[time-nuts] Frequency counters
Hi guys, I want to find a frequency counter that will read to 1 hz precision up to a minimum of 30 Mhz that I can clock using the output from my Efratom 101 Rb frequency standard. I am quite happy to make one if there is a suitable design out there. Any suggestions? 72/3 de Steve G0XAR -- It is vain to do with more that which can be done with less. ___ 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] Frequency counters
Virtually any HP counter made after 1975 will do that. You might also look at a Tektronix TM-500 counter (DC503, ...) and mainframe. -John == > Hi guys, > > I want to find a frequency counter that will read to 1 hz precision up to > a > minimum of 30 Mhz that I can clock using the output from my Efratom 101 Rb > frequency standard. I am quite happy to make one if there is a suitable > design out there. Any suggestions? > > 72/3 de Steve G0XAR > > -- > It is vain to do with more that which can be done with less. > ___ > 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] Frequency counters
On Aug 20, 2010, at 10:35 AM, Stephen Farthing wrote: > I want to find a frequency counter that will read to 1 hz precision up to a > minimum of 30 Mhz that I can clock using the output from my Efratom 101 Rb > frequency standard. I am quite happy to make one if there is a suitable > design out there. Any suggestions? I'm also beginning to look for a counter with very similar requirements. Studying eBay the other day, I came to the conclusion that an HP 5384A would be a good option, combining small size (compared to older rackmount counters), adequate resolution, an external reference input, and availability at fairly low prices. I decided that I probably don't need to hold out for one with the TCXO or OCXO options, since I'd generally only use it on my bench with my TBolt's OCXO as a reference, and it simply switches between its built-in reference and the external one rather than phase-locking its own reference (so I wouldn't be using its internal reference, and thus its performance wouldn't matter). -- Mark J. Blair, NF6X Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Frequency counters
On 08/20/2010 07:39 PM, J. Forster wrote: Virtually any HP counter made after 1975 will do that. You might also look at a Tektronix TM-500 counter (DC503, ...) and mainframe. A HP5335A or HP5334A should be good value for the money in that category, just to get you started in finding something. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Frequency counters
> I'm also beginning to look for a counter with very similar requirements. > Studying eBay the other day, I came to the conclusion that an HP 5384A would > be a good option, combining small size (compared to older rackmount > counters), adequate resolution, an external reference input, and > availability at fairly low prices. One thing to add to your checklist... Does it have a (noisy) fan? I suspect anything that is low cost won't have a lot of parts it in so won't make much heat and won't need a fan. But you might find a good deal on a fancy/noisy unit. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Frequency counters
Hi I never liked the display on the 5384. The LED's on the 5335 or 5334 always seemed easier to read. Bob On Aug 20, 2010, at 2:44 PM, Hal Murray wrote: > >> I'm also beginning to look for a counter with very similar requirements. >> Studying eBay the other day, I came to the conclusion that an HP 5384A would >> be a good option, combining small size (compared to older rackmount >> counters), adequate resolution, an external reference input, and >> availability at fairly low prices. > > One thing to add to your checklist... Does it have a (noisy) fan? > > I suspect anything that is low cost won't have a lot of parts it in so won't > make much heat and won't need a fan. But you might find a good deal on a > fancy/noisy unit. > > > > -- > 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] Frequency counters
