Re: [time-nuts] Basic question regarding comparing two frequencies
Thats great 2 months more then I would have thought On Fri, Jul 30, 2010 at 10:37 AM, Chuck Harris cfhar...@erols.com wrote: The November deadline on the shared stations that hold positions in both the US and Canadian Loran chains is to allow operation to continue in Canada until they close their system... in November. -Chuck Harris paul swed wrote: Oh indeed I agree John. LORAN has spoiled me also at least till nov I hear. The Canadians are a drop better then us at saving the system. I am definitely figuring out the old ways and can't say that I like it all that much. Always have gps for the moment. On Fri, Jul 30, 2010 at 10:08 AM, J. Forsterj...@quik.com wrote: Partly. There are hourly jogs in the WWVB signal and also diurnal shifts of the order of a cycle at 60 KHz. The Fluke receivers havs a counter for microseconds, but it's difficult to intrerpret w/o the stripchart too. Frankly, 60 KHz is a PITA IMO. Oh for LORAN! -John ___ 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] Basic question regarding comparing two frequencies
So on a 60 khz signal the long strip chart recorder is simply a super long low pass filter averaging out the doppler somewhat. It really doesn't do that well. The mark-1 eyeball does a better job. Right? On Tue, Jul 27, 2010 at 4:53 AM, Geoff vk2...@ozemail.com.au wrote: On Tue, 27 Jul 2010 09:08:49 am Chuck Harris wrote: I suppose that you could always cheat? Since you know where the transmitter is going to be, if you could get a timenut near to the transmitter to give you a beacon to measure 24hrs prior to the event, you could use the diurnal variations that you observed (observe?) on the beacon to predict the skywave offset due to Doppler at the time of the event. -Chuck Harris Murray Greenman wrote: You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. snipped There is one possible way of getting an accurate reading from a sky wave signal over a short(ish) period. Plot a doppler shift curve with as fine a resolution as you can manage. Then look for a point of inflexion in the curve, that is a point where the second derivative of the curve function is zero. The frequency at that time will be that transmitted as at that instant the path length is not changing. You may have to examine your data set visually and mathematically examine a much smaller section. Of course if you don't get a point of inflexion you'll need much more data :-). Cheers, Geoff vk2tfg. ___ 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] Basic question regarding comparing two frequencies
Partly. There are hourly jogs in the WWVB signal and also diurnal shifts of the order of a cycle at 60 KHz. The Fluke receivers havs a counter for microseconds, but it's difficult to intrerpret w/o the stripchart too. Frankly, 60 KHz is a PITA IMO. Oh for LORAN! -John == So on a 60 khz signal the long strip chart recorder is simply a super long low pass filter averaging out the doppler somewhat. It really doesn't do that well. The mark-1 eyeball does a better job. Right? On Tue, Jul 27, 2010 at 4:53 AM, Geoff vk2...@ozemail.com.au wrote: On Tue, 27 Jul 2010 09:08:49 am Chuck Harris wrote: I suppose that you could always cheat? Since you know where the transmitter is going to be, if you could get a timenut near to the transmitter to give you a beacon to measure 24hrs prior to the event, you could use the diurnal variations that you observed (observe?) on the beacon to predict the skywave offset due to Doppler at the time of the event. -Chuck Harris Murray Greenman wrote: You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. snipped There is one possible way of getting an accurate reading from a sky wave signal over a short(ish) period. Plot a doppler shift curve with as fine a resolution as you can manage. Then look for a point of inflexion in the curve, that is a point where the second derivative of the curve function is zero. The frequency at that time will be that transmitted as at that instant the path length is not changing. You may have to examine your data set visually and mathematically examine a much smaller section. Of course if you don't get a point of inflexion you'll need much more data :-). Cheers, Geoff vk2tfg. ___ 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] Basic question regarding comparing two frequencies
The strip chart recorder is, of course, a hangover of days when data- logging could not be done digitally. However I still plot the results out from a data logger or time stamped data so I can see what is happening. The scatter of adjacent readings shows the noise and measurement uncertainty, any periodicity is visible as sign waves and the drift is visible even through a considerable amount of noise. The reason I still use a chart recorder is that I can see the data in real time, and I can see the effects of any adjustments that I make. One problem of chart recorders is when they run off scale so I often process signals so they fold back instead of running off scale. For setting a rubidium, a chart recorder showing the phase of the difference between GPS and the rubidium is very useful, you only have to make adjustments to steer down the middle of the chart. The recorder is more of an integrator than low pass filter. Incidentally, I constructed an early data logger in about 1963. We had an HP digital voltmeter attached to a an HP printer. I constructed a 500Hz tuning fork time standard, divided down with decatrons, to trigger the voltmeter printer to record a measurement. I then had to punch the numbers from the printout onto IBM punch cards to calculate the process being monitored. We have come a long way since then. cheers, Neville Michie On 30/07/2010, at 11:52 PM, paul swed wrote: So on a 60 khz signal the long strip chart recorder is simply a super long low pass filter averaging out the doppler somewhat. It really doesn't do that well. The mark-1 eyeball does a better job. Right? On Tue, Jul 27, 2010 at 4:53 AM, Geoff vk2...@ozemail.com.au wrote: On Tue, 27 Jul 2010 09:08:49 am Chuck Harris wrote: I suppose that you could always cheat? Since you know where the transmitter is going to be, if you could get a timenut near to the transmitter to give you a beacon to measure 24hrs prior to the event, you could use the diurnal variations that you observed (observe?) on the beacon to predict the skywave offset due to Doppler at the time of the event. -Chuck Harris Murray Greenman wrote: You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. snipped There is one possible way of getting an accurate reading from a sky wave signal over a short(ish) period. Plot a doppler shift curve with as fine a resolution as you can manage. Then look for a point of inflexion in the curve, that is a point where the second derivative of the curve function is zero. The frequency at that time will be that transmitted as at that instant the path length is not changing. You may have to examine your data set visually and mathematically examine a much smaller section. Of course if you don't get a point of inflexion you'll need much more data :-). Cheers, Geoff vk2tfg. ___ 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] Basic question regarding comparing two frequencies
Oh indeed I agree John. LORAN has spoiled me also at least till nov I hear. The Canadians are a drop better then us at saving the system. I am definitely figuring out the old ways and can't say that I like it all that much. Always have gps for the moment. On Fri, Jul 30, 2010 at 10:08 AM, J. Forster j...@quik.com wrote: Partly. There are hourly jogs in the WWVB signal and also diurnal shifts of the order of a cycle at 60 KHz. The Fluke receivers havs a counter for microseconds, but it's difficult to intrerpret w/o the stripchart too. Frankly, 60 KHz is a PITA IMO. Oh for LORAN! -John == So on a 60 khz signal the long strip chart recorder is simply a super long low pass filter averaging out the doppler somewhat. It really doesn't do that well. The mark-1 eyeball does a better job. Right? On Tue, Jul 27, 2010 at 4:53 AM, Geoff vk2...@ozemail.com.au wrote: On Tue, 27 Jul 2010 09:08:49 am Chuck Harris wrote: I suppose that you could always cheat? Since you know where the transmitter is going to be, if you could get a timenut near to the transmitter to give you a beacon to measure 24hrs prior to the event, you could use the diurnal variations that you observed (observe?) on the beacon to predict the skywave offset due to Doppler at the time of the event. -Chuck Harris Murray Greenman wrote: You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. snipped There is one possible way of getting an accurate reading from a sky wave signal over a short(ish) period. Plot a doppler shift curve with as fine a resolution as you can manage. Then look for a point of inflexion in the curve, that is a point where the second derivative of the curve function is zero. The frequency at that time will be that transmitted as at that instant the path length is not changing. You may have to examine your data set visually and mathematically examine a much smaller section. Of course if you don't get a point of inflexion you'll need much more data :-). Cheers, Geoff vk2tfg. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
The November deadline on the shared stations that hold positions in both the US and Canadian Loran chains is to allow operation to continue in Canada until they close their system... in November. -Chuck Harris paul swed wrote: Oh indeed I agree John. LORAN has spoiled me also at least till nov I hear. The Canadians are a drop better then us at saving the system. I am definitely figuring out the old ways and can't say that I like it all that much. Always have gps for the moment. On Fri, Jul 30, 2010 at 10:08 AM, J. Forsterj...@quik.com wrote: Partly. There are hourly jogs in the WWVB signal and also diurnal shifts of the order of a cycle at 60 KHz. The Fluke receivers havs a counter for microseconds, but it's difficult to intrerpret w/o the stripchart too. Frankly, 60 KHz is a PITA IMO. Oh for LORAN! -John ___ 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] Basic question regarding comparing two frequencies
On Tue, 27 Jul 2010 09:08:49 am Chuck Harris wrote: I suppose that you could always cheat? Since you know where the transmitter is going to be, if you could get a timenut near to the transmitter to give you a beacon to measure 24hrs prior to the event, you could use the diurnal variations that you observed (observe?) on the beacon to predict the skywave offset due to Doppler at the time of the event. -Chuck Harris Murray Greenman wrote: You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. snipped There is one possible way of getting an accurate reading from a sky wave signal over a short(ish) period. Plot a doppler shift curve with as fine a resolution as you can manage. Then look for a point of inflexion in the curve, that is a point where the second derivative of the curve function is zero. The frequency at that time will be that transmitted as at that instant the path length is not changing. You may have to examine your data set visually and mathematically examine a much smaller section. Of course if you don't get a point of inflexion you'll need much more data :-). Cheers, Geoff vk2tfg. ___ 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] Basic question regarding comparing two frequencies
Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity of a setup like this? The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. Is 2.5 ns good enough? What would you gain by using a 16 bit DAC? A ratiometric ADC where the ADC uses the (low pass filtered) CMOS supply as its reference is probably advisable when using high resolution ADCs. A high resolution sigma delta ADC that aloows an external reference to be used may be useful for this application. If 2.5 ns is good enough, I'll bet you can do the whole thing in digital logic. Just get a fast FPGA/CPLD. I haven't done a serious design, but a quick check at some old data sheets shows it's not silly. You could probably bump it up by another factor of 2 with some external (p)ECL chips. If one used an FPGA with an internal 500MHz (use the internal PLL available in some FPGAs) clock and dual edge clocking or a 1GHz internal clock, 1ns resolution should be readily achievable. However it may be advisable to use something like LVDS inputs to alleviate the effects of ground and Vcc bounce. If you need more resolution then one could always sample the outputs of an internal tapped delay line using internal gates as delay elements. With a suitable FPGA a resolution of a few hundred ps is feasible. If the delay line delay is more than 1 clock period then an embedded calibration of the delay line is possible from the coarse (1ns) count and the fine count from the internal tapped delay line. Bruce ___ 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] Basic question regarding comparing two frequencies
Hi, the original was built using a HP10811 oscillator and a Garmin 17 GPS that delivered PPS. The HP10811 ran a divider by 10 by 10 by 10 down to 1 hz. I was the servo that adjusted the EFC of the OCXO so that the PPS matched the 1Hz. The divider clocked a counter of three decades of BCD, with latches driving a 3 decade DAC. (about 12 bits of modified R-2R chain) The latches were triggered by a pendulum clock being observed, or the PPS of the Garmin GPS receiver. That delivered a DC signal that could be logged to observe phase drift on a chart recorder or data logger. For higher frequencies, I used the D FF phase detector, which could be used at 1MHz, 100kHZ, 10kHz, 1kHz or 100Hz, depending on how sensitive I wanted the frequency (phase) comparison. The test was that the phase noise must be less than one tenth of a period, so the automatic regeneration of the more significant digits in XL afterwards did not have ambiguities. For any oscillator under examination I used a 4046 PLL to generate a high enough frequency to drive the phase detector. My 1 Hz pendulum clock generated a 1kHz signal via the 4046 so the phase detector gave 1ms full scale on the chart recorder, with a resolution of 1 microsecond. The low pass filtering inherent in the PLL was not a worry as I was concerned with longer term drift. It all avoids using digital processing and other instruments, the main reason for that was to be able to leave it running for weeks with only low battery backup power required. cheers, Neville Michie On 26/07/2010, at 3:12 PM, Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity of a setup like this? The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. Is 2.5 ns good enough? What would you gain by using a 16 bit DAC? If 2.5 ns is good enough, I'll bet you can do the whole thing in digital logic. Just get a fast FPGA/CPLD. I haven't done a serious design, but a quick check at some old data sheets shows it's not silly. You could probably bump it up by another factor of 2 with some external (p)ECL chips. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Hi, ten years ago not having a super counter I copied the input circuit of the Austron 2110 that using an XOR gate mixes 5 MHz with 500 Hz getting 5.0005 MHz. It is devided down to 1.0001 Mhz which in turn is mixed in 74 HC 74 D F/F giving 100 Hz, that most counters are able to count at high resolution. Still use it today. May be a time-nuts project. Bert Kehren In a message dated 7/26/2010 2:15:57 A.M. Eastern Daylight Time, bruce.griffi...@xtra.co.nz writes: Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity of a setup like this? The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. Is 2.5 ns good enough? What would you gain by using a 16 bit DAC? A ratiometric ADC where the ADC uses the (low pass filtered) CMOS supply as its reference is probably advisable when using high resolution ADCs. A high resolution sigma delta ADC that aloows an external reference to be used may be useful for this application. If 2.5 ns is good enough, I'll bet you can do the whole thing in digital logic. Just get a fast FPGA/CPLD. I haven't done a serious design, but a quick check at some old data sheets shows it's not silly. You could probably bump it up by another factor of 2 with some external (p)ECL chips. If one used an FPGA with an internal 500MHz (use the internal PLL available in some FPGAs) clock and dual edge clocking or a 1GHz internal clock, 1ns resolution should be readily achievable. However it may be advisable to use something like LVDS inputs to alleviate the effects of ground and Vcc bounce. If you need more resolution then one could always sample the outputs of an internal tapped delay line using internal gates as delay elements. With a suitable FPGA a resolution of a few hundred ps is feasible. If the delay line delay is more than 1 clock period then an embedded calibration of the delay line is possible from the coarse (1ns) count and the fine count from the internal tapped delay line. Bruce ___ 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] Basic question regarding comparing two frequencies
Sorry Bert, I don't follow the last part about the 100Hz - can you explain further please? (and is that 100.00 or 100.01 Hz?) Peter On 26 July 2010 14:27, ewkeh...@aol.com wrote: Hi, ten years ago not having a super counter I copied the input circuit of the Austron 2110 that using an XOR gate mixes 5 MHz with 500 Hz getting 5.0005 MHz. It is devided down to 1.0001 Mhz which in turn is mixed in 74 HC 74 D F/F giving 100 Hz, that most counters are able to count at high resolution. Still use it today. May be a time-nuts project. Bert Kehren ___ 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] Basic question regarding comparing two frequencies
Hi I believe what they do is: DSB modulate the 5 MHz with 500 Hz to get 5.0005 and 4.9995 MHz Filter out the 4.9995 MHz with a crystal filter or by using an I/Q modulator (I believe Austron did the I/Q thing rather than the filter). Divide the result by 5 to get 1.0001 MHz Mix the 1.0001 with an incoming 1 MHz from the DUT Look at the 100 Hz beat note out of the mixer. That all (of course) assumes you have 1 MHz out of the DUT in the first place. Otherwise there's a divide the DUT to 1 MHz step in there as well. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Vince Sent: Monday, July 26, 2010 10:32 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sorry Bert, I don't follow the last part about the 100Hz - can you explain further please? (and is that 100.00 or 100.01 Hz?) Peter On 26 July 2010 14:27, ewkeh...@aol.com wrote: Hi, ten years ago not having a super counter I copied the input circuit of the Austron 2110 that using an XOR gate mixes 5 MHz with 500 Hz getting 5.0005 MHz. It is devided down to 1.0001 Mhz which in turn is mixed in 74 HC 74 D F/F giving 100 Hz, that most counters are able to count at high resolution. Still use it today. May be a time-nuts project. Bert Kehren ___ 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] Basic question regarding comparing two frequencies
Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I'm wondering why divide the frequency at all. Seems to me you would get much greater resolution if you did the phase comparison at the native frequency. Regards. Max. K 4 O D S. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com - Original Message - From: Neville Michie namic...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 26, 2010 1:19 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Hi, the original was built using a HP10811 oscillator and a Garmin 17 GPS that delivered PPS. The HP10811 ran a divider by 10 by 10 by 10 down to 1 hz. I was the servo that adjusted the EFC of the OCXO so that the PPS matched the 1Hz. The divider clocked a counter of three decades of BCD, with latches driving a 3 decade DAC. (about 12 bits of modified R-2R chain) The latches were triggered by a pendulum clock being observed, or the PPS of the Garmin GPS receiver. That delivered a DC signal that could be logged to observe phase drift on a chart recorder or data logger. For higher frequencies, I used the D FF phase detector, which could be used at 1MHz, 100kHZ, 10kHz, 1kHz or 100Hz, depending on how sensitive I wanted the frequency (phase) comparison. The test was that the phase noise must be less than one tenth of a period, so the automatic regeneration of the more significant digits in XL afterwards did not have ambiguities. For any oscillator under examination I used a 4046 PLL to generate a high enough frequency to drive the phase detector. My 1 Hz pendulum clock generated a 1kHz signal via the 4046 so the phase detector gave 1ms full scale on the chart recorder, with a resolution of 1 microsecond. The low pass filtering inherent in the PLL was not a worry as I was concerned with longer term drift. It all avoids using digital processing and other instruments, the main reason for that was to be able to leave it running for weeks with only low battery backup power required. cheers, Neville Michie On 26/07/2010, at 3:12 PM, Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity of a setup like this? The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. Is 2.5 ns good enough? What would you gain by using a 16 bit DAC? If 2.5 ns is good enough, I'll bet you can do the whole thing in digital logic. Just get a fast FPGA/CPLD. I haven't done a serious design, but a quick check at some old data sheets shows it's not silly. You could probably bump it up by another factor of 2 with some external (p)ECL chips. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] Basic question regarding comparing two frequencies
Hi, Bob since has explained how the 1.0001 MHz are generated. My Austron uses a Xtal filter. If you want a scan of the circuit contact me direst. The resulting 100 Hz out of the D F/F results in a high resolution representation. 1 Hz is equal to 1E 6. If you now count the 100Hz with a counter that has a recipical mode like the 5345, 5335 or Racal Dana 1992 you easily get 1 E-12 resolution or better. Bert In a message dated 7/26/2010 10:35:53 A.M. Eastern Daylight Time, pvi...@theiet.org writes: Sorry Bert, I don't follow the last part about the 100Hz - can you explain further please? (and is that 100.00 or 100.01 Hz?) Peter On 26 July 2010 14:27, ewkeh...@aol.com wrote: Hi, ten years ago not having a super counter I copied the input circuit of the Austron 2110 that using an XOR gate mixes 5 MHz with 500 Hz getting 5.0005 MHz. It is devided down to 1.0001 Mhz which in turn is mixed in 74 HC 74 D F/F giving 100 Hz, that most counters are able to count at high resolution. Still use it today. May be a time-nuts project. Bert Kehren ___ 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] Basic question regarding comparing two frequencies
-Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal frequency: 1. Set Rx to approximate frequency of unknown signal, AM mode 2. Adjust generator to create a clean audio beat note (power, freq + 600 Hz audio freq, narrow AM filter) 3. Be sure clockwise rotation of generator frequency knob increases audio beat note frequency. Tune generator to upper side of signal if necessary 4. Read peak audio frequency from Spectrum Lab display 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz error) from generator dial reading for result. Example measuring WWV @ 10 MHz: Rx tuned to 10 MHz, AM mode, Narrow Filter Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) generator signal. Adjust level for cleanest audio tone. Generator frequency tuned to generate 600 Hz beat note reading in Spectrum Lab Generator frequency reads 10.000599954 Audio frequency increases as generator frequency is increased Spectrum Lab reads audio frequency 600.00 Hz Spectrum Lab frequency readout error known to be .046 Hz high (actual audio frequency is 599.954Hz) Calculation: Unknown freq = Fgen-(Fspeclab-Fspeclaberr) WWV freq = 10,000,599.954Hz-(600-.046Hz) = 10,000,000.000Hz +/-.01Hz Any suggestions appreciated. Guy N2GL ___ 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] Basic question regarding comparing two frequencies
Hi Rather than having the 940 in there, why not just build a (simple) direct conversion receiver? Feed something like the 3335 or 6061 into one port of a suitable mixer. Feed the band pass filtered signal from the antenna into another port. Run the IF output into a preamp / filter and then into the sound card. You'll get DSB down to the audio chain, but that can be fixed with more hardware. Often it's a non-issue. It all depends on what sort of signal you are after. Another idea: Butcher the sound card and feed it a synthesized clock that's locked to the z3816. One less step in the data reduction / one less thing to worry about. The sound card *might* even run off of one of the outputs the z3816 already generates. You'd have an odd sample rate, but that's not a big deal. A comment: Cleaner is always going to be better on the RF generator that is your ultimate reference. Anything you can do to improve close in phase noise will likely help things out. Lots of possibilities. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Guy Lewis Sent: Monday, July 26, 2010 4:51 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies -Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal frequency: 1. Set Rx to approximate frequency of unknown signal, AM mode 2. Adjust generator to create a clean audio beat note (power, freq + 600 Hz audio freq, narrow AM filter) 3. Be sure clockwise rotation of generator frequency knob increases audio beat note frequency. Tune generator to upper side of signal if necessary 4. Read peak audio frequency from Spectrum Lab display 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz error) from generator dial reading for result. Example measuring WWV @ 10 MHz: Rx tuned to 10 MHz, AM mode, Narrow Filter Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) generator signal. Adjust level for cleanest audio tone. Generator frequency tuned to generate 600 Hz beat note reading in Spectrum Lab Generator frequency reads 10.000599954 Audio frequency increases as generator frequency is increased Spectrum Lab reads audio frequency 600.00 Hz Spectrum Lab frequency readout error known to be .046 Hz high (actual audio frequency is 599.954Hz) Calculation: Unknown freq = Fgen-(Fspeclab-Fspeclaberr) WWV freq = 10,000,599.954Hz-(600-.046Hz) = 10,000,000.000Hz +/-.01Hz Any suggestions appreciated. Guy N2GL ___ 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] Basic question regarding comparing two frequencies
What about using an HP 3586 B or C, locked to a local standard, and GPIB interface and averaging the data? It goes to 0.1 Hz right out of the box as I remember. FWIW, -John = Hi Rather than having the 940 in there, why not just build a (simple) direct conversion receiver? Feed something like the 3335 or 6061 into one port of a suitable mixer. Feed the band pass filtered signal from the antenna into another port. Run the IF output into a preamp / filter and then into the sound card. You'll get DSB down to the audio chain, but that can be fixed with more hardware. Often it's a non-issue. It all depends on what sort of signal you are after. Another idea: Butcher the sound card and feed it a synthesized clock that's locked to the z3816. One less step in the data reduction / one less thing to worry about. The sound card *might* even run off of one of the outputs the z3816 already generates. You'd have an odd sample rate, but that's not a big deal. A comment: Cleaner is always going to be better on the RF generator that is your ultimate reference. Anything you can do to improve close in phase noise will likely help things out. Lots of possibilities. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Guy Lewis Sent: Monday, July 26, 2010 4:51 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies -Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal frequency: 1. Set Rx to approximate frequency of unknown signal, AM mode 2. Adjust generator to create a clean audio beat note (power, freq + 600 Hz audio freq, narrow AM filter) 3. Be sure clockwise rotation of generator frequency knob increases audio beat note frequency. Tune generator to upper side of signal if necessary 4. Read peak audio frequency from Spectrum Lab display 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz error) from generator dial reading for result. Example measuring WWV @ 10 MHz: Rx tuned to 10 MHz, AM mode, Narrow Filter Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) generator signal. Adjust level for cleanest audio tone. Generator frequency tuned to generate 600 Hz beat note reading in Spectrum Lab Generator frequency reads 10.000599954 Audio frequency increases as generator frequency is increased Spectrum Lab reads audio frequency 600.00 Hz Spectrum Lab frequency readout error known to be .046 Hz high (actual audio frequency is 599.954Hz) Calculation: Unknown freq = Fgen-(Fspeclab-Fspeclaberr) WWV freq = 10,000,599.954Hz-(600-.046Hz) = 10,000,000.000Hz +/-.01Hz Any suggestions appreciated. Guy N2GL ___ 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] Basic question regarding comparing two frequencies
The only way to have that kind of meaningful accuracy with an on-air signal outside of ground wave range (a.k.a FMT) is to average over a long time (days) to average out the shift due to variations in propagation. The altitude of the layer reflecting the signals changes over time, so the distance the signal has to travel changes too, causing a Doppler shift. Measuring WWV at 15MHz over a 24 hour period shows about 1Hz pp variation (that's what I found the last time I did with my Thunderbolt locked HP3586). If you make a short term measurement (a few minutes) you may be off by 1/2Hz easily regardless of the accuracy of your equipment. You may well be able to measure the frequency of the incoming signal to 0.001Hz, but it will be sheer luck if it is the same frequency they are transmitting. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Guy Lewis g...@coho.net Sender: time-nuts-boun...@febo.com Date: Mon, 26 Jul 2010 13:50:49 To: 'Discussion of precise time and frequency measurement'time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Basic question regarding comparing two frequencies -Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal frequency: 1. Set Rx to approximate frequency of unknown signal, AM mode 2. Adjust generator to create a clean audio beat note (power, freq + 600 Hz audio freq, narrow AM filter) 3. Be sure clockwise rotation of generator frequency knob increases audio beat note frequency. Tune generator to upper side of signal if necessary 4. Read peak audio frequency from Spectrum Lab display 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz error) from generator dial reading for result. Example measuring WWV @ 10 MHz: Rx tuned to 10 MHz, AM mode, Narrow Filter Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) generator signal. Adjust level for cleanest audio tone. Generator frequency tuned to generate 600 Hz beat note reading in Spectrum Lab Generator frequency reads 10.000599954 Audio frequency increases as generator frequency is increased Spectrum Lab reads audio frequency 600.00 Hz Spectrum Lab frequency readout error known to be .046 Hz high (actual audio frequency is 599.954Hz) Calculation: Unknown freq = Fgen-(Fspeclab-Fspeclaberr) WWV freq = 10,000,599.954Hz-(600-.046Hz) = 10,000,000.000Hz +/-.01Hz Any suggestions appreciated. Guy N2GL ___ 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] Basic question regarding comparing two frequencies
Here's data showing Doppler (and other effects) on WWV as received in Dayton, OH over several days. I took this by reading an HP 3586C frequency counter output via GPIB -- which seems to be a good technique for long-term HF frequency gathering. You need to figure out a way to remove outliers and signal loss periods from any averaging, but the 0.01 dB amplitude readout gives you a tool to help do that. http://www.febo.com/pages/hf_stability/ John Didier Juges wrote: The only way to have that kind of meaningful accuracy with an on-air signal outside of ground wave range (a.k.a FMT) is to average over a long time (days) to average out the shift due to variations in propagation. The altitude of the layer reflecting the signals changes over time, so the distance the signal has to travel changes too, causing a Doppler shift. Measuring WWV at 15MHz over a 24 hour period shows about 1Hz pp variation (that's what I found the last time I did with my Thunderbolt locked HP3586). If you make a short term measurement (a few minutes) you may be off by 1/2Hz easily regardless of the accuracy of your equipment. You may well be able to measure the frequency of the incoming signal to 0.001Hz, but it will be sheer luck if it is the same frequency they are transmitting. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Guy Lewis g...@coho.net Sender: time-nuts-boun...@febo.com Date: Mon, 26 Jul 2010 13:50:49 To: 'Discussion of precise time and frequency measurement'time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Basic question regarding comparing two frequencies -Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal frequency: 1. Set Rx to approximate frequency of unknown signal, AM mode 2. Adjust generator to create a clean audio beat note (power, freq + 600 Hz audio freq, narrow AM filter) 3. Be sure clockwise rotation of generator frequency knob increases audio beat note frequency. Tune generator to upper side of signal if necessary 4. Read peak audio frequency from Spectrum Lab display 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz error) from generator dial reading for result. Example measuring WWV @ 10 MHz: Rx tuned to 10 MHz, AM mode, Narrow Filter Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) generator signal. Adjust level for cleanest audio tone. Generator frequency tuned to generate 600 Hz beat note reading in Spectrum Lab Generator frequency reads 10.000599954 Audio frequency increases as generator frequency is increased Spectrum Lab reads audio frequency 600.00 Hz Spectrum Lab frequency readout error known to be .046 Hz high (actual audio frequency is 599.954Hz) Calculation: Unknown freq = Fgen-(Fspeclab-Fspeclaberr) WWV freq = 10,000,599.954Hz-(600-.046Hz) = 10,000,000.000Hz +/-.01Hz Any suggestions appreciated. Guy N2GL ___ 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
