Re: [time-nuts] New +/- 1 sec in 100 days mech clock
Perhaps it is not a good analogy, but I think of the cesium beam tube in the 5071A. The plans alone are very non-trivial. Then there are a bunch of proprietary machining details that I can't disclose, that are way beyond the merely having access to a CNC tool. The systematic error due to the CBT is below something like 1 part in 10^14, which is 1 second in 3 million years. Perhaps that is in some sense equivalent to Harrison's 1 second in 0.3 years. 7 orders of magnitude difference. As many time-nuts are probably aware of, most if not all cesium clocks that are better than the 5071A have reversible beams to cancel out CBT assymmetry. Rick Karlquist N6RK ___ 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] Ultra High Stability Time Base Options for 53132A
On 4/13/2015 3:11 AM, John Miles wrote: A comparator with less open-loop gain was what they needed. Somebody at HP really liked ECL line receivers, though. Those were very noisy at HF, but this had little or nothing to do with their bandwidth (see my other post.) To square up a 10 MHz signal from an OCXO it's hard to beat a simple diff amp with a pair of bipolars, a la Wenzel. -- john, KE5FX Miles Design LLC The HP counters all used ECL line receivers for the A and B channel to convert the input frequency signal to be counted into a digital square wave. Naive engineers then ape'd this for use on the timebase clock. Engineers at HP who actually knew what they were doing, such as Tom Falkner, did use differential pairs. However, HP being a huge company, the word did not necessarily get disseminated to all the other HP engineers. Rick Karlquist N6RK ___ 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] Ultra High Stability Time Base Options for 53132A
On 4/13/2015 12:14 PM, Magnus Danielson wrote: Oh yes. Some people say that you should not overcomplex things. My experience is that oversimplifying them can cause a long stretch of complex problems and complex workarounds making the total solution more expensive in development, customer relations and more complex than starting with a more advanced solution, that actually attempts to address the design issues. Ah well. This is extremely good advice. The ultimate example of the oversimplified design is the Muntz TV set, where few parts are used, but they all interact with each other in mysterious ways that depend on unknown unspecified parameters. The ultimate example of the overcomplicated design is the Japanese VCR, circa 1980. Schematic looks like it was designed by committee. The parts count has become bloated to the point of redundancy. Neither is desirable. Rick Karlquist N6RK ___ 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] Ultra High Stability Time Base Options for 53132A
On 4/12/2015 6:30 PM, Attila Kinali wrote: It might be that I'm already too sleepy, but I don't see why a faster comparator would add more jitter. Actually, my intuition (which is clearly wrong) would say the contrary. So, which effect does increase the jitter with comparator speed? The faster the comparator, the greater its analog bandwidth. Thus there is more total noise to cause jitter. The DC to daylight comparator is the opposite of the John Dick (JPL) paper on zero crossing detectors in PTTI around 1990. John teaches that you use the MINIMUM bandwidth amplifier to square up a sine wave. BTW: If anyone here has any good text to read on oscillator design, please let me know. I'm collecting those :-) Attila Kinali Start by reading everything by: Marv Frerking Mike Driscoll John Vig Oh, and I wrote a few papers on oscillators myself :-) 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] Ultra High Stability Time Base Options for 53132A
On 4/12/2015 2:22 PM, Magnus Danielson wrote: Hi, The buffer transistors has not AC-bypass of the emitter resistance, so that the DC current becomes large and thus contributes flicker noise. The comparator at the bottom isn't doing a beutifull work of squaring things up without contributing noise, considering the sine output of the 10811. Was that it, Rick? Cheers, Magnus The resolution of page 13 is poor, and it seems to be a bitmap instead of a vector file. The fuzzy thing in the lower right corner looks like it might be a comparator. I think this was the smoking gun. There was a saying by H.L. Menken to the effect that for every complex problem, there is a simple, obvious, invalid solution. Squaring up a 10811 with a comparator is a perfect example of this principle. Non-time-nuts always seem to gravitate to this design. Of course you're right, any comparator will add jitter to a 10811. The faster they are, the more jitter they add. I noticed that the standard 10 MHz oscillator is built with an ECL line receiver. Another example of Menken's saying. This is a TERRIBLE oscillator design, but one that would appeal to the non-initiated. I built one of these oscillators in 1976 at the suggestion of my boss. After seeing how bad it was, I quietly designed it out and never used it again. Rick Karlquist N6RK ___ 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] 5 to 10 MHz doublers
The 5071A doublers I designed use MCL ASK-1 mixers. The LO and RF ports are connected in series. This arrangement is self limiting. So you drive them fairly hard and the output is level. The IF port needs to see a DC short circuit of course. This was essential in the 5071A since there were 5 doublers in cascade. The input impedance is about 30 ohms and you need a fair amount of drive, like 30 mA peak to peak. I tested and rejected other approaches like putting the ports in parallel or driving them with a quadrature hybrid. The series connection just worked better. It's going on 25 years, but this is what I remember. The filtering is another non-trivial story. Buying DBM's doesn't make that job any easier. Rick Karlquist N6RK On 4/12/2015 3:10 PM, Perry Sandeen via time-nuts wrote: List, There has been a lot ofinformation on the list for 5 MHz frequency doublers. As it is easier for me to buythan make, would using something like a Mini-Circuits surplus DBM’s be anacceptable way to go? Regards, Perrier ___ 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] Distribution Amps
On 4/12/2015 3:04 PM, Perry Sandeen via time-nuts wrote: List, For me it was simpler to buy asurplus HP 5087A for best offer which turned out to be $300 delivered. The 5087 series is ancient technology that has mediocre performance. I remember looking at the circuit designs in the series in case I wanted to leverage them for the 5071A. There was nothing that would be of interest for the 5071A. If the 5087 meets your needs, then fine. But many time nuts need something better. Rick Karlquist N6RK ___ 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] Ultra High Stability Time Base Options for 53132A
On 4/12/2015 1:03 AM, Adrian Godwin wrote: What caused that degradation ? I'm interested in dos/don'ts for best use of a 10811. I don't remember the details much after 25 years, but basically they have a distribution amplifier that allows for internal or external 10 MHz and what I remember is that I looked at the schematic and concluded that no one with a background in precision time and frequency would design it that way. And it turned out that the person who designed it did not have any such background. I vaguely require some measurement that had disappointing results that caused me to want to look at the schematic of it in the first place. 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] Ultra High Stability Time Base Options for 53132A
On 4/11/2015 5:01 AM, J. L. Trantham wrote: Unless the design has been changed, the 10811 option for the 53132 has poor short term stability and degrades the performance of the 10811 by something like an order of magnitude. I complained about this when the counter first came out 25 years ago but no one would listen. At the time I had recently transferred out of counter RD to work on the 5071A. Rick Karlquist N6RK ___ 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] Obscure HP T/F instruments in ebay.fr
Before the Keysight split, there was an Agilent museum at HQ in Santa Clara. It was packed full of interesting old HP stuff and even had a part time archivist. I'm now retired and don't know what became of this museum in the split. I feel I got out while the getting was good. Rick Karlquist N6RK HP/Agilent 1979-2014 On 3/19/2015 9:01 PM, Tom Van Baak wrote: If that is the case, then this stuff belongs to a museum and not on ebay. IMHO. Hi Attila , I completely understand how you feel, but this happens all the time with niche collections. You just can't find a brick and mortar museum interested in taking all that inventory. How many people would travel to city X in country Y to see a collection of electronics made by company Z? So these collections tend to last only as long as the original pioneer behind them is active. Once they are gone, there's a good chance that it all ends up on eBay, scattered around the globe. At least it doesn't end up in recycling or the trash. Checking current vs. completed auctions for that seller, you'll note that a large number of the good or exotic items have already been sold. I noted that high value items like hp rubidium and cesium standards apparently never made it to eBay, suggesting some cherry picking occurred before the collection went out for bid. I once thought HP should have their own museum. But then they split into Agilent, then Symmetricom bought out their TF line, then they became Keysight, then Symmetricom became Microsemi. With these companies, there isn't strong technical, moral, or business justification to allocate office space and resources to host dusty museums that might only attract tens or hundreds of people a year. They are rightly focused on current and future products, leaving us bottom feeders and nostalgic historians to collect and display the old stuff in our own homes, or on the web. For me the greatest museum loss occurred when The Time Museum in Rockford, IL closed in 1999. This was the best collection of clocks in the world, 1500 pieces from an ancient Egyptian water clock to a vintage hydrogen maser and everything in between. But the heirs of the founder were not into Time or into Museums. So it went to a massive international auction (Sotheby's) and was scattered for all of time. /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. ___ 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] OXCO insulation
On 2/25/2015 4:32 AM, Attila Kinali wrote: On Wed, 25 Feb 2015 10:16:58 +0100 Attila Kinali att...@kinali.ch wrote: Actually, you should put the temp sensor close to the heater, not the crystal. The delay between the actuator (heater) and the feedback (temperature sensor) defines the dead time. The presence of a crystal somewhere in the system is of no importance to the oven controller, it's just additional thermal weight. Bob Camp just reminded me of Rick Karlquist's papers on this topic: A low Profile High-Performance Crystal Oscillator for Timekeeping Applications, by Karlquist, Cutler, Ingman, Johnson, Parisek, 1997 http://www.karlquist.com/osc.pdf The Theory of Zero-Gradient Crystal Ovens, by Karlquist, Cutler, Ingman, Johnson, Parisek, 1997 http://www.karlquist.com/oven.pdf More can be found on his homepage: http://www.karlquist.com/ A quick summary of the insulation issue in OCXO's: Virtually any kind of foam, or just still air has similar insulating properties in an OCXO. Exotic kinds of insulation like aerogel, or vacuum, are impractical because you have to get rid of the heat generated by the electronics. The E1938A oscillator described in the above references achieved a thermal gain in excess of 1,000,000 (in a single stage oven) in prototype testing, and routinely achieved many 100's or thousands on a production basis and had only 1/4 inch of foam that was nothing special thermally. We also were able to get high thermal gain with a still air experiment. At HP, the main issues with foam were outgassing and mechanical fatigue, like a mattress getting flat and the foam had to withstand the oven temperature continuously. Another issue was what happens if the oven runs away and the foam burns and produces toxic gases. Generally, we are talking manufacturability issues. The one thing the choice of foam had little to do with was performance. Rick Karlquist N6RK ___ 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] 10544A vs. 10811
The other big difference is that the 10811 uses an SC cut crystal instead of an AT cut crystal. From a cold start, the SC achieves a given stability much faster than an AT cut. If you are just going to run the oven continuously (likely mode for time nuts), this isn't any big deal to you. The reason why the phase noise is better is not so much due to the SC cut crystal, but rather to the grounded base output buffer in the 10811. A 10811 is guaranteed to work in any 10544 socket in HP equipment. They had to do this so that they could stop making 10544's as soon as the 10811 was introduced. Rick Karlquist N6RK On 2/1/2015 12:54 AM, Bruce Griffiths wrote: Since the 10544A uses a PWM oven controller there are significant oven PWM frequency related sidebands.The PN noise floor of the 10811A (-160dBc/Hz) is significantly lower than that of the 10544A (-145dBc/Hz). Bruce On Sunday, 1 February 2015 2:57 PM, Bill b...@hsmicrowave.com wrote: I have a choice. Can I assume the 10811 is the better OCXO for phase noise and ADEV compared with the 10544A? Thanks and regards...Bill ___ 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] 10544A vs. 10811
On 2/1/2015 2:31 PM, Magnus Danielson wrote: As I recall it, the 10544 is a BT-cut and not AT-cut. We discussed this a few years back, and even checked the cold temperature before heating up, and it matched BT-cut and not AT-cut. Anyway, go with the 10811. Cheers, Magnus On 02/01/2015 07:51 PM, Richard (Rick) Karlquist wrote: The other big difference is that the 10811 uses an SC cut crystal instead of an AT cut crystal. I stand corrected. 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] 510 doubler