Almost any counter with a 10 sec (hz) resolution time is fine. Doesn't even need to have provisions for an external clock , ( you can wire that in), as long as it has a 10mhz time base. You're going to drive it with an external 10mhz disciplined anyhow. Thank You Kiss-Electronics Ms Ashley Hall 183 N 5th Avenue Cornelius, Oregon 97113 W7DUZ www.kiss-electronics.com -Original Message- From: Hal Murray To: Discussion of precise time and frequency measurement Sent: Fri, Aug 20, 2010 11:44 am Subject: Re: [time-nuts] Frequency counters I'm also beginning to look for a counter with very similar requirements. Studying eBay the other day, I came to the conclusion that an HP 5384A would be a good option, combining small size (compared to older rackmount counters), adequate resolution, an external reference input, and availability at fairly low prices. One thing to add to your checklist... Does it have a (noisy) fan? I suspect anything that is low cost won't have a lot of parts it in so won't ake much heat and won't need a fan. But you might find a good deal on a ancy/noisy unit. -- hese are my opinions, not necessarily my employer's. I hate spam. __ ime-nuts mailing list -- time-nuts@febo.com o unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts nd 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] Frequency counters
Hi Stephen, I assume from the callsign that you are in the UK. You could do worse than to buy a used HP 5316A for £75 from Stewart of Reading < http://www.stewart-of-reading.co.uk/Frequency%20Counters.htm > A quality compact universal counter with reciprical counting, external reference input and HPIB. I've no association with Stewarts apart from being a happy customer personally and for work for nearly 30 years! Regards, Robert G8RPI. --- On Fri, 20/8/10, Stephen Farthing wrote: From: Stephen Farthing Subject: [time-nuts] Frequency counters To: time-nuts@febo.com Date: Friday, 20 August, 2010, 18:35 Hi guys, I want to find a frequency counter that will read to 1 hz precision up to a minimum of 30 Mhz that I can clock using the output from my Efratom 101 Rb frequency standard. I am quite happy to make one if there is a suitable design out there. Any suggestions? 72/3 de Steve G0XAR -- It is vain to do with more that which can be done with less. ___ 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] Frequency counters
> I want to find a frequency counter that will read to 1 hz precision up to a > minimum of 30 Mhz that I can clock using the output from my Efratom 101 Rb > frequency standard. I am quite happy to make one if there is a suitable > design out there. Any suggestions? Do you want to read the answer with your eyes, or get it into a computer? Most of the older HP counters have HP-IB/GP-IB. I think you could build everything you need in a small FPGA. I'm thinking of something like this: Assuming a reference clock, generate a pulse every second. Count cycles on your unknown clock. On each second pulse, copy the cycle-counter to another register and reset the counter. That gives you the number of cycles in the previous second. If you count in decimal rather than binary, it's simple to send out the digits as ASCII. With a bit more work, you could feed them to a small LCD display. One complication is avoiding metastability. My straw man would be to run the internal logic at 100 MHz (derived from the 10 MHz reference) and just run the input signal through a classic pair of FFs. I pulled 100 MHz out of the air. It's a nice round number. It might be too fast for a simple design with 8 digits in the counter chain. This whole problem is easily pipelined so you can run it at close to the max toggle rate in your chip, but that adds complexity. In the simplest version of the synchronizer, the receiving clock has to run at over 2X the sending clock. Then the receiving logic just looks for rising edges in the input data stream. You can gain a factor of 2 if you divide the sending clock by 2 and look for either rising or falling edges. That would let you run the main clock at 40 MHz which might be slow enough to avoid having to think about pipelines. You can probably to do the whole thing in software if you pick a chip with the right counter/timer blocks. I'd have to check the fine print on the data sheet carefully to see how fast the counter/timers will go. Some of them have prescalers so the counter can watch a fast signal, but if you divide the input signal too much you won't be able to get your 1 Hz resolution. But maybe you can count for several seconds... -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Frequency counters
