Re: [time-nuts] Cs standard stability

separate units would cancel out for two GPSDOs but add for the > Cs. > > Bob > > > > > ----- > From: Bruce Griffiths <bruce.griffi...@xtra.co.nz> > To: Bob Stewart <b...@evoria.net>; Dis

Re: [time-nuts] Cs standard stability

me conditions, yet the ADEV of the Cs is obviously not as good as > that of the GPSDO. Also, the ADEV of the GPSDO pretty much tracks what is to > be expected when run on a good 5370, isn't it? > > Bob > > > > --------- >

Re: [time-nuts] Cs standard stability

bably be useful > for such measurements." > > What would such an "inexpensive" device be? What's inexpensive for you > would probably be way out of my reach. > > Bob > > > > > ---

Re: [time-nuts] Cs standard stability

. Of course, I don't know anything more than that. Correct? > > Bob > > > From: Bruce Griffiths <bruce.griffi...@xtra.co.nz> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency > measurement <time-nuts@febo.com> > Sent: Saturd

Re: [time-nuts] Cs standard stability

Bob That doesn't seem inconsistent with the specs given the contribution of the 5370A to the measured ADEV is likely to be of the same order as the PRS45A spec. The ADEV of the GPSDO also needs to be taken into account. The contribution of the 5370A to ADEV will gradually become insignificant

Re: [time-nuts] advice

"cells". Bruce  On Thursday, 23 February 2017 3:09 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: It would be better to lock the laser to a suitable optical absorption line or other optical transition.Long term stability can be better than an optical

Re: [time-nuts] advice

For a spherical body of uniform density the value of g below the surface is proportional to  the radial distance of the location from the centre of the sphere.  For a spherically symmetric body only the mass contained within the sphere  below the point has any effect on the measured value of g.

Re: [time-nuts] advice

On Tuesday, February 21, 2017 11:13:34 AM Rhoderick Beery wrote: > Greetings Time-Nuts! > > I'm a physics theorist interested in performing an experiment to measure > the gravitational time dilation beneath the surface of the Earth. Boulby > Labs in the UK is 1.1 km down which would generate a

Re: [time-nuts] hm H Maser

An entire room kept near to absolute zero with a simple door access???Unlikely, likely the writer is unfamiliar with science/engineering. Bruce On Saturday, 14 January 2017 11:39 AM, Gary Woods wrote: Hydrogen maser in radio astronomy to sync worldwide

Re: [time-nuts] hm H Maser

Angus Read the paper I posted on the current state of the art. ADEV ~ 2E-13/SQRT(Tau) is feasible with large cells and using a laser instead of rubidium lamp.In principle, one can use the same cell to lock the laser to the rubidium absorption line and lock the microwave signal.Suitable laser

Re: [time-nuts] hm H Maser

One could always use a cryo pump. The following paper is a summary of the current state of the art for rubidium vapour frequency standards:http://www.euramet.org/Media/docs/Repository/A169/IND55/micalizio_02182015.pdf Bruce On Wednesday, 11 January 2017 5:15 PM, Ole Petter Ronningen

Re: [time-nuts] hm H Maser

of the diffusing coating (typically Barium sulphate with an organic binder). Roughening (fine grind   followed by HF etch for stress relief) the outer surface of the cell is also advisable to eliminate light pipe effects in the cell wall. Bruce On Wednesday, 11 January 2017 3:54 PM, Bruce Griffiths

Re: [time-nuts] hm H Maser

A possible RF chain for a Rubidium standard using off the shelf parts plus a couple of custom microwave filters:https://arxiv.org/pdf/1204.4215.pdf Bruce On Wednesday, 11 January 2017 2:10 PM, Bob Camp wrote: Hi The gotcha is that 5065’s never were a popular item in

Re: [time-nuts] hm H Maser

:33 PM Bruce Griffiths wrote: > Possible sources of Rubium vapour > cells:https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1470 > > http://www.precisionglassblowing.com/custom-solutions/optical-glassware/vapo > r-wavelength-reference-cells/ > > https://www.sach

