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] Symmetricom X72
Brice, On 26/07/2010, Heathkid heath...@heathkid.com wrote: Last night, as suggested by several people on this list... I ordered a Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty good shape there to get started once it arrives. Sounds like your starting on the long path to time-nuttiness :) Bob has supplied a lot of stuff to people on this list and he will look after you if anything is amiss. The counter I mentioned (it's a DFD4 - modified with the tcxo as the a ... anyway). :) By the way, when I built it, I calibrated it by zero beating against WWV at 10 and 20 MHz. That was the best way I had at the time and if the DFD4 is now 7 Hz off after all these years... it's not doing so bad (based on it's limitations). Not bad considering it's a TCXO. So... that's what that counter is for and not for what I'm doing now. I'm currently looking for a nice/used HP counter. Please don't think I'm going to use the DFD4 for measuring my Rb standards. It's a wonderful counter for what it was designed for and that's it. Dependant upon what your looking for in a counter, you could broaden your choices as there are other useful counters out there that may be more affordable but still as good. Try looking for a Racal-Dana 1992, preferably with the high stability option timebase (although these turn up seperately anyway and are a doddle to fit). It makes a nice footprint 1ns counter and can be referenced to your T'Bolt. I'm not giving up on the FEI's anytime soon. I understand now that along with the Trimble Thunderbolt (and a decent counter) I'll be on my way to getting started. You'll have to see if those FEI's are the programmable types which can be set to produce frequencies up to 20MHz. Do they have jut the D'Sub connector or have an RF connector as well. There are different variants of these produced by FEI under the same product code. 73 de Steve ZL3TUV G8KVD 73 Brice KA8MAV - Original Message - From: Steve Rooke sar10...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 8:40 AM Subject: Re: [time-nuts] Symmetricom X72 Excuse my replying to my own posting please. This post is really about the DFD1 frequency counter. Heathkid: You are comparing a Rb against a frequency counter with a TCXO that you tweaked yourself to calibrate it against no known frequency standard. Try running the three FEI-5660s for 24 hours and then measure the output of each with your frequency counter. Pick the mean of them and adjust your DFD1 to match that. At least you should be in a better position than you are now. As you built the DFD1 yourself, you should have the schematic and may be able to engineer in a connection for an external reference. There is plenty of people here who would be happy to advise you on a suitable interface if you can attach the part of the circuit where the TCXO is located. If you do get a T'Both, you would be able to use it as a reference or, perhaps, build in one of the FEI-5660s as an internal reference. The limiting factor though is how good is the circuit used in the DFD1 which will limit it's stability and accuracy. There are many factors, including input circuit, voltage regulation, counter stage design, level detection, etc. which have a major impact here. What I'm getting at is that to write-off a bunch of FEI-5660s after checking them with such a device as this, is a very poor decision. Maybe you could look at a better counter on fleeBay before you make further assumptions. 73, Steve On 26/07/2010, Steve Rooke sar10...@gmail.com wrote: Sage advice Bill! Heathkid, you don't need another Rb unit when you have 3 perfectly decent ones! You really need a standard to calibrate your Rb units to, a Trimble Thunderbolt is likely to be the cheapest choice for you. Bob Mokia, fluke.l, on fleeBay sells them separately or as a starter kit with everything there to get you going. Once you have this up and running for quite some time and see that things are looking stable in the Lady Heather application, then you can start to think about calibrating the FEI-5680's but only after you have run them in well. I don't know your counter but does it have an input for an external reference source? If so you will be able to use the T'Bolt as an external reference for it, providing the required reference is 10MHz. If it's not, you can divide down the T'Bolt's output to match. If your frequency counter has no reference input (apart from throwing it in the bin) you should be able to engineer it into the instrument, depending on your skill set. So, first get yourself a frequency standard to work with, IE. a T'Bolt or the like. My 2c worth, Steve On 25/07/2010, WB6BNQ wb6...@cox.net wrote: To Bob and Stan (W1LE), [p.s. But not just to you two alone] Why complicate the answers to Heathkid (now Brice KA8MAV) with a bunch of different
