Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

I don't know of any particular reason why a DVD-player laser should be faster, since neither CD nor DVD players need to deliberately modulate the lasers anyway. At least, that's the first blush answer. However, these diode lasers are generally noisy, apparently due to the inevitable presence of

Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

I've been told that CD player type diodes can be successfully modulated up to about 600 MHz, but that going much further is either difficult or perhaps impossible. This came from a guy (at Tektronix) who worked with various types of diode lasers a lot, back in the 1980's. But at least they are

Re: [time-nuts] Spectracom 8140T Line Tap Schematic

Hi Bob & Julien, Why bother with the short on the downstream end of that DC-blocking attenuator? At 10 MHz I'd expect leakage radiation to be negligible. Dana On Thu, Jun 14, 2018 at 10:43 AM, Bob kb8tq wrote: > Hi > > > On Jun 14, 2018, at 9:31 AM, gandalfg8--- via time-nuts < >

Re: [time-nuts] Casio Wave Ceptor wrist watch - quick accuracy test

ocks have been quite good. It is the higher-end > line with tighter specs and they actually have a trimmer inside. > > David N1HAC > > > > On 6/11/18 6:30 AM, Dana Whitlow wrote: > >> I bought a Casio 'atomic watch" about 3 months ago, one which uses the >> '3405' modu

Re: [time-nuts] where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

power densities of the 1064nm laser required for > efficient frequency doubling. > > Brue > > On 11 June 2018 at 22:52 Dana Whitlow wrote: > > > > > > Mark's description about how (most) green laser pointers work The better > is a bit in > > error, and is

Re: [time-nuts] where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

Mark's description about how (most) green laser pointers work is a bit in error, and is perhaps over-simplified- the reality is actually more fascinating yet: First a diode laser operating at around 808 or 809 nm is used to optically pump a solid state laser which generates light at 1064 nm.

Re: [time-nuts] Casio Wave Ceptor wrist watch - quick accuracy test

I bought a Casio 'atomic watch" about 3 months ago, one which uses the '3405' module. I've also been running checks with radio setting turned off, and mine is coming in at just under 1 sec per month, based on seeing how long it takes to drift one second. But I find that visual/aural coordination

Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

What is an 'FRK'? Thanks, Dana On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts wrote: > Having followed the conversation and having looked at the p[possibility > using a FRK with laser diode, it is low on our list because of all the > ongoing projects but please if you want to spend time

Re: [time-nuts] Terminators on empty outputs/connectors

I recommend putting terminators on unused ports, on general principles. But I don't think it would ordinarily be necessary to use big-bucks terms, unless the distro amp is really cheaply made. If you have access to a VNA, it would be interesting to measure the complex transmission coefficient

Re: [time-nuts] Cesium Clock Avialable

Don't Cesium clocks have a beam current integrator of sorts so that it's possible to pretty accurately assess the remaining life of the tube? If not, I'm terribly surprised and disappointed. Also, beginning with a new tube, roughly how long can one be run until it reaches exhaustion? Are we

Re: [time-nuts] Bodnar "Precision Frequency Reference (GPS Clock)" AND LeoNTP Networked Time NTP Server Questions

Caution, folks, about USB cable radiation. While the intended signals flowing through the cable presumably contribute a bit to the overall picture, common-mode currents on the cable are the most likely cause of severe radiation problems. These currents arise not merely from intended USB signals,

Re: [time-nuts] GPS Timing Antenna Failure - Long

Flux can provide just the right kind of ionic leakage path that leads to whisky growth and eventual sudden shorts. Dana On Sun, May 13, 2018 at 12:23 AM, Hal Murray wrote: > > lmcda...@lmceng.com said: > > To make this very long story into a short one, I learned that

Re: [time-nuts] Anybody have suggestions for time related science fair projects?

wrote: > Even with single mode fiber its finite group delay dispersion will likely > restrict the usable light source bandwidth. > > Bruce > > On 13 May 2018 at 03:38 Dana Whitlow <k8yumdoo...@gmail.com> wrote: > > > > > > It may be that a nicely

Re: [time-nuts] Anybody have suggestions for time related science fair projects?

