Hello Mathias, I think you did not quite understand how the calibration process works with that unit. The factory procedure is to set the pot to minimum and then bring the DDS up to the step that produces the closest frequency just below the wanted one and then use the C-field pot as the final tweak. The "R" value is composed of a number of factors that can only be determined after the Rb cell is made. A number of variables, in the Rb cell itself, will determine the actual "ON" resonance frequency and that is what is programmed into the "R" number at the end of final assembly. That "R" number is actually the Rb frequency divided by 136 plus the upward fine tuning of the C-field pot. See PDF page 16 & 17 of the attached PDF operational manual for the FEI-5650. The only difference between all the variants comes after the Physics Package as shown on PDF page 16 block diagram. The "F" number is truly a 32 bit number, not just the first 8 digits but all 16 of them. Your problem is being able to have a frequency reference that is, obviously, way better then the Rb. As Cesium and Hydrogen references are quite expensive that leaves just the GPS satellites as the only other reference available that will do the job. Of course that entails more than just the GPS "timing" receiver as you will need some other equipment to help in the comparison process. Also it takes time to do many small adjustments to achieve that final comparison. It won't happen in just one day. It would probably have been better to purchase one of the Rb's that already output 10 MHz instead of hacking the option 58. BUT that is just my opinion. Good luck, Bill Houlne....WB6BNQ Mathias Weyland wrote: > Hello guys > > I'm new to this list. I got myself a FE-5650A Rubidium Standard off of > ebay. > It's the "option 58" 1 pps output variant, hence I have to modify the > tuning > word used in the DDS phase accumulator to get 10 MHz out. I found a > vast amount > of awesome descriptions on how to do that on the web and in particular > on this > list. One write-up that stood out was this one by Mark Sims: > > http://www.mail-archive.com/time-nuts@febo.com/msg13486.html > > I think I can pull this off since everything is documented so nicely. > However, > I'm having trouble calculating the right tuning word and this is why: > Mark notes > that the reference frequency reported by the unit is the one with the > C-field > pot at the lowest frequency position. He gives a number of suggestions > on how to > deal with that. Since I didn't get that hydrogen maser for Christmas, > the best > approach seems to be "to calculate the true reference frequency from > the saved > (minimum C-field) R=reference frequency and F=divisor word and use > that value to > calculate divisor words." I don't understand how the saved minimum > C-field > reference ties into this calculation. > > My approach would have been to calculate the true reference frequency > from the > saved divisor alone, ignoring the minimum C-field calculation. I don't > see how > the minimum C-field reference frequency would help me since the > C-field pot is > not in the min position anymore due to factory tweaking. To be > specific, this is > what I would do: > > The unit returns the following string upon 'S': > > OK50255055.760840Hz F=2ABB5046B34A2E00 > > Now based on this, the tuning word should be coded in the first 8 > characters, of > F, i.e. '2ABB5046'. I'm a bit confused about the remaining characters > being > non-zero. Any documentation I came across has a number that ends in 8 > zeroes... > In any case, 0x2ABB5046 is 716918854 in decimal and the resolution would > therefore be > > 2^23 / 716918854 = approx. 0.0117 Hz which makes sense. > > The physics package would then output a frequency of > > f_ref = (2^23 / 716918854) * 2^32 = approx. 50255055.809934 Hz > > This is higher than the reference given in the 'S' output, which is in > line with > what Mark wrote. However, scaling this with the average correction > factor he > gave yields > > f_ref * 1.000000002150 = approx. 50255055.917982 Hz > > Which is higher than what I would expect. Then again I'm not entirely > sure what > I would expect because various errors add up in the above calculation. > I'd be > interested in what people with more experience think about those results. > > I would then use > > M = 10000000/(2^23/716918854) = approx. 854633872.509003 > > to find the 10 MHz tuning word, which I would then round up > (unfortunately it's > smack in the middle between two integers...) and convert to hex, yielding > 0x32F0AD91. This does in fact result in a 10.000 MHz output waveform > but I have > no means to check its accuracy (yet?). I'd appreciate any hints about > where > things could have potentially gone wrong, especially with respect to > the minimum > C-field reference frequency that I ended up not using. > > On a slightly related note, I have cooked up a small PCB with a local 5 V > regulator and status LEDs that mates with the amphenol connector used > on this > standard. I have to complete the write-up on it and will probably put > up a > video about the mod on my youtube channel; once this is done I'll be > sitting on > 9 spare boards since I got 10 boards done. If there is interest, I > could send > off the spares without profit, i.e. for about 5 bucks or so. I imagine > this > could be of use to those who have the same standard. The board doesn't do > anything funky, it is just neat. In any case I'd like to ask if it > would be OK > to formally place this offer on the list once I got everything ready. > > Thanks a lot and best regards! > > Matt > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