Re: [time-nuts] Symmetricom X72
Hi One issue with the FE's is they often show up as conversions. Various sellers take the 1 pps version and hack in a 10 MHz output. There is a lot of room for error in the conversion process. Bob On Jul 26, 2010, at 7:06 AM, Steve Rooke sar10...@gmail.com wrote: Brice, On 26/07/2010, Heathkid heath...@heathkid.com wrote: Last night, as suggested by several people on this list... I ordered a Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty good shape there to get started once it arrives. Sounds like your starting on the long path to time-nuttiness :) Bob has supplied a lot of stuff to people on this list and he will look after you if anything is amiss. The counter I mentioned (it's a DFD4 - modified with the tcxo as the a ... anyway). :) By the way, when I built it, I calibrated it by zero beating against WWV at 10 and 20 MHz. That was the best way I had at the time and if the DFD4 is now 7 Hz off after all these years... it's not doing so bad (based on it's limitations). Not bad considering it's a TCXO. So... that's what that counter is for and not for what I'm doing now. I'm currently looking for a nice/used HP counter. Please don't think I'm going to use the DFD4 for measuring my Rb standards. It's a wonderful counter for what it was designed for and that's it. Dependant upon what your looking for in a counter, you could broaden your choices as there are other useful counters out there that may be more affordable but still as good. Try looking for a Racal-Dana 1992, preferably with the high stability option timebase (although these turn up seperately anyway and are a doddle to fit). It makes a nice footprint 1ns counter and can be referenced to your T'Bolt. I'm not giving up on the FEI's anytime soon. I understand now that along with the Trimble Thunderbolt (and a decent counter) I'll be on my way to getting started. You'll have to see if those FEI's are the programmable types which can be set to produce frequencies up to 20MHz. Do they have jut the D'Sub connector or have an RF connector as well. There are different variants of these produced by FEI under the same product code. 73 de Steve ZL3TUV G8KVD 73 Brice KA8MAV - Original Message - From: Steve Rooke sar10...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 8:40 AM Subject: Re: [time-nuts] Symmetricom X72 Excuse my replying to my own posting please. This post is really about the DFD1 frequency counter. Heathkid: You are comparing a Rb against a frequency counter with a TCXO that you tweaked yourself to calibrate it against no known frequency standard. Try running the three FEI-5660s for 24 hours and then measure the output of each with your frequency counter. Pick the mean of them and adjust your DFD1 to match that. At least you should be in a better position than you are now. As you built the DFD1 yourself, you should have the schematic and may be able to engineer in a connection for an external reference. There is plenty of people here who would be happy to advise you on a suitable interface if you can attach the part of the circuit where the TCXO is located. If you do get a T'Both, you would be able to use it as a reference or, perhaps, build in one of the FEI-5660s as an internal reference. The limiting factor though is how good is the circuit used in the DFD1 which will limit it's stability and accuracy. There are many factors, including input circuit, voltage regulation, counter stage design, level detection, etc. which have a major impact here. What I'm getting at is that to write-off a bunch of FEI-5660s after checking them with such a device as this, is a very poor decision. Maybe you could look at a better counter on fleeBay before you make further assumptions. 73, Steve On 26/07/2010, Steve Rooke sar10...@gmail.com wrote: Sage advice Bill! Heathkid, you don't need another Rb unit when you have 3 perfectly decent ones! You really need a standard to calibrate your Rb units to, a Trimble Thunderbolt is likely to be the cheapest choice for you. Bob Mokia, fluke.l, on fleeBay sells them separately or as a starter kit with everything there to get you going. Once you have this up and running for quite some time and see that things are looking stable in the Lady Heather application, then you can start to think about calibrating the FEI-5680's but only after you have run them in well. I don't know your counter but does it have an input for an external reference source? If so you will be able to use the T'Bolt as an external reference for it, providing the required reference is 10MHz. If it's not, you can divide down the T'Bolt's output to match. If your frequency counter has no reference input (apart from throwing it in the bin) you should be able to engineer it into the instrument, depending on your skill set.