It may be that a nicely-written request to Corning could yield the loan of a big spool of fiber for the duration of a science fair project. Another alternative, perhaps easier to implement, might be an electrically-driven light modulator at the detector end. For the source, an LED or diode

Re: [time-nuts] HP 5372A

When I was working at the Arecibo Observatory and we were running the ionospheric heater at 5.1 MHz (think Mini-HAARP), I'd sometimes go home (about 3 miles away) and listen to the signal there.There was frequently substantial random fading of the signal, suggesting that I was hearing the

Re: [time-nuts] Anybody have suggestions for time related science fair projects?

How about measuring variations in propagation delay for WWV on various frequencies, or WWVB, using GPS ticks as a reference. DanaK8YUM On Fri, May 11, 2018 at 9:41 AM, Van Horn, David < david.vanh...@backcountryaccess.com> wrote: > > Measuring the speed of light (Fizeau or Michelson

Re: [time-nuts] Question about frequency counter testing

I'm a bit fuzzy, then, on the definition of ADEV. I was under the impression that one measured a series of "phase samples" at the desired spacing, then took the RMS value of that series, not just a single sample, as the ADEV value. Can anybody say which it is? The RMS approach seems to make

Re: [time-nuts] WWVB: measuring local 60 KHz noise

Alex- how many turns on that loop? Dana On Sat, May 5, 2018 at 2:35 PM, Alexander Pummer wrote: > tuned,[ fine-tuning with vari-caps remotely] large size frame antenna 1 > meter dia provides mV size 60kHz in the Livermore area in California from > the Colorado WWVB TX > 73 >

Re: [time-nuts] WWVB: measuring local 60 KHz noise

Hal, Some SDRs can tune that low and should provide a means to determine if noise is really the problem as well as give some clues as to the character of said noise. But they are much less likely to help with delay determination, unless you can figure out a practical way to ascertain the latency

Re: [time-nuts] nuts about position

It is true that most handheld GPS receivers have WAAS capability these days; however the accuracy is more like 3 to 4 meters even with several minutes of averaging. I've always been puzzled by why it is so much worse than good professional equipment can apparently achieve with similar "features".

Re: [time-nuts] nuts about position

While I was at the Arecibo Observatory it became desirable to get a good surveyed position for a new GPS antenna we had installed for the NIST TMAS system. We found a resource at the Univ of Puerto Rico who had a Trimble (I think) unit. He set it up on the site, "turned on the bubble machine",

Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)

kins > > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dana > Whitlow > Sent: Friday, April 13, 2018 8:39 AM > To: Tom Van Baak; Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Pulsars, clocks,

Re: [time-nuts] getting accurate timing on RTL-SDR output

in effectively comparing the outputs of the two receivers, not so much in absolute timing. Try your best to keep the two receivers identical. Dana On Fri, Apr 13, 2018 at 2:15 PM, jimlux <jim...@earthlink.net> wrote: > On 4/13/18 10:33 AM, Dana Whitlow wrote: > >> Jim, >> &g

Re: [time-nuts] getting accurate timing on RTL-SDR output

Jim, I'm curious:In what RF bandwidth will you be recording? My first thought would be to search for a cross-correlation peak between the two antenna outputs, but quickly realized that this does not tell you anything about the timing differences between the two receivers. I think you need

Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)

Tom's discussion about pulsars brought back some memories... Many pulsars exhibit skipped pulses. And one curiosity that I didn't see mentioned in Tom's discussion is that some pulsars even exhibit behavior reminiscent of the "sawtooth jitter" so evident in the PPS outputs of most GPS receivers.