On 1/29/2015 5:41 PM, Alexander Pummer wrote: And the narrow notch for the harmonic is not required anyway, since the fundamental is fare enough, therefore a high Q LC trap will work better, also with the setting of the biasing af the active devices the Alex KJ6UHN When I designed the 5071A RF chain, I used five cascaded frequency doublers to go from 10 MHz to 320 MHz. I definitely used traps to reduce the 10, 30, and 40 MHz spurs (using 10-20 MHz as an example). It was no easy thing because I could only use coils of moderate Q (less than 50) and I needed at least 80 dB suppression. You might wonder why I needed to reduce 40 MHz spurs in the 20 MHz output. It turns out (little known fact) that the if I drove the 20-40 MHz doubler with 20 MHz contaminated with 40 MHz harmonics, it would degrade the spectral purity of the 40 MHz output. Strange but true. The 5071 filters are basically cascaded notch filters, as opposed to band pass filters. Doing this allowed me to have zero adjustments. Previous atomic clocks used narrow high-Q filters that had to be tuned up, and were temperature sensitive. The production engineers had to constantly stay on top of these filters because they were so temperamental. OTOH, the 5071 filters just work. There was never even a production change to them AFAIK. The key to getting the notch filters to work was to use 2% components, and use two coils and or two capacitors together to get around the fact that the standard values are quantized to 10%. Additionally, I measured each tank circuit in situ on the PC board and tweaked it to take into account the de facto board parasitics. Rick Karlquist N6RK ___ 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] Usefulness of high end counters for ADEV plots of oscillators
First of all, the oven oscillator option of the 53230 is no where near as stable in ADEV as a 10811 for example. The counter itself is 1 or 2 orders of magnitude better than the built in timebase. So don't waste your money on the OCXO option when you, as a time nut, undoubtably already own something like a 10811. When I was still with Agilent, I made innumerable measurements of ADEV with a 53230 down into the low parts in 10^11, which was the DUT ADEV, not limited by the counter. I vaguely remember measuring a 10811 as a sanity check and using the internal OCXO (not knowing any better). After wasting a lot of time, I eventually measured one 10811 against another and discovered that the ADEV floor was down to 1E-12 at least, and that the internal OCXO was junk. About the only good thing about the 53230 is that it is a self contained box that makes ADEV measurements and displays them in real time without requiring an external computer with software. In 1974, HP made a computing counter (5360 I think) that did this. Customers loved this box, but the HP engineers hated the box. Therefore, no HP/Agilent counter ever did ADEV again, until the product line was offshored to engineers who didn't know any better and put the feature back in. For serious ADEV measurements, you want two DUT's offset by a few 100 Hz and mixed, as originated in the HP 5490 system. Rick Karlquist N6RK On 1/30/2015 8:38 AM, James via time-nuts wrote: Though I'm new to the list I've lurked for quite a while and from reading various posts I am in a slightly confused state as to whether buying an expensive counter (eg Keysight 53230A or a Tek fca 3100) will be useful as a measurement tool for developing a GPSDO. Given a one shot measurement resolution of 50 psecs (on the Tek which is a pendulum CNT91) means that the uncertainty is around 50E-12 at 1 sec or 5 x 10^-11 or 10^-10 in round numbers for a ADEV at 1 sec? For this noise floor to get well below 10^-11 (the sort of ADEV of an OCXO) requires the interval to be increased to nearer to 100 seconds? So does this mean that an expensive counter allows useful ADEV plots from 100 seconds on but not the lower time frames? (By useful I mean able to measure down to and below 10^-11 not down to 10^-14!) The extra cost of the 53230A over the 3100 gets down to 20 psecs so possibly reduces the period to a bit less than 100 seconds but still above 10 seconds probably? Does paying extra for an OCXO gain significantly on this basis? Have I got the basic numbers right, and if one of my main aims is to have a good instrument for playing with GPSDO development will investing in such an expensive (for an individual hobbyist) instrument buy me a useful measurement capability or would it just be good for measuring long term frequency and say 1pps jitter from the GPS? Sorry for the long post, James ___ 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] 510 doubler
On 1/28/2015 11:28 AM, Charles Steinmetz wrote: Gerhard wrote: It is a different game when you want to notch away sub/harmonics. One problem with using crystals as traps (notch filters) is that the series resistance of a crystal is several orders of magnitude higher than that of a good series-resonant LC -- generally in the 50-100 ohm range. So, although the notch is very narrow, it will not be very deep unless it is in a high-impedance circuit. For example, in a 50 ohm It is very straightforward to use LC networks to transform the impedance of the crystal to a much lower value and get around this problem. Rick Karlquist N6RK ___ 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] New Years Eve TV countdown
We have DirecTV with some receivers standard definition and others High Definition. The delay is considerably greater on the HD version. Even OTA HD is delayed considerably, as noted if you try to listen to a football game on the radio while watching. Sometimes you hear touchdown before the ball is even snapped on TV. 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] 100 MHz VCXOs
On 12/11/2014 4:20 PM, Bob Camp wrote: Hi Those OCXO’s were made to the spec’s of an OEM customer. The spec’s are owned by that customer and can not be released without authorization from them. Anybody who wants to stay in the business would be a bit crazy to release somebody else’s intelectual property to the public. That’s not an uncommon issue with surplus OCXO”s. Rouglly 99.9% of them are built to customer spec. Bob The reminds me of when I worked for HP. We had a division that made diodes, which all had a part number of the form 5082-. There was a special series of part numbers of the form 5082-5XXX that never appeared in the catalog. I remember I was working on a step recovery diode multiplier and was trying to reverse engineer various multipliers that were designed into commercial equipment. I got the HP part number of the diode which was of the form 5082-5XXX from the manual and found out that there was no data available on these part numbers in the HP internal system. I called the Microwave Semiconductor Division and got the story Bob gave about OEM spec's. I said, sure I understand that, but I work for HP. I was told that you have to work for MSD, not just HP to get access to this information, and in any event, they would NOT sell us these diodes, even as an internal transfer. Rick Karlquist N6RK HP 1979-1999 (then Agilent) ___ 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] Linear voltage regulator hints...
Hittite introduced a low noise reference a few years ago, but it was only low noise when filtered with a big cap. IOW, the cap did all the heavy lifting and the IC was nothing special. Good marketing, bad engineering. Rick On 12/9/2014 4:30 AM, Bob Camp wrote: Hi On Dec 8, 2014, at 10:35 PM, Brooke Clarke bro...@pacific.net wrote: Hi Rich: Did you use the 723 or . . . .? As far as I know the 723 is supposed to have low noise. There are more modern parts with lower close in noise. Linear Technology has a number of them. Your filter caps take out the broadband stuff, close in is all that really matters. Bob Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Richard (Rick) Karlquist wrote: On 12/8/2014 4:53 PM, Bert Kehren via time-nuts wrote: We solved that problem by attaching the regulators to the FRK back plate which is with fan control is kept within 0.01C. We did not do it for that purpose but found that we needed some more heat in order to keep the fan in an optimum fan speed. Rb, OCXO and Fan power transistor are on the back plate. Works for us. Bert Kehren When I designed the E1938A, I chose a reasonable looking voltage reference IC and put it inside the oven. I figured that was the end of it as far as tempco was concerned. It was, but it turned out that the *noise* of the reference was unacceptable and of course the oven does nothing to fix that. I had to switch to a lower noise reference. Rick Karlquist N6RK ___ 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] Linear voltage regulator hints...
I don't remember, but it wasn't a 723. Rick On 12/8/2014 7:35 PM, Brooke Clarke wrote: Hi Rich: Did you use the 723 or . . . .? As far as I know the 723 is supposed to have low noise. Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Richard (Rick) Karlquist wrote: On 12/8/2014 4:53 PM, Bert Kehren via time-nuts wrote: We solved that problem by attaching the regulators to the FRK back plate which is with fan control is kept within 0.01C. We did not do it for that purpose but found that we needed some more heat in order to keep the fan in an optimum fan speed. Rb, OCXO and Fan power transistor are on the back plate. Works for us. Bert Kehren When I designed the E1938A, I chose a reasonable looking voltage reference IC and put it inside the oven. I figured that was the end of it as far as tempco was concerned. It was, but it turned out that the *noise* of the reference was unacceptable and of course the oven does nothing to fix that. I had to switch to a lower noise reference. Rick Karlquist N6RK ___ 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] Linear voltage regulator hints...
On 12/9/2014 1:30 PM, ed breya wrote: buried zener for lowest noise - this eliminates all the low voltage references and three-terminal etc regulators that use band-gap references. The down side is that the good kind of reference ICs will need a higher (like 10V and up) operating voltage than may be available, so that complicates it. Great post, Ed. I might add that my understanding of band gap regulators is that they rely on amplifying a small DC difference in voltage between two transistors. This also amplifies the SUM of the noise of the respective inputs, which jacks up the noise to much more than a good zener. Because of physics, no band gap reference will ever be low noise. Rick Karlquist N6RK ___ 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] Linear voltage regulator hints...
On 12/9/2014 3:02 PM, Bob Camp wrote: Here's an overnight ADEV plot against the new Cs of where we are in the project. Red is ADEV. Green is the TIC. Blue is the output of the GPSDO to Channel A and the Cs to Channel B of my 5335A measuring TI, using the 1PPS from my GPSDO to trigger the external gate. I see that the Cs phase has drifted down slightly vs my GPSDOe. I wonder if this is an indication of a calibration problem with the Cs or some subtle issue on my board? Looks perfectly normal to me. Your Cs is sensitive to magnetic field. Have you “zeroed” it out? No of course not, nobody does. (almost nobody …). Bob This reminds me of the great CBT demagnetizer debate at HP. Even Len Cutler didn't think this was necessary, at least in the 5071, and possibly the 5061. When Len says something is overkill, you can be sure of it. Anyway, we still had to support a CBT demagnetizer for customers who wanted it. The customer (with money to spend) is always right. The 5071 measures the C-field with a Zeeman line measurement and adjusts it if necessary. Rick Karlquist N6RK ___ 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] Minicircuits specs
Please Gerhard, more details on your choke (medium size red Amidon core two 220 uH Siemens chokes). Maybe I can use it for 160 meter antennas. Your T1-1 measurements make sense according to my experience with these things. The -6 series (T1-6, etc) has larger cores and should withstand more DC. (I like to take apart MCL stuff to see what is inside; very enlightening). I always use the -6 series for 160 meter work. Thanks, 73 Rick Karlquist N6RK On 12/7/2014 10:14 PM, Gerhard Hoffmann wrote: Am 29.11.2014 um 20:01 schrieb Gerhard Hoffmann: DG8SAQ VNWA, my best DC block from PSPL because it also has the lowest lower corner. It took some experimenting to find a choke that would not modify S21 and carry the current. Finally: a medium size red Amidon core two 220uH Siemens chokes with a looong air gap. ___ 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] Linear voltage regulator hints...
On 12/8/2014 4:53 PM, Bert Kehren via time-nuts wrote: We solved that problem by attaching the regulators to the FRK back plate which is with fan control is kept within 0.01C. We did not do it for that purpose but found that we needed some more heat in order to keep the fan in an optimum fan speed. Rb, OCXO and Fan power transistor are on the back plate. Works for us. Bert Kehren When I designed the E1938A, I chose a reasonable looking voltage reference IC and put it inside the oven. I figured that was the end of it as far as tempco was concerned. It was, but it turned out that the *noise* of the reference was unacceptable and of course the oven does nothing to fix that. I had to switch to a lower noise reference. Rick Karlquist N6RK ___ 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] How can one measure ADEV of a good oscillator?
On 11/30/2014 11:09 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: I think I have a flaw in my understanding of this. How can something like an SR620 measure the ADEV of an oscillator, if the oscillator is of a similar or better than the reference fed into the SR620? What HP did with the 10811 was to make a few special crystals that were 500 Hz off frequency and build them into oscillators. These oscillators were mixed with the DUT and the 500 Hz beat note was then squared up and its ADEV measured with a frequency counter. After measuring a bunch of production line oscillators, they could establish a minimum ADEV that would be attributed to the offset oscillator. If this level of performance wasn't good enough, other offset crystals could be tried until a golden crystal was found. I was thinking it might be possible if one has 3 oscillators and 3 time interval counters to perhaps solve 3 simultaneous equations. I can't prove that, but it seems intuitively correct. In theory this makes sense, however, it would require a high offset crystal and a low offset crystal to do a 3 way round robin. There wasn't enough need to go to the trouble of having 2 crystal designs. There is an NBS paper written maybe 40 years ago explaining the magic of the beat note method. Rick Karlquist N6RK I must be missing something! Also I have seen graphs of both Allan variance and Allen deviation. Both are typically 10^-12 for a decent oscillator, but given the variance and standard deviation are related by a square root, they can't both be around 10^-12. I would expect to see values of 10^-6 or 10^-24, but I don't see such dramatic differences from 10^-12. If I see numbers around 10^-12 on an OCXO, is that the Allen variance or Allen Deviation? Dave ___ 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] How can one measure ADEV of a good oscillator?
