Re: [time-nuts] Counter Internal Oscillator Importance with External Reference?
CERN have flagged another potential issue with the 53230A in that every so often seemingly randomly communications go hawire. Bruce > > On 10 May 2017 at 04:46 "Richard (Rick) Karlquist" > wrote: > > On 5/9/2017 12:05 AM, Poul-Henning Kamp wrote: > > > > > > > > I'm sure that modern counters like 53230 are better at this than > > > > > > The 53230 oven oscillator option in an inferior oscillator to > the 10811, by an order of magnitude. So in this case, > modern != better. > > Rick > > ___ > 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] Counter Internal Oscillator Importance with External Reference?
On 5/9/2017 12:05 AM, Poul-Henning Kamp wrote: I'm sure that modern counters like 53230 are better at this than The 53230 oven oscillator option in an inferior oscillator to the 10811, by an order of magnitude. So in this case, modern != better. Rick ___ 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] Counter Internal Oscillator Importance with External Reference?
In message <54ee7bdd-0a49-cc49-540d-2812e70dd...@rubidium.dyndns.org>, Magnus Danielson writes: >Wither it is proper side bands or other systematic noise, it is bad >indeed, [...] It's more subtle than that, it can be things like thresholds in the counters trigger being sensitive to the phase of the internal clock because of (very slight) cross-talk. I reported data on this a couple of years ago, as I recall my setup were something like this: House-10MHz --> HP3336C clk-in and HP5370B clk-in. HP3336C output -> HP5370B start then 3m coax then HP5370B stop. Measure TI(start->stop), for different settings of output phase angle on the HP3336C. Theoretically that plot should be a flat line. In practice it is not even close. I think I convinced myself that the majority of the problem was trigger-noise the HP5370B, but my notes are not accessible at this time. -- 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] Counter Internal Oscillator Importance with External Reference?
Hi Poul-Henning, On 05/09/2017 02:39 PM, Poul-Henning Kamp wrote: In message <60c74d75-41e5-7112-d8b6-721664b89...@rubidium.dyndns.org>, Magnus Danielson writes: Indeed. On the other hand some measurements is hard not to do that way. One should think about how isolation is created if needed, and this includes AC and DC, common mode and differential mode. Isolation amplifier should be part of the arsenal. EMI is part of it, but there raw synchronism is a significant source of systematic errors because the "noise" is no longer gaussian. Wither it is proper side bands or other systematic noise, it is bad indeed, that would be part of the RF differential mode disturbances. This assumes the source is "clean", and if it is not it should not be used to start with. What remains is really issues from the setup, and that's when signal integrity/EMI care and isolation amplifiers comes in. 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] Counter Internal Oscillator Importance with External Reference?
Hi, In HP5370A/B you mux sources. In SR620 there is a lockup PLL, as far as I remember. Cheers, Magnus On 05/09/2017 01:11 PM, Bob kb8tq wrote: Hi If you grab the schematic of pretty much any of these counters, you find a fairly common approach. Somewhere inside is a VHF oscillator. The internal TCXO, OCXO, or Rb acts as a phase lock source for that VHF oscillator. Typical PLL bandwidths are pretty low (10’s of Hz). When you put in an external reference, it acts as the reference to the same PLL. This does a couple of things. You take care of spurs on the external reference. That is the same thing you do locking up a VHF oscillator to your GPSD for microwave work. You get the long term accuracy (1 second and out) of the external reference. Your phase noise (and thus broadband mask jitter) is improved. Does every counter on the planet work this way? - of course not. Somewhere somebody did it a different way. As long as they *did* do it this way, the internal reference does not matter once you switch to an external standard. Even if they did it in some other way, if they did it right, the same statement would apply. Bob On May 8, 2017, at 9:02 PM, Tom Knox wrote: Hi All; How important is the standard, medium, or high stability reference in counters like the 53230A, or FCA3120 when locked to an ultra low phase noise external reference? Particularly when making measurements and adjustments on other ultra high performance references? I know Agilent sold 53132A counters with an option (H01 I believe) that bypassed the internal reference completely when and external reference is applied, but I think standard configuration on most counter is to discipline the internal reference. Thanks for your thoughts. Thomas Knox ___ 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] Counter Internal Oscillator Importance with External Reference?
In message <60c74d75-41e5-7112-d8b6-721664b89...@rubidium.dyndns.org>, Magnus Danielson writes: >Indeed. On the other hand some measurements is hard not to do that way. >One should think about how isolation is created if needed, and this >includes AC and DC, common mode and differential mode. Isolation >amplifier should be part of the arsenal. EMI is part of it, but there raw synchronism is a significant source of systematic errors because the "noise" is no longer gaussian. -- 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] Counter Internal Oscillator Importance with External Reference?