Re: [time-nuts] Cheap jitter measurements

Pity the poor man who has (n>1) clocks, for he knows not what time it is. Dana On Sun, Apr 8, 2018 at 4:29 PM, John Ackermann N8UR wrote: > I want to jump on Tom's post, and Bob's note at 1:14 on Saturday (that > begins with "Just to be very clear..." They both raise an

Re: [time-nuts] quartz / liquid nitrogen

Many years ago, circa 1977, I was moved to try some crude tests on a few semiconductor devices at LN2 temperature (77K). These tests were very crude, involving dunking the parts into the LN2 bath, and many failed outright. Most of the devices tested were in plastic packages. Here are the

Re: [time-nuts] quartz / liquid nitrogen

Is the thermal noise generated in the loss in a quartz resonator a significant part of the overall phase noise picture? I would have not thought so. I'd think that a greater benefit ought to be derived from chilling the other parts in the oscillator, such as the active devices. Unless, of

Re: [time-nuts] TV Signals as a frequency reference

I'e always been curious as to why TV stations did not lock at least their in-house equipment to the network feed as a means to avoid spending money on frame syncs. Remote coverage, on the other hand, would of course open a new can of worms. But compared to the cost of building and powering a TV

Re: [time-nuts] What does determine the short term stability of an Rb vapor cell standard?

illumination. Dana Whitlow On Sun, Mar 25, 2018 at 8:18 AM, Attila Kinali <att...@kinali.ch> wrote: > Moikka moi, > > In the past, it has been again and again claimed that the HP 5065 has > such an outstanding short term stability because of its large vapor cell. > But the mo

Re: [time-nuts] EFTF 2018

Speaking of forums etc, does anybody in Time-Nuts attend anyof the NIST Time and Frequency Seminars? I'm wondering if I'd get much from it. I've thought about doing so for years, but never got around to pushing for it while employed. Now it's looking awfully expensive. Dana On Fri, Mar 16,

Re: [time-nuts] Need a Watch Recommendation

... Dana On Thu, Mar 15, 2018 at 8:13 AM, Bob kb8tq <kb...@n1k.org> wrote: > Hi > > > > On Mar 15, 2018, at 1:33 AM, Dana Whitlow <k8yumdoo...@gmail.com> wrote: > > > > I concur with Bill. And even if one keeps tabs on the current watch > error,

Re: [time-nuts] Need a Watch Recommendation

I concur with Bill. And even if one keeps tabs on the current watch error, as is the usual practice by celestial navigators, once that error reaches or exceeds more than a minute the process frankly gets more clumsy and error prone. And if a watch drifts in time very rapidly, one loses faith in

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

Now I'm getting interested in this. My concept is to take the 60 Hz in, do reasonable HW filtering to knock off the HF junk that commonly rides on the sinewave, then use an RC quadrature phase splitter to yield I & Q signals. Then sample at 1PPS with my Rb's PPS as the sample trigger, and

Re: [time-nuts] Assorted replies, and request for info

In connection with ground loops, why not put "ferrite beads" on coaxial cables in the system? In this case where the offending frequencies would be in the 60 Hz regime one would probably need large toroids with multiple turns, but the approach ought to do some real good, without introducing the

Re: [time-nuts] HP 5065A super

Keep in mind that soldermask will also change the field distributions around a microstrip line, and will somewhat mitigate the microstrip's dispersive behavior as well. I once worked with some miccrostrip couplers at around 2-4 GHz and found that directivity was significantly improved by adding

Re: [time-nuts] The "NAKED" 5065A optical unit

I'm curious: Is the lamp RF-excited, or by DC going to internal electrodes? And if by RF, is the energy coupled in magnetically by a loop, or by capacitive electrodes? Thanks, Dana On Mon, Feb 19, 2018 at 7:08 PM, wrote: > Here is a PIX of the optical unit from a 5065A

Re: [time-nuts] eBay GPS antenna test results.

I would surmise that the antenna has (or rather had) a protection network to protect against voltage spikes or surges. Your description of events seems consistent with an triggered SCR crowbar circuit, and the 2nd attempt at the higher current limit shorted the SCR. Note that this may not have

Re: [time-nuts] minimalist sine to square

. And there's always the 74AC04 if you wanted faster edges. Dana Whitlow On Fri, Jan 19, 2018 at 1:31 PM, Tom Van Baak <t...@leapsecond.com> wrote: > John's TADD-2-mini [1] uses the Wenzel sine-to-square converter. It > performs very well but requires +10 V. > > I'm looking for a solution