Re: [time-nuts] hm H Maser

andard …. not really easy at all. Bob > On Jan 8, 2017, at 3:55 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> > wrote: > > The rubidium standard appears much more manageable given that the cavity > dimensions are somewhat more compact and rubidium vapour cells are readily > a

Re: [time-nuts] hm H Maser

You could try a cavity like the one in;http://tf.nist.gov/general/pdf/156.pdf This avoids the requirement for a fused quartz storage bulb. Bruce On Sunday, 8 January 2017 11:33 PM, timeok wrote: Hi, the thought of being able to work on building a H Maser has always

Re: [time-nuts] FE-5650A option 58 tuning word for 10 MHz output

January 2017 11:46 AM, Bob Camp <kb...@n1k.org> wrote: Hi > On Jan 2, 2017, at 5:02 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> > wrote: > > > Maybe a waterjet cutter would  imapct less on the shielding properties of > tthe mumetal? > Maybe …. pretty

Re: [time-nuts] new year crashes

Make that a dual rate moon camera.These were used to measure variations in Earth's rotation period. Bruce On Tuesday, 3 January 2017 11:10 AM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: Carter did have a couple of small historic brass transit instruments which were neve

Re: [time-nuts] new year crashes

2017 10:35 AM, Will Kimber <zl1...@gmx.com> wrote: Apologies Bruce, It is a good many years since I was there last. Cheers, Will On 01/03/2017 12:40 AM, Bruce Griffiths wrote: > You mean the Dominion observatory surely not Carter. It was close by and also > had a Danjon Astrol

Re: [time-nuts] FE-5650A option 58 tuning word for 10 MHz output

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 wrote: > > > > Hello Mathias, > > > > I think you did not quite understand how

Re: [time-nuts] new year crashes

You mean the Dominion observatory surely not Carter. It was close by and also had a Danjon Astrolabe. Bruce On Tuesday, 3 January 2017 12:10 AM, Hal Murray wrote: tract...@ihug.co.nz said: > The 'landline' networks also have significant (and variable)

Re: [time-nuts] Measuring sidereal/solar time?

Attila Lookup "Stellar compass" as used for determining space probe attitude.Can also be used to determine the direction of the centre of an image of a field of bright stars.Subarcsecond accuracy is fairly routine.Pattern recognition techniques combined with measures of the relative brightness

Re: [time-nuts] Totally unrelated, but..

Yes, the very low frequency noise of these regulators isn't anywhere near as impressive as their high frequency noise.However for some RF circuits the low frequency power supply noise may not be as significant as other effects. Bruce   On Thursday, 8 December 2016 2:59 PM, Gerhard Hoffmann

Re: [time-nuts] New Timestamping / Time Interval Counter: the TICC

device currently available. On 11/24/2016 01:03 PM, Bruce Griffiths wrote: > John > > There is an application note or similar on the 53230A that indicates that > the single shot noise for time interval measurement is typically about 13ps > or so. > > Bruce > On Thursday,

Re: [time-nuts] New Timestamping / Time Interval Counter: the TICC

John There is an application note or similar on the 53230A that indicates that the single shot noise for time interval measurement is typically about 13ps or so. Bruce On Thursday, November 24, 2016 09:43:54 AM John Ackermann N8UR wrote: > Hi Anders -- > > Thanks, and thanks for the info on

Re: [time-nuts] New Timestamping / Time Interval Counter: the TICC

1-2ps rms single shot noise timestamping is feasible with embedded (occurs as part of the interpolation process) interpolator calibration. Only calibration of the differential delay between channels is required, as is required by all such instruments. However the cost for such a timestamping

Re: [time-nuts] Question about AD9832 "I out Full Scale" (what does it mean?)