Re: [time-nuts] Symmetricom X72
Yes, it's because of the various types that you need to verify exactly what you have. A number of them are made to customer specifications with undocumented option numbers but if you have anything like an option 8 then you have the 1Hz to 20MHz version. Beware that to program the thing you need to provide +5V as well as the +15V to run it. Along with the output options, there are a slew of options on such things as ageing and temperature stability. If you have one from a telecom's cellular tower, it's likely to be of higher spec. Steve On 26/07/2010, Bob Camp li...@rtty.us wrote: Hi One issue with the FE's is they often show up as conversions. Various sellers take the 1 pps version and hack in a 10 MHz output. There is a lot of room for error in the conversion process. Bob On Jul 26, 2010, at 7:06 AM, Steve Rooke sar10...@gmail.com wrote: Brice, On 26/07/2010, Heathkid heath...@heathkid.com wrote: Last night, as suggested by several people on this list... I ordered a Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty good shape there to get started once it arrives. Sounds like your starting on the long path to time-nuttiness :) Bob has supplied a lot of stuff to people on this list and he will look after you if anything is amiss. The counter I mentioned (it's a DFD4 - modified with the tcxo as the a ... anyway). :) By the way, when I built it, I calibrated it by zero beating against WWV at 10 and 20 MHz. That was the best way I had at the time and if the DFD4 is now 7 Hz off after all these years... it's not doing so bad (based on it's limitations). Not bad considering it's a TCXO. So... that's what that counter is for and not for what I'm doing now. I'm currently looking for a nice/used HP counter. Please don't think I'm going to use the DFD4 for measuring my Rb standards. It's a wonderful counter for what it was designed for and that's it. Dependant upon what your looking for in a counter, you could broaden your choices as there are other useful counters out there that may be more affordable but still as good. Try looking for a Racal-Dana 1992, preferably with the high stability option timebase (although these turn up seperately anyway and are a doddle to fit). It makes a nice footprint 1ns counter and can be referenced to your T'Bolt. I'm not giving up on the FEI's anytime soon. I understand now that along with the Trimble Thunderbolt (and a decent counter) I'll be on my way to getting started. You'll have to see if those FEI's are the programmable types which can be set to produce frequencies up to 20MHz. Do they have jut the D'Sub connector or have an RF connector as well. There are different variants of these produced by FEI under the same product code. 73 de Steve ZL3TUV G8KVD 73 Brice KA8MAV - Original Message - From: Steve Rooke sar10...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 8:40 AM Subject: Re: [time-nuts] Symmetricom X72 Excuse my replying to my own posting please. This post is really about the DFD1 frequency counter. Heathkid: You are comparing a Rb against a frequency counter with a TCXO that you tweaked yourself to calibrate it against no known frequency standard. Try running the three FEI-5660s for 24 hours and then measure the output of each with your frequency counter. Pick the mean of them and adjust your DFD1 to match that. At least you should be in a better position than you are now. As you built the DFD1 yourself, you should have the schematic and may be able to engineer in a connection for an external reference. There is plenty of people here who would be happy to advise you on a suitable interface if you can attach the part of the circuit where the TCXO is located. If you do get a T'Both, you would be able to use it as a reference or, perhaps, build in one of the FEI-5660s as an internal reference. The limiting factor though is how good is the circuit used in the DFD1 which will limit it's stability and accuracy. There are many factors, including input circuit, voltage regulation, counter stage design, level detection, etc. which have a major impact here. What I'm getting at is that to write-off a bunch of FEI-5660s after checking them with such a device as this, is a very poor decision. Maybe you could look at a better counter on fleeBay before you make further assumptions. 73, Steve On 26/07/2010, Steve Rooke sar10...@gmail.com wrote: Sage advice Bill! Heathkid, you don't need another Rb unit when you have 3 perfectly decent ones! You really need a standard to calibrate your Rb units to, a Trimble Thunderbolt is likely to be the cheapest choice for you. Bob Mokia, fluke.l, on fleeBay sells them separately or as a starter kit with everything there to get you going. Once you have this up and running for quite some time and see that things are looking stable in
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] This group will appreciate this
On 24/07/2010 1:47 PM, Jim Palfreyman wrote: I picked up an old black bakelite phone in an antique shop and have it nicely on display on a table. I have wired it through to my workshop where it is connected to the old Australian speaking clock (sync'ed to the GPS of course). So when you pick up the phone you hear: At the third stroke it will be one, forty five, and ten seconds...beep...beep...beep. Even my girlfriend thinks it's cool. Jim ___ 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. Hey Jim, Have you got that talking clock streaming on the web yet? I remember being fascinated by it as a kid. Tim ___ 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] Austron 2100 going...