Re: [time-nuts] Basic question regarding comparing two frequencies
Thanks Didier, John, John, Bob, all: You may have noticed, I came in next to last out of 35 entries in the last FMT. I was using the power line as an audio reference, but even that unstable reference was minor considering my 30 Hz lissajou error or 60 Hz error wrong sideband error! I am taking this as a challenge! I do see the shift on the on-air signals and try to mentally average them out over the 30 seconds or so I will get after setting up the equipment for each FMT frequency. I am learning a lot from this list. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Didier Juges Sent: Monday, July 26, 2010 2:28 PM To: Time-Nuts Subject: Re: [time-nuts] Basic question regarding comparing two frequencies The only way to have that kind of meaningful accuracy with an on-air signal outside of ground wave range (a.k.a FMT) is to average over a long time (days) to average out the shift due to variations in propagation. The altitude of the layer reflecting the signals changes over time, so the distance the signal has to travel changes too, causing a Doppler shift. Measuring WWV at 15MHz over a 24 hour period shows about 1Hz pp variation (that's what I found the last time I did with my Thunderbolt locked HP3586). If you make a short term measurement (a few minutes) you may be off by 1/2Hz easily regardless of the accuracy of your equipment. You may well be able to measure the frequency of the incoming signal to 0.001Hz, but it will be sheer luck if it is the same frequency they are transmitting. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Guy Lewis g...@coho.net Sender: time-nuts-boun...@febo.com Date: Mon, 26 Jul 2010 13:50:49 To: 'Discussion of precise time and frequency measurement'time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Basic question regarding comparing two frequencies -Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal frequency: 1. Set Rx to approximate frequency of unknown signal, AM mode 2. Adjust generator to create a clean audio beat note (power, freq + 600 Hz audio freq, narrow AM filter) 3. Be sure clockwise rotation of generator frequency knob increases audio beat note frequency. Tune generator to upper side of signal if necessary 4. Read peak audio frequency from Spectrum Lab display 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz error) from generator dial reading for result. Example measuring WWV @ 10 MHz: Rx tuned to 10 MHz, AM mode, Narrow Filter Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) generator signal. Adjust level for cleanest audio tone. Generator frequency tuned to generate 600 Hz beat note reading in Spectrum Lab Generator frequency reads 10.000599954 Audio frequency increases as generator frequency is increased Spectrum Lab reads audio frequency 600.00 Hz Spectrum Lab frequency readout error known to be .046 Hz high (actual audio frequency is 599.954Hz) Calculation: Unknown freq = Fgen-(Fspeclab-Fspeclaberr) WWV freq = 10,000,599.954Hz-(600-.046Hz) = 10,000,000.000Hz +/-.01Hz Any suggestions appreciated. Guy N2GL
Re: [time-nuts] Basic question regarding comparing two frequencies
I like the 3586 a lot, it's amazing what you can do with it. However, if you send the audio (beat note) to a computer or other instrument, keep in mind that the BFOs are not phase locked to the reference, they are just free standing crystal oscillators, and they may be off by a few Hz. If you want to use the beat note for high accuracy frequency measurement, it would be a good idea to phase lock the BFOs to the reference (at least the one you are going to use, you don't need to do both). The carrier frequency measurement system is independant of the BFOs. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: J. Forster j...@quik.com Sender: time-nuts-boun...@febo.com Date: Mon, 26 Jul 2010 14:23:02 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: j...@quik.com, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Basic question regarding comparing two frequencies What about using an HP 3586 B or C, locked to a local standard, and GPIB interface and averaging the data? It goes to 0.1 Hz right out of the box as I remember. FWIW, -John = Hi Rather than having the 940 in there, why not just build a (simple) direct conversion receiver? Feed something like the 3335 or 6061 into one port of a suitable mixer. Feed the band pass filtered signal from the antenna into another port. Run the IF output into a preamp / filter and then into the sound card. You'll get DSB down to the audio chain, but that can be fixed with more hardware. Often it's a non-issue. It all depends on what sort of signal you are after. Another idea: Butcher the sound card and feed it a synthesized clock that's locked to the z3816. One less step in the data reduction / one less thing to worry about. The sound card *might* even run off of one of the outputs the z3816 already generates. You'd have an odd sample rate, but that's not a big deal. A comment: Cleaner is always going to be better on the RF generator that is your ultimate reference. Anything you can do to improve close in phase noise will likely help things out. Lots of possibilities. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Guy Lewis Sent: Monday, July 26, 2010 4:51 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies -Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal frequency: 1. Set Rx to approximate frequency of unknown signal, AM mode 2. Adjust generator to create a clean audio beat note (power, freq + 600 Hz audio freq, narrow AM filter) 3. Be sure clockwise rotation of generator frequency knob increases audio beat note frequency. Tune generator to upper side of signal if necessary 4. Read peak audio frequency from Spectrum Lab display 5. Subtract audio frequency (Spectrum Lab reading -measured .046 Hz error) from generator dial reading for result. Example measuring WWV @ 10 MHz: Rx tuned to 10 MHz, AM mode, Narrow Filter Antenna signal mixed with -70 dbm (-30dbm if leaked across Rx switch) generator
Re: [time-nuts] Basic question regarding comparing two frequencies
It's a remarkable, and largely unappreciated, instrument. I passed them up for years, thinking they were only useful for analog multiplex telephony. It was not until I bought one, almost by accident, at the tail end of a flea and started to play with it, did its utility became apparent. Thje ability to lock onto a received carrier and count it is a delight, IMO. A note on the data you get out. If you digitally high pass filter it, you should be able to get a measure of the path stability. I've done this with both an HP 117A on WWVB and WWV but not yet with the 3586C. The day-to-day variation is dramatic. Best, -John I like the 3586 a lot, it's amazing what you can do with it. However, if you send the audio (beat note) to a computer or other instrument, keep in mind that the BFOs are not phase locked to the reference, they are just free standing crystal oscillators, and they may be off by a few Hz. If you want to use the beat note for high accuracy frequency measurement, it would be a good idea to phase lock the BFOs to the reference (at least the one you are going to use, you don't need to do both). The carrier frequency measurement system is independant of the BFOs. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: J. Forster j...@quik.com Sender: time-nuts-boun...@febo.com Date: Mon, 26 Jul 2010 14:23:02 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: j...@quik.com, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Basic question regarding comparing two frequencies What about using an HP 3586 B or C, locked to a local standard, and GPIB interface and averaging the data? It goes to 0.1 Hz right out of the box as I remember. FWIW, -John = Hi Rather than having the 940 in there, why not just build a (simple) direct conversion receiver? Feed something like the 3335 or 6061 into one port of a suitable mixer. Feed the band pass filtered signal from the antenna into another port. Run the IF output into a preamp / filter and then into the sound card. You'll get DSB down to the audio chain, but that can be fixed with more hardware. Often it's a non-issue. It all depends on what sort of signal you are after. Another idea: Butcher the sound card and feed it a synthesized clock that's locked to the z3816. One less step in the data reduction / one less thing to worry about. The sound card *might* even run off of one of the outputs the z3816 already generates. You'd have an odd sample rate, but that's not a big deal. A comment: Cleaner is always going to be better on the RF generator that is your ultimate reference. Anything you can do to improve close in phase noise will likely help things out. Lots of possibilities. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Guy Lewis Sent: Monday, July 26, 2010 4:51 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies -Original Message- There is another way to compare two frequencies, relevant when they are very close together... - I am trying to measure the frequency of a distant on-air signal, with path fading, Doppler shift, and maybe even AM modulation and would appreciate comments that might improve accuracy to better than .01Hz. The idea is to measure the frequency of an audio beat between a disciplined synthesized generator and the on-air signal, the subtract out the difference. Here is what I am doing: Equipment: GPS Disciplined Oscillator (HP 3816A with antenna) Synthesized generator with .001Hz resolution (HP3335A locked to GPS 10 MHz reference) PC running Spectrum Lab sound card audio spectrum analyzer software Second locked synthesizer (Fluke 6061A) to determine Spectrum Lab frequency error AM receiver (TS940 for 30kHz to 30 MHz) and antenna covering unknown frequency to be measured Input signal combiner (Merrimac 50 ohm combiner) or leak into receiver across Ext Rx switch Setup: 1a. Disable TS940 transmit mode (power set to minimum, PTT disabled, don't touch SEND) Install power splitter at Rx input to mix unknown and synthesized generator signals --or:-- 1b. (preferred alternative, to avoid accidently transmitting into the generator), leak generator signal into TS940 across Rx antenna switch at a higher level 2. Lock generator to external GPSDO. All OCXOs run full time 3. Connect audio out to PC running Spectrum Lab 4. Allow PC to warm up for at least 30 minutes and measure second locked synthesized generator near the expected unknown frequency to determine Spectrum Lab measurement error Measurement of unknown signal