Re: [time-nuts] PBS, Tue evening, The Secret of Tuxedo Park

I could only afford a single Accutron, so I got in the habit of storing it overnight in an orientation estimated to correct bedtime error by wake up time. I got pretty good at it. BTW thanks very much for the tip on the book- I must definitely get a copy. Dana On Tue, Jan 16, 2018 at 9:04 AM,

Re: [time-nuts] AM vs PM noise of signal sources

One point about oscillator design I've not yet seen mentioned is this: the limiter must not degrade the resonator Q when in action. Hence, a pair of diodes connected in parallel back to back, across a shunt resonator, would be a bad thing to do from the perspective of low phase noise. A

Re: [time-nuts] AM vs PM noise of signal sources

tone is summed with “baseband" noise. 1/F noise seems > to be the flavor of the day in recent postings. The only reason to use > audio > in the example is that it is really easy to demonstrate things at audio > with > a sound card. > > Bob > > > On Jan 5, 2018, at 1

Re: [time-nuts] AM vs PM noise of signal sources

Is this an audio tone, summed with audio noise whose spectrum surrounds that of the tone? Dana On Fri, Jan 5, 2018 at 9:56 AM, Bob kb8tq wrote: > Hi > > If I pass both a sine wave tone and a pile of audio noise through a > perfectly > linear circuit, I get no AM or PM noise

Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

I think I need to clarify what I mean by "backlash". It is not simple free play in the adjustment mechanism- it is something much more irritating, as follows: I sneak up on the desired result, but manage to overshoot slightly. So I back off on the screw, and find that at first the result

Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

I should comment that my bad experiences were in trimming out opamp DC offsets. As I recall, the amount of backlash was equivalent to a fair fraction of one turn of the shaft. I never fully trusted the philosophy of sneaking up on the sweet spot and then walking away- I felt it was necessary to

Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

John, Do you notice a backlash effect when homing in on the desired setting with those tripots? I last used such things back in the 1980's, and remember often having enough backlash to make close trimming rather difficult. I wonder if they have gotten better in that regard. Dana On Sun, Dec

Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

Mark is correct, but with a caveat: Unless the pot slider sees a load impedance that is much much larger than the pot's end-to-end resistance, contact resistance variations can also play a big role, especially when the pot gets old. For this reason alone I favor sticking with the 3-terminal

Re: [time-nuts] End of Range Oscilloquartz 8600-3

I looked at the photos, but can't make any sense of your comments about the multivibrator. Was this a joke? Dana On Tue, Dec 12, 2017 at 11:37 AM, Bob Albert via time-nuts < time-nuts@febo.com> wrote: > You found the secret. There is no RF wiring to the crystal. The > oscillator frequency

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Checkhttps://en.wikipedia.org/wiki/Earth_tide According to that, a foot of motion is easily plausible. The Wiki article says that displacements around a meter in the solid crust can be seen over the right intervals. This must wreak havoc in VLBI geodesy work, except that for some in the

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

I saw that about the N atom trapped inside a C60 molecule, but also took note of the present cost of the material. I wonder how much is going to be required to make a good standard. Dana On Fri, Dec 8, 2017 at 11:40 AM, Tom McDermott wrote: > There's an interesting

Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

Use of a smaller opening would be the first strategy for getting higher Q. Making sure that the walls of the vessel were solid reflectors would be an important factor, too. I noted that several of his sustained oscillators were basically either relaxation or blocking oscillators, neither of which

Re: [time-nuts] New ISO8601 ?

I believe the phrase "circa 1967" fits the bill pretty well, although it may fall a little bit short of "...but it’s all a bit of a blur”. Dana On Thu, Nov 23, 2017 at 7:18 AM, Poul-Henning Kamp wrote: > > In message <4bec82c4-583e-4632-8589-d898cc2bd...@n1k.org>,

Re: [time-nuts] Next upgrade

I once did make a token attempt at tweaking the disciplining parameters in that SRS-10, but seemed to be getting nowhere and gave up on the effort. Dana On Wed, Nov 22, 2017 at 8:12 PM, Mark Sims wrote: > The PRS-10 does have disciplining parameters that you can tweak.