+1 on the 5315 / 5316A/B. 5316's come with HPIB. Both can be surprisingly cheap, and, they have no fan. Adrian Robert Atkinson schrieb: Hi Stephen, I assume from the callsign that you are in the UK. You could do worse than to buy a used HP 5316A for £75 from Stewart of Reading< http://www.stewart-of-reading.co.uk/Frequency%20Counters.htm> A quality compact universal counter with reciprical counting, external reference input and HPIB. I've no association with Stewarts apart from being a happy customer personally and for work for nearly 30 years! Regards, Robert G8RPI. --- On Fri, 20/8/10, Stephen Farthing wrote: From: Stephen Farthing Subject: [time-nuts] Frequency counters To: time-nuts@febo.com Date: Friday, 20 August, 2010, 18:35 Hi guys, I want to find a frequency counter that will read to 1 hz precision up to a minimum of 30 Mhz that I can clock using the output from my Efratom 101 Rb frequency standard. I am quite happy to make one if there is a suitable design out there. Any suggestions? 72/3 de Steve G0XAR ___ 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hello, I just joined the group a couple of weeks ago and have one remark about an HP counter that I bought on ebay and also one question. The HP 5386A I own incorporates a 12-character display which works out wonderfully when using the 10 MHz output of a Rubidium source to clock the counter. The one I bought goes up to 3 GHz but there is a less expensive version of the same thing which although doesn't go to 3 Gig, has the same resolution. I found this unit to be a great way to compare the Rubidium's frequency with an HP GPS clock source. I bought a Frequency Electronics FE 5680A Rubidium card on ebay too and found that when comparing it's output at 10 MHz to the output of the HP GPS standard that they did not agree when comparing the two using the above mentioned HP counter (using the HP GPS as the clock for the counter). The Rubidium I purchased is a few years old but locks up every time in just three minutes so I know it is in good shape but yet it didn't agree to the -9 on the frequency counter. So, here is my question, do Rubidium standards drift that much over a period of years to where they have to be brought back on frequency? If so, what is tuned on the Rubidium to do so, C-field? I didn't touch anything on the physics package of the FE 5680A but the unit has a DDS divider built into it so I was able to adjust the Rubidium to agree with the HP GPS standard through an RS 232 serial connection and hexidecimal inputs to change the frequency of the dividers output. The divider they use can adjust the frequency far finer than the best resolution of any Rubidium standard so I thought that would be a good way to match the output of the GPS standard. I'm new to time standards, GPS or Rubidium units and purchased it for some telecom work so I'd appreciate any suggestions or comments anyone here might have. One last question in regard to counters. Is it possible, or does anyone make a frequency counter which has 12 digits but only displays 1 Hz and below regardless of the frequency which is fed into it? i.e. 1 Ghz reads out as 1.000 000 000 00 (if on frequency) only displaying the last cycle of the count down to -11 ? Thanks for the bandwidth 73 K L 7 Fox Bravo. - Original Message - From: <[EMAIL PROTECTED]> To: Sent: Wednesday, September 26, 2007 8:00 AM Subject: time-nuts Digest, Vol 38, Issue 36 > Send time-nuts mailing list submissions to > time-nuts@febo.com > > To subscribe or unsubscribe via the World Wide Web, visit > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > or, via email, send a message with subject or body 'help' to > [EMAIL PROTECTED] > > You can reach the person managing the list at > [EMAIL PROTECTED] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of time-nuts digest..." > > > Today's Topics: > > 1. Re: FMT on October 13 (Magnus Danielson) > > > -- > > Message: 1 > Date: Wed, 26 Sep 2007 13:15:15 +0200 (CEST) > From: Magnus Danielson <[EMAIL PROTECTED]> > Subject: Re: [time-nuts] FMT on October 13 > To: time-nuts@febo.com, [EMAIL PROTECTED] > Message-ID: <[EMAIL PROTECTED]> > Content-Type: Text/Plain; charset=us-ascii > > From: "Didier Juges" <[EMAIL PROTECTED]> > Subject: Re: [time-nuts] FMT on October 13 > Date: Wed, 26 Sep 2007 05:57:14 -0500 > Message-ID: <[EMAIL PROTECTED]> > > Didier, > >> I just wanted to point out that with reciprocal counters, you can get >> resolution much better than the 1Hz/s you would get with conventional >> frequency counters, even though the actual accuracy of the measurement >> may >> be way off. > > These days conventional counteras are reciprocal counters. It is only the > old-school counters which is not reciprocal. Nothing wrong with > old-school, > but a conventional counter of the shelf today is probably a reciprocal > jobbie. > >> The original question seemed to imply that with a short transmission >> time, >> you could not guarantee a frequency accuracy of 1e-6 Hz, which you >> probably >> can't anyhow, but the limit is not the resolution of the instrument or >> the >> measurement method. >> >> I do not know how far off calibration my HP 5370s are, but the 20pS >> resolution is at best only usable under some circumstances that I have >> not >> isolated yet, due to jitter. >> >> When measuring a 3.5 MHz signal (@1dBm) from my HP 8657B through 1 meter >> of >> good coax cable (with counter and generator phase locked to the >> Thunderbolt >> GPSDO) in Frequency mode with a 1s gate time, the resolution is 1e-5Hz, >> with >> about 1e-3Hz p-p variation. When measuring over 1 period with 10,000 >> periods >> sample size, the resolution is only 1e-1Hz with a standard deviation of >> ~400 >> Hz (or about 0.1%). Of course, over the air, it will be much worse due to >> noise, let alone propagation, fading