With no internal PLL to generate a higher internal frequency than the 25MHz MCLK, that 1MHz waveform looks a bit too smooth for an unfiltered 1MHz output. Bruce On Friday, 18 November 2016 5:12 PM, Richard (Rick) Karlquist wrote: Trying to figure out what "Iout

Re: [time-nuts] Fluke Voltage Standards.

On Thursday, November 10, 2016 02:23:19 PM xaos wrote: > I wonder if there is a way to get a voltage standard out of a frequency > standard (GPS Disciplined). > I think the big problem is probably voltage stability due to temperature > variations. > > Any thoughts on this ? > > -George > > On

Re: [time-nuts] Thinking outside the box a super reference

Neither Rb cells nor isolators are difficult to source.They are both catalog items. However if using a cavity it may need to be tailored to the available cells.Walk-off isolators using double refraction are somewhat more convenient than those requiring a strong magnetic field. Bruce On

Re: [time-nuts] I love the smell of tantalum in the morning

On Saturday, November 05, 2016 12:12:18 PM Tom Van Baak wrote: > See C13 in the attached photo. I need to replace some blown caps on a few > boards [1]. In one instance the cap got so hot it melted itself off the > board. Quiet convenient, actually -- it acts like its own fuse -- but I > don't

Re: [time-nuts] Logging SPAD pulses on synced devices (was: Linux PPS clues?)

Ilia Circuit diagrams are  posted here from time to time, so it should be OK. Bruce On Saturday, 5 November 2016 7:02 PM, Ilia Platone wrote: Hi, and thank you for these suggestions. Currently this project becomes reality (slowly): this kind of

Re: [time-nuts] Thinking outside the box a super reference

The N resonance discussedd in:http://walsworth.physics.harvard.edu/publications/2005_Smallwood_HUBAThesis.pdf May be a better bet than traditional CPT. Bruce On Saturday, 5 November 2016 12:17 PM, Magnus Danielson wrote: Poul-Henning, On 11/05/2016 12:04

Re: [time-nuts] Thinking outside the box a super reference

Hej Magnus A quarter waveplate doesn't depolarise, it can however convert a linearly polarised beam to a circularly polarised one.If you really need to depolarise a laser beam, scattering from a colloidal suspension of Titanium dioxide is very effective.There are no macroscopic moving

Re: [time-nuts] Thinking outside the box a super reference

On Friday, November 04, 2016 09:27:59 PM Poul-Henning Kamp wrote: > > In message <2af27ebe-9200-c348-c89b-b98f9c973...@karlquist.com>, "Richard > (Rick) Karlquist" w > rites: > >Also, one of the Rb isotopes is slightly radioactive. > >35 years ago, the guy in the next cubicle got away

Re: [time-nuts] Thinking outside the box a super reference

Suitable ECDL laser for Rb clock:https://www.sacher-laser.com/home/industrial-lasers/point_and_line_laser_module.html the 784.8 nm version has 0.2nm of tuning range, Bruce On Friday, 4 November 2016 2:43 PM, Tim Shoppa wrote: Zero. But the answer is also zero for a

Re: [time-nuts] Thinking outside the box a super reference

at the University of Neuchatel. Bruce On Friday, 4 November 2016 11:58 AM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: There is at least one recent thesis where a dual resonance rubidium vapor cell was built and used to lock a low noise OCXO,The machining of the cavity didnt

Re: [time-nuts] Thinking outside the box a super reference

There is at least one recent thesis where a dual resonance rubidium vapor cell was built and used to lock a low noise OCXO,The machining of the cavity didnt appear particularly challenging nor did the locking of the laser to the relevant wavelength using an auxiliary rubidium vapour cell.IIRC

Re: [time-nuts] Linux PPS clues?

Another issue is that the finer the timestamp quantisation step size the larger the signal of interest (Intensity correlation). The signal doesn't vanish as the timestamp quantisation step size increases however the signal decreases requiring a longer observation time to achieve a given SNR.

Re: [time-nuts] Linux PPS clues?