On 12/1/2014 4:08 PM, Bob Camp wrote: Others did a similar thing by simply taking production OCXO’s to the limit of their EFC range. That let you do a coarse sort to find some number of “likely” units. Next step was to pop a few of them open and short this or that out to get a reasonable beat note. Numbers in the 10 to 20 Hz range were pretty common. After that a single mixer setup followed by a simple limiter got things good enough to screen the production lots. Bob I am fairly sure they would have done that if it was workable, to avoid special crystals. One rather huge problem with a 10 Hz beat note is that you are never going to measure ADEV at short (1 second) sample times that way. Rick N6RK ___ 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] Minicircuits 10% discount in December
On 11/28/2014 10:08 AM, Dave M wrote: Rick, Thanks for the brief review of MiniCircuits stuff (I'm not connected with them in any way except as a customer). Since you've characterized some of their parts, perhaps you could help answer a question that someone else posted, and one that I would like to have answered as well. Have you measured the effects of DC current in the windings of an RF transformer, such as is seen if the transformer is in the collector circuit of an amplifier? If so, could you provide a generalization of the effects, such as changes in frequency response, losses, etc.? Many Thanks!, Dave M The very tiny cores on MiniCircuits transformers will start to saturate at hundreds of mA. The effect is that the magnetizing inductance drops, which matters more at low frequencies than high frequencies. I try to avoid feeding DC to an amplifier through a transformer winding. Instead I use a separate RF choke for that. However, it would probably work OK for, say, up to 25 mADC for a small signal transistor, but why take a chance. If you are using a DC feed through a transformer winding, be careful not to accidently short circuit it, causing the full available current from the power supply to flow through the transformer. This can actually magnetize the core and permanently damage it. Saturation via DC is much more deleterious than saturation via AC. It is easy to calculate the flux density using Ampere's law, which is one of the four Maxwell's equations. H = I/(2piR). Since R (radius) is in the denominator, cores saturate from the inside first before the whole core is saturated. Multiply H by mu, (as any time nut knows) to get B. If R is 1 mm, and I is 628 mA, then H = 10 ampere turns per meter. If mu-relative is 1000, then B = 4piX10^-7 X 1000 X 10 = 125 mT. That is a hefty 1250 Gauss. Some materials may be affected at 1/10 this flux density. Now a days, a lot of RF is differential, in which case you are free to feed DC through the output transformer without worrying about this issue. I worked for several companies where those 6 hole cylindrical chokes were ubiquitous. I specifically characterized those and established a maximum current rating of only 100 mA. Of course, many production designs exceeded this limit and worked anyway. I actually observed someone try to put 20A through one of these. The tantalum capacitors on the cold side of the bead actually exploded due to RF current. Rick Karlquist N6RK ___ 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] Minicircuits 10% discount in December
On 11/28/2014 1:04 PM, Bob Camp wrote: If you do need to run substantial current through a choke core, the larger binocular cores with a half turn through them are a better choice. Still useless for 20A (or even 2A) though … Bob The binocular cores come in several hole sizes. All other things being equal, current handling capacity is directly proportional to hole size. One thing to watch out for with putting DC thru binocular cores happens in push pull RF power amplifiers. The output transformer is usually a binocular core on steroids, or its equivalent constructed with beads or sleeves, etc, threaded over a single turn made from brass tubes connected together at the end away from the transistors. In cheap (illegal) CB amplifiers, you will frequently see +13.6 VDC connected to the junction of the brass tubes, as if it were a center tap. It actually isn't a center tap in terms of core saturation, and the DC currents to the transistors are unmitigated in terms of magnetizing the core. Although the cores are larger, so are the currents, and these amplifiers just live with the degradation including the magnetization. This occurs because each core sees only a half-turn. If you replace the tubes with a 2 turn wire primary, then the problem goes away, but of course then the amplifier would never work as high as 27 MHz, which is does normally only by resonating stray PC board trace inductance with peaking capacitors on the transformer. This forms a two stage step up structure. If you improve the layout to get rid of the trace inductance, the amplifier no longer works! See Motorola AN-762. Rick Karlquist N6RK ___ 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] Minicircuits 10% discount in December
On 11/27/2014 7:07 AM, Tim Shoppa wrote: For a hobbyist doing things a few at a time, what advantage is there to buying RF transformers made by Mini-circuits etc., vs winding them using commonly available ferrite cores/binocular cores? If I needed to do a production run of 1000+ boards with tiny SMT transformers, sure, no problem buying them from mini-circuits or a distributor etc. But for hobbyist stuff seems far more flexible to wind them onesy-twosy using not so tiny cores and windings selected for the particular application. Tim N3QE You need the tiny cores to get the performance of the MiniCircuits transformers. You just can't get the same bandwidth using macro sized binocular cores. Now, if you don't need a lot of bandwidth, then what you are saying could make sense. Another issue is stray capacitance. Considerably lower with a tiny core. I have spent many hours characterizing MiniCircuits transformers beyond the data sheet specs, and dissecting them to learn how they do it. They really do have a lot of rocket science in them. In terms of the engineering I am buying (especially in a one-off application) they are ridiculously cheap. And I say that as a fairly knowledgeable transformer designer in my own right. I do keep binocular cores around for higher power transformers, and for emergencies when I need a transformer yesterday. Rick Karlquist N6RK ___ 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] Minicircuits 10% discount in December
On 11/27/2014 9:09 AM, Tim Shoppa wrote: On Thu, Nov 27, 2014 at 10:28 AM, Bob Camp kb...@n1k.org wrote: The main complaint is the difficulty of getting the correct cores. I seem to have a few dozen bags of cores. The mainline distributors (Allied, Newark, Mouser, etc.) have excellent selection of Fair-Rite and other cores. Admittedly to a neophyte the equivalence of Fair-Rite or Laird part numbers to an Amidon-style number may not be evident. I recently needed some binocular cores for a transformer for a client. After checking all the distributors, I had to buy 500 of them. Minimum quantity. So much for one-off hobbyist projects. The reason why I did not use a MiniCircuits transformer for this client is that the impedance was much less than 50 ohms. This is one area that MiniCircuits really does not address. Rick Karlquist N6RK ___ 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] Minicircuits 10% discount in December
On 11/27/2014 11:03 AM, Didier Juges wrote: Another reason is reproducibility. If you or someone else wants to reproduce your design, using a well defined and available commercial part makes it much easier to achieve the same performance, particularly for RF components. Didier KO4BB Exactly right. I wrote an article on receiving loops and showed a design with a 50:5 (turns ratio) transformer wound on a toroid. Again, this is not available from MiniCircuits. I have wasted time dealing with numerous dumb questions about can I use XXX core that I have laying around the lab? or can I use a different gauge wire to wind it, etc. So many people complained about the shipping cost to buy one core that I stocked the cores and included them with PC boards I was already selling to reduce the shipping cost to zero. BTW, 73 material would NOT work in this application. I was asked about that multiple times even though the article specifically said it would not work and explained why. Rick Karlquist N6RK ___ 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] Low Additive Phase Noise 10 MHz Amps
I did some checking around for low noise buffer amps earlier this year. They needed to have 200 MHz bandwidth, so this isn't directly applicable to 10 MHz. I also needed isolation. About the only information in print is from the usual suspects at NIST. They wrote a series of papers taking a fairly classic discrete design and refining it. Check FCS proceedings. My idea was to take ideas from 10 MHz and extend them to 200 MHz. I didn't see any really profound ideas in the NIST papers. There is a reproducibility problem because the original discrete devices may not be available, or NIST might have used special hand picked devices. BTW, I cringe when I see the term additive phase noise. Phase noise, as all time nuts know, is NOT ADDITIVE NOISE, as in AWGN. It is multiplicative. The correct term, IMHO, is residual phase noise. What additive noise refers to is the classic noise figure type noise involving small signals. Again, as all time nuts know, low NF is necessary but not sufficient for low phase noise. Rick Karlquist N6RK ___ 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] MIT 2 inch cesium fountain, optically pumped
See: http://newsoffice.mit.edu/2014/portable-atomic-clocks-1112 Any comments? Rick Karlquist N6RK ___ 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] 10811
On 11/17/2014 5:54 PM, Bert Kehren via time-nuts wrote: I ground one side of the tuning diode and use the 2 to 12 V as the external OCXO for my FRK's along with increasing the time constant. I have not verified it but I think removing the zener Voltage should also improve ADEV. Bert Kehren The choice for the Zener diode came from my old boss at HP, who was very knowledgeable about using discrete zener diodes as low noise references. According to him, this particular part number has very respectable noise. This is just something you have to know experientially, there is no theory of zener noise AFAIK. You might try measuring the noise of the 6.2V reference voltage directly at baseband, and then multiplying by the 1 Hz/volt sensitivity. Let us know your results. Rick Karlquist N6RK (Now retired from HP/Agilent/Keysight) ___ 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] 10811
Yes, 5.1V Zeners (or something like that) have a magic zero tempco if you put a conventional diode in series with it. I used to know stuff like that during the Jurassic period. However, the diode in the 10811 is ovenized, so that is not so important. 6.2V was chosen to get +/- 5V tuning range, which was probably a spec inherited from the 10544. Everything was done for a reason relevant to HP, which may or may not be a reason relevant to you. The frequency of the 10811 is more sensitive to the temperature of the oscillator transistor (a selected 2N5179) than the diode. This inspired the E1938A. Rick On 11/18/2014 2:31 PM, Brooke Clarke wrote: Hi Rick: When working on Tunnel Diode amplifiers we used (AFAICR) 5.1 V Zener diodes to stabilize the lower voltage that drive the diode. 5.1V was supposed to have excellent temperature characteristics in terms of repeatability (don't remember if low noise was part of the selection criteria). http://www.prc68.com/I/Aertech.shtml#TDA The boards with the terminals have the Zener and a custom compensation network using both Veco (spelling?) (-TC) and Balco (+TC) and fixed resistors so that the gain stays constant over mil temperature ranges. Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Richard (Rick) Karlquist wrote: On 11/17/2014 5:54 PM, Bert Kehren via time-nuts wrote: I ground one side of the tuning diode and use the 2 to 12 V as the external OCXO for my FRK's along with increasing the time constant. I have not verified it but I think removing the zener Voltage should also improve ADEV. Bert Kehren The choice for the Zener diode came from my old boss at HP, who was very knowledgeable about using discrete zener diodes as low noise references. According to him, this particular part number has very respectable noise. This is just something you have to know experientially, there is no theory of zener noise AFAIK. You might try measuring the noise of the 6.2V reference voltage directly at baseband, and then multiplying by the 1 Hz/volt sensitivity. Let us know your results. Rick Karlquist N6RK (Now retired from HP/Agilent/Keysight) ___ 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] 2.5V reference IC in HP E1938 oscillator.
Hi, I was the designer of the board, but I don't remember the part number of the reference. I will try to consult my paper schematic when I get a chance, if no one else can help you. I do remember that I originally used some convenient reference which seemed OK from the data sheet, but turned out to be too noisy. I changed it to a different one. When asking questions such as this, it is helpful to know why you need to know the part number. Rick Karlquist N6RK On 11/9/2014 12:54 PM, Rob040 . wrote: Dear time-nuts, Can anyone enlighten me by telling which IC has been used for creating the +2.5V reference voltage on the oscillator board of the E1938?It's the only IC in the diagram where the type number is not mentioned. In a post of years back I found LT1121, but that one is a voltage regulator and is used on the control board. Cheers! ___ 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] If any of your USB devices have stopped working lately...
This dispute reminds me of another one. A long long time ago, .gif was the internet standard for encoding photographs. Far and away the favorite. Then the owner (was it AOL?) decided to enforce their patent by getting snotty with end users. Almost overnight, .gif virtually disappeared off the face of the earth, to be replaced by .jpg, previously an also-ran. The IP holder got their wish We wish people would stop free loading on our IP.. Be careful what you wish for as the saying goes. Let's see if history repeats itself. Rick Karlquist N6RK On 10/23/2014 6:45 PM, Mark Sims wrote: Happened to a friend of mine. All his Arduino stuff died. This could be the reason: http://www.eevblog.com/forum/reviews/ftdi-driver-kills-fake-ftdi-ft232 Short story: FTDI released a new version of their USB driver (via Windows automatic updates no less) that bricks other vendor's compatible versions of their interface chip. They also updated their license file to indicate that this may happen... except you never get a chance to decline the new license with automatic driver updates. I can just hear the class action lawyers drooling... ___ 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] fast switching quiet synthesizer
On 10/7/2014 10:02 AM, Jim Lux wrote: At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. Possibly overkill, but Agilent has a very state of the art arbitrary waveform generator that is light years ahead of anything else. It uses a chip with the internal codename Griffin that was developed in the department I worked in at Agilent until I retired in March. IIRC, the complete price for the generator in a box is about $60K. You didn't mention budget constraints, but this is an off the shelf solution vs who knows how much of your time. Rick Karlquist N6RK ___ 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] How long do ovens take to cool to ambient after power is removed?