I have a now useless 2100 Loran receiver / comparator here, does anyone have any use for this? Before I recycle it. (Here is southern California.) Dan ac6ao ___ 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] Wanted dead oven T'bolt
I have an insane desire to marry up a T'bolt with an E1938 OCXO which I have here and can't think of a better use for. Does anyone have a T'bolt with a duff or dead OCXO? TAPR reject pile maybe? Best wishes Dan ___ 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] Symmetricom X72
Hi One gotcha on the conversions: How close did they set the DDS before they shipped it. A few seem to do a less than perfect job of it. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Steve Rooke Sent: Monday, July 26, 2010 7:54 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Symmetricom X72 Yes, it's because of the various types that you need to verify exactly what you have. A number of them are made to customer specifications with undocumented option numbers but if you have anything like an option 8 then you have the 1Hz to 20MHz version. Beware that to program the thing you need to provide +5V as well as the +15V to run it. Along with the output options, there are a slew of options on such things as ageing and temperature stability. If you have one from a telecom's cellular tower, it's likely to be of higher spec. Steve On 26/07/2010, Bob Camp li...@rtty.us wrote: Hi One issue with the FE's is they often show up as conversions. Various sellers take the 1 pps version and hack in a 10 MHz output. There is a lot of room for error in the conversion process. Bob On Jul 26, 2010, at 7:06 AM, Steve Rooke sar10...@gmail.com wrote: Brice, On 26/07/2010, Heathkid heath...@heathkid.com wrote: Last night, as suggested by several people on this list... I ordered a Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty good shape there to get started once it arrives. Sounds like your starting on the long path to time-nuttiness :) Bob has supplied a lot of stuff to people on this list and he will look after you if anything is amiss. The counter I mentioned (it's a DFD4 - modified with the tcxo as the a ... anyway). :) By the way, when I built it, I calibrated it by zero beating against WWV at 10 and 20 MHz. That was the best way I had at the time and if the DFD4 is now 7 Hz off after all these years... it's not doing so bad (based on it's limitations). Not bad considering it's a TCXO. So... that's what that counter is for and not for what I'm doing now. I'm currently looking for a nice/used HP counter. Please don't think I'm going to use the DFD4 for measuring my Rb standards. It's a wonderful counter for what it was designed for and that's it. Dependant upon what your looking for in a counter, you could broaden your choices as there are other useful counters out there that may be more affordable but still as good. Try looking for a Racal-Dana 1992, preferably with the high stability option timebase (although these turn up seperately anyway and are a doddle to fit). It makes a nice footprint 1ns counter and can be referenced to your T'Bolt. I'm not giving up on the FEI's anytime soon. I understand now that along with the Trimble Thunderbolt (and a decent counter) I'll be on my way to getting started. You'll have to see if those FEI's are the programmable types which can be set to produce frequencies up to 20MHz. Do they have jut the D'Sub connector or have an RF connector as well. There are different variants of these produced by FEI under the same product code. 73 de Steve ZL3TUV G8KVD 73 Brice KA8MAV - Original Message - From: Steve Rooke sar10...