Re: [time-nuts] Basic question regarding comparing two frequencies
Didier Juges wrote: I like the 3586 a lot, it's amazing what you can do with it. However, if you send the audio (beat note) to a computer or other instrument, keep in mind that the BFOs are not phase locked to the reference, they are just free standing crystal oscillators, and they may be off by a few Hz. If you want to use the beat note for high accuracy frequency measurement, it would be a good idea to phase lock the BFOs to the reference (at least the one you are going to use, you don't need to do both). The carrier frequency measurement system is independant of the BFOs. I've measured the BFO frequency in my 3586Cs and while the absolute frequencies are off by a Hertz or two (and USB and LSB come from separate crystals), they are remarkably stable once the receiver is warmed up. They're derived from an ~1.9 MHz crystal that's divided by a large number (IIRC 1000) so any crystal drift is reduced significantly. Therefore, you don't want to derive frequency directly from the audio output tone, but for relative measurements the BFO is stable enough for any off-air measurement. And as Didier notes, the BFO isn't in the frequency counter path, so doesn't create an error there. John ___ 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] Basic question regarding comparing two frequencies
You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. For what it's worth, the method I use for HF frequency measurements is much simpler. I use a receiver which I can lock to my GPSDO (RACAL RA6790/GM and HP Z3801A), and thereafter calibration is simply an issue of getting the sound card sampling rate correct at the software spectrum analyser, which you can do with a 1kHz reference from the GPSDO. No complicated signal generators, signal injection, or AM mode with AGC problems. I use Peter G3PLX's SBSpectrum as the analyser, where you can trim the sample rate in tiny steps. It also has a frequency resolution of 25mHz, which is more than adequate for HF. My combination has won FMCs, but I still can't resolve 0.01Hz off-air. Whatever you do (with a sky wave signal) must be done over a long time frame in order to be sure of getting closer than 1ppm. 73, Murray ZL1BPU ___ 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] Basic question regarding comparing two frequencies
The reason to divide was that the signal from the phase detector folds back as the phase shift gets to 360*. At 10Mhz the fold back occurs every 100ns. At 100kHz it is every 10usec. As the fold back (359.9 - 0.1degree) zone may have false triggering or other noise it made sense for it to be made a less frequent event. Also I did not have faith in the CMOS output giving a true PWM average when clocking so fast. Chip capacitance produces a more significant amount of current at the higher clock rate. It may well work OK at the 10MHz rate. I also needed to divide to increase the full scale time to account for large time jitter of mechanical clocks so I set it up to divide at any of a wide range of frequencies. Cheers, Neville Michie On 27/07/2010, at 3:12 AM, Max Robinson wrote: Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I'm wondering why divide the frequency at all. Seems to me you would get much greater resolution if you did the phase comparison at the native frequency. Regards. Max. K 4 O D S. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com - Original Message - From: Neville Michie namic...@gmail.com To: Discussion of precise time and frequency measurement time- n...@febo.com Sent: Monday, July 26, 2010 1:19 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Hi, the original was built using a HP10811 oscillator and a Garmin 17 GPS that delivered PPS. The HP10811 ran a divider by 10 by 10 by 10 down to 1 hz. I was the servo that adjusted the EFC of the OCXO so that the PPS matched the 1Hz. The divider clocked a counter of three decades of BCD, with latches driving a 3 decade DAC. (about 12 bits of modified R-2R chain) The latches were triggered by a pendulum clock being observed, or the PPS of the Garmin GPS receiver. That delivered a DC signal that could be logged to observe phase drift on a chart recorder or data logger. For higher frequencies, I used the D FF phase detector, which could be used at 1MHz, 100kHZ, 10kHz, 1kHz or 100Hz, depending on how sensitive I wanted the frequency (phase) comparison. The test was that the phase noise must be less than one tenth of a period, so the automatic regeneration of the more significant digits in XL afterwards did not have ambiguities. For any oscillator under examination I used a 4046 PLL to generate a high enough frequency to drive the phase detector. My 1 Hz pendulum clock generated a 1kHz signal via the 4046 so the phase detector gave 1ms full scale on the chart recorder, with a resolution of 1 microsecond. The low pass filtering inherent in the PLL was not a worry as I was concerned with longer term drift. It all avoids using digital processing and other instruments, the main reason for that was to be able to leave it running for weeks with only low battery backup power required. cheers, Neville Michie On 26/07/2010, at 3:12 PM, Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity of a setup like this? The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. Is 2.5 ns good enough? What would you gain by using a 16 bit DAC? If 2.5 ns is good enough, I'll bet you can do the whole thing in digital logic. Just get a fast FPGA/CPLD. I haven't done a serious design, but a quick check at some old data sheets shows it's not silly. You could probably bump it up by another factor of 2 with some external (p)ECL chips. -- These are my opinions, not necessarily my employer's. I hate
Re: [time-nuts] Basic question regarding comparing two frequencies
I suppose that you could always cheat? Since you know where the transmitter is going to be, if you could get a timenut near to the transmitter to give you a beacon to measure 24hrs prior to the event, you could use the diurnal variations that you observed (observe?) on the beacon to predict the skywave offset due to Doppler at the time of the event. -Chuck Harris Murray Greenman wrote: You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. For what it's worth, the method I use for HF frequency measurements is much simpler. I use a receiver which I can lock to my GPSDO (RACAL RA6790/GM and HP Z3801A), and thereafter calibration is simply an issue of getting the sound card sampling rate correct at the software spectrum analyser, which you can do with a 1kHz reference from the GPSDO. No complicated signal generators, signal injection, or AM mode with AGC problems. I use Peter G3PLX's SBSpectrum as the analyser, where you can trim the sample rate in tiny steps. It also has a frequency resolution of 25mHz, which is more than adequate for HF. My combination has won FMCs, but I still can't resolve 0.01Hz off-air. Whatever you do (with a sky wave signal) must be done over a long time frame in order to be sure of getting closer than 1ppm. 73, Murray ZL1BPU ___ 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] Basic question regarding comparing two frequencies
... I use Peter G3PLX's SBSpectrum as the analyser, where you can trim the sample rate in tiny steps. It also has a frequency resolution of 25mHz, which is more than adequate for HF. My combination has won FMCs, but I still can't resolve 0.01Hz off-air. ... 73, Murray ZL1BPU You might also take a look at fldigi. It uses libsamplerate for conversion so you can do +/- ppm correction on the sound input, and also offers a tracking frequency measurement mode. A couple of years ago, I calibrated my radio clock against WWV at 10 MHz, then applied the resampling correction to get the sound card right, and then placed highly in the ARRL 7 Mhz FMT using this method. Leigh. ___ 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] Basic question regarding comparing two frequencies
Hi I've used the 6790 for this sort of thing before. It's a good choice since the whole signal chain is synthesized (if I remember correctly ..). It's still going to be tough to hit the originally requested accuracy with one. Bob On Jul 26, 2010, at 6:34 PM, Murray Greenman wrote: You guys are trying to crack a nut with a sledgehammer! For a start, as Didier says, you can't possibly read the frequency of a sky-wave signal to 0.01Hz in any short time frame since the Doppler on the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only infer it closer than that by studying the frequency in the very long term. In addition, you'll never know how much of the daily variation is ionospheric, and how much is due to thermal changes at the source. For what it's worth, the method I use for HF frequency measurements is much simpler. I use a receiver which I can lock to my GPSDO (RACAL RA6790/GM and HP Z3801A), and thereafter calibration is simply an issue of getting the sound card sampling rate correct at the software spectrum analyser, which you can do with a 1kHz reference from the GPSDO. No complicated signal generators, signal injection, or AM mode with AGC problems. I use Peter G3PLX's SBSpectrum as the analyser, where you can trim the sample rate in tiny steps. It also has a frequency resolution of 25mHz, which is more than adequate for HF. My combination has won FMCs, but I still can't resolve 0.01Hz off-air. Whatever you do (with a sky wave signal) must be done over a long time frame in order to be sure of getting closer than 1ppm. 73, Murray ZL1BPU ___ 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] Basic question regarding comparing two frequencies