Len Cutler was pretty much allowed to do whatever he wanted on the HP106 and he produced the proverbial doomsday machine. I think the SR-71 analogy is good here, except that Kelly Johnson had a lot more support from his management. Len always wanted to make an optically pumped cesium as his ultimate doomsday machine, but management never funded it. He proudly had a 106 on display in his office. I wish I had asked him how he got such low aging crystals. 10811 crystals never got much lower than about 1 part in 10^-10 per day. Rick Karlquist N6RK On 10/2/2014 11:58 AM, Tom Van Baak wrote: The most extreme example of slow ovenized oscillator warm-up I've seen is the vintage hp106. These mid-1960's oscillators were designed as the ultimate, hp way, pre-atomic, frequency standard -- expected to be powered up, uninterrupted, for years and decades. So there was no hurry in the (perhaps once-in-a-lifetime) initial warm-up. Here's a plot/photo of one I recently tested: http://leapsecond.com/museum/hp106a/ These HP-106 oscillators are among the best I have ever measured: stability and daily drift rates in the very low -13's. Like the SR-71, these were designed by gut and slide rule. And yet achieved extreme performance, even by today's standards. The amazing thing -- as you know from your enviable career at HP -- is that an instrument produced in 1964 can still work 50 years later in 2014. No blown fuses, no electrolytics, no filaments, no f/w upgrades, no Y2K, no decaying EEPROM, no batteries, not even any IC's. No user s/w, no USB, no drivers, no OS. Not even an on/off switch! Just a 5-pin 24VDC backup or 2-prong AC cord in and a pure 5 MHz BNC out, that's all. How many of the instruments we use today will still work out-of-the-box in 2064? /tvb - Original Message - From: Richard (Rick) Karlquist rich...@karlquist.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Wednesday, October 01, 2014 9:03 PM Subject: Re: [time-nuts] How long do ovens take to cool to ambient after power is removed? On 10/1/2014 1:04 PM, Hal Murray wrote: drkir...@kirkbymicrowave.co.uk said: Anyway, later today (tomorrow ??) I will post a plot of frequency vs time. The question is though, how long is thing thing likely to take too cool? I'd expect an exponential decay so you need to specify how close to ambient you want to get. I'd guess a ballpark of 10x the warm up rate. You can probably measure it if you have the warmup graph. Turn it off, wait a while, turn it on, measure the freq, consult warmup graph. When I was still with Agilent, I did some experiments with unpowered 10811's. Both the oven and oscillator were unpowered and I measured the temperature by looking at the B mode resonance of the crystal. I wanted to get rid of any linear frequency drift. As a rough rule of thumb, 1 hour of cool down is pretty good for most purposes. For extreme measurements, I would allow 10 hours. This reduced any exponential tail to below the ability to measure temperature and/or below the effects of the ambient. I had to put a box over it to reduce the effects of air currents. If I did not do that, then 1 hour was all I needed. Rick Karlquist N6RK ___ 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] How long do ovens take to cool to ambient after power is removed?
On 10/1/2014 1:04 PM, Hal Murray wrote: drkir...@kirkbymicrowave.co.uk said: Anyway, later today (tomorrow ??) I will post a plot of frequency vs time. The question is though, how long is thing thing likely to take too cool? I'd expect an exponential decay so you need to specify how close to ambient you want to get. I'd guess a ballpark of 10x the warm up rate. You can probably measure it if you have the warmup graph. Turn it off, wait a while, turn it on, measure the freq, consult warmup graph. When I was still with Agilent, I did some experiments with unpowered 10811's. Both the oven and oscillator were unpowered and I measured the temperature by looking at the B mode resonance of the crystal. I wanted to get rid of any linear frequency drift. As a rough rule of thumb, 1 hour of cool down is pretty good for most purposes. For extreme measurements, I would allow 10 hours. This reduced any exponential tail to below the ability to measure temperature and/or below the effects of the ambient. I had to put a box over it to reduce the effects of air currents. If I did not do that, then 1 hour was all I needed. Rick Karlquist N6RK ___ 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] Mc Coy OCXO in HP equipment.
I am just speculating that this oscillator was used instead of the 10811 because the 10811 would not fit. Therefore, it would NOT be used in other equipment. I would guess the specs would be similar to the 10811. The 70,000 series had some general purpose power bus that the McCoy would have to run off of. It might use different voltages than the 10811. Rick On 8/18/2014 8:55 AM, ewkeh...@aol.com wrote: I am presently downsizing and that has also resulted in shrinking my HP 70 000 series spectrum analyzer. Out with the 70310A OCXO reference. The unit has a McCoy OSC92-13B OCXO. The original price was $ 5000 and the option with out OCXO was a $ 2500 saving. Some OCXO. Does any one have any information on the unit and is it used in other equipment. Thank you Bert Kehren ___ 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] Cutler NAA on 24.0kHz....
On 8/17/2014 12:30 PM, paul swed wrote: OK That said I shared the tracor d-msk-r circuit with the group that removes the msk. How does it pull that trick off? I do not get how it gets rid of the msk and leaves the carrier. A common way to remove BPSK is to simply run the signal through a frequency doubler (implemented as a full wave rectifier). This converts 0/180 degrees to 0/360 degrees which is the same as 0/0 degrees, or no modulation. Rick N6RK ___ 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] WWVB BPSK patent status
Without having seen the specific patent, what worries me is that there is a trend these days to write blanket patents that say you can't build any black box that, for example, receives this format, no matter how it works. They don't have to prove what is in your FPGA code. They then can shut down any competition with such a weak patent unless the competition has deep pockets for a lawyer. If they can prove you willfully infringed (whatever that means), they get triple damages. If you do any kind of patent search, do not keep any records or tell anyone about it. Possibly you could make the FPGA code available on the internet and have the end user be the infringer. Not being a lawyer, I'm not sure if this would get you off the hook. Maybe they can hang their hat on the digital copyright law (DCMA?) , in which case you become a criminal too. Rick Karlquist N6RK On 8/8/2014 3:24 PM, Brooke Clarke wrote: Hi Mike: Do you have any patent numbers. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Mike Harpe wrote: From my reading of the archives and research it appears that the design for a BPSK WWVB receiver probably has a patent conflict. Isn't this a rehash of the old Heathkit patent on radio clocks that held back their adoption for years? I have begun work on a BPSK receiver for WWVB using an FPGA. Someone should look into why the NIST did this at all since the receiver design got a patent slapped on it right away. Mike Harpe, N4PLE Sellersburg, IN ___ 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] OT Gel Cell question
On 7/28/2014 1:12 AM, David C. Partridge wrote: Back to time related discussions please. Thanks Dave I worked on cesium standards (5071A) at HP/Agilent with Len Cutler of flying clock fame. You better believe that batteries are time related. We jumped through all sorts of hoops to get the 5071A power consumption down to a few dozen watts so it could run off of batteries. The other reason for minimizing power consumption was to avoid fans. HP also used to sell auxiliary battery systems in case the user needed more battery run time than the internal battery was capable of. Rick Karlquist N6RK ___ 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] IMD in Broadband Transformers and be careful with that enamel insulation!
On 7/24/2014 9:37 AM, Tim Shoppa wrote: The data and tests presented in this source: http://www.cliftonlaboratories.com/imd_in_broadband_transformers.htm is a great resource on measured large-signal performance of binocular/toroidal transformers. One factor found that can really degrade IMD performance it turns out, is not the magnetic material itself, but but physical damage to enamel insulation in winding around corners of unfinished cores. My large signal usage of BN73-202's aka 287300202's, is that not only do they make great 160M transformers, I've also been putting them to use in multi-watt DC-to-DC step up converters! Similar to the Clifton labs test, in HV step-up usage I usually find the enamel insulation limits and/or winding-around-corner damage to be a much more prominent limitation on performance than the magnetics. Tim N3QE At HP, we once had a bad run of Mini Circuits transformers that would fail if used in a high impedance circuit that had different DC voltages on the windings. Turns out MCL left off the Parylene coating on the cores that protected the magnet wire insulation. Rick Karlquist N6RK ___ 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] Noise and non-linear behaviour of ferrite transformers
I did some tests of residual phase noise using an Agilent E5505A and found that air coil inductors did not add noise (at least down to my noise threshold) but that ferrite core inductors had easily seen noise. It was on the order of ADEV = 1E-10 close to the carrier. I would describe this as noise rather than non-linearity. In my case, the inductors were used to make tuned circuits. This is different than your case where the ferrite is being used to make a transformer. So as they say your milage may vary. And you probably don't have the option of an air core. After obtaining the E5505A and using it for a while, it became clear that anyone who is serious about component noise has to measure the components of interest to them in the application of interest to them on the E5505A or equivalent. (And the Agilent E5202A Signal Source Analyzer isn't equivalent.) Unfortunately, the E5505A is quite expensive and requires a highly skilled user. You mentioned theory several times. This sort of thing is 1% theory and 99% experiment. Or another way of putting it is you do a bunch of measurements and then construct a theory to explain what you already know experimentally. Rick Karlquist N6RK On 7/19/2014 3:09 PM, Attila Kinali wrote: Hi, I'm currently looking at some way of breaking the ground loop between several systems. The obvious idea would be to use transformers. I would like to have some kind of rule of thumb to guess how much noise such a transformer would add. But unfortunately i cannot find any theory or measurements of this. Does anyone have some pointers to documents on what kind of noise i could expect (type, and strength) and what/how strong the non-linear behaviour of transformers would be? Thanks in advance Attila Kinali PS: although this started as something with a real application in mind, i'm now interested in this as an endavour of its own. So all and any data, theory or rule of thumb would be appreciated ___ 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] VNA design
On 6/2/2014 7:43 AM, Attila Kinali wrote: Also, any good resource on how to build a directional coupler that does 10-3000MHz without going to exotic materials would be much I once had the opportunity to discuss directional couplers with Julius Botka, then with HP/Agilent. Specifically, a true directional coupler he designed that approached the range of 10-3000 MHz. IMHO, Botka was one of the greatest experts of all time in this area. It took extreme attention to detail to get it to work. It didn't so much involve exotic materials, but rather expertise. Don't try this at home kids. Julius said that he designed it before the era of cheap calibration. Now that everyone has calibration, you don't need a good directional coupler. You can get away with a MiniCircuits coupler. But in fact it is even easier to just use a resistive bridge. Four ordinary resistors will easily go to 3 GHz. Use a differential amplifier at the output. Lots of info on this in the literature. Another way to make in effect a directional coupler is to use a 180 degree hybrid. I also had the opportunity to study Alan Podell's amazing designs and even have discussions with him. I dissected one of his 10-3000 MHz hybrids. (Originally made by Anzac, now available from Macom Technology for about 5 Benjamins). Don't even think about trying this at home. BTW, you didn't mention software, but that's a big part of the job. Rick Karlquist N6RK ___ 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] VNA design
On 6/2/2014 12:41 PM, Brooke Clarke wrote: Hi: I started with the HP 8410 and added an external computer. Since it can be used manually I think it's an excellent way to learn about VNAs. http://www.prc68.com/I/MWTE.shtml#NA For my last 8 years at Agilent before retiring in March, I was doing advanced RD on network analyzers. The newer guys coming up didn't have an intuitive understanding of network analyzer architectures like I did. I started using the 8410 back in 1973 before I even worked for HP. Because of the modular design, it was like a teaching tool that forced you to understand what was going on. When I mentored the young guys, I would explain to them a lot of principles based on the 8410. Modern network analyzers are too automatic. The 8410 puts modern VNA's into perspective. BTW, I used to sit next to Dick Lee, who was a member of the 8410 design team in 1963 at the dawn of the golden age of microwave instruments based on YIG tuned oscillators and step recovery diode samplers. As you noted, the architecture was built around the YIG tuned oscillator and certain things were done that way they were because of that. Rick Karlquist N6RK ___ 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] Caveats on Allan Deviation with ultra stable oscillators