10us deadtime is somewhat excessive for average detection rates much greater than 1kcps (kilo counts/sec).Higher rates will tend to have the correlations between detectors suppressed. This will be particulalrly acute for Intensity correlations.Active detector (Geiger mode APD) quenching is

Re: [time-nuts] Linux PPS clues?

On Thursday, October 20, 2016 08:12:12 PM Attila Kinali wrote: > On Thu, 20 Oct 2016 10:59:21 +0100 > > "David J Taylor" wrote: > > Actually, of the 15 Raspberry Pi cards I have only one is used in a > > graphics application. > > Yes, the rpi are used for all kind

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On Thursday, September 22, 2016 01:37:02 AM Gerhard Hoffmann wrote: > Am 22.09.2016 um 00:24 schrieb Bruce Griffiths: > > Another issue is the requirement to trim the current sink for low output > > offset. > > And _that_ FET is made from Unobtainium. > > > If o

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On Wednesday, September 21, 2016 08:59:18 PM Attila Kinali wrote: > On Wed, 21 Sep 2016 09:16:18 -0700 > > Dan Rae wrote: > > On 9/21/2016 9:01 AM, David C. Partridge wrote: > > > Yes, I fear a timepod is a bit out of my budget (I can dream tho'). > > > Over here in the UK

Re: [time-nuts] Normal operating specs of a Morion MV89?

On Tuesday, September 20, 2016 01:53:49 PM Tim Lister wrote: > On Tue, Sep 20, 2016 at 12:56 PM, Bryan _ wrote: > > May also want to check the output amplitude. If memory serves me correct > > it is very common for a capacitor inside this model number to fail. It > > can be

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

on set internally to the analyser. The results are attached. Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 18 September 2016 12:52 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thunderbolt

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

The signal level is also very low. Brue On Sunday, 18 September 2016 11:47 PM, Magnus Danielson wrote: The phase-noise still looks fairly high. How do you measure this? Cheers, Magnus On 09/18/2016 01:27 PM, David C. Partridge wrote: > Now that's

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

The PN should be considerably lower than that even with the noisy output buffer the PN floor should be considerably lower (>40db lower). The OCXO by itself should have somewhat lower PN. Bruce On Sunday, 18 September 2016 11:14 PM, David C. Partridge wrote:

Re: [time-nuts] Hobbyist grade or homebrew temperature testing chamber?

Also avoids thermomechanical fatigue failure in the Peltier device. On Wednesday, 7 September 2016 12:14 AM, jimlux wrote: On 9/6/16 1:19 AM, Adrian Godwin wrote: > On Tue, Sep 6, 2016 at 4:24 AM, Bob Darlington > wrote: > >> Rick, >> >>

Re: [time-nuts] Anybody want a Thunderbolt power supply?

Post should have been: Acts like noise current flowing in the voltage setting network (R || C).Flicker noise appears to kick in below 1Hz or so. Bruce On Thursday, 1 September 2016 8:23 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: Acts like current  noise f

Re: [time-nuts] Anybody want a Thunderbolt power supply

~22nV/rtHz) isn't significant in comparison with other sources. Bruce On Thursday, 1 September 2016 5:56 PM, Gerhard Hoffmann <dk...@arcor.de> wrote: Am 01.09.2016 um 06:07 schrieb Bruce Griffiths: > I have a quad LT3042 PCB that I must get around to assembling.One potential

Re: [time-nuts] Anybody want a Thunderbolt power supply

Just split  the 1uF coupling cap into 2x 2u2 in series in the Cuk dc-dc converter add a 1:1 transformer (should be small at 2MHz) between the pair of 2u2 caps to produce a floating output and use an LT3042 as a post regulator.With a mains transformer input supply a separate isolated winding for

Re: [time-nuts] Anybody want a Thunderbolt power supply

If onen is going to use a dc-dc converter the Cuk converter used here is a nice topology in that it can have low input and output ripple currents. However input and output filters like the Murata BNX002/BNX005 series would have been useful as would an LM3042 linear post regulator for the -12V