Understood. Regards. Max. K 4 O D S. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com - Original Message - From: Neville Michie namic...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 26, 2010 5:48 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies The reason to divide was that the signal from the phase detector folds back as the phase shift gets to 360*. At 10Mhz the fold back occurs every 100ns. At 100kHz it is every 10usec. As the fold back (359.9 - 0.1degree) zone may have false triggering or other noise it made sense for it to be made a less frequent event. Also I did not have faith in the CMOS output giving a true PWM average when clocking so fast. Chip capacitance produces a more significant amount of current at the higher clock rate. It may well work OK at the 10MHz rate. I also needed to divide to increase the full scale time to account for large time jitter of mechanical clocks so I set it up to divide at any of a wide range of frequencies. Cheers, Neville Michie On 27/07/2010, at 3:12 AM, Max Robinson wrote: Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I'm wondering why divide the frequency at all. Seems to me you would get much greater resolution if you did the phase comparison at the native frequency. Regards. Max. K 4 O D S. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com - Original Message - From: Neville Michie namic...@gmail.com To: Discussion of precise time and frequency measurement time- n...@febo.com Sent: Monday, July 26, 2010 1:19 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Hi, the original was built using a HP10811 oscillator and a Garmin 17 GPS that delivered PPS. The HP10811 ran a divider by 10 by 10 by 10 down to 1 hz. I was the servo that adjusted the EFC of the OCXO so that the PPS matched the 1Hz. The divider clocked a counter of three decades of BCD, with latches driving a 3 decade DAC. (about 12 bits of modified R-2R chain) The latches were triggered by a pendulum clock being observed, or the PPS of the Garmin GPS receiver. That delivered a DC signal that could be logged to observe phase drift on a chart recorder or data logger. For higher frequencies, I used the D FF phase detector, which could be used at 1MHz, 100kHZ, 10kHz, 1kHz or 100Hz, depending on how sensitive I wanted the frequency (phase) comparison. The test was that the phase noise must be less than one tenth of a period, so the automatic regeneration of the more significant digits in XL afterwards did not have ambiguities. For any oscillator under examination I used a 4046 PLL to generate a high enough frequency to drive the phase detector. My 1 Hz pendulum clock generated a 1kHz signal via the 4046 so the phase detector gave 1ms full scale on the chart recorder, with a resolution of 1 microsecond. The low pass filtering inherent in the PLL was not a worry as I was concerned with longer term drift. It all avoids using digital processing and other instruments, the main reason for that was to be able to leave it running for weeks with only low battery backup power required. cheers, Neville Michie On 26/07/2010, at 3:12 PM, Hal Murray wrote: There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity
Re: [time-nuts] Basic question regarding comparing two frequencies
jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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] Basic question regarding comparing two frequencies
The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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] Basic question regarding comparing two frequencies
You can always use the ready, fire, aim, approach. Make a tiny adjustment and see if it makes the Lissajous figure move faster, so you know your going the wrong way, or slower, and then you'll know your on the correct path. Steve On 26/07/2010, J. L. Trantham jlt...@att.net wrote: The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ 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] Basic question regarding comparing two frequencies
No, if it's moving left to right the OCXO is low (I just had my coffee). Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. L. Trantham Sent: Sunday, July 25, 2010 7:05 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
J. Forster wrote: Probably yes. There are also a number of lower cost instruments (just above consumer grade)like HF-VHF VNAs that implement much of the smarts in a PC on the market. As to high end instruments w/ USB or Ethernet, I'm not so sure. The USA is doing less and less hardware development, so instruments are not being bought in anything like the quantity as in the past. A lot of the new Agilent and Tek gear (at all price points) seem to have Ethernet, especially if it has a LCD front panel. (there's that LXI interface thing, too) Even power supplies. Not much USB (at least for control.. these days, using a USB stick for data transfer seems ubiquitous.. they've replaced the floppy drive on scopes, etc.), except for RF power meters.. There's a whole raft of power meter heads that are USB, which makes sense.. the hard part is in the actual sensor, not in the meter which displays the power reading. Mind you, because they do this by using single board PCs instead of the dedicated instrument controller inside, they're subject to all the ills of PCs (e.g. expectation of patch cycles, etc.) It also seems that there's a more rapid turnover of equipment these days (probably because accounting rules allow 3 or 5 year depreciation) and so the idea of a place hanging onto a signal generator for 20 years is less common. So that newer gear will show up used sooner (I hope!) ___ 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] Basic question regarding comparing two frequencies
Hal Murray wrote: jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. Yes.. I was at a meeting at work last week where we discussed this. Seems it works like this: The equipment mfrs have about 6 month turnaround on patch cycles, so your instrument is almost always vulnerable. But, if you don't connect it to anything or use it as a browser, you're ok. Then, someone plugs a USB stick in (that is infected from some other PC).. and that infects the instrument. SInce the instrument isn't running anti virus (they're of limited value anyway, and usually have a performance impact that's unacceptable in embedded systems), the virus lurks there. Then, when you DO connect to the network, it leaps into action, or, it infects the USB stick of the next poor schlub to use 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] Basic question regarding comparing two frequencies
That seems to indicate these devices are running a version of embedded Windows for them to get infected by a virus and I wonder why they need such a sledgehammer internally. Steve PS. sorry for top-posting but that's the only way I can reply at the moment (basic HTML Gmail). On 26/07/2010, jimlux jim...@earthlink.net wrote: Hal Murray wrote: jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. Yes.. I was at a meeting at work last week where we discussed this. Seems it works like this: The equipment mfrs have about 6 month turnaround on patch cycles, so your instrument is almost always vulnerable. But, if you don't connect it to anything or use it as a browser, you're ok. Then, someone plugs a USB stick in (that is infected from some other PC).. and that infects the instrument. SInce the instrument isn't running anti virus (they're of limited value anyway, and usually have a performance impact that's unacceptable in embedded systems), the virus lurks there. Then, when you DO connect to the network, it leaps into action, or, it infects the USB stick of the next poor schlub to use 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. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ 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] Basic question regarding comparing two frequencies
Steve Rooke wrote: That seems to indicate these devices are running a version of embedded Windows for them to get infected by a virus and I wonder why they need such a sledgehammer internally. Steve PS. sorry for top-posting but that's the only way I can reply at the moment (basic HTML Gmail). Yes.. most are running some flavor of Windows Embedded (formerly known as WinCE) or WinXP. It's a cost driven thing.. small form factor motherboards are readily available, windows gives you a familiar (to most users) interface for doing things like setup of the network interface, file system, etc. I'd say it's probably cheaper (in a capital investment sense) to put a small PC into the instrument than to design your own custom controller board, write embedded software for it, etc.) Especially if you want commonality across your whole line, where the higher end instruments have fairly sophisticated add-on software (all those slick applications that analyze signals, set things up), choosing some sort of popular OS platform makes sense. MS makes it pretty easy to do the development.. The Visual Studio products are inexpensive, well integrated, etc. They've got decent documentation for generating stripped down installs suitable for instruments. They also have update management, etc. Some flavor of Linux is really the alternative, and the learning curve to get started with embedded applications is a bit steeper, especially if you want more than what can be done by a command line interface. Which GUI toolkit do you use? Where do you get it? etc. With Windows, that whole list of choices has been made for you. ___ 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] Basic question regarding comparing two frequencies
ROFLMAO! -John == jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Jim, It might appear on the 2nd user market sooner, but the odds are you won't be able to either repair it or calibrate it as the manufacturer will have been the only supplier of either of these services, and no service manuals will exist. If it is still in support, the mfr will calibrate/fix it for you if your pockets are deep enough (probably as much or more than you pay for it). If (as is likely), it is out of support, then it will only be good for re-cycling or land-fill :-( H does anyone but us old fogies see anything wrong with a business model where stuff can't be fixed and has a support lifetime of 5 years or so ? Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux Sent: 25 July 2010 14:16 To: j...@quik.com Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies J. Forster wrote: Probably yes. There are also a number of lower cost instruments (just above consumer grade)like HF-VHF VNAs that implement much of the smarts in a PC on the market. As to high end instruments w/ USB or Ethernet, I'm not so sure. The USA is doing less and less hardware development, so instruments are not being bought in anything like the quantity as in the past. A lot of the new Agilent and Tek gear (at all price points) seem to have Ethernet, especially if it has a LCD front panel. (there's that LXI interface thing, too) Even power supplies. Not much USB (at least for control.. these days, using a USB stick for data transfer seems ubiquitous.. they've replaced the floppy drive on scopes, etc.), except for RF power meters.. There's a whole raft of power meter heads that are USB, which makes sense.. the hard part is in the actual sensor, not in the meter which displays the power reading. Mind you, because they do this by using single board PCs instead of the dedicated instrument controller inside, they're subject to all the ills of PCs (e.g. expectation of patch cycles, etc.) It also seems that there's a more rapid turnover of equipment these days (probably because accounting rules allow 3 or 5 year depreciation) and so the idea of a place hanging onto a signal generator for 20 years is less common. So that newer gear will show up used sooner (I hope!) ___ 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] Basic question regarding comparing two frequencies