will also look better than it really is, and for the same reasons. (Some people have even reported similar behavior with cesium standards, although I don't see how that could happen. There aren't supposed to be any first-order temperature effects in a CBT, and I'd think that any lower-order effects would be way beneath the tube's flicker floor...) The 5061 had problems with microwave field leakage known as the top cover effect (see papers by DeMarchi.) This is at least a possible mechanism for injection locking 5061's. The 5071A has a completely different microwave assembly without leakage problems. The 5071A outputs have very high reverse isolation. Tests showed that there are no detectable systematic environmental effects in the 5071A (whatever ones there are fall below the noise). Rick Karlquist N6RK ___ 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] Caveats on Allan Deviation with ultra stable oscillators
On 5/29/2014 9:15 AM, cdel...@juno.com wrote: On these latest oscillators at the longer Tau (100sec.) the Quartz versus Quartz data shows much better performance than the Quartz versus Maser! What is happening (I think) in this case is that both Quartz units have exceptionally low and similar ageing. Or alternately, the quartz units are injection locking to each other. 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] HP5334A Option 010 replacement connector J8
I was the Project Manager for the 5334B. The A version (unlike the B version) has a very weak power supply due to insufficient capacitors and/or transformer. I can't remember now after 25 years. When you power it up with a cold 10544 or 10811, the oven circuit looks like a 47 ohm resistor. The 5334A can only muster 12V into this load. This is way below the 20V minimum operating voltage. However, the 10811 turns out to work well enough on 12V to get the oven warmed up. Once the oven current cuts back, the voltage will zoom up to something like 24V, being unregulated. This passes for normal in the 5334A design. So do not be alarmed by this behavior if you are trying to do a sanity check. Rick Karlquist N6RK On 5/21/2014 1:18 PM, Hendrik Dietrich wrote: Dear group, as I just yesterdays implanted a non-original OCXO (C-MAC STP2390C) into a recently ebayed counter, I wanted to share my experience: Swapping C8 to C100 position as per 5334B Service Manual (the B) is fine. J8, the connector for Option 010, is not in the 10811 layout as in the B. As I cannot find a A service manual, I had to poke and trace. This table will give you the pinout of the connector J8, with the lowest row representing the pins that are closer to the front, seen from component side top and the left column closer to the right edge of the PCB: OFF State +30V I +30V GNDI GND I I +15V I +15V I 10 MHz out ON State +29V I +29V GNDI GND I -5V I -5V +15V I +15V I 10 MHz out A 10 turn pot was mounted on the hole on the backside of the unit, connected to the EFC input of the Osc. as a voltage divider of course. All wires are twisted pairs (or twisted triple talking about the EFC.) even the 10 MHz is not a coax - yet. Having the rig open, I discovered burnt resistors at the 50 Ohm Termination of Channel A (only used B terminated so far), where the previous owner even stacked new resistors right on top of the original ones. (both pairs burned). A 619 Ohm Resistor in the ARM Path was also burned but Diodes OK, so I replaced it with a 620 Ohm Resistor, as expected without adverse effects. Counter and OCXO cost me about the price of a single 10811. Greetings Hendrik ___ 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] Time Nuts at Dayton Hamvention
I will be at Dayton this year. I'll see if I can rattle the cage. Rick N6RK On 5/12/2014 6:32 PM, Robert LaJeunesse wrote: Just a note that there will be some Time Nuts at the Dayton Hamvention this weekend. Don't be surprised to run into one or more at Flea Market spaces FW 1902/3/4/5. We'll have shade and chairs to sit yourself in. Bob LaJeunesse p.s. Unless John Ackermann or Tom Holmes grabs it first I'll have a 10MHz rated commercial video distribution amp for sale there. Be sure to ask for the Time Nut discount! ___ 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] Rb vs.Crystal OCXO
My understanding is that a really good Rb standard use a fairly wide bandwidth loop to control its own internal XO, and therefore improve its close in phase noise to be better than you can get with quartz alone. The Rb standard is able to do this because the S/N ratio of its rubidium vapor frequency reference (RVFR) is fairly high, and in any event considerably better than the S/N out of a CBT. Also, Rb standards have much smaller frequency jumps, if any, than quartz. Phase noise specs conveniently don't include the effects of jumps. Newer laser diode pumped Rb standards may make the comparison even more lopsided. Rick On 4/25/2014 9:12 AM, Shane Kirkbride wrote: Hi Everyone, I'm newer to this forum but I really enjoy reading the discussions. I have a pretty basic question. I'm wondering why one would chose an Rb Oscillator over a traditional OCXO? It does not immediately appear there is a phase noise advantage in the Rb.. Thanks, ~Shane On Fri, Apr 25, 2014 at 10:00 AM, time-nuts-requ...@febo.com wrote: Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Low SNR GPS reception and cheap LNAs (Attila Kinali) 2. Re: Symmetricom chip scale atomic clock (Tom Knox) 3. Re: How to accurately measure an oscillator's temperature. (Didier Juges) 4. Re: Low SNR GPS reception and cheap LNAs (Chris Albertson) -- Message: 1 Date: Fri, 25 Apr 2014 15:28:22 +0200 From: Attila Kinali att...@kinali.ch To: time-nuts@febo.com Subject: [time-nuts] Low SNR GPS reception and cheap LNAs Message-ID: 20140425152822.203775c003a761042e269...@kinali.ch Content-Type: text/plain; charset=US-ASCII Hi, I recently bought a bladeRF[1] to experiment a bit with GPS decoding. I tried to get GNSS-SDR[2] which seems quite good, but has its flaws. One of the things was that i cannot seem to get a fix in my environment. One of the problems seems that my antenna position is far from optimal. Aparently, GNSS-SDR uses only a very rudimentary acquisition technique (at least so i have been told). Now i wonder what techniques for low SNR acquisition are around. Would someone be so kind and give me some key words to google for? I also am looking to add an LNA to my reception chain, which is a mix of a 50R antenna with 75R Coaxcable (sat coax stuff is just a lot cheaper :-). Has anyone a recomendation for a good LNA that can be used in a flying construction (soldering onto two back-to-back glued connectors)? Ie it shouldnt be a QFN or BGA. DFN works but i'd rather have something with pins, like SC-70/SOT-323 or similar/larger. Attila Kinali [1] www.nuand.com/bladeRF [2] www.gnss-sdr.org -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin -- Message: 2 Date: Fri, 25 Apr 2014 08:53:25 -0600 From: Tom Knox act...@hotmail.com To: Time-Nuts time-nuts@febo.com Subject: Re: [time-nuts] Symmetricom chip scale atomic clock Message-ID: col130-w35b7069ee8d042e122a563df...@phx.gbl Content-Type: text/plain; charset=iso-8859-1 For the sake of discussion let me just add that even if medesigns comments were true of Microsemi, the Microsemi responses on this form have been from long time Time-Nuts who have for years contributed their knowledge to the betterment of the community in the proudest traditions of acadimia. Never have I seen them use the form for financial gain. Sure corporate greed is a problem in todays society but knowing some of the individuals at Microsemi it is clearly not a black and white issue. Further where it may be acceptable in some cases to release a product early and perform some of the final development on the backs of the customers to better serve their needs such as in the case of the fantastic TimeLab. In a mission critical product like the CSAC a problem like this will cost Microsemi far more then they would profit from a premature release. These manufacturing defects were clearly something they could not anticipate. I for one will be purchasing many more Microsemi products in the future and viewing their performance on TimeLab with full confidence. Please keep the group update on your progress resolving this issue. It will be interesting to see if a single point of failure is found, a smoking gun so
Re: [time-nuts] Frequency of LC Tank
It is very easy to make an impedance phase detector by inserting a toroidal current transformer in series with the load under test. The center of the secondary is connected to the load through a capacitor. Each end of the secondary goes to a diode detector. When the load is resistive, the DC outputs of the two detectors are equal. You can see this in the literature back as far as at least the 1950's for autotuning antennas. It is closely related to various FM discriminator circuit like the ratio detector. Rick On 4/12/2014 12:23 PM, d...@irtelemetrics.com wrote: Magnus, You are very much on the track that I was thinking. I belive you are absolutly correct in that a 90 degree phase shift would be ideal. I did a bit more digging last night, and it turns out that an XOR phase comparator looking at the tank voltage and drive voltage may be ideal, as you have suggested here. My main concern was that I plan to adjust the pulse width of the push-pull the drive circuit to adjust the power into the tank circuit. (Actually the drive will be full bridge, transformer coupled to the tank). That change in pulse width is where I was stuck, mentall. However since I'm in the 10Khz to 100Khz range and am generating the push-pull PWM digitally, I can just generate a second output at the same frequency and phase (or even different phase) than the drive signal to compare to the tank voltage. As you say away you go with a phase detector! Didier, I guess the thing that's different here than in most situations, is that normally you try not to load the tank circuit more than necessary. Here I'm loading the tank circuit considerablly, knowing that it will change frequency with the change in Q. This change in frequency is what I need to find, track, and follow. The tank will be very lossy (Maybe consuming 20Kw to 30Kw of power if all goes well). I'm also certian Q will move all over the place. I just want to stay near the peak of the bell, even if it's a short fat bell shaped curve. Since the frequecny is low, I was thinking that even a modern optocoupler should get me phase information well. At these power levels a little loading souldn't be a big deal! :) Dan As you drive it with a pulse, you induce energy to it. If you sample the voltage (or current) 90 degrees of from your drive-pulse, that quadrature will indicate if you are early, late or prompt. As your sampling point is also a sign of your current rate, and the pulse forced the LC tank and your oscillator into sync, the frequency error will cause the phase difference and hence voltage difference to be observeable. As you are fairly close in frequency, so will the phase error and you can assume the phase to voltage to be almost linear and away you go with a phase detector. Cheers, Magnus -- Keep in mind that anything you connect across your tank circuit will affect its resonant frequency and Q (signal source and measuring device). You need to make sure your equipment is very loosely coupled to the UUT through small value capacitors for instance. Didier KO4BB ___ 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] GPSDO Crystal Aging
I worked for the HP Santa Clara Division during the Smart Clock days and knew all the players. In terms of holdover, the report cited mentions temperature compensation and learning aging. The temperature compensation was simply a crutch for the 10811 to fix its tempco problems. The E1938A had much better tempco and eliminated the need for this crutch. As for the concept of learning aging is concerned, there was definitely no secret sauce I ever heard about in all the Smart Clock powerpoints I sat through. They simply measured linear aging and possibly its derivative and hoped that past performance would predict future results. It did to some extent, but how well it worked depended on the particular crystal. A misbehaving crystal could not be fixed by any cleverness in the algorithm. Attempts were made to screen crystals to get predictable ones, and this was someone successful by getting rid of bad actors. Still, there was no way to guarantee that a crystal in the future would never have a jump or sudden change in aging. What was really needed was an ensemble of oscillators, but that was not economically competitive with rubidium. Rick On 4/11/2014 3:06 AM, Ulrich Bangert wrote: Hi Brooke, HP had some way around SA that improved the timekeeping. HP called it the Smartclock Algorithm and you can find some very basic information about it here: http://www.hpl.hp.com/hpjournal/96dec/dec96a9.pdf I have been trying months to find a reference on how it REALLY works but it seems that this is one of the better kept secrets of HP. Best regards Ulrich -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Brooke Clarke Gesendet: Donnerstag, 10. April 2014 22:56 An: Tom Van Baak; Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] GPSDO Crystal Aging Hi Tom: That makes sense because the GPS was just coming on line and not anywhere near a full compliment of satellites and SA was on. HP had some way around SA that improved the timekeeping. Has that ever been disclosed? Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Tom Van Baak wrote: Hi Brooke, True, except that in most cases the long-term frequency drift rate is so tiny compared to all the short- and mid-term instability that it is not worth worrying about. In other words, I agree it is modeled as a linear ramp, but the ramp, even at huge timescales, is so close to flat, what's the point? Look at the output of a typical OCXO. Short-term the frequency varies by tens or hundreds of ps/s; that's parts in 10^11 or 10^10. By contrast, you have wait an entire day or week before you get that level of frequency error due to drift. When you're in a rowboat outside SF bay, it's the 3 m waves every 5 to 10 seconds that you need to steer against, not the 3 m tides that occur gradually over 12 hours. Can someone show me a counter-example? Why is it better to include aging rate into the PID. What quantitative improvement in performance does this actually represent? I don't disbelieve it, I just have never seen the numbers. One case where knowing the aging rate is important is during multi-hour or multi-day holdover. Perhaps that's why HP included the 128-hour circular record of frequency/aging into their firmware. /tvb Hi: AFAICR the HP GPSDOs included the idea of measuring the aging rate of the crystal and applying that correction during holdover. This was also mentioned by Brooks Shera in relation to his GSPDO (there was a plot), but I don't think it was part of the firmware? So rather than just locking the control voltage to the last used value it would be much better to add a linear ramp. http://www.rt66.com/%7Eshera/ ___ 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] GPSDO Crystal Aging