Re: [time-nuts] Optical link connects atomic clocks over 1400 kmof fibre

wrote: From: Bruce Griffiths You'd need a rather thick copper jacket to shield effectively against the 50Hz magnetic field. Bruce == Would mu-metal be any use?   https://en.wikipedia.org/wiki/Mu-metal   http://mumetal.co.uk/ Cheers, David -- SatSignal Software - Q

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

the EM field? André Esteves 2016-08-25 0:33 GMT+01:00 Bruce Griffiths <bruce.griffi...@xtra.co.nz>: > The Kerr effect is Proportional to the square of the field so one would > expect a strong 100Hz component from this. > > The magneto optical Kerr eefect which rotates the plane of

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

The Kerr effect is Proportional to the square of the field so one would expect a strong 100Hz component from this. The magneto optical Kerr eefect which rotates the plane of polarisation is linear however. Bruce On Wednesday, August 24, 2016 07:04:31 AM Bob kb8tq wrote: > Hi > > I would not

Re: [time-nuts] GPSDO - probably a stupid question.

The stability of the typical GPS receiver oscillator is usually inadequate to be useful as a GPSDO. An OCXO (as in the Trimble Thunderbolt for example) or equivalent is usually required. One can't usually just add a varicap to adjust the frequency of a packaged oscillator. If an external

Re: [time-nuts] Shera revisted

On Friday, August 12, 2016 12:21:55 PM David wrote: > On Fri, 12 Aug 2016 13:56:40 +0200, you wrote: > >Hi everyone, > > > >On 2016-08-11 21:06:12, Attila Kinali wrote: > >> Hoi Bert, > >> > >> I'm asking, because if you go the way of using a CPLD anyways, you could > >> throw in another $2 for

Re: [time-nuts] Effect of EFC noise on phase noise

On Tuesday, August 02, 2016 01:03:58 PM Gerhard Hoffmann wrote: > Am 02.08.2016 um 09:14 schrieb Bruce Griffiths: > > > ... and a screen dump for the LTspice challenged > > ;-) Gerhard Uually a zero is needed in the bias stabilisation loop to eliminate low frequency ga

Re: [time-nuts] Effect of EFC noise on phase noise

the conventional approach. Bruce On Tuesday, 2 August 2016 6:19 PM, Alex Pummer <a...@pcscons.com> wrote: Ja Gerhard, bitte schicke mir den LTSpice file, Danke im Voraus und 73 KJ6UHN Alex On 8/1/2016 6:34 PM, Gerhard Hoffmann wrote: > Am 02.08.2016 um 02:42 schrieb Bruce Griffiths:

Re: [time-nuts] Effect of EFC noise on phase noise

"I'm working on a new amplifier based on IF3602 or BF862 FETs that can use 10u foil only." Similar to that published by Groner in Linear Audio? Bruce On Tuesday, 2 August 2016 12:12 PM, Gerhard Hoffmann wrote: Am 01.08.2016 um 22:16 schrieb David: > This duplicates the

Re: [time-nuts] NCOCXO anyone?

art.This issue was discussed on the list some time ago, Bruce On Friday, 29 July 2016 6:31 AM, Attila Kinali <att...@kinali.ch> wrote: On Fri, 22 Jul 2016 08:19:43 + (UTC) Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > No, the first one merely uses a pair of casc

Re: [time-nuts] Precision DACs

On Wednesday, July 27, 2016 08:55:20 PM Robert LaJeunesse wrote: > The concept of track & hold was well understood in 1966 and documented in > the classic Philbrick Researches amplifier application book, now available > at >

Re: [time-nuts] The home time-lab

The PFC power supply architecture I had in mind uses a flyback inverter to regulate the input rail voltage for the output dc-dc converter stage. The flyback stage peak current is modulated by a sinewave. A feedback loop adjusts the effective amplitude of this sinusoidal modulation to regulate

Re: [time-nuts] The home time-lab

The PFC stage needs a line frequency sinewave reference, if this is produced by attenuating the line input, then it may not function well with badly distorted line input waveforms (modified sine, square wave etc).Phase locking a sinewave to the line input may be a better approach. Bruce

Re: [time-nuts] Precision DACs (was: NCOCXO anyone?)