Re: [time-nuts] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY CHazlitt wrote: > > So, here is my question, do Rubidium standards drift that much over a period > of years to where they have to be brought back on frequency? If so, what is > tuned on the Rubidium to do so, C-field? Yes, they do drift over time. There is a spec provided on the data sheet; you can expect the unit to drift at perhaps half of that specified maximum rate. You can adjust the magnetic field to bring it back to center frequency, but sometimes they drift so much (over >10 years) that you have to replace a factory-selected resistor to get the trimmer into range. The only type of commercially available frequency standard that doesn't drift is a cesium beam clock; their frequency of operation doesn't depend on magnetic fields or buffer gas pressure or anything like that. That's why they're used for GPS etc. ___ 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Rb's drift typically 10^-10 to 10^-11 per month, about 100X better than the best quartz. We hit the latter number on the pilot run of the HP10816 Rb. There are many drift mechanisms, which can be related to physics, chemistry, optics, magnetics, or electronics. If an Rb apparently has no drift, it really means the drift mechanisms are temporarily cancelling. They won't do this over the long run. Newer Rb units may use adjustment of the internal synthesizer in place of modifying the C-field. There are many disadvantages to modifying the C-field. Rick Karlquist N6RK David Forbes wrote: > ); SAEximRunCond expanded to false > Errors-To: [EMAIL PROTECTED] RETRY > > CHazlitt wrote: >> >> So, here is my question, do Rubidium standards drift that much over a >> period >> of years to where they have to be brought back on frequency? If so, what >> is >> tuned on the Rubidium to do so, C-field? > > Yes, they do drift over time. There is a spec provided on the data > sheet; you can expect the unit to drift at perhaps half of that > specified maximum rate. You can adjust the magnetic field to bring it > back to center frequency, but sometimes they drift so much (over >10 > years) that you have to replace a factory-selected resistor to get the > trimmer into range. > > The only type of commercially available frequency standard that doesn't > drift is a cesium beam clock; their frequency of operation doesn't > depend on magnetic fields or buffer gas pressure or anything like that. > That's why they're used for GPS etc. > > ___ > 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I picked up one of the Lucent RFG-RB units on ebay and sure enough it was off, but not by much. It was manufactured mid 2001. I adjusted the C-field pot while comparing it to my best z3801a. I'm waiting on a new GPIB interface to see just how well I did. The LPRO-101 in the RFG-RB makes about 15W of heat. I gently clamped it to the back heatsink of the RFG unit and left it on for an hour or two before adjusting with my counter in TI mode. I thought about drilling a small hole in the top of the RFG chassis so I could access the C-field pot, but decided I just liked taking the thing apart... Scott David Forbes wrote: > CHazlitt wrote: >> So, here is my question, do Rubidium standards drift that much over a period >> of years to where they have to be brought back on frequency? If so, what is >> tuned on the Rubidium to do so, C-field? > > Yes, they do drift over time. There is a spec provided on the data > sheet; you can expect the unit to drift at perhaps half of that > specified maximum rate. You can adjust the magnetic field to bring it > back to center frequency, but sometimes they drift so much (over >10 > years) that you have to replace a factory-selected resistor to get the > trimmer into range. > > The only type of commercially available frequency standard that doesn't > drift is a cesium beam clock; their frequency of operation doesn't > depend on magnetic fields or buffer gas pressure or anything like that. > That's why they're used for GPS etc. > > ___ > 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY From: "CHazlitt" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] time-nuts, frequency counters Date: Wed, 26 Sep 2007 13:41:30 -0800 Message-ID: <[EMAIL PROTECTED]> Hi! > I just joined the group a couple of weeks ago and have one remark about an > HP counter that I bought on ebay and also one question. The HP 5386A I own > incorporates a 12-character display which works out wonderfully when using > the 10 MHz output of a Rubidium source to clock the counter. The one I > bought goes up to 3 GHz but there is a less expensive version of the same > thing which although doesn't go to 3 Gig, has the same resolution. I found > this unit to be a great way to compare the Rubidium's frequency with an HP > GPS clock source. The cheaper ones is the HP 5384A (50 Hz - 225 MHz) and HP 5385A (50 Hz - 1 GHz). > I bought a Frequency Electronics FE 5680A Rubidium card on ebay too and > found that when comparing it's output at 10 MHz to the output of the HP GPS > standard that they did not agree when comparing the two using the above > mentioned HP counter (using the HP GPS as the clock for the counter). The > Rubidium I purchased is a few years old but locks up every time in just > three minutes so I know it is in good shape but yet it didn't agree to > the -9 on the frequency counter. > > So, here is my question, do Rubidium standards drift that much over a period > of years to where they have to be brought back on frequency? Yes. > If so, what is tuned on the Rubidium to do so, C-field? You can either tune the C-field or you can tune the synthesis-chain. For my old R&S Rubidium the synthesis-chain is fixed and the C-field is adjusted instead. Big vernier knob on the front and a CV-input on the back. > I didn't touch anything on the physics package of the FE 5680A but the unit > has a DDS divider built into it so I was able to adjust the Rubidium to agree > with the HP GPS standard through an RS 232 serial connection and hexidecimal > inputs to change the frequency of the dividers output. The divider they use > can adjust the frequency far finer than the best resolution of any Rubidium > standard so I thought that would be a good way to match the output of the GPS > standard. I think it is a good strategy. > I'm new to time standards, GPS or Rubidium units and purchased it for some > telecom work so I'd appreciate any suggestions or comments anyone here might > have. We tend to use time interval counters and the HP 5370A or HP 5370B is popular. Get once of those. > One last question in regard to counters. Is it possible, or does anyone make > a frequency counter which has 12 digits but only displays 1 Hz and below > regardless of the frequency which is fed into it? i.e. 1 Ghz reads out as > 1.000 000 000 00 (if on frequency) only displaying the last cycle of the > count down to -11 ? I have counters which display more digits than 12 if needed. Also, for stable sources we use spaced time-interval measures and plot those over time. We time-nuts seems eager to calculate our Allan Deviation charts, mumble obscuria about not optimal here and there... and for tau this and that you would have to consider... :) Welcome to the group! > Thanks for the bandwidth You didn't waste any bandwidth, but you did use up some bits. Not the same! :) (time-nuts are notorious nitpickers too!) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi CHazlitt: Yes, rubidum standards drift with time. There's usually a pot and/or an external fine tune voltage input to make fine adjustments. But over many years the drift will excedd the capability of the pot. The unit your have and a number of the modern units, like the Stanford Research PRS10, have a programmable divider so you can get the pot/external input back in range. http://www.prc68.com/I/PRS10.shtml The Stanford Research SR620 counter comes close to what you're asking for. It has 16 digits and depending on mode display: Frequency: GHz1, MHz3, kHz3, Hz3, mHz3, uHz3 = total of 16 digits Time: sec3, ms 3, us3, ns 3, ps 3 = total of 15 digits The digits are always in the same place, i.e. the front panel has the above labels directly below the digits, there are no units indicators to cause confusion. Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam CHazlitt wrote: > ); SAEximRunCond expanded to false > Errors-To: [EMAIL PROTECTED] RETRY > > Hello, > > I just joined the group a couple of weeks ago and have one remark about an > HP counter that I bought on ebay and also one question. The HP 5386A I own > incorporates a 12-character display which works out wonderfully when using > the 10 MHz output of a Rubidium source to clock the counter. The one I > bought goes up to 3 GHz but there is a less expensive version of the same > thing which although doesn't go to 3 Gig, has the same resolution. I found > this unit to be a great way to compare the Rubidium's frequency with an HP > GPS clock source. > > I bought a Frequency Electronics FE 5680A Rubidium card on ebay too and > found that when comparing it's output at 10 MHz to the output of the HP GPS > standard that they did not agree when comparing the two using the above > mentioned HP counter (using the HP GPS as the clock for the counter). The > Rubidium I purchased is a few years old but locks up every time in just > three minutes so I know it is in good shape but yet it didn't agree to > the -9 on the frequency counter. > > So, here is my question, do Rubidium standards drift that much over a period > of years to where they have to be brought back on frequency? If so, what is > tuned on the Rubidium to do so, C-field? I didn't touch anything on the > physics package of the FE 5680A but the unit has a DDS divider built into it > so I was able to adjust the Rubidium to agree with the HP GPS standard > through an RS 232 serial connection and hexidecimal inputs to change the > frequency of the dividers output. The divider they use can adjust the > frequency far finer than the best resolution of any Rubidium standard so I > thought that would be a good way to match the output of the GPS standard. > I'm new to time standards, GPS or Rubidium units and purchased it for some > telecom work so I'd appreciate any suggestions or comments anyone here might > have. > > One last question in regard to counters. Is it possible, or does anyone make > a frequency counter which has 12 digits but only displays 1 Hz and below > regardless of the frequency which is fed into it? i.e. 1 Ghz reads out as > 1.000 000 000 00 (if on frequency) only displaying the last cycle of the > count down to -11 ? > > Thanks for the bandwidth > > 73 K L 7 Fox Bravo. ___ 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Rick, >Newer Rb units may use adjustment of the internal synthesizer >in place of modifying the C-field. There are many disadvantages >to modifying the C-field. I'm also relatively new to the area - could you please elaborate on why modifying the C-field is a bad idea? Thnaks, Peter Vince ___ 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The simple answer, is it introduces another place for drift to occur. If the power supply that provides the current to create the C-field drifts with temperature, component aging, power line voltages, phases of the moon, ... your reference's frequency will also drift. -Chuck Harris Peter Vince wrote: > ); SAEximRunCond expanded to false > Errors-To: [EMAIL PROTECTED] RETRY > > Hi Rick, > >> Newer Rb units may use adjustment of the internal synthesizer >> in place of modifying the C-field. There are many disadvantages >> to modifying the C-field. > > I'm also relatively new to the area - could you please elaborate on > why modifying the C-field is a bad idea? > > Thnaks, > > Peter Vince > > ___ > 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Chuck Harris wrote: > ); SAEximRunCond expanded to false > Errors-To: [EMAIL PROTECTED] RETRY > > The simple answer, is it introduces another place for drift > to occur. If the power supply that provides the current to > create the C-field drifts with temperature, component aging, > power line voltages, phases of the moon, ... your reference's > frequency will also drift. > > -Chuck Harris > I must be missing something. Aren't all those bad things going to happen whether you adjust the C-field or leave it untouched? Isn't the C-field required for the Rb to work dependably and on freq? I think the question pertains to Rb sources that already have a screw to make the adjustment. Maybe you are saying the screw is there to put the C-field back where it belongs. I would have no way of knowing how to tell if it was right or wrong other than frequency. Rick said it is not a good way to adjust the frequency. I don't really understand why exactly either. > Peter Vince wrote: > >> ); SAEximRunCond expanded to false >> Errors-To: [EMAIL PROTECTED] RETRY >> >> Hi Rick, >> >> >>> Newer Rb units may use adjustment of the internal synthesizer >>> in place of modifying the C-field. There are many disadvantages >>> to modifying the C-field. >>> >> I'm also relatively new to the area - could you please elaborate on >> why modifying the C-field is a bad idea? >> >> Thnaks, >> >> Peter Vince >> >> > ___ 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY >> The simple answer, is it introduces