Re: [time-nuts] Next upgrade

For the most part the SRS-10 is a nice choice, although I'd always be wary of buying a used one. My only real beefs are that the tuning granularity is rather coarse, about 2E-12, and the disciplining loop seems to be a bit aggressive so that the poor oscillator gets jerked around quite a bit by

Re: [time-nuts] H-maser drift

Thank you John. That was most informative. dana On Tue, Nov 21, 2017 at 2:26 PM, John Ponsonby wrote: > There seem to be a lot of misunderstandings about H-masers. To set the > record straight note: > 1. The flow of hydrogen is generally controlled using a palladium >

Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

Hi Ole, What does 'EFOS' mean? I hadn't heard the term before. I think I've heard the one-second lifetime figure before. I do hear mixed reports about where the conversion to atomic H occurs, and consider the jury to still be out on that question. I had thought that the volume of the storage

Re: [time-nuts] ***SPAM*** Re: Why discipline Rubidium oscillator?

1:39 AM, Mike Cook <michael.c...@sfr.fr> wrote: > > > Le 20 nov. 2017 à 20:53, Dana Whitlow <k8yumdoo...@gmail.com> a écrit : > > > > > > > > In my pre-retirement job I rode herd on an active Hydrogen maser > system,and even > > that has a

Re: [time-nuts] Why discipline Rubidium oscillator?

As far as I knew, the highest level steps *actually on the market* are the Cesium beam clocks and the active hydrogen masers. Are any of the newer technologies available for purchase today? Dana On Mon, Nov 20, 2017 at 6:13 PM, Hal Murray wrote: > > aren’t too many

Re: [time-nuts] Why discipline Rubidium oscillator?

And even without problems like external magnetic fields, Rb oscillators do drift with age. Over a period of several years they may drift as much as ~1E-9, which is a *huge* error for serious time nuts. In my pre-retirement job I rode herd on an active Hydrogen maser system, and even that has a

Re: [time-nuts] Recommendation for cheap GBIP adapter for Linux

Beware- Many GPIB-to-Ethernet adapters are also very prolific RFI generators- learned the hard way at Arecibo. Dana On Sat, Nov 18, 2017 at 5:03 PM, Bob Bownes wrote: > > All GPIB to Ethernet adapters are not created equal. > > The NI GPIB-E is no longer supported for

Re: [time-nuts] Absolute phase

Hello Arthur, Might be interesting to try the same experiment both with the two receivers on the same antenna and on the two different antennas. In an ideal world I'd expect the time output(s) to track as well either way, but it would be interesting to know how well this works out in practice.

Re: [time-nuts] Oscillators and Ovens

Bob, This discussion is getting really interesting. In thinking about the crystal Q versus tuning range conundrum, two (presumably-overlapping) concerns come to mind: 1. The motional parameters of a high-Q crystal are such that the external network needed to pull it very far would be wholly

Re: [time-nuts] Thunderbolt - Lady Heather altitude does report abt 240m too high

Remember that GPS normally displays altitude with respect to the WGS84 datum geoid, not with respect to MSL. There can easily be a hundred feet or so of difference. Dana On Wed, Oct 25, 2017 at 9:18 PM, Arnold Tibus wrote: > Hello fellow time nuts, > > after the

Re: [time-nuts] I've been thinking about a GPS receiver experiment

What "naughty schoolboy"? How else is one supposed to learn feedback theory? Dana On Wed, Oct 25, 2017 at 6:30 PM, Mark Sims wrote: > > No, you set up an oscillator so that is why you have that problem. > > I hooked the two rubidiums together just to see what would

Re: [time-nuts] I've been thinking about a GPS receiver experiment

Hello Skip, I have a theory, but it will be interesting to see what others say. Assuming that the 1 PPS error to which you refer is the so-called "sawtooth" error, I've come to suspect that the rate at which the individual PPS pulses walk across the sawtooth is related to, and likely proportional

Re: [time-nuts] Spice simulation of PSRR and phase noise

Hello Attila, It seems to me that an AC simulation could never work since the very generation of phase noise by the mechanisms that matter is a modulation process at heart, automatically forcing one into the realm of transient simulations. But I am surprised about the simulation times that you