The AD5791 evaluation board has an unpopulated area for what appears to be an LTZ1000 reference circuit. Bruce On Sunday, 24 July 2016 7:00 AM, Attila Kinali wrote: On Fri, 22 Jul 2016 12:15:25 -0500 David wrote: > If you expect analog

Re: [time-nuts] NCOCXO anyone?

No, the first one merely uses a pair of cascaded heterodyne PLLs as shown on p3 of the manual.A diophantine setup may be useful here if one wished to construct something similar. Bruce From: Anders Wallin To: Discussion of precise time and frequency

Re: [time-nuts] HP5370 power supply measurements

The most effective approach would be to design a replacement with lower jitter (< 5ps ) and lower power consumption (< 10W??).The hard/interesting part is the higher resolution lower jitter interpolator.Preliminary testing suggests this part isnt as difficult as first thought. As soon (within a

Re: [time-nuts] OXCO Spurious Output at Line Frequencies

I can't seem to get the line related spurs much below -170dBc/Hz for the fundamental and -180dBc/Hz for the line frequency related harmonics. Everything was bolted down to a 12mm thick aluminium slab. Avoiding an Earth loop by isolating the Timepod Ch0 and CH2 inputs from the aluminium plate

Re: [time-nuts] DMTD downmixer question

The optimum sine to square converter is embodied in the Collins style limiter approach consisting of a cascade of limiting amplifiers each with suitable individual gain and individual bandwidth, the gain and bandwidth increasing for each successive stage until the output slew rate is sufficient

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

On Sunday, June 19, 2016 07:23:09 PM Attila Kinali wrote: > Good evening, > > I have recently been looking into BJT's and their switching properties. > Because a time-to-amplitude converter does similar things as I would like > to, I have been looking in what people do with those. First thing

Re: [time-nuts] 3120A issues

It almost sounds like something has been found not to be ROHS compliant.Could be as simple as the alodined (conventional process uses hexavalent chromium ) case or perhaps a non ROHS part was used. Bruce On Sunday, 19 June 2016 8:02 PM, John Miles wrote: > On 6/18/16

Re: [time-nuts] DIY TimePod

be required.  Bruce On Tuesday, 14 June 2016 6:01 PM, Chris Caudle <ch...@chriscaudle.org> wrote: On Mon, June 13, 2016 9:38 pm, Bruce Griffiths wrote: > If the quantisation noise is random and spread uniformly over the Nyquist > bandwidth (~40MHz??) then the noise floor is about -82

Re: [time-nuts] DIY TimePod

The subsequent all digital mixdown and low pass filtering, if done correctly, will increase the resolution provided that the signal and reference periods are uniformly sampled at a sufficient equivalent number of points. But with a starting point some 70dB or more behind an ADC, the system

Re: [time-nuts] DIY TimePod

or less. The problem lies in ensuring that the quantisation noise is actually random..With a high resolution RF ADC internal noise is usually sufficient (>= 1 lsb)) to ensure this. Bruce On Tuesday, 14 June 2016 2:11 PM, Bruce Griffiths <bruce.griffi...@xtra..co.nz&

Re: [time-nuts] DIY TimePod

have lower phase noise than CMOS at low offset frequencies. Bruce On Monday, 13 June 2016 8:12 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: Adjusting the sampling clock frequency so that is neither a harmonic nor a harmonic of a subharmonic of either of the clock frequ

Re: [time-nuts] DIY TimePod

Adjusting the sampling clock frequency so that is neither a harmonic nor a harmonic of a subharmonic of either of the clock frequencies being compared ensures that each clock waveform isnt repeatedly sampled at a small set of  points.i.e. fsample != (m/n)*ftest andfsample != (p/q)*freference