There is a cute way to use a scope. It requires a power splittere, a quadrature hybrid, and two mixers (all appropriate for the frequencies you are comparing), and an X-Y scope. Mini-Circuits sells appropriate parts. The stuff is hooked up like this: X Axis S | H P MIX Y REF 1--L B -- REF2 I MIX R T | I Y Axis D The 'scope display will be roughly a circle if the frequencies are a bit different and the spot will go around CW or CCW depending on which Ref is higher. -John = The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Yup. Newer equipment is just not fixable. I have a HP 8753D VNA with the 6 GHz option. The 3-6 GHz band is sick and I cannot get any response out of Agilent for anything more than a simplified block diagram from the manual. They want me to send the module back for a $7500 fix. I can buy a used module on eBay for about $4300. Neither are in the budget. I think the thing is fixable, but not w/o the info. FWIW, -John == Jim, It might appear on the 2nd user market sooner, but the odds are you won't be able to either repair it or calibrate it as the manufacturer will have been the only supplier of either of these services, and no service manuals will exist. If it is still in support, the mfr will calibrate/fix it for you if your pockets are deep enough (probably as much or more than you pay for it). If (as is likely), it is out of support, then it will only be good for re-cycling or land-fill :-( H does anyone but us old fogies see anything wrong with a business model where stuff can't be fixed and has a support lifetime of 5 years or so ? Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux Sent: 25 July 2010 14:16 To: j...@quik.com Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies J. Forster wrote: Probably yes. There are also a number of lower cost instruments (just above consumer grade)like HF-VHF VNAs that implement much of the smarts in a PC on the market. As to high end instruments w/ USB or Ethernet, I'm not so sure. The USA is doing less and less hardware development, so instruments are not being bought in anything like the quantity as in the past. A lot of the new Agilent and Tek gear (at all price points) seem to have Ethernet, especially if it has a LCD front panel. (there's that LXI interface thing, too) Even power supplies. Not much USB (at least for control.. these days, using a USB stick for data transfer seems ubiquitous.. they've replaced the floppy drive on scopes, etc.), except for RF power meters.. There's a whole raft of power meter heads that are USB, which makes sense.. the hard part is in the actual sensor, not in the meter which displays the power reading. Mind you, because they do this by using single board PCs instead of the dedicated instrument controller inside, they're subject to all the ills of PCs (e.g. expectation of patch cycles, etc.) It also seems that there's a more rapid turnover of equipment these days (probably because accounting rules allow 3 or 5 year depreciation) and so the idea of a place hanging onto a signal generator for 20 years is less common. So that newer gear will show up used sooner (I hope!) ___ 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] Basic question regarding comparing two frequencies
This is close to the project I showed at the SF Bay Area Maker Faire in May. I showed fractional ppb difference measurements using a $25 flea market scope. The photo below is by a former NIST Cs fountain researcher who stopped by: http://www.flickr.com/photos/oskay/4640673869/in/set-72157623988565617/ Leigh/WA5ZNU On 07/24/2010 10:28 AM, Mark Spencer wrote: Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter.I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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] Basic question regarding comparing two frequencies
My attempt to understand your diagram, not sure about how the quadrature hybrid is connected. Stanley - Original Message From: J. Forster j...@quik.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sun, July 25, 2010 10:29:23 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies There is a cute way to use a scope. It requires a power splittere, a quadrature hybrid, and two mixers (all appropriate for the frequencies you are comparing), and an X-Y scope. Mini-Circuits sells appropriate parts. The stuff is hooked up like this: X Axis S | H P MIX Y REF 1--L B -- REF2 I MIX R T | I Y Axis D The 'scope display will be roughly a circle if the frequencies are a bit different and the spot will go around CW or CCW depending on which Ref is higher. -John snipattachment: Jfoster.jpg___ 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] Basic question regarding comparing two frequencies
The splitter makes two identical signals from Ref 1 The quadrature hybrid makes two signals out of Ref 2, but with a 90 degree phase shift between the signals. It's essentially a QPSK Demodulator, but set up to run in the linear region, rather than clipping. It's also sometimes called an I-Q detector. There is some closely related info here: http://www.minicircuits.com/pages/pdfs/mod11-2.pdf -John === My attempt to understand your diagram, not sure about how the quadrature hybrid is connected. Stanley - Original Message From: J. Forster j...@quik.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sun, July 25, 2010 10:29:23 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies There is a cute way to use a scope. It requires a power splittere, a quadrature hybrid, and two mixers (all appropriate for the frequencies you are comparing), and an X-Y scope. Mini-Circuits sells appropriate parts. The stuff is hooked up like this: X Axis S | H P MIX Y REF 1--L B -- REF2 I MIX R T | I Y Axis D The 'scope display will be roughly a circle if the frequencies are a bit different and the spot will go around CW or CCW depending on which Ref is higher. -John snip ___ 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] Basic question regarding comparing two frequencies
Corrected Drawing.attachment: Jfoster.jpg___ 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] Basic question regarding comparing two frequencies
Hi, Yes Stanley, that's what I has in mind. My appologies for not noticing the drawing attached to your OP. Thanks, -John == Corrected Drawing.___ 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] Basic question regarding comparing two frequencies
There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. There may be a small amount of missing data in the vicinity of the foldback, but if life threatening this could be avoided by running a second unit with the signals delayed to be near quadrature, and using the better data of the two. I use a lower frequency version of this system to monitor clocks (mechanical ones with pendulums). Cheers, Neville Michie ___ 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] Basic question regarding comparing two frequencies
Hi Neville, There are plenty of ways to compare frequencies. I posted the BPSK demod scheme as a simple way to quickly tweek in the correct direction without Lissajous Figures. Best, -John There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. There may be a small amount of missing data in the vicinity of the foldback, but if life threatening this could be avoided by running a second unit with the signals delayed to be near quadrature, and using the better data of the two. I use a lower frequency version of this system to monitor clocks (mechanical ones with pendulums). Cheers, Neville Michie ___ 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] Basic question regarding comparing two frequencies
On 26/07/2010, jimlux jim...@earthlink.net wrote: Some flavor of Linux is really the alternative, and the learning curve to get started with embedded applications is a bit steeper, especially if you want more than what can be done by a command line interface. Which GUI toolkit do you use? Where do you get it? etc. With Windows, that whole list of choices has been made for you. This is really an old excuse now as Linux has been around a long time and there are already a lot of embedded systems running it. As for a GUI toolkit, you have choices with Linux, ie. QT and GTK, to name but two, and Windows only gives you a single choice. As for development environments, the World is your oyster with Linux and it all comes without expensive licensing issues. Steve -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ 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] Basic question regarding comparing two frequencies
There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity of a setup like this? The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. Is 2.5 ns good enough? What would you gain by using a 16 bit DAC? If 2.5 ns is good enough, I'll bet you can do the whole thing in digital logic. Just get a fast FPGA/CPLD. I haven't done a serious design, but a quick check at some old data sheets shows it's not silly. You could probably bump it up by another factor of 2 with some external (p)ECL chips. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Hi If you have a fast enough scope you can also use the: Moved X ns in 10 seconds = X/10 ppb of frequency error. Bob On Jul 24, 2010, at 1:28 PM, Mark Spencer wrote: Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter.I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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] Basic question regarding comparing two frequencies
Thanks. I'll try that, with the x10 trace magnifier turned on my scope can resolve down to 2ns per division so that should work. - Original Message From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 10:51:21 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Hi If you have a fast enough scope you can also use the: Moved X ns in 10 seconds = X/10 ppb of frequency error. Bob On Jul 24, 2010, at 1:28 PM, Mark Spencer wrote: Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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] Basic question regarding comparing two frequencies
Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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] Basic question regarding comparing two frequencies
Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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] Basic question regarding comparing two frequencies
.. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
I would agree. GPIB (aka HPIB) is ubiquitous and is a great place to start. Unfortunately, I haven't gotten that up to the top of my 'to-do' list yet. I have a computer, HP and National interface cards, cables, but no time to find the software to make everything communicate yet. I think it has a lot to do with the fact that I have relatively old HP equipment that is relatively 'tongue-tied' but I think I will be able to figure it out once I get the time. Certainly the right place to start though, IMO. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Saturday, July 24, 2010 5:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies .. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
