[time-nuts] Differences / Jitter Between Frequency Standard Sources
I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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] Differences / Jitter Between Frequency Standard Sources
Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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] Differences / Jitter Between Frequency Standard Sources
On 11/24/2011 10:01 AM, Robin Kimberley wrote: Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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. actually, any digital display system would be +-1 count in the least significant position. counters, voltmeters, etc. randy ___ 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] Differences / Jitter Between Frequency Standard Sources
Just as an aside, you /can /get rid of the 'dithering digit' problem if you use a counter which employs a reciprocal counting technique. I use a Thandar Thirlby TF830 locked to a 10MHz reference derived from a Tbolt, but I'm sure there must be others. David Bobbett, G4IRQ On 24/11/2011 18:01, Robin Kimberley wrote: Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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] Differences / Jitter Between Frequency Standard Sources
Or modern counters where internally every type of measurement is reduced to a time interval measurement like the HP53132 (150pS resolution). On Thu, Nov 24, 2011 at 8:04 PM, David Bobbett d.bobb...@tiscali.co.ukwrote: Just as an aside, you /can /get rid of the 'dithering digit' problem if you use a counter which employs a reciprocal counting technique. I use a Thandar Thirlby TF830 locked to a 10MHz reference derived from a Tbolt, but I'm sure there must be others. David Bobbett, G4IRQ On 24/11/2011 18:01, Robin Kimberley wrote: Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Differences / Jitter Between Frequency Standard Sources
Thanks to all who replied. I thought that it was a counter artifact, but I didn't know why. Any suggestions for a reasonably priced good frequency counter that uses the reciprocal method? I saw there were a couple TF830's on ebay, but they were outside the U.S. The HP 5340A looks like it might do the job, but I have heard that there are repair issues if it fails. Thanks. Fred Bray W6WAW ___ 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] Differences / Jitter Between Frequency Standard Sources
On Thu, 24 Nov 2011 12:54:12 -0800, Frederick Bray wrote: Thanks to all who replied. I thought that it was a counter artifact, but I didn't know why. Any suggestions for a reasonably priced good frequency counter that uses the reciprocal method? I saw there were a couple TF830's on ebay, but they were outside the U.S. The HP 5340A looks like it might do the job, but I have heard that there are repair issues if it fails. Thanks. Fred Bray W6WAW Isn't your 5385A counter a reciprocal type ? Quote The Agilent 5385A frequency counter utilizes interpolar-enhanced reciprocal counting http://www.home.agilent.com/agilent/product.jspx? nid=-536902484.536879843.00lc=engcc=US CFO ___ 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] Differences / Jitter Between Frequency Standard Sources
Looks like my counter is reciprocal. Thanks for the info. Fred Bray W6WAW ___ 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] Differences / Jitter Between Frequency Standard Sources
I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Fred, This is normal (for both gated and reciprocal counters). Never trust a frequency counter that gives you the same number every time. In fact it is very advantages. If you log hundreds or thousands of these frequency readings and compute the mean you will get a more precise value for your long-term average frequency. It's unlikely you will get a 50/50 split between the two readings; the actual ratio between them allows you to interpolate somewhat between 9 and 0 in the last digit. Try it. /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.