Re: [time-nuts] A Symmtricom GPSDO Board

Perhaps a location for an alternate receiver used in another model/version that shared the same PCB albeit populated with different OCXOs etc?. Interesting that 2 ocxos appear to be in use. Bruce On Sunday, 5 June 2016 5:53 PM, Charles Steinmetz wrote: Isn't

Re: [time-nuts] A Symmtricom GPSDO Board

More likely the missing GPS receiver board is installed over the ground plane. Bruce On Sunday, 5 June 2016 4:11 PM, Hui Zhang wrote: Dear group:     Does anyone familiar with this Symmtricom GPSDO board? I have searched on internet but I have not found any manual or

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

, the crystal parameters can be extracted without knowledge of the phase shift. Bruce On Saturday, 4 June 2016 11:01 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: On reflection, building a jig to measure the crystal transmission as a function of frequency may be much easie

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Some idea of the crystal equivalent circuit at the oscillation frequency would help considerably. Usually lower frequency crystals have a considerably higher series resistance than those operated at 1MHz or above. At frequencies below 100kHz or so a Meacham bridge using something likke a

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

to design a suitable oscillator circuit. Measuring the location of spurious resonances may also be useful. Bruce On Saturday, 4 June 2016 9:52 PM, Bruce Griffiths <bruce.griffi...@xtra..co.nz> wrote: Some idea of the crystal equivalent circuit at the oscillation frequency would

Re: [time-nuts] HP 106a oscillator connectors question

Microdot (now available from TE connectivity) made these for 50 ohm, 75 ohm and 93 ohm coax. Digikey have 50 ohm coax male versions. Bruce On Saturday, 4 June 2016 3:02 PM, Tom Miller wrote: I've seen these used for accelerometer cables.

Re: [time-nuts] Commercial software defined radio for clock metrology

t; On May 28, 2016, at 11:04 AM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> > wrote: > > One can just measure the TDEV performance.I can measure the TDEV performance > at 10MHz later today if that's useful.It should be somewhat similar to the > singl

Re: [time-nuts] Commercial software defined radio for clock metrology

On Sunday, 29 May 2016 2:04 AM, Attila Kinali <att...@kinali.ch> wrote: On Sat, 28 May 2016 08:47:45 + (UTC) Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > This SDR setup appears to have a higher PN (at least 2 ADC's per signal > are required  to achieve lower PN ) than

Re: [time-nuts] Commercial software defined radio for clock metrology

A low pass filter will reduce the source broadband noise aliased into the ADC output signal. Using the LVDS ADC outputs rather than the CMOS outputs may help in reducing noise generated on the board. NB the ADC performance is specified when the LVDS outputs are used. This SDR setup appears to

[time-nuts] Fw: Commercial software defined radio for clock metrology

lone V SoC FPGA running at 800MHz.  Installments to his series have been slow coming, but I've been wondering if this could be the basis for a Timepod type of unit. Bob On Fri, 5/27/16, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote:

Re: [time-nuts] Commercial software defined radio for clock metrology

circuitry may degrade the performance compared to that achieved with lower  maximum sampling rate ADC pairs. Bruce On Saturday, 28 May 2016 4:01 PM, Bob Camp <kb...@n1k.org> wrote: Hi > On May 27, 2016, at 8:17 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> > wrote

Re: [time-nuts] Commercial software defined radio for clock metrology

than that of the TI ADC used in the ETTUS 210 SDR. Bruce On Saturday, 28 May 2016 3:08 PM, Bruce Griffiths <bruce.griffi...@xtra..co.nz> wrote: The Red Pitaya FPGA may be a little too small.Its not clear if a single chip ADC is used.If not, the performance will suffer.Dc c

Re: [time-nuts] Commercial software defined radio for clock metrology

The Red Pitaya FPGA may be a little too small.Its not clear if a single chip ADC is used.If not, the performance will suffer.Dc coupled inputs will degrade the performance somewhat compared to transformer coupled inputs. Input bandwidth would be around 40MHz or so for the Nyquist band of