On 2017-01-02 01:31, wb6bnq wrote: Hello Bill Thanks for your response and the pdf manual. There's lots of good information in there. You are certainly right in that there's a few things that I have not understood. Unfortunately this has not changed after having read your response: > That "R" number is actually the Rb frequency divided by 136 plus the > upward fine tuning of the C-field pot.  See PDF page 16 & 17 of the > attached PDF operational manual for the FEI-5650. In the comprehensive post[*] that I quote in my original request, Mark states that "THE R= REFERENCE FREQUENCY IS NOT THE FREQUENCY THAT THE PHYSICS PACKAGE IS SHIPPED TUNED TO!!! It is the frequency produced by the physics package at the minimum setting of the C-field potentiometer." This seems to be contradictory to what you wrote. Either the R value is determined at the C-field pot minimum frequency position as Mark stated, in which case it does not contain the upward C-field tweaking. Or it is determined after the final tweaking as you say. Either way I don't understand how to incorporate the R reference frequency into my calculations, which is what Mark seems to be suggesting. > The "F" number is truly a 32 bit number, not just the first 8 digits > but all 16 of them. The F number has 16 hex digits. Since each of those digits represents a nibble (i.e. half a byte, 4 bits), I end up with 16*4 = 64 bits. Not just 32. The first 8 digits of the F number however represent a 32 bit number, which is also the size of the the phase accumulator in the AD9830 which makes sense in my opinion. I think I absolutely failed to grasp what you're trying to tell me here :-( Re-reading the paragraph in [*] that starts with "You can set the divisor" did clear up something for me though -- looks like there's nothing weird with the F-number stored in my unit; the last byte is indeed 0x00. I still don't quite understand why this parameter is potentially stored at a higher precision than what the DDS can deliver. > It would probably have been better to purchase one of the Rb's that > already output 10 MHz instead of hacking the option 58.  BUT that is > just my opinion. You are probably right on that, yet getting any of those surplus standards off of ebay seems to be a bit of a hit-or-miss thing anyway. At least I get the learning experience, that's gotta count for something :-). Thanks again for your response and best regards Matt