On 4/11/2014 11:04 AM, Hal Murray wrote: How many would you need? Is 3 enough? How well could you do with several low(er) cost oscillators relative to one good but expensive one? It might be an interesting experiment in a nutty sort of way. My guess would be 3 would be a minimum, so you could have a majority vote. Len Cutler's group actually built an experimental ensemble of 9 or 10, but it didn't seem to come to fruition. For this to make any sense, you would need to be able to cherry pick 9 or 10 really good oscillators. However, there was no way to get the production line to sign on to this. David Allan had this interesting concept to the effect that if you had a sufficient number of wristwatches (maybe 1000) and you averaged them together you could somehow get a quality clock, or at least 31.6 times better. Kind of like the notion of 1000 monkeys with 1000 typewriters... 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] Clock quality: alternatives to ADEV
The trouble with ADEV is that if you average a long time it papers over anomalous events like crystal jumps. An alternative measure might be to, instead of averaging, simply keep track of the worse case change in frequency during 1 sample period. Sort of like peak jitter versus rms jitter. Rick On 4/9/2014 3:38 PM, Hal Murray wrote: I've been watching the discussions and graphs for a while. ADEV seems appropriate for cases where the noise pattern is nice. How does ADEV work if the noise isn't nice? Are there alternatives? What's the mathematical term for the type of noise that works well with ADEV? I can think of 3 examples: Crystal jumps GPSDOs going into holdover. Power lines make all sorts of interesting not-quite jumps. Is there a way of characterizing that sort of event? How do I turn a pile of data into a useful graph or chart? What does an ADEV graph look like if the data has crystal jumps? I'd expect that something like crystal jumps would follow some sort of power law: the bigger jumps would be less frequent. But it wouldn't surprise me if the GPS or power lines had an underlying mechanism that turned into a different pattern. ___ 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] A small piece on HP's hydrogen maser in 1968
Solid dielectric cable and connectors of 3.5 mm size are mode limited to 18 GHz. That is why there is so much stuff rated at 18 GHz as opposed to 16 or 20 GHz. The next jump up is 26.5 GHz where 3.5 mm size works in air dielectric. It costs more to make these components and the volume is lower, hence the higher price. Also, the low price vendors may just stop at 18 GHz. Rick On 2/25/2014 9:03 PM, Bob Bownes wrote: Lot's of connectors change specification @ 18Ghz or are not rated bast 18Ghz. On Tue, Feb 25, 2014 at 11:55 PM, Hal Murray hmur...@megapathdsl.netwrote: jim...@earthlink.net said: there's a BIG jump in cost when you cross that 18GHz boundary line. What's magic about 18 GHz? Why not 16 or 20? -- These are my opinions. I hate spam. ___ 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] A small piece on HP's hydrogen maser in 1968
I couldn't get the link to work (it just hangs). However, I vaguely remember when we were starting work on the 5071A that the reason why we used the model number 5071A instead of 5070A was that the latter number had been reserved for a hydrogen maser that was never sold. The person in charge of checking out model numbers used to complain about wasting numbers and was probably not pleased about this. Rick Karlquist N6RK On 2/24/2014 8:00 AM, Pete Lancasout hire wrote: http://www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/pdf/1968_09.pdf pages 8 9 -pete ___ 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] A small piece on HP's hydrogen maser in 1968
On 2/24/2014 8:54 AM, Pete Lancashire wrote: Does this hang ? http://www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/ That works, but when i click on the actual link to the actual, my browser still hangs. 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] A small piece on HP's hydrogen maser in 1968
Still doesn't work for me. On 2/24/2014 8:57 AM, Had wrote: http://www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/pdf/1968_09 .pdf Rick, I got the above to work with no problem. The original link was busted. Had K7MLR ___ 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] A small piece on HP's hydrogen maser in 1968
On 2/24/2014 1:59 PM, dlewis wrote: The.pdf got caught up in a linefeed/carriagereturn Wouldn't that problem result in a file not found error rather than just hanging? I eventually got the link to work from Internet Explorer, which took 5 minutes to download it. It never worked from Firefox. 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] New WWVB modulation format receivers (NOT)
It may be true that WWVB is sending out a new format, but the receivers for it don't seem to exist. The exclusive rights are held by this company, which is clearly on hold while it tries to find a customer who will pay for a wafer run: http://eversetclocks.com/ I've seen this sort of thing many times before. Don't be surprised if this goes the way of AM stereo, etc. Does anyone have any positive news about this? 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] Looking for WWVB digital wall clock with digital 24 hour UTC display
Can anyone recommend a atomic wall clock that displays in digital 24 hour UTC? Looking for largest possible digits and LED preferred over LCD, under $100. Any brands to avoid? 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] Looking for WWVB digital wall clock with digital 24 hour UTC display
Thanks for the suggestions, but the MFJ121 does not display the date and the Lacrosse 8055 and 8016 do not display seconds. I need hour minutes seconds day and date. You wouldn't think that would be so hard. It looks like my only choice is this smallish wall clock (more like a desk clock): LaCrosse WS-8005U-W The seconds are in rather small type. I also do not need temperature, but I'm stuck with it apparently. All the really large clocks I have seen do not do GMT. You know this right away when they have a time zone map on the display. 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] Looking for WWVB digital wall clock with digital 24 hour UTC display
On 2/19/2014 6:35 PM, Chris Albertson wrote: On Wed, Feb 19, 2014 at 3:52 PM, Richard (Rick) Karlquist rich...@karlquist.com wrote: Can anyone recommend a atomic wall clock that displays in digital 24 hour UTC? Any reason why it was to by WWVB? What if it used some other means of saying accurate? The larger professional quality clocks generally don't Non technical reason. I want to use WWVB because I want to be able to mention to visitors that the clock links to an ensemble of 5071A cesium standards, and I was one of the designers of the 5071A, the actual atomic clock. I do also want to use the clock for my ham station. 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] Looking for WWVB digital wall clock with digital 24 hour UTC display
CORRECTION: The 8005 series (with indoor temperature) does not support GMT Only the 8115 and 8119 series (with indoor and outdoor temperature) support GMT. On 2/19/2014 5:47 PM, Richard (Rick) Karlquist wrote: so hard. It looks like my only choice is this smallish wall clock (more like a desk clock): LaCrosse WS-8005U-W ___ 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] New WWVB modulation format receivers (NOT)
On 2/19/2014 9:10 PM, John Marvin wrote: I guess my question is who has the right to grant exclusive rights for the ability to decode a very simple protocol? Was a patent actually granted for this? John They have exclusive rights to the IP core for their IC. I guess someone else could design their own IC... 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] 60 Hz power glitch, US West coast (Silicon Valley)
On 2/5/2014 9:37 AM, Bill Hawkins wrote: Then there is the load side, with who knows what equipment making large swings. This reminds me of the time I visited the John Deere foundry in Waterloo, IA. They had an arc furnace with graphite rods the size of small utility poles. I remember the meters indicating 50,000 amps at 208 volts. Anyway, they told me that they had to call the power company and get permission before turning this thing on, or it might stall the generator. One time they forgot to call, and got fined $10,000 or something like that. 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] Looking for high reverse isolation amplifier
On 1/30/2014 7:50 PM, John Miles wrote: Exactly, for unity gain you'd design for +6 dB and series-terminate the output with 50R. Good for capacitive loads as well as isolation. Do you run it in inverting or non-inverting configuration? I've only used the non-inverting configuration (figure 1 from the datasheet). Takes about 20 minutes to dead-bug with 0603 resistors over bare copper. -- john, KE5FX Miles Design LLC The LMH6702 has 50 dB of reverse isolation at 200 MHz (good) but the phase noise is 15 dB above my DUT, so the search continues. 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] Looking for high reverse isolation amplifier
On 1/30/2014 12:30 AM, John Miles wrote: Depending on how much forward gain you're after, I'd suggest looking at the LMH6702 current feedback opamp. I keep a few of them around in Hammond boxes, powered by NiMH rechargeables. Measured S12 is about 70 dB at 100 MHz, and I'm sure it could do at least 40 dB at 200. If I remember correctly the 3 dB point is about 400 MHz in a stage designed for +8 dB of gain, and unity gain is about 700 MHz. Residual PN at 80 MHz is around -135 dBc/Hz @ 1 Hz, flicker corner around 1 kHz, floor around -165 dbc/Hz. You can do better with discretes but you can also do a lot worse... -- john, KE5FX Miles Design LLC Great suggestion! TI has eval boards available for them so I can get up to speed quickly. I guess the idea is that I set it up for a gain of 2, and put a 50 ohm resistor in series with the output. Now it is a unity gain buffer in a 50 ohm system. A signal trying to go through it backwards has a source impedance of 100 ohms driving the output impedance of the amplifier, which is spec'ed at 30 milliohms, at least at low frequencies. That works out to 70 dB, which is what you observed. So I can see how it could have good reverse isolation. Do you run it in inverting or non-inverting configuration? Rick N6RK ___ 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] Looking for high reverse isolation amplifier
Can anyone direct me to an amplifier with: 1. High reverse isolation (over 40 dB). Note: the spec of interest is *reverse* isolation, not port to port isolation in a distribution amplifier. 2. Low phase noise (less than -100 dBc/Hz at 1 Hz offset) 3. Works at 200 MHz The Q-Bit QBH-1401PM seems promising...if I can get one. If necessary I will build the amplifier if I can get a known good schematic to follow, but prefer to buy one. Thanks in advance. Rick Karlquist N6RK ___ 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] Mini Circuits RF TX question
On 1/28/2014 10:26 AM, cdel...@juno.com wrote: Hi, Does anyone know where to find the primary inductance value for Mini Circuits RF Transformers? I need to know so I can pick one to resonate with a particular capacitor at 5Mhz. At 5 MHz, the core is probably more resistive than inductive and in any event, is not specified for inductance. What I have done in the past is to shunt the transformer with a real inductor. 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] Interesting HP oscillators...
On 1/13/2014 7:36 PM, Rex wrote: This document lists that part number... http://www.leapsecond.com/museum/10811a/90027-1.pdf It says (I think -- in a quick scan) that it is mostly the same specs as a 10811 D/E except a narrower EFC tuning range. When HP was doing the smart clocks circa 1997, they ignored my advice against trying to steer the EFC in favor of using a fix tuned oscillator followed with a synthesizer. The reason for this was the lack of suitable DAC's, and even if you found one, then you have to have a suitable reference source with low enough noise, and even if you found one, it would have to be ovenized. The E1938A had an available ovenized reference, however, the 10811 (as everyone knows) has only a Zener diode, and it is not very well ovenized This version (which I never heard of until now) probably ditched the Zener diode which (besides eliminating drift from the Zener) narrowed the EFC range. Narrowing the EFC range on the 10811 was a band aid that contributed another bit or three to the error budget. You had to make some assumption about long term aging and how often it was OK to ask the customer to readjust the mechanical trimmer. Also, there was the fact that no base station was going to be in service for more than a few years, as it would be obsolete by that time. Rick N6RK ___ 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] HP 4815A vector impedance meter repair service
FYI: http://www.hp4815a.com/ This guy did great work for me in 1995. Seems to know everything about this instrument. Had no idea he was still in business. Rick Karlquist N6RK ___ 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] sysclock source for AD9912 DDS?