If you have NI card(s) it is easy. National makes the simple SW available for free. Last time I looked there is a console command line utility and a VB and C interfaces. Labview is a different story. A new version is $$$. You can sometimes find older versions on eBay. Some versions are PW keyed, so be careful. NI has a stunning selection of virtual instruments for free, I think. The HP-IB cards are much more problematic. AFAIK, there is little to no SW support. I have a couple, but only because they are required to run a specific instrument (a Laser Interferometer) with a PC and HP system SW. There are also 2nd source GPIB cards (Prologix, etc). The SW support is spotty, although I'm told that Prologix is pretty good. FWIW, -John == I would agree. GPIB (aka HPIB) is ubiquitous and is a great place to start. Unfortunately, I haven't gotten that up to the top of my 'to-do' list yet. I have a computer, HP and National interface cards, cables, but no time to find the software to make everything communicate yet. I think it has a lot to do with the fact that I have relatively old HP equipment that is relatively 'tongue-tied' but I think I will be able to figure it out once I get the time. Certainly the right place to start though, IMO. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Saturday, July 24, 2010 5:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies .. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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
Re: [time-nuts] Basic question regarding comparing two frequencies
J. Forster wrote: .. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John these days, ethernet and USB are becoming more popular. My own preference is Ethernet and I long for the day when I can ditch the last GPIB cable (and the stacking connectors where you always seem to need the one on the bottom of the stack) Yes, GPIB provides some clever triggering across the interface, useful for things like sweepers and vector voltmeters, but I suspect that it's not much used these days.. rather you wind up sending binary or ascii strings across the interface. ___ 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] Basic question regarding comparing two frequencies
Speaking of which, should have or stumble a gpib for said 5328a, I'm looking for one to go in my counter. Thanks, Bob On 7/24/10, Mark Spencer mspencer12...@yahoo.ca wrote: Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
I very much doubt that the majority on this list have major govenmental or corporate funding and shop from the new Agilent catalog that just came in the mail. As a result, I'd guess almost all the commercial test gear in the posession of listers is from 1970 to 2000. That says GPIB and almost nothing else. A very few instruments did use dedicated ISA, LSI-11, or RS-232, but the numbers are tiny. The fact is that with GPIB you can cobble up a system to almost anything from simple to complex very quickly. YMMV, -John === J. Forster wrote: .. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John these days, ethernet and USB are becoming more popular. My own preference is Ethernet and I long for the day when I can ditch the last GPIB cable (and the stacking connectors where you always seem to need the one on the bottom of the stack) Yes, GPIB provides some clever triggering across the interface, useful for things like sweepers and vector voltmeters, but I suspect that it's not much used these days.. rather you wind up sending binary or ascii strings across the interface. ___ 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] Basic question regarding comparing two frequencies
Thanks for the insight re the GPIB interface. I'm curious if any has any insight as to a suitable usb or pci to GPIB interface module or card ? It sounds as though other surplus test gear is likely to have a GPIB interface. Regards Mark Spencer On Sat Jul 24th, 2010 6:40 PM EDT J. L. Trantham wrote: I would agree. GPIB (aka HPIB) is ubiquitous and is a great place to start. Unfortunately, I haven't gotten that up to the top of my 'to-do' list yet. I have a computer, HP and National interface cards, cables, but no time to find the software to make everything communicate yet. I think it has a lot to do with the fact that I have relatively old HP equipment that is relatively 'tongue-tied' but I think I will be able to figure it out once I get the time. Certainly the right place to start though, IMO. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Saturday, July 24, 2010 5:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies .. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
EDN magazine published a simple USB to GPIB design back in 2005, and someday I might build one up for myself. Hence this email is meant to be informational and not an endorsement. The original author has updated his design since then, check out the info and links at http://lpvo.fe.uni-lj.si/gpib/ where the original design is well documented for DIY and the updated version available as a kit if that interests you. Bob LaJeunesse From: Mark Spencer mspencer12...@yahoo.ca To: time-nuts@febo.com; j...@quik.com Sent: Sat, July 24, 2010 9:15:20 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Thanks for the insight re the GPIB interface. I'm curious if any has any insight as to a suitable usb or pci to GPIB interface module or card ? It sounds as though other surplus test gear is likely to have a GPIB interface. Regards Mark Spencer On Sat Jul 24th, 2010 6:40 PM EDT J. L. Trantham wrote: I would agree. GPIB (aka HPIB) is ubiquitous and is a great place to start. Unfortunately, I haven't gotten that up to the top of my 'to-do' list yet. I have a computer, HP and National interface cards, cables, but no time to find the software to make everything communicate yet. I think it has a lot to do with the fact that I have relatively old HP equipment that is relatively 'tongue-tied' but I think I will be able to figure it out once I get the time. Certainly the right place to start though, IMO. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Saturday, July 24, 2010 5:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies .. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions
Re: [time-nuts] Basic question regarding comparing two frequencies
Check http://www.ko4bb.com/Test_Equipment/GPIB.php Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Mark Spencer mspencer12...@yahoo.ca Sender: time-nuts-boun...@febo.com Date: Sat, 24 Jul 2010 18:15:20 To: time-nuts@febo.com; j...@quik.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Thanks for the insight re the GPIB interface. I'm curious if any has any insight as to a suitable usb or pci to GPIB interface module or card ? It sounds as though other surplus test gear is likely to have a GPIB interface. Regards Mark Spencer On Sat Jul 24th, 2010 6:40 PM EDT J. L. Trantham wrote: I would agree. GPIB (aka HPIB) is ubiquitous and is a great place to start. Unfortunately, I haven't gotten that up to the top of my 'to-do' list yet. I have a computer, HP and National interface cards, cables, but no time to find the software to make everything communicate yet. I think it has a lot to do with the fact that I have relatively old HP equipment that is relatively 'tongue-tied' but I think I will be able to figure it out once I get the time. Certainly the right place to start though, IMO. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Saturday, July 24, 2010 5:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies .. more generic interface. ?? The vast majority of professional test equipment has GPIB. Virtually anything else is an also ran. FWIW, -John Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. Best regards Mark Spencer - Original Message From: J. L. Trantham jlt...@att.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sat, July 24, 2010 1:49:51 PM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Sounds about right. One cycle per 5 seconds or about 0.2 Hz difference. Therefore, 9,999,999.8 Hz. I would feed the GPSDO to trigger your scope and look at the output of the time base on one channel of the scope. You could also look at the GPSDO on the other channel. Then you could adjust your counter time base to 'freeze' the display. Probably good to 'align' the counter time base but for long term comparison, probably better to use a counter and plot the difference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Saturday, July 24, 2010 12:29 PM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ 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
Re: [time-nuts] Basic question regarding comparing two frequencies
J. Forster wrote: I very much doubt that the majority on this list have major govenmental or corporate funding and shop from the new Agilent catalog that just came in the mail. As a result, I'd guess almost all the commercial test gear in the posession of listers is from 1970 to 2000. That says GPIB and almost nothing else. A very few instruments did use dedicated ISA, LSI-11, or RS-232, but the numbers are tiny. The fact is that with GPIB you can cobble up a system to almost anything from simple to complex very quickly. But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on 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] Basic question regarding comparing two frequencies
Probably yes. There are also a number of lower cost instruments (just above consumer grade)like HF-VHF VNAs that implement much of the smarts in a PC on the market. As to high end instruments w/ USB or Ethernet, I'm not so sure. The USA is doing less and less hardware development, so instruments are not being bought in anything like the quantity as in the past. FWIW, -John == J. Forster wrote: I very much doubt that the majority on this list have major govenmental or corporate funding and shop from the new Agilent catalog that just came in the mail. As a result, I'd guess almost all the commercial test gear in the posession of listers is from 1970 to 2000. That says GPIB and almost nothing else. A very few instruments did use dedicated ISA, LSI-11, or RS-232, but the numbers are tiny. The fact is that with GPIB you can cobble up a system to almost anything from simple to complex very quickly. But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on 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] Basic question regarding comparing two frequencies
Thanks for the insight re the GPIB interface. I'm curious if any has any insight as to a suitable usb or pci to GPIB interface module or card ? It sounds as though other surplus test gear is likely to have a GPIB interface. I've been happy with the Prologix unit. I got mine through Sparkfun: http://www.sparkfun.com/commerce/product_info.php?products_id=549 It's USB to GPIB, but it uses one of the popular USB-serial chips so drivers should be easy to find. (if you don't have them already) That lets you talk to it, but you may have to write some low level code to do what you want. I'm happy with that stuff. Some people don't like it. Thanks, I'm glad to hear I am on the right track. At some point it would be nice to obtain a counter that can measure the drift of the time base in the 5328A. The 5328A has a GPIB interface but as the display only varies by a few counts I'm not inclined to track down a GPIB adapter just to plot this.) Hopefully a newer counter would have a more generic interface. I'm not familiar with the 5328A. On the 5334B, you can get a two more digits via GPIB. For example: F +2.997105E+06 (The display only has 9 digits.) -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