Hi > On Jan 1, 2017, at 7:31 PM, wb6bnq <wb6bnq@cox.net> wrote: > > Hello Mathias, > > I think you did not quite understand how the calibration process works with that unit. The factory procedure is to set the pot to minimum and then bring the DDS up to the step that produces the closest frequency just below the wanted one and then use the C-field pot as the final tweak. > > The "R" value is composed of a number of factors that can only be determined after the Rb cell is made. A number of variables, in the Rb cell itself, will determine the actual "ON" resonance frequency and that is what is programmed into the "R" number at the end of final assembly. > > That "R" number is actually the Rb frequency divided by 136 plus the upward fine tuning of the C-field pot. See PDF page 16 & 17 of the attached PDF operational manual for the FEI-5650. The only difference between all the variants comes after the Physics Package as shown on PDF page 16 block diagram. > > The "F" number is truly a 32 bit number, not just the first 8 digits but all 16 of them. > > Your problem is being able to have a frequency reference that is, obviously, way better then the Rb. As Cesium and Hydrogen references are quite expensive that leaves just the GPS satellites as the only other reference available that will do the job. Of course that entails more than just the GPS "timing" receiver as you will need some other equipment to help in the comparison process. Also it takes time to do many small adjustments to achieve that final comparison. It won't happen in just one day. > > It would probably have been better to purchase one of the Rb's that already output 10 MHz instead of hacking the option 58. BUT that is just my opinion. > This heads you down another rabbit hole. Since the 10 MHz output units sell better than the PPS only versions, there is a cottage industry going to convert one to the other. Parts are missing on the board to make a “proper” 10 MHz unit. The conversion often is a bit ugly. No matter how well it is done electrically, bashing a hole in the magnetic shield case for the SMA is a really bad idea unless you have the proper gear to heat create it after you are done. So yes, the 10 MHz version is a better way to go, but only if it came from the factory as a 10 MHz unit ….. Bob > Good luck, > > Bill Houlne....WB6BNQ > > Mathias Weyland wrote: > >> Hello guys >> >> I'm new to this list. I got myself a FE-5650A Rubidium Standard off of ebay. >> It's the "option 58" 1 pps output variant, hence I have to modify the tuning >> word used in the DDS phase accumulator to get 10 MHz out. I found a vast amount >> of awesome descriptions on how to do that on the web and in particular on this >> list. One write-up that stood out was this one by Mark Sims: >> >> http://www.mail-archive.com/time-nuts@febo.com/msg13486.html >> >> I think I can pull this off since everything is documented so nicely. However, >> I'm having trouble calculating the right tuning word and this is why: Mark notes >> that the reference frequency reported by the unit is the one with the C-field >> pot at the lowest frequency position. He gives a number of suggestions on how to >> deal with that. Since I didn't get that hydrogen maser for Christmas, the best >> approach seems to be "to calculate the true reference frequency from the saved >> (minimum C-field) R=reference frequency and F=divisor word and use that value to >> calculate divisor words." I don't understand how the saved minimum C-field >> reference ties into this calculation. >> >> My approach would have been to calculate the true reference frequency from the >> saved divisor alone, ignoring the minimum C-field calculation. I don't see how >> the minimum C-field reference frequency would help me since the C-field pot is >> not in the min position anymore due to factory tweaking. To be specific, this is >> what I would do: >> >> The unit returns the following string upon 'S': >> >> OK50255055.760840Hz F=2ABB5046B34A2E00 >> >> Now based on this, the tuning word should be coded in the first 8 characters, of >> F, i.e. '2ABB5046'. I'm a bit confused about the remaining characters being >> non-zero. Any documentation I came across has a number that ends in 8 zeroes... >> In any case, 0x2ABB5046 is 716918854 in decimal and the resolution would >> therefore be >> >> 2^23 / 716918854 = approx. 0.0117 Hz which makes sense. >> >> The physics package would then output a frequency of >> >> f_ref = (2^23 / 716918854) * 2^32 = approx. 50255055.809934 Hz >> >> This is higher than the reference given in the 'S' output, which is in line with >> what Mark wrote. However, scaling this with the average correction factor he >> gave yields >> >> f_ref * 1.000000002150 = approx. 50255055.917982 Hz >> >> Which is higher than what I would expect. Then again I'm not entirely sure what >> I would expect because various errors add up in the above calculation. I'd be >> interested in what people with more experience think about those results. >> >> I would then use >> >> M = 10000000/(2^23/716918854) = approx. 854633872.509003 >> >> to find the 10 MHz tuning word, which I would then round up (unfortunately it's >> smack in the middle between two integers...) and convert to hex, yielding >> 0x32F0AD91. This does in fact result in a 10.000 MHz output waveform but I have >> no means to check its accuracy (yet?). I'd appreciate any hints about where >> things could have potentially gone wrong, especially with respect to the minimum >> C-field reference frequency that I ended up not using. >> >> On a slightly related note, I have cooked up a small PCB with a local 5 V >> regulator and status LEDs that mates with the amphenol connector used on this >> standard. I have to complete the write-up on it and will probably put up a >> video about the mod on my youtube channel; once this is done I'll be sitting on >> 9 spare boards since I got 10 boards done. If there is interest, I could send >> off the spares without profit, i.e. for about 5 bucks or so. I imagine this >> could be of use to those who have the same standard. The board doesn't do >> anything funky, it is just neat. In any case I'd like to ask if it would be OK >> to formally place this offer on the list once I got everything ready. >> >> Thanks a lot and best regards! >> >> Matt >> _______________________________________________ >> 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. >> > > <FE5650A_Operation-Maint.pdf>_______________________________________________ > 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.