On 12/30/2013 9:37 AM, Gerhard Hoffmann wrote: Driving the DDS system clock from an expensive RF generator (e.g. HP 8648A) would be possible but I'd prefer a PLL from 10MHz if it's doable simply/cheaply. Although expensive from a hobbyist viewpoint, the HP8648A is far from HP/Agilent's best, and even the best (8662A) is still not adequate to use as a clock in most cases. No general purpose sig gen is. (disclaimer: I work for Agilent). Rick Karlquist N6RK ___ 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] The 5MHz Sweet Spot
On 11/1/2013 7:12 PM, Tom Knox wrote: A while ago I mentioned 5MHz oscillators were used in most metrology applications compared to the more commonly available 10MHz because 5MHz was a sweet spot for quartz. At the time I didn't know why. I finally had a chance to ask the person I learned this from why. The main reason is simply physical size. The larger crystal lattice allows many manufacturing advantages that allow for a higher Q. He also explained I was wrong in an earlier statement, metal/quartz migration on quartz oscillator was not a major problem even after decades, but could become more of a factor if driven hard. That does not mean the deposition and lead bonding has no negative effect. The BVA solves this by capacitive coupling the quartz rather then direct metal deposition. Thomas Knox A lot of issues conflated together here. 1. There is a theoretical QF product for quartz. Being at 5 MHz basically doubles your Q, all other things being equal. 2. Having a higher Q reduces the contribution of the sustaining amplifier, but only within the 3 dB bandwidth. With the Q being in the millions, this is only a few Hz. 3. In general, the sustaining amplifier is not a player in a well designed quartz oscillator in the first place. 4. Q probably has a negative correlation with flicker noise, meaning higher Q is associated with lower flicker noise. However, the correlation is not strong. There is no theory that says that Q puts a bound on flicker noise. 5. So that leaves us with the larger physical size. Perhaps it allows higher Q, but again it is unclear how this is connected with flicker noise. 6. You didn't mention the theory that more total atoms of quartz provides averaging flicker noise over a large population. 7. You didn't mention the notion that larger physical size permits higher drive level. Since the Q is also large, perhaps it doesn't. Also, a higher drive level is probably only going to help with far out noise. 8. Many, or maybe most, 5 MHz resonators are made with undersized blanks which are enabled by energy trapping. So we don't have a simple scaling of all 3 dimensions. What is the effect of this cheating? If someone can shed additional light on this, please jump in and educate us. Rick Karlquist N6RK ___ 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] The 5MHz Sweet Spot
On 11/1/2013 8:28 PM, Bob Camp wrote: HI If you doubled the diameter of the blank each time you cut the frequency in half, all sorts of nice things might happen. If you start with a 1/2” blank in at 10 MHz that goes to 1” at 5 MHz and 2” at 2.5 MHz. Around 1 MHz you would get to a 5” blank. Good luck finding high grade quartz bars to cut 5” (or even 1”) blanks out of. You are going to have to go back to the autoclave fixtures at the very least. Since growth is (at best) linear you cost of quartz will scale with the size of the blank. I’d bet it scales a bit more than that if you want to keep the material at a high level of performance. You've explained the excuses vendors give for not making full size crystals. But the question is, given these realities, does this reduce the theoretical advantage of the lower frequency and by how much? Rick Karlquist N6RK ___ 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] The 5MHz Sweet Spot
In a free running (non crystal controlled) oscillator, the oscillator with the highest Q (regardless of frequency) will have the best phase noise, if all oscillators are normallized to the same frequency by ideal multiplication. So the Q gain doesn't go away in that sense. Having said that, in crystal oscillators, Q doesn't determine noise in the first place, so the point is moot. Rick Karlquist N6RK On 11/1/2013 8:48 PM, Hal Murray wrote: 1. There is a theoretical QF product for quartz. Being at 5 MHz basically doubles your Q, all other things being equal. Doesn't that Q gain from the QF product go away if you have to PLL it up to 10 MHz or 100 MHz which is what you really want? [I was about to ask why not go to 1 MHz, but Bob Camp answered that already.] ___ 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] Need to measure frequencies of two sources simultaneously
We have two sources and we want to be able to measure their frequencies at the same time. We want to get a time record of frequency each second. Apparently, what is meant by a two channel frequency counter is that you get the frequency of either channel A or channel B but not both at once. Some can also measure the ratio of A to B, but that doesn't work for us. We seem to be left with using a separate counter for each source and doing data logging with time stamping. We can then reconstruct the two frequency records after the fact in a spread sheet. There is the problem of synchronizing the time stamping clocks in the two counters. Can anyone on the list point me to a true two channel counter that would just measure the two sources? We are working around 200 MHz, but could possibly prescale. Thanks Rick Karlquist N6RK ___ 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] Looking for 1 GHz low phase noise amplifier
Thanks for the info. I wouldn't have suspected those little gain blocks were so good, and the voltage bias problem makes sense. Rick On 9/30/2013 5:53 AM, Garry Thorp wrote: Mini-Circuits' GALI- series of InGaP MMICs work pretty well. They typically have ~4dB NF, and the noise performance seems to be maintained up to a couple of dB below 1dB compression. I haven't measured added phase noise, but absolute phase noise measurements, where the MMICs are used to amplify multiplied-up crystal oscillators, appear to indicate added noise less than -180dBc/Hz at 10kHz offset when scaled to 120MHz (using 20log(N) relationship). The GALI- series are traditional MMICs that require a resistor or current source to bias them. We have had problems with Some TriQuint InGaP MMICs that are designed for voltage biasing. Noise from their internal bias circuitry seems to get on to the signal, and the NF started to increase well below compression. Mini-Circuits' GVA- series may well be similar, as they are also voltage-biased. Garry Thorp Date: Fri, 27 Sep 2013 10:53:10 -0700 From: Richard Karlquist rich...@karlquist.commailto:rich...@karlquist.com Can anyone suggest a low phase noise amplifier covering something like 10-1000 MHz? Gain should be 10 to 20 dB and phase noise should be spec'ed at +10 to +13 dBm output. Both close in and far out phase noise are of interest. Thanks in advance. Rick Karlquist ___ 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] DIY HP/Agilent 53131A 010 High Stability Timebase Option
I have an 18 GHz HP 5342A frequency counter, which I don't seem to see a lot, as members of my radio club borrow it. But it has no oven. There is an option for an oven, but my model does not have the optional oven fitted. I don't know if it would take a 10811A - if so I might fit one, since I have a spare of them around. Dave When the 10811 was being designed, the prime directive was that it had to be retrofittable into any 10544 socket. (Note that the converse is not necessarily true.) Therefore you should be able to install a 10811 in an old counter, if you have the infrastructure that fitted the 10544. IIRC, the 5342 came out in the 1970's before the 10811. Rick Karlquist N6RK ___ 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] Mounting quartz crystals with epoxy: help needed
I'm looking for information about mounting (packaging) quartz crystals with conductive epoxy such as: 1. Recommended type of epoxy. 2. Curing time and temperature. 3. Surface preparation of the gold. 4. Experts/consultants in this area you could recommend. (Note: this refers to mounting the quartz blank in a package; not mounting a packaged device on a PC board, etc) Can anyone help me out? Thanks in advance. Rick Karlquist N6RK ___ 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] Quartz crystal aging and applied voltage
On 6/30/2013 8:47 AM, Attila Kinali wrote: Most of the oscillator circuits out there place a small, but constant DC voltage on the crystal, which has the same effect on the ions as FWIW, the HP 10811 definitely does not do this (according to its designers) since the crystal is capacitively coupled. Furthermore, they added a 1 megohm resistor across the crystal to make sure it has no DC on it. I would be surprised if any precision oscillator applied DC to the crystal. Rick Karlquist N6RK ___ 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] Grinding crystals...
An interesting technique used many places including HP is to have a radio receiver connected to a pickup coil in the vicinity of the grinding machine. The vibrations of the abrasive wheel cause pings in the receiver at the resonant frequency. It doesn't seem like this would work, but it reportedly works quite well. Rick N6RK On 6/20/2013 5:47 PM, Bob Camp wrote: Hi Crystal processing is typically monitored either by time or by frequency shift. Grind in this lap powder for frequency change. Etch in x stuff for 30 seconds. Different factories do it different ways. The ones that I am familiar with seem to mostly monitor by frequency change. Bob On Jun 20, 2013, at 7:57 PM, Gary n...@lazygranch.com wrote: A common scheme in metal deposition measurement is to measure the frequency of a crystal prior to starting the deposition process, then monitoring the frequency shift of the crystal as the metal is sputtered. I was told crystals are tuned this way at the factory, but don't know this for a fact. Burt I. Weiner b...@att.net wrote: Brian, I remember grinding FT-243 crystals. I had a TV set safety glass about 18 square and about 1/4 thick. That and some Comet type cleanser mixed with water to make a thin paste would work wonders. I was taught to put my finger on the corners and grind an equal amount on the 8 corners (4 on each side) so as not to remove the bevel of the quartz. Once I applied this lesson I was able to grind crystals that were more stable and more active. When I over-leaded them I was generally able to remove the lead using alcohol. I've still got the old TV safety glass although it has an area near one corner that is very opaque do to all the grinding that was done in that area. Those were fun days! Burt, K6OQK From: Brian Alsop als...@nc.rr.com Reminds me of the FT-243 xtal controlled transmitter Novice days. Xtals of the frequency you wanted were hard to come by. We would grind xtals a bit on a bed of very fine abrasive to raise their frequency. The other trick was taking a pencil and adding graphite to the xtal faces to lower it's frequency. You couldn't add too much or it would stop oscillating-- forever. Never did understand the forever part. Removing the graphite didn't bring it back to life. Brian K3KO Burt I. Weiner Associates Broadcast Technical Services Glendale, California U.S.A. b...@att.net www.biwa.cc K6OQK ___ 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. -- Sent from my Android device with K-9 Mail. Please excuse my brevity. ___ 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] Oscillator temperature compensation
1. Is the 200 Hz drift measured at 660 kHz or at the final frequency, perhaps 1.8 MHz? Even in the latter case, we are talking about 100 ppm. 2. Was the rig stable before and something changed? You didn't say. 3. Have you verified that the drift is not simply due to the crystal itself? A 660 kHz crystal might not be AT cut, due to the low frequency. It is easier to believe a crystal drifted 100 ppm than an oscillator accidentally pulled it 100 ppm.l Rick N6RK On 6/20/2013 9:09 PM, Joseph Gray wrote: This is not strictly Time Nuts, but it is about a crystal oscillator that needs some temperature compensation, or something. Please ignore this posting if you like. In fact, so as not to clutter up the list, it would be best to email me directly about this. I have an old AM transmitter that has three 6AL11 compactrons. The crystal is a fundamental, cut for 660 KHz. I don't have a schematic for this thing, but I believe that one half of one 6AL11 is used for the oscillator. The problem is, the frequency decreases as the rig warms up. It will eventually stabilize, but the final frequency is over 200 Hz low. Not as good as it should be. I think the original specification was well under half of that. I have replaced the electrolytic caps. The others are mostly silver/mica with a few ceramics. I checked all of the resistors and only found one that was out of tolerance (I replaced it).Three NOS tubes were installed. There are no tunable components in the oscillator section. Only the output section has anything tunable. I know that there are many Amateurs on the list and I'm sure many know more about old tube rigs than I do. Does anyone have a suggestion as to what the trouble might be? Joe Gray W5JG ___ 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] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
At HP in the 1990's, Len Cutler's group built some experimental mercury ion standards for USNO (IIRC). They were of the trapped ion type. BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. When people say rubidium is inferior to cesium, they really mean a gas call is inferior to an atomic beam, etc. Rick Karlquist N6RK On 5/5/2013 8:20 AM, Bob Camp wrote: Hi Mercury was tried very early on as a vapor standard. They had some significant problems with it in the 1950's. It's not surprising that after 60 years somebody might want to take another swing at it. Bob On May 5, 2013, at 9:59 AM, Jim Lux jim...@earthlink.net wrote: On 5/5/13 1:48 AM, Magnus Danielson wrote: On 05/05/2013 10:05 AM, Attila Kinali wrote: On Sat, 4 May 2013 12:36:20 -0700 Tom Van Baak (lab)t...@leapsecond.com wrote: Rule of thumb: quartz is best short term, Rb or H-maser mid-term, and Cs by far the best long-term. Ah.. so it's a fundamental limitation. And i was looking for something GPS specific. Any references i could read on those limitations? A quick google did not produce any good results. There is a handful of references but picking up a book like Quantum Leap is a good start. Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, mounted in some hermetic sealed chamber with residue dirt, and mounting snip For rubidium gas-cell, there is a bunch of systematics, including snip The caesium atomic beam does not have wall-shifts, but rather it has much lower systematics. One of the major onces being magnetic field. snip The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. ___ 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] LTC6957 Low Phase Noise Buffer/Driver