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 8:40 AM Subject: Re: [time-nuts] Symmetricom X72 Excuse my replying to my own posting please. This post is really about the DFD1 frequency counter. Heathkid: You are comparing a Rb against a frequency counter with a TCXO that you tweaked yourself to calibrate it against no known frequency standard. Try running the three FEI-5660s for 24 hours and then measure the output of each with your frequency counter. Pick the mean of them and adjust your DFD1 to match that. At least you should be in a better position than you are now. As you built the DFD1 yourself, you should have the schematic and may be able to engineer in a connection for an external reference. There is plenty of people here who would be happy to advise you on a suitable interface if you can attach the part of the circuit where the TCXO is located. If you do get a T'Both, you would be able to use it as a reference or, perhaps, build in one of the FEI-5660s as an internal reference. The limiting factor though is how good is the circuit used in the DFD1 which will limit it's stability and accuracy. There are many factors, including input circuit, voltage regulation, counter stage design, level detection, etc. which have a major impact here. What I'm getting at is that to write-off a bunch of FEI-5660s after checking them with such a device as this, is a very poor decision. Maybe you could look at a better counter on fleeBay before you make further assumptions. 73, Steve On 26/07/2010, Steve Rooke sar10...@gmail.com wrote: Sage advice Bill! Heathkid, you don't
Re: [time-nuts] Austron 2100 going...
It isn't useless until the Canada chain goes away in November... And then you might still be able to catch a European chain. -Chuck Harris Dan Rae wrote: I have a now useless 2100 Loran receiver / comparator here, does anyone have any use for this? Before I recycle it. (Here is southern California.) Dan ac6ao ___ 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 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] Austron 2100 going...
Dan Rae wrote: I have a now useless 2100 Loran receiver / comparator here, does anyone have any use for this? Before I recycle it. (Here is southern California.) The Austron is on it's way to a good home where it may still work. dr ___ 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] Austron 2100 going...
Glad if found a good home. Good to hear Nov on Can chain. But they are still usable if you build the simple LORAN C simulator. Single pic chip/cheap. You can compare references and offsets just like you do today. Thats why I designed the simulator so the austrons would have something to do in retirement. On Mon, Jul 26, 2010 at 11:30 AM, Dan Rae dan...@verizon.net wrote: I have a now useless 2100 Loran receiver / comparator here, does anyone have any use for this? Before I recycle it. (Here is southern California.) Dan ac6ao ___ 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] Austron 2100 going...
In message 4c4daa05.2000...@verizon.net, Dan Rae writes: I have a now useless 2100 Loran receiver / comparator here, does anyone have any use for this? Before I recycle it. (Here is southern California.) Is it the Frequency or the Time version ? Does it do 4-digit GRI ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Austron 2100 going...
Hello Dan, If it is a 2100T I would be glad to adopt that child. I have already a 2100F currently receiving in Portugal the European LESSAY 6731 Chain. Thanks, Antonio CT1TE Quoting Dan Rae dan...@verizon.net: I have a now useless 2100 Loran receiver / comparator here, does anyone have any use for this? Before I recycle it. (Here is southern California.) Dan ac6ao ___ 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] Austron 2100 going... Gone!
asma...@fc.up.pt wrote: Hello Dan, If it is a 2100T I would be glad to adopt that child. Antonio, as I thought I said before, it is on it's way to a new home. Dan ___ 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 To
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.
[time-nuts] Heathkid - New time-nut needs help...
Steve, I changed the subject line because everything that follows has nothing to do with the X72. I hope this doesn't confuse anyone but this subject is probably much better related... Yes, the FEI 5680A's I got are programmable from 1Hz to 20MHz (SMA output / currently set to 10MHz) plus has the RS232 for programming and one of those pins (besides the Rb lock pin that goes low and I've got a LED on it) has the 1pps. Besides the C field potentiometer it also has a 0 to 5V fine tune voltage. The slowest of the three takes only about 4 seconds to achieve Rb lock. Here are the exact units I got (and flyingbest is a great and honest seller): http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItemitem=180435915714 The Thunderbolt I bought from fluke.l as he seems to be the TBolt seller of choice around here. I also got the LCD display option (looks like fun to see what it's doing when not connected to a PC). Okay, so today... I bought a real frequency counter. After a LOT of looking and reading... I chose a HP 5335A. It has option 10 (Oven Oscillator) and 030 (C Channel 1.3 GHz ) plus the HPIB plus math and statistics functions standard and includes operating and service manuals on CD. It'll also be calibrated just prior to shipping to me (current Date Due 03/19/11) but it will be re-calibrated just for me so at least I know it'll work and if there is a problem, I can return it. :) So, now I have the following (when the rest shows up): (3) FEI 5680A Programmable Rubidium Frequency Standards w/ 1pps (1) Thunderbolt Complete Kit w/ LCD display - from fluke.l (1) HP 5335A Universal Counter w/ Options 10 (Oven Oscillator) 030 (C Channel 1.3 GHz) Hopefully, Stanley got my payment for the PICTIC II boards and I got an email back from Bob about getting me on the list for the programmed PICs. That's where I'm at right now. 73 Brice KA8MAV - Original Message - From: Steve Rooke sar10...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, July 26, 2010 7:54 AM Subject: Re: [time-nuts] Symmetricom X72 Yes, it's because of the various types that you need to verify exactly what you have. A number of them are made to customer specifications with undocumented option numbers but if you have anything like an option 8 then you have the 1Hz to 20MHz version. Beware that to program the thing you need to provide +5V as well as the +15V to run it. Along with the output options, there are a slew of options on such things as ageing and temperature stability. If you have one from a telecom's cellular tower, it's likely to be of higher spec. Steve On 26/07/2010, Bob Camp li...@rtty.us wrote: Hi One issue with the FE's is they often show up as conversions. Various sellers take the 1 pps version and hack in a 10 MHz output. There is a lot of room for error in the conversion process. Bob On Jul 26, 2010, at 7:06 AM, Steve Rooke sar10...@gmail.com wrote: Brice, On 26/07/2010, Heathkid heath...@heathkid.com wrote: Last night, as suggested by several people on this list... I ordered a Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty good shape there to get started once it arrives. Sounds like your starting on the long path to time-nuttiness :) Bob has supplied a lot of stuff to people on this list and he will look after you if anything is amiss. The counter I mentioned (it's a DFD4 - modified with the tcxo as the a ... anyway). :) By the way, when I built it, I calibrated it by zero beating against WWV at 10 and 20 MHz. That was the best way I had at the time and if the DFD4 is now 7 Hz off after all these years... it's not doing so bad (based on it's limitations). Not bad considering it's a TCXO. So... that's what that counter is for and not for what I'm doing now. I'm currently looking for a nice/used HP counter. Please don't think I'm going to use the DFD4 for measuring my Rb standards. It's a wonderful counter for what it was designed for and that's it. Dependant upon what your looking for in a counter, you could broaden your choices as there are other useful counters out there that may be more affordable but still as good. Try looking for a Racal-Dana 1992, preferably with the high stability option timebase (although these turn up seperately anyway and are a doddle to fit). It makes a nice footprint 1ns counter and can be referenced to your T'Bolt. I'm not giving up on the FEI's anytime soon. I understand now that along with the Trimble Thunderbolt (and a decent counter) I'll be on my way to getting started. You'll have to see if those FEI's are the programmable types which can be set to produce frequencies up to 20MHz. Do they have jut the D'Sub connector or have an RF connector as well. There are different variants of these produced by FEI under the same product code. 73 de Steve ZL3TUV G8KVD 73 Brice KA8MAV - Original Message - From: Steve Rooke
[time-nuts] Minor correction in Pictic II parts list
R25 a 10 K resistor only used with the TTL computer interface option, not used with the RS232 chip, is listed twice as 1% or 5% either will work but you don't need both. Stanley ___ 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