Maybe a waterjet cutter would imapct less on the shielding properties of tthe mumetal? Bruce On Monday, January 02, 2017 12:58:55 PM Bob Camp wrote: > Hi > > > On Jan 1, 2017, at 7:31 PM, wb6bnq <wb6bnq@cox.net> wrote: > > > > Hello Mathias, > > > > I think you did not quite understand how the calibration process works > > with that unit. The factory procedure is to set the pot to minimum and > > then bring the DDS up to the step that produces the closest frequency > > just below the wanted one and then use the C-field pot as the final > > tweak. > > > > The "R" value is composed of a number of factors that can only be > > determined after the Rb cell is made. A number of variables, in the Rb > > cell itself, will determine the actual "ON" resonance frequency and that > > is what is programmed into the "R" number at the end of final assembly. > > > > That "R" number is actually the Rb frequency divided by 136 plus the > > upward fine tuning of the C-field pot. See PDF page 16 & 17 of the > > attached PDF operational manual for the FEI-5650. The only difference > > between all the variants comes after the Physics Package as shown on PDF > > page 16 block diagram. > > > > The "F" number is truly a 32 bit number, not just the first 8 digits but > > all 16 of them. > > > > Your problem is being able to have a frequency reference that is, > > obviously, way better then the Rb. As Cesium and Hydrogen references are > > quite expensive that leaves just the GPS satellites as the only other > > reference available that will do the job. Of course that entails more > > than just the GPS "timing" receiver as you will need some other equipment > > to help in the comparison process. Also it takes time to do many small > > adjustments to achieve that final comparison. It won't happen in just > > one day. > > > > It would probably have been better to purchase one of the Rb's that > > already output 10 MHz instead of hacking the option 58. BUT that is just > > my opinion. > This heads you down another rabbit hole. Since the 10 MHz output units sell > better than the PPS only versions, there is a cottage industry going to > convert one to the other. Parts are missing on the board to make a “proper” > 10 MHz unit. The conversion often is a bit ugly. No matter how well it is > done electrically, bashing a hole in the magnetic shield case for the SMA > is a really bad idea unless you have the proper gear to heat create it > after you are done. > > So yes, the 10 MHz version is a better way to go, but only if it came from > the factory as a 10 MHz unit ….. > > Bob > > > Good luck, > > > > Bill Houlne....WB6BNQ > > > > Mathias Weyland wrote: > >> Hello guys > >> > >> I'm new to this list. I got myself a FE-5650A Rubidium Standard off of > >> ebay. It's the "option 58" 1 pps output variant, hence I have to modify > >> the tuning word used in the DDS phase accumulator to get 10 MHz out. I > >> found a vast amount of awesome descriptions on how to do that on the web > >> and in particular on this list. One write-up that stood out was this one > >> by Mark Sims: > >> > >> http://www.mail-archive.com/time-nuts@febo.com/msg13486.html > >> > >> I think I can pull this off since everything is documented so nicely. > >> However, I'm having trouble calculating the right tuning word and this > >> is why: Mark notes that the reference frequency reported by the unit is > >> the one with the C-field pot at the lowest frequency position. He gives > >> a number of suggestions on how to deal with that. Since I didn't get > >> that hydrogen maser for Christmas, the best approach seems to be "to > >> calculate the true reference frequency from the saved (minimum C- field) > >> R=reference frequency and F=divisor word and use that value to calculate > >> divisor words." I don't understand how the saved minimum C-field > >> reference ties into this calculation. > >> > >> My approach would have been to calculate the true reference frequency > >> from the saved divisor alone, ignoring the minimum C-field calculation. > >> I don't see how the minimum C-field reference frequency would help me > >> since the C-field pot is not in the min position anymore due to factory > >> tweaking. To be specific, this is what I would do: > >> > >> The unit returns the following string upon 'S': > >> > >> OK50255055.760840Hz F=2ABB5046B34A2E00 > >> > >> Now based on this, the tuning word should be coded in the first 8 > >> characters, of F, i.e. '2ABB5046'. I'm a bit confused about the > >> remaining characters being non-zero. Any documentation I came across has > >> a number that ends in 8 zeroes... In any case, 0x2ABB5046 is 716918854 > >> in decimal and the resolution would therefore be > >> > >> 2^23 / 716918854 = approx. 0.0117 Hz which makes sense. > >> > >> The physics package would then output a frequency of > >> > >> f_ref = (2^23 / 716918854) * 2^32 = approx. 50255055.809934 Hz > >> > >> This is higher than the reference given in the 'S' output, which is in > >> line with what Mark wrote. However, scaling this with the average > >> correction factor he gave yields > >> > >> f_ref * 1.000000002150 = approx. 50255055.917982 Hz > >> > >> Which is higher than what I would expect. Then again I'm not entirely > >> sure what I would expect because various errors add up in the above > >> calculation. I'd be interested in what people with more experience think

Hi > On Jan 2, 2017, at 5:02 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > > Maybe a waterjet cutter would imapct less on the shielding properties of > tthe mumetal? > Maybe …. pretty good bet that the guys modifying these in their living room aren’t focused on much more than getting them working as fast as they possibly can. Bob > Bruce > > On Monday, January 02, 2017 12:58:55 PM Bob Camp wrote: >> Hi >> >>> On Jan 1, 2017, at 7:31 PM, wb6bnq <wb6bnq@cox.net> wrote: >>> >>> Hello Mathias, >>> >>> I think you did not quite understand how the calibration process works >>> with that unit. The factory procedure is to set the pot to minimum and >>> then bring the DDS up to the step that produces the closest <snip>

On Tuesday, 3 January 2017 11:46 AM, Bob Camp <kb8tq@n1k.org> wrote:

One could always wrap the assembly with its impaired mu metal shield in several layers of flexible magnetic shielding foil to regain the desired magnetic shielding e.Most such foils can be cut with scissors without significant effect on their magnetic properties. Bruce On Tuesday, 3 January 2017 11:46 AM, Bob Camp <kb8tq@n1k.org> wrote: Hi > On Jan 2, 2017, at 5:02 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > > Maybe a waterjet cutter would  imapct less on the shielding properties of > tthe mumetal? > Maybe …. pretty good bet that the guys modifying these in their living room aren’t focused on much more than getting them working as fast as they possibly can. Bob > Bruce > > On Monday, January 02, 2017 12:58:55 PM Bob Camp wrote: >> Hi >> >>> On Jan 1, 2017, at 7:31 PM, wb6bnq <wb6bnq@cox.net> wrote: >>> >>> Hello Mathias, >>> >>> I think you did not quite understand how the calibration process works >>> with that unit.  The factory procedure is to set the pot to minimum and >>> then bring the DDS up to the step that produces the closest <snip> _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.

On Tuesday, 3 January 2017 11:46 AM, Bob Camp <kb8tq@n1k.org> wrote:

Hi My biggest concern is that they magnetize the shield as they drill it. It’s a “static” field, but it’s a static *near* field. I doubt that is a good thing …. Bob > On Jan 2, 2017, at 5:53 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > One could always wrap the assembly with its impaired mu metal shield in several layers of flexible magnetic shielding foil to regain the desired magnetic shielding e.Most such foils can be cut with scissors without significant effect on their magnetic properties. > Bruce > > On Tuesday, 3 January 2017 11:46 AM, Bob Camp <kb8tq@n1k.org> wrote: > > > Hi > > >> On Jan 2, 2017, at 5:02 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: >> >> >> Maybe a waterjet cutter would imapct less on the shielding properties of >> tthe mumetal? >> > > Maybe …. pretty good bet that the guys modifying these in their living room > aren’t focused on much more than getting them working as fast as they possibly > can. > > Bob > >> Bruce >> >> On Monday, January 02, 2017 12:58:55 PM Bob Camp wrote: >>> Hi >>> >>>> On Jan 1, 2017, at 7:31 PM, wb6bnq <wb6bnq@cox.net> wrote: >>>> >>>> Hello Mathias, >>>> >>>> I think you did not quite understand how the calibration process works >>>> with that unit. The factory procedure is to set the pot to minimum and >>>> then bring the DDS up to the step that produces the closest > <snip> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > _______________________________________________ > 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.

		Attila Kinali

On Tue, 03 Jan 2017 11:02:54 +1300 Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > Maybe a waterjet cutter would imapct less on the shielding properties of > tthe mumetal? I doubt it. mu-metal is pretty sensitive to vibration as well and a waterjet creates plenty of that. But anealing mu-metal is pretty simple, if one has enough space to build a furnace in the backyard. All you have to do is find a wall material that can withstand the 1000-1500°C annealing temperature and which can be flooded with hydrogen is enough. Flooding the furnace with hydrogen is not dangerous, as long as the interior is completely flooded (no oxygen) and the hydrogen leaks out at well controlled points, where it can burn off. There are descriptions how to do that out there. The only problem is that you need enough space around the furnace for the hydrogen flames to not cause any trouble. Being outside also helps to prevent hydrogen build-ups on the ceiling while initially flooding the furnace or shuting it off. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson

		Attila Kinali

and if you glue a piece of non-magnetic material -- which could hold that connector -- it could be even some plastic, to the surface of the mu-metal , you do not need to worry about disturbing the magnetic conditions 73 KJ6UHN Alex On 1/2/2017 3:44 PM, Attila Kinali wrote: > On Tue, 03 Jan 2017 11:02:54 +1300 > Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > >> Maybe a waterjet cutter would imapct less on the shielding properties of >> tthe mumetal? > I doubt it. mu-metal is pretty sensitive to vibration as well and a > waterjet creates plenty of that. But anealing mu-metal is pretty simple, > if one has enough space to build a furnace in the backyard. All you have > to do is find a wall material that can withstand the 1000-1500°C annealing > temperature and which can be flooded with hydrogen is enough. > > Flooding the furnace with hydrogen is not dangerous, as long as the > interior is completely flooded (no oxygen) and the hydrogen leaks > out at well controlled points, where it can burn off. There are > descriptions how to do that out there. The only problem is that you need > enough space around the furnace for the hydrogen flames to not cause any > trouble. Being outside also helps to prevent hydrogen build-ups on the > ceiling while initially flooding the furnace or shuting it off. > > > Attila Kinali