On 4/14/2013 7:48 AM, Brian Davis wrote: Not sure if it's already been mentioned, but Linear has introduced a new part that looks interesting : LTC6957 Low Phase Noise Buffer/Driver http://www.linear.com/product/LTC6957-1 This is VERY interesting, especially the low noise PECL output. I have never seen any ECL device ever come close to that noise level. It would be interesting to see how they did that. 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] Connectors
OK, so we seem to have: 1) Scotch 130 rubber tape 2) Scotch 33 electrical tape 3) Scotchkote in that order. So the rubber tape waterproofs the connection and the scotch kote protects it from UV, so what does the electrical tape do? Or maybe, the electrical tape does the waterproofing and the rubber tape just keeps goo off the connector. But of course, that can be done with the well known technique of winding the connector with electrical tape adhesive side out. Do we know that the rubber tape is not UV proof? Or none of the above. Can someone in the know clarify this? Thanks, 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] Low-pass Filter for 5 and 10 MHz
On 4/12/2013 7:58 AM, Volker Esper wrote: ...but what about the phase jitter of the filter itself? While absolute phase shift may not (or may?) be an issue I guess that passive filters do have a phase jitter, too, due to mechanical vibration, tempco, and what else. Particularly at frequencies where the filter response has sharp slopes (resonance or corner frequency) the phase variation (d phi / d f) is quite big. Thus small frequency changes lead to considerable phase shift variation what in turn should lead to phase jitter added to our holy signal - what about overall ADEV? Wouldn't it be better to not filter the 10 MHz signal when used solely as a frequency standard? Most of the time, you don't have to worry about jitter in passive filters unless you are in a high vibration environment. The other common cause of jitter is permeability modulation of magnetic cores in inductors from power line fields. However, in an atomic clock, the clock stability is so high that phase tempco becomes significant. A temperature ramp becomes a phase ramp which becomes a frequency offset. In the 5071A, I multiply the 10811 crystal oscillator to 80 MHz. This 80 MHz is used for both the microwave synthesizer chain and also to generate a stepped approximation to a 10 MHz sine wave. This greatly reduces harmonics up to 60 MHz, which allows a much less severe output filter to be used. This alleviates the effects noted above. The multiplier to 80 MHz, another possible source of phase drift, is common moded out in this architecture. For further details, see my FCS paper. Rick I understand, that a high Q filter in a PLL reduces the phase noise of that oscillator - until the jitter of the filter becomes important. Am I wrong? Volker Am 12.04.2013 02:31, schrieb Richard (Rick) Karlquist: Actually, the opposite is true. Notches have the least phase shift at the frequency being passed, which is what matters. It is true that the phase shift at the notch frequency is uncontrolled, but that is not important. The HP8662A had an interesting PLL synthesizer where they had 10 notch filters for the first 10 harmonics of the sampling frequencies. This minimized phase shift within the loop bandwidth that detracted from phase margin. I designers of the 8662 definitely know what they were doing. Rick Karlquist N6RK On 4/11/2013 5:02 PM, Alan Melia wrote: Maybe a silly question but isnt the phase response of the filter important in this application ?? notches have fairly vicious phase shifts. Alan G3NYK - Original Message - From: Luciano Paramithiotti timeok...@gmail.com To: time-nuts@febo.com Sent: Thursday, April 11, 2013 5:42 PM Subject: [time-nuts] Low-pass Filter for 5 and 10 MHz A simple low pass filter to cut second and third harmonics from a 5 or 10 MHZ signal. See the paper: http://www.timeok.it/files/5_and_10mhz_low_pass_notch_filter.pdf Luciano Timeok ___ 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. ___ 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] Low-pass Filter for 5 and 10 MHz
Actually, the opposite is true. Notches have the least phase shift at the frequency being passed, which is what matters. It is true that the phase shift at the notch frequency is uncontrolled, but that is not important. The HP8662A had an interesting PLL synthesizer where they had 10 notch filters for the first 10 harmonics of the sampling frequencies. This minimized phase shift within the loop bandwidth that detracted from phase margin. I designers of the 8662 definitely know what they were doing. Rick Karlquist N6RK On 4/11/2013 5:02 PM, Alan Melia wrote: Maybe a silly question but isnt the phase response of the filter important in this application ?? notches have fairly vicious phase shifts. Alan G3NYK - Original Message - From: Luciano Paramithiotti timeok...@gmail.com To: time-nuts@febo.com Sent: Thursday, April 11, 2013 5:42 PM Subject: [time-nuts] Low-pass Filter for 5 and 10 MHz A simple low pass filter to cut second and third harmonics from a 5 or 10 MHZ signal. See the paper: http://www.timeok.it/files/5_and_10mhz_low_pass_notch_filter.pdf Luciano Timeok ___ 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] HP53132A vs SR625
On 3/17/2013 4:54 PM, Volker Esper wrote: The HP seems to be the more modern design. As I guess, the analog circuits are to blame, maybe HP was able to make use of newer technologies. FWIW, the 53132A design goes back 20 years 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] Low noise power supplies?
One more thought: Many oscillators have internal regulators that are not nearly as good as what you can build. No sense using an external supply with 5 nV per root Hz noise density if it will be re-regulated inside the oscillator by a circuit that has a noise density of 250 nV per root Hz. Best regards, Charles Good point. Just to clarify my original request, my colleagues are currently using batteries, and they don't have internal regulators. Their problem is not that the batteries don't work, but they want to travel around and give demos and the batteries obviously are a PITA. BTW, one of papers cited had a reference to Fred Walls paper on battery noise. Fred knocks it out the park as usual. He was like a rock star at FCS in those days. A rare example of government productivity. Rick Karlquist N6RK ___ 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] Low noise power supplies?
I know this topic has been discussed in the past on the list, but a colleague is asking if there are any off the shelf low noise power supplies for testing oscillators. Something a cut above an HP brick lab power supply etc. They are hoping to avoid having to homebrew a power conditioning circuit. Did we ever arrive at a concensus as to the state of the art in homebrew power conditioning circuits? Any help would be appreciated. Rick Karlquist N6RK ___ 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] Best phase detector / mixer for 100MHz?
The old Watkins Johnson M9 series was the state of the art for stacked diode mixers. You can still get the M9E and M9H from MaCom Technology Solutions. The M9E is better, but only if you have the 1/2 watt! of LO drive needed. As you have done already, it is probably possible to homebrew something like these. There were a series of papers written by WJ people 20 years ago or so in Microwave Journal or maybe it was Microwaves and RF that explained all about these things. These should be required reading if you are going to homebrew. Try to match the diodes so you get low DC offset. Some mixers also use resistors and capacitors to assist the diodes; again read the WJ papers. The horsepower race in phase detectors was somewhat rendered unnecessary by the cross correlation techniques developed 10 or 15 years ago. You can extend the effective noise floor by dozens of dB this way. Rick Karlquist N6RK On 11/23/2012 7:42 AM, Anders Time wrote: I have been using an minicircuits mixer as a phase detector for measuring low frequency(5-10MHz) and it is usually good enough. But when I want to measure 100MHz the sensitivity of the mixer decreases a lot, so when I want to measure some really low noise 100MHz(Pascall -178dBc floor with 18dBm out) oscillators the sensitivity is not good enough. I read in an old article by Walls, Stein et al(Design considerations in state-of-the-art signal processing and phase noise measurement system) that one can use two diodes in series in the double balanced mixer to increase the sensitivity. I tried this with some standard 1n5711 Schottky and the sensitivity is now 1V/rad, but is there a easier way to do this? /Anders ___ 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] Best phase detector / mixer for 100MHz?
On 11/23/2012 9:38 AM, Bruce Griffiths wrote: NIST have shown (at least at 10MHz) that the high level mixers they tested are noisier than the ZRPD1. Bruce Do you have a citation to where they said that? What you quoted doesn't make sense, at least, out of context. We need to clarify phase detector sensitivity specs. For conventional (IE 50 ohm) phase detectors, it is apples vs apples to just go by the volts per radian number. However, mixers like the ZRPD1 artificially triple the voltage sensitivity by operating at 500 ohms, and using transformers to connect to 50 ohm equipment. Doing this doesn't increase the possible signal to noise ratio. Consider this thought experiment. Build your best 500 ohm phase detector and postamp. Now replace with a 50 ohm phase detector and connect 3 postamps in parallel. It is a wash. Of course, you don't have to actually do this. You can simply use an op amp like the LT1028 with very low noise voltage. To actually put a 500 ohm detector on a par with a 50 ohm detector, the 500 ohm detector would need to use 3 diodes in series compared to one in the 50 ohm case. With only one diode per arm, the maximum drive power utilization is considerably lower. Rick Karlquist N6RK ___ 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] HP 10811A failure
On 10/13/2012 8:30 AM, Adrian wrote: 12V for the oven because inside the outer oven lives a 10811-60158 ( see http://www.realhamradio.com/GPS-oven-journey.htm ) that, as by the specs sheet, is specified 12 to 30 V DC, 11 W max. at turn on (mine draws some 9 W), and Steady state power drops to approximately 2 W at 25°C in still air at 20 V (mine draws some 1.9 W at 12 V without powering the outer oven). This is surprising to me. Can you give us a citation to this spec? AFAIK, all 10811 ovens are the same, and the ones I have looked at sort of work at 15V, but they don't really work properly on 12V. One source of confusion is the case of the 5334A counter. The power supply IMHO is poorly designed and the voltage sags down to 12V during 10811 warm up. (All 10811's and 10544's are guaranteed not to draw more current than a 47 ohm resistor). It turns out that you can count on the 10811 oven to function sufficiently at 12V to turn on the heater transistors and get the oven warmed up. After the oven warms up, the current drops back and the 5334A power supply voltage gets back up over 20V. This is different than saying that it is OK to just connect a 10811 heater to a constant 12V supply. When I was project manager of the 5334B version (a cost reduction exercise), I took the opportunity to redesign the power supply so that it worked correctly, in my opinion, meaning that the voltage did not have a huge sag. I don't like design shenanigans. Rick Karlquist N6RK ___ 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] 5071A Cs Oven
On 10/4/2012 9:45 AM, Tom Van Baak wrote: Bob, Right, not good. There should be a fault message associated with it. Check the internal log. OTOH, to conserve cesium, I've heard that some people run 5071A in standby mode most of the time and only turn on the cesium for a fraction of an hour a day or a week (to recal the quartz). Running in this standby mode is also advisable if one wants the best short-term performance out of a 5071A, without the loop noise. In this respect it's just like a GPSDO - you get the best short-term performance if you turn off disciplining. /tvb Hi Is Cs oven: 0.0V a good thing on a 5071A? I suspect not, since either it or GPS is off frequency. Bob ___ 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] 5071A Cs Oven
These ideas are interesting. AFAIK, there is very little chance of running out of Cs in many years, long past the time when something else in the tube will have reached its end of life. Where did this idea come from? Certainly, not anyone working at HP, Agilent or Symmetricom. A LONG time ago, if you bought a high performance 5061, the increased Cs beam flow might have been an issue, but the amount of Cs shipped with the tube was increased before the 5071A such that running out of Cs is no longer an issue. If you turn off the Cs, you simply have a 10811 to connect to your GPS. Except this 10811 has 10X the EFC range vs a stock 10811. Again, this doesn't make a whole lot of sense, IMHO. BTW, another interesting idea is degaussing the CBT. According to Len Cutler, this is completely unnecessary in the 5071A. As anyone who knew Len can attest, if he thought something was good enough and didn't need to be improved, you could be sure about that. For example, Len wanted us to use tantalum filter capacitors for energy storage in the power supply. Fortunately, we talked him out of that (actually the $100+ cost helped to convince him). Due to customer demand (the customer is always right :-) the Santa Clara Division eventually released a degausser. One of the reasons why this is not necessary in the 5071A is the Zeeman line measurement of the magnetic C field. The 5061 was open loop. So again there may have been a grain of truth behind the folklore. Rick Karlquist N6RK Member of the 5071A design team On 10/4/2012 9:45 AM, Tom Van Baak wrote: Bob, Right, not good. There should be a fault message associated with it. Check the internal log. OTOH, to conserve cesium, I've heard that some people run 5071A in standby mode most of the time and only turn on the cesium for a fraction of an hour a day or a week (to recal the quartz). Running in this standby mode is also advisable if one wants the best short-term performance out of a 5071A, without the loop noise. In this respect it's just like a GPSDO - you get the best short-term performance if you turn off disciplining. /tvb Hi Is Cs oven: 0.0V a good thing on a 5071A? I suspect not, since either it or GPS is off frequency. Bob ___ 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] E1938A PN measurments
I recently modified an old 10811 to bring out the crystal leads on miniature coax (instead of having them connect to the oscillator circuit). This allowed me to measure the crystal's inherent flicker noise of frequency. The measurements indicate that the 10811 phase noise out