Re: [time-nuts] Commercial software defined radio for clock metrology

On Thursday, May 26, 2016 06:40:26 PM Bob Camp wrote: > Hi > > Very interesting paper, thanks for sharing !! > > One question: > > In many DMTD (and single mixer) systems, a lowpass and high pass filter are > applied to the signal coming out of the mixer. This is done to improve the > zero

Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

However the value of the second time constant in the active PI filter required to achieve reasonable damping will be around 1600 seconds. This corresponds to an active PI filter proportional gain of 16. Bruce On Wednesday, 25 May 2016 3:20 PM, Bruce Griffiths <bruce.griffi...@xtra.co

Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

When comparing a 10MHz OCXO divided down to 1Hz with a GPS PPS signal, the effective VCO gain (Ko/N) is likely to be around 6E-7 rad/s/V (eg HP10811A) and the phase detector gain around 1V/rad. Consequently a PLL loop bandwidth of 100uHz only requires an Integrator time constant of around  100

Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

The grid current of most tubes (apart from electrometer tubes operated at low voltage) is much larger than most FETs (apart from very large area ones).. The other issue with tube grid currents is that zero current corresponds to a delicate balance between electon and ion currents so the grid

Re: [time-nuts] Late Model HP 105B shematic

Search for 105B on Didier's site.There are 2 files that contain the relevant schematics and change data for versions with10811A's. Although my 10811A equipped HP105B variant appears to have the old power supply with MC1468's rather than the later version using LM317's. Bruce On

Re: [time-nuts] DMTD was: high rev isolation amps

PM, Bruce Griffiths <bruce.griffi...@xtra..co.nz> wrote: The input noise of a 125 series gate will be far larger than the noise at the mixer output at the beat frequency. A 125 may be useful as the output stage of a Collins style limiter chain wherein which the gain and bandwidth o

Re: [time-nuts] DMTD was: high rev isolation amps

by ensuring that the DDS only contributes a small fraction of the offset frequency.   At least a modular system will allow these issues to be explored. Bruce On Thursday, 12 May 2016 5:00 PM, Bruce Griffiths <bruce.griffi...@xtra..co.nz> wrote: For DMTD service with an offset fre

Re: [time-nuts] DMTD was: high rev isolation amps

raises the ugly sepctre of unwanted close in spurs, unless one chooses one of the magic frequency outputs that is free of such spurs. Bruce On Thursday, 12 May 2016 3:33 PM, Bruce Griffiths <bruce.griffi...@xtra..co.nz> wrote: For DMTD service with an offset frequency of 100Hz o

Re: [time-nuts] DMTD was: high rev isolation amps

For DMTD service with an offset frequency of 100Hz or less the flicker phase noise of the mixer is more important than its wideband PN floor.The RDP series phase detectors are amongst the lowest PN noise mixer/phase detectors commercially available. They are considerably quieter than the TUF

Re: [time-nuts] High rate, high precision/accuracy time interval counter methods

Bruce On Tuesday, 10 May 2016 9:17 PM, Attila Kinali <att...@kinali.ch> wrote: Hoi Bruce, On Mon, 9 May 2016 23:34:24 + (UTC) Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > Its probably easier/cheaper to construct a suitable filter for a GSPS ADC > than

Re: [time-nuts] High rate, high precision/accuracy time interval counter methods

custom IC is probably  the only effective solution for such a TAC. The somewhat heroic measures employed in the Wavecrest counters is perhaps the limit of discrete construction techniques. Bruce On Tuesday, 10 May 2016 1:08 AM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote:

Re: [time-nuts] High rate, high precision/accuracy time interval counter methods

Since the GSPS sampling ADCs all appear to use an input buffer with relatively low value resistors between the differential inputs or connected to a midpoint bias voltage, some kind of high impedance buffer is needed between the TAC capacitor and the ADC input when using such ADCs. The highest

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