However, no improvement in performance resulted. Also the blocking capacitor referred to turns out to be an inductor. DC is making it through to the antenna amp, and there is continuity along the whole route from N-connector to the Furuno GPS receiver input. The status screen on Hyperterminal shows that something is happening, however. The SYNCHRONIZATION section on the display showed outputs invalid, TFOM = 9 and FFOM = 3 (i.e. no sync). But the ACQUISITION section showed that although no satellites had been tracked, several had been detected - in fact 9 of them. Also, the correct date and time were displayed. The LAT and LONG data was incorrect, being the original northern hemisphere figures. Health monitor reads OK and there are no ALARMS. So the receiver appears to be picking up enough information to show the satellites' PRN, EL and AZ (and furthermore they change between readings) as well as the date and time. What's more the time displayed is local time! Any suggestions as to what's going on? Morris ___ 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] Fun with the Z3815
Hi As I recall, this was a 3815 that was working and then stopped working. If it's back to it's original location, then the new location from the survey was never saved to eprom. Once he gets a new survey, make sure to save it. If it's not saved, the unit will revert to the old location every time the power is cycled. Bob On Aug 11, 2012, at 7:27 AM, Morris Odell vilgo...@bigpond.net.au wrote: HI all, I posted a question recently here for a friend re a Z3815 not receiving, having formerly been perfect. Here's what he says now: I've done more testing with my HP3815A. Firstly I rewired the coax cable between the external antenna connector and the PCB - there was some evidence of snagging on the outside of the cable where it passes through the metal casing. However, no improvement in performance resulted. Also the blocking capacitor referred to turns out to be an inductor. DC is making it through to the antenna amp, and there is continuity along the whole route from N-connector to the Furuno GPS receiver input. The status screen on Hyperterminal shows that something is happening, however. The SYNCHRONIZATION section on the display showed outputs invalid, TFOM = 9 and FFOM = 3 (i.e. no sync). But the ACQUISITION section showed that although no satellites had been tracked, several had been detected - in fact 9 of them. Also, the correct date and time were displayed. The LAT and LONG data was incorrect, being the original northern hemisphere figures. Health monitor reads OK and there are no ALARMS. So the receiver appears to be picking up enough information to show the satellites' PRN, EL and AZ (and furthermore they change between readings) as well as the date and time. What's more the time displayed is local time! Any suggestions as to what's going on? Morris ___ 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] Fun with the Z3815
On 8/11/12 4:16 AM, Azelio Boriani wrote: Very strange the inductor on the antenna cable: my Z3815A has a capacitor also because there is a different power for the antenna and I suspect that you have a short between the Furuno antenna power and the Z3815A antenna power. Think you looking at different things. There should be an inductor at the DC injection point, connecting to the signal line. And a cap as a DC block twards the receiver in-line with it. ___ 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] Fun with the Z3815
Of course, but they say that there is a DC continuity from the N connector downto the Furuno receiver: this is very strange. These the exact words: DC is making it through to the antenna amp, and there is continuity along the whole route from N-connector to the Furuno GPS receiver input. Very strange also because the inductor will prevent the receiver from getting any signal. Another strange thing: I haven't never saved any survey in my Z3815A and I have seen that in case of a power cycle the survey is repeated. The faulty Z3815A seems always acquiring and never tracking: maybe a Furuno clock problem? What can prevent a GPS receiver to enter the tracking state? On Sat, Aug 11, 2012 at 10:03 PM, Christopher Brown cbr...@woods.netwrote: On 8/11/12 4:16 AM, Azelio Boriani wrote: Very strange the inductor on the antenna cable: my Z3815A has a capacitor also because there is a different power for the antenna and I suspect that you have a short between the Furuno antenna power and the Z3815A antenna power. Think you looking at different things. There should be an inductor at the DC injection point, connecting to the signal line. And a cap as a DC block twards the receiver in-line with it. ___ 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] Trimble 38687 GPS receiver
Good Morning from Australia, I am looking for information on Trimble 38687 GPS receiver. Thank you 73 Gary VK2KYP ___ 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] Fixed my 1804M
On 25/07/12 22:18, Chuck Forsberg WA7KGX N2469R wrote: How about a 10 MHz OCXO and a divide by two chip? Maybe an op-amp to change and/or invert the control voltage? In the end that's exactly what I did. Details on eevblog - http://www.eevblog.com/forum/projects-designs-and-technical-stuff/rapco-1804m-repair-10mhz-conversionbodge-(-teardown)/ Found a 10MHz ocxo which seems to have very similar specs to the 10Mhz 1804Ms running without GPS and dropped that in. There's a handy 22ohm damping resistor in the track which takes the 5MHz round to the logic so lifting that allows one to insert a divide by two bodge, leaving 10MHz at the rear BNC. Didn't have too many problems achieving fine control for the oscillator - took about 24 hours, although I did tweak the DAC output manually to be in the right ball park - it needed quite a large shift I wasn't sure whether the firmware would make such a large correction, or take a very long time to do it. ___ 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] ADEV drop