another place for drift >> to occur. If the power supply that provides the current to >> create the C-field drifts with temperature, component aging, >> power line voltages, phases of the moon, ... your reference's >> frequency will also drift. >> >> -Chuck Harris >> > I must be missing something. Aren't all those bad things going to happen > whether you adjust > the C-field or leave it untouched? Isn't the C-field required for the Rb > to work dependably > and on freq? I think the question pertains to Rb sources that already > have a screw to make > the adjustment. Maybe you are saying the screw is there to put the > C-field back where it belongs. > I would have no way of knowing how to tell if it was right or wrong > other than frequency. > > Rick said it is not a good way to adjust the frequency. I don't really > understand why exactly either. There is an optimum range for the C-field. Too little will result in insufficent Zeeman splitting and too much makes the frequency too sensitive to magnetic field. Remember that frequency is proportional to the SQUARE of the C-field intensity. The C field screw is not designed to "put the C-field back where it belongs" but rather to move it away from its comfort zone to pull the frequency. I'm not an expert on Zeeman splitting, but I have heard people talking about finding a setting to avoid any spurious lines, as if the setting was like finding a clearing in a forest of lines. It is true that an adjustable C-field has the potential to drift more than a fixed C-field, but this is only one issue, that may or may not be pivotal. Another issue with changing the C-field is that it may affect the magnetic hysteresis in the magnetic shields. With a synthesizer, you introduce no drift due to adjustability, you always operate at the optimum C-field value, the adjustment is linear and predictable, and the range of adjustment is not limited, so you can introduce any offset you want, and it is remotely, digitally, programmable. And with modern synthesizers, this capability may well be virtually free. Even the HP10816 Rb standard, designed in the 1970's, had a synthesizer that we set to get on frequency, however this synthesizer was not intended to be user programmable. BTW, "C-field" is a bastardized term borrowed from cesium beam technology where there were "A" and "B" magnets to select the state and the C-field to bias the magnetic field in the interaction region. Hence "A-field" "B-field" and "C-field". Of course, Rb standards have no A or B fields. It is sort of logical in an "inside baseball" sense. Rick Karlquist N6RK ___ 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] time-nuts, frequency counters
>One last question in regard to counters. Is it possible, or does anyone make >a frequency counter which has 12 digits but only displays 1 Hz and below >regardless of the frequency which is fed into it? i.e. 1 Ghz reads out as >1.000 000 000 00 (if on frequency) only displaying the last cycle of the >count down to -11 ? I am new in the list and reading old postings. Sorry if this was already answered. I am using an HP53132A, and I can program an offset and a scale factor. I use to measure 10 MHz, so I program an scale factor of 1E-7 and offset of -1, so it displays relative offsets in a very pleasant way. Regards Luis Miguel Brugarolas ___ 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY > I am using an HP53132A, and I can program an offset and a scale factor. I use > to measure 10 MHz, so I program an scale factor of 1E-7 and offset of -1, so > it displays relative offsets in a very pleasant way. > > Regards > Luis Miguel Brugarolas That's a good point. In addition, the 53131A/53132A output the full resolution of the measurement over GPIB / RS232 regardless of the number of digits on front display. And, if you enable statistics (effectively extending the gate time), you get even more digits. Here, for example, is an excerpt from a set of 60 10-second readings made by a 53132A. The mean frequency is given to 14 or 15 digits: 10.000,000,000,190 MHz 10.000,000,000,224 MHz 10.000,000,000,170 MHz N : 60 STD DEV: 29.8 uHz MEAN : 10.000,000,000,204,3 MHz MAX: 10.000,000,000,279 MHz MIN: 10.000,000,000,148 MHz 10.000,000,000,215 MHz 10.000,000,000,191 MHz 10.000,000,000,181 MHz /tvb ___ 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] time-nuts, frequency counters
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Luis Miguel Brugarolas, The Fluke/Pendulum PM668x & 669x (AKA, CNT-8x,9x) have the same math functions available. Regards, Pwete Rawson ___ 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.