Hi If you grab the schematic of pretty much any of these counters, you find a fairly common approach. Somewhere inside is a VHF oscillator. The internal TCXO, OCXO, or Rb acts as a phase lock source for that VHF oscillator. Typical PLL bandwidths are pretty low (10’s of Hz). When you put in an external reference, it acts as the reference to the same PLL. This does a couple of things. You take care of spurs on the external reference. That is the same thing you do locking up a VHF oscillator to your GPSD for microwave work. You get the long term accuracy (1 second and out) of the external reference. Your phase noise (and thus broadband mask jitter) is improved. Does every counter on the planet work this way? - of course not. Somewhere somebody did it a different way. As long as they *did* do it this way, the internal reference does not matter once you switch to an external standard. Even if they did it in some other way, if they did it right, the same statement would apply. Bob > On May 8, 2017, at 9:02 PM, Tom Knox wrote: > > Hi All; > > How important is the standard, medium, or high stability reference in > counters like the 53230A, or FCA3120 when locked to an ultra low phase noise > external reference? Particularly when making measurements and adjustments on > other ultra high performance references? > > I know Agilent sold 53132A counters with an option (H01 I believe) that > bypassed the internal reference completely when and external reference is > applied, but I think standard configuration on most counter is to discipline > the internal reference. > > Thanks for your thoughts. > > Thomas Knox > > ___ > 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] Counter Internal Oscillator Importance with External Reference?
Hi, On 05/09/2017 09:05 AM, Poul-Henning Kamp wrote: In message , Magnus Danielson writes: Also, there is a reason that you can buy different internal oscillators, this is one of them. For labs with their frequency distribution there is no need to waste money on stand-alone performance. Please don't forget that running the counter of the same signal as the circuits being measured runs the risk of masking noise processes. Indeed. On the other hand some measurements is hard not to do that way. One should think about how isolation is created if needed, and this includes AC and DC, common mode and differential mode. Isolation amplifier should be part of the arsenal. I'm sure that modern counters like 53230 are better at this than the 5370, but you should always sanity-check your measurements using the counters internal, undisturbed timebase. Indeed. When you think you have a risc of disturbance, please do measurements to verify the setup. 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] Counter Internal Oscillator Importance with External Reference?
In message , Magnus Danielson writes: >Also, there is a reason that you can buy different internal oscillators, >this is one of them. For labs with their frequency distribution there is >no need to waste money on stand-alone performance. Please don't forget that running the counter of the same signal as the circuits being measured runs the risk of masking noise processes. I'm sure that modern counters like 53230 are better at this than the 5370, but you should always sanity-check your measurements using the counters internal, undisturbed timebase. -- 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] Counter Internal Oscillator Importance with External Reference?
Hi Tom! On 05/09/2017 03:02 AM, Tom Knox wrote: Hi All; How important is the standard, medium, or high stability reference in counters like the 53230A, or FCA3120 when locked to an ultra low phase noise external reference? Particularly when making measurements and adjustments on other ultra high performance references? I know Agilent sold 53132A counters with an option (H01 I believe) that bypassed the internal reference completely when and external reference is applied, but I think standard configuration on most counter is to discipline the internal reference. Thanks for your thoughts. When you provide an external reference, the long term stability becomes relatively unimportant. Let's view the two cases: 1) Bypass internal oscillator: If you bypass the internal oscillator and always supply an external oscillator, don't waste money on the internal reference, it has no use. 2) Lock internal oscillator: If the oscillator is PLL steered, the short term noise, i.e. phase-noise, is of relevance, but the long-term only cares in the aspect that you can maintain lock, and you can probably trim the oscillator to every 5 years to ensure lock, but other than that you don't need to waste mony on it. If the phase noise is an issue, you could possibly see that in the datahseet/performance spec, but for all I have seen, only long term performance is given, so I'd say that you should not waste your money there either. So, unless it will operate as a stand-alone, don't waste money on internal reference. Also, there is a reason that you can buy different internal oscillators, this is one of them. For labs with their frequency distribution there is no need to waste money on stand-alone performance. Look at the HP5335A for instance. Standard performance is an XO, and you need to trim that regularly to have any kind of performance. The high stability option is a 10811. That is quite a jump in performance. 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.
[time-nuts] Counter Internal Oscillator Importance with External Reference?
Hi All; How important is the standard, medium, or high stability reference in counters like the 53230A, or FCA3120 when locked to an ultra low phase noise external reference? Particularly when making measurements and adjustments on other ultra high performance references? I know Agilent sold 53132A counters with an option (H01 I believe) that bypassed the internal reference completely when and external reference is applied, but I think standard configuration on most counter is to discipline the internal reference. Thanks for your thoughts. Thomas Knox ___ 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.