Fellow time-nuts, As David insisted that I get and then read the ITU Handbook Selection and Use of Precise Frequency and Time Systems (1997) and in particular Chapter 3 I took the time to get it and start reading it. In there I found clause 3.3.2.4.4 Truncation effects, which addresses this issue, which also aligns up with my own writing on Allan Deviation, and the Measurement bandwidth limit (I will have to update that one). The key point is that the main lobe of the kernel function (the way that the sin(pi*tau*f)^4/x^n look), will be affected by the system bandwidth and values will be not matching up to the brick-wall analysis of the traditional system. The result will be that the ADEV measure will be lower than it should. This situation was analysed by Bernier in 1987 as part of analysing the modified Allan deviation, which has a software bandwidth filter in the form of the n*tau_0 average filter. So, the first low n values is even expected to give systematic low values, which is the reason for the ITU-T to put minimum requirements on the tau_0 to lowest tau to ensure that repeatability is achieved. This is also the same effect that Sam Steiner mentioned in his presentation during this years NIST seminars. Sam also went on to discuss the effect of aliasing, which helps to bring even more false values in that region. Conclusion: Just don't look all that hard on the lower tau values, as they can be systematically off. Make sure that you have a tau_0 well below the taus you are interested in to ensure that your values is reasonably valid. 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] ADEV drop
The basic problem is that one can not meet Allan's requirement of the integral of the instantaneous frequencies over tau0 time and Nyquist-Shannon sampling theorem requirement if taking just one raw phase sample per displayed ADEV tau0. The two requirements are then mutually exclusive. This is especially true when that sample is coming from a DTMD zero crossing detector. The way I get ADEV tau answers that do not droop at all near tau0, and that are independent of the displayed tau0, the oversample rate and the NEQ.BW filter (if BW 2* tau0) without having to throw away the low tau answers or save data files with more than tau0 number of samples, is by oversampling the raw data and then reducing it in an appropriate way before saving it as tau0. With high speed oversampling it is also very simple to avoid any aliasing problems. Using an external DC coupled sound card, oversampling at 48KHz for any tau0, both the TPLL2.0 and the XOR-LPD give non-drooping tau0 answers that are not a function of the oversample rate or the tau0 reduction rate. That is, get the same ADEV tau 1sec answer if the tau0 is 1KHz, 1Hz or anywhere in-between. ws Fellow time-nuts, As David insisted that I get and then read the ITU Handbook Selection and Use of Precise Frequency and Time Systems (1997) and in particular Chapter 3 I took the time to get it and start reading it. In there I found clause 3.3.2.4.4 Truncation effects, which addresses this issue, which also aligns up with my own writing on Allan Deviation, and the Measurement bandwidth limit (I will have to update that one). The key point is that the main lobe of the kernel function (the way that the sin(pi*tau*f)^4/x^n look), will be affected by the system bandwidth and values will be not matching up to the brick-wall analysis of the traditional system. The result will be that the ADEV measure will be lower than it should. This situation was analysed by Bernier in 1987 as part of analysing the modified Allan deviation, which has a software bandwidth filter in the form of the n*tau_0 average filter. So, the first low n values is even expected to give systematic low values, which is the reason for the ITU-T to put minimum requirements on the tau_0 to lowest tau to ensure that repeatability is achieved. This is also the same effect that Sam Steiner mentioned in his presentation during this years NIST seminars. Sam also went on to discuss the effect of aliasing, which helps to bring even more false values in that region. Conclusion: Just don't look all that hard on the lower tau values, as they can be systematically off. Make sure that you have a tau_0 well below the taus you are interested in to ensure that your values is reasonably valid. 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.
[time-nuts] T-Bolt output harmonics
First post as a new owner participant. I tamed the provided switching power supply noise with some L's and C's, and am now looking at the 10MHz output on a spectrum analyzer. Here is what I measured: 10MHz +9dbm 20MHz-50dbm 30 MHz -37dbm no obvious higher harmonics broad noise envelope at 60 75MHz @ -60dbm peak Are these results typical or might I have an adjustment or other problem? I've looked back about 6 months through the posts (is there a search function I've missed?) and not found anything except some 10MHz filter designs which I intend to try. Thanks, Grant KZ1W ___ 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] FRK specs.....
I used to be of the opinion that the Efratom FRK-H was the best of the models of FRK Rb standards for both short-term stability and overall performance. Is that still true today? I know there are better solutions for short-term (BVA OCXO) and long term (Cs MASERS). But where to things stack up today? I'm looking to buy an Rb that's better than my LPROs and other models. But I do not own an FRK-H. Looking for comments, please. Thanks in advance, -Brian, WA1ZMS ___ 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.
