[time-nuts] a better LO for an HP4352B.
Hello, After playing a bit with phase-noise measurement on a 4532B I realized that the contribution of the external LO it requires to function dominates the setup noise floor (...no surprise here). There are quite a few generators out there (reasonable prices, surplus etc.) up to 1 or 2GHz to choose from and I have already tested a few different models I have here. Seems the 4352B noise floor on itself is not too bad but it ends up showing the PN of the external LO, that in reality does not need to be a full blown HP or R etc. bench-top instrument. Knowing that the 4352B it only requires the LO in 100kHz steps, I'm tempted to build something myself (say up to 500MHz or 1GHz) aiming for the very best possible crazy lowest PN a one can get. ... and now I can't get out of my head the search for the architecture for such synthesizer (kind of 250-500MHz for a start, divided down for lower freqs. I don't fear building myself the best VCO's possible and I don't mind to have several to cover an octave.) But the very best synthesizer architecture to lock them aiming solely for low PN is what I would like to hear comments about. My initial idea is direct sampling the VCO with a 100KHz reference. (a micro-controller would get the VCO close enough to the lock point and then gets out of the way and let the loop grab it). Can't think of anything else simpler or with less noise contributions... but... (needless to mention using the best OCXO reference can have) I would be happy to hear all sort of comments. Including suggestions of existing commercial models that can't be beaten by any of my attempts. Luis Cupido ct1dmk. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FA2 counter
An impedance sweep of the input might give a clue about the LPF. When I get mine I'll measure it. On 9/27/2019 11:43 AM, Mark Sims wrote: A list member did some experimenting with the unit and came up with this very useful information: "press and hold RST button, then MODE toggles LPF (low pass filter), GATE toggles input impedance" I wonder what the LPF cutoff freq is? I am currently doing a noise floor test (connect ref out to input) on my FA2. The initial (12 hour) results are REALLY good... ADEVs at long (1+) tau are in the high E-15 range. I'll post results after I get 24 hours of data. That annoying freq offset of the FA1 is gone. A 12 hour average of the FA2 freq readings is 10,000,000.000 001 Hz (FA2 clocked by a 5071A). ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] FA2 counter
A list member did some experimenting with the unit and came up with this very useful information: "press and hold RST button, then MODE toggles LPF (low pass filter), GATE toggles input impedance" I wonder what the LPF cutoff freq is? I am currently doing a noise floor test (connect ref out to input) on my FA2. The initial (12 hour) results are REALLY good... ADEVs at long (1+) tau are in the high E-15 range. I'll post results after I get 24 hours of data. That annoying freq offset of the FA1 is gone. A 12 hour average of the FA2 freq readings is 10,000,000.000 001 Hz (FA2 clocked by a 5071A). ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FA2 counter
Thanks for the input. I just ordered one. (My 78th birthday will be next month. I should be downsizing but here I am buying more stuff.) Wes N7WS On 9/26/2019 6:25 PM, Mark Sims wrote: Miy FA2 came in today. A very quick test shows that it works. It does not appear to have the -0.0002 Hz freq measurement bias that the FA1 has. The 0.1 second gate time mode is pretty useless... there appears to be a 300 msec dead time between measurements in 0.1 (and 10 sec) gate time modes so you only get a new reading every 400 msecs. 10 second gate time produces a reading every 10300 msecs. 1 sec gate time outputs readings every 1100 msecs (like the FA1). It auto-detects the presence of an external reference... no way to manually switch between internal and exterrnal references. I have not done any testing on the internal ref or the high freq channel. The screen shows a LPF setting and a 50 ohm setting... no idea if these are switchable there is no documentation. The screen shows the input signal level. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Time-Nuts: Who was that person...?
Hello, Time-Nutters-- A month or so ago I posted a query on this list asking if anyone was interested in a collection of old (1950 - 1970) quartz crystals in evacuated glass tubes plus an assortment of crystals and crystal ovens from the same vintage. Two Time-Nut List members responded. I shipped one small box of assorted crystals and ovens to the interested person in Germany. However, I have lost my note of who the other interested Time-Nuts List member is. Would that person please email me with your shipping address and I will follow-through with my offer to ship to you in return for shipping costs ? I apologize for my carelessness in losing your shipping address!! Mike Baker WA4HFR Gainesville / Micanopy Florida USA mp...@clanbaker.org * ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] chrony vs other NTP
Any quick opinions re use of chrony vs other NTP implementations? THANKS Don = Don, I don't see any reason /not/ to use the reference NTP implementation. It's well documented, and allows for stratum-1 servers on Windows, which Chrony does not, meaning that I can use and manage the same program on both Linux and Windows. Works with a wide range of reference clock sources. It's always worked well here without issues. Cheers, David -- SatSignal Software - Quality software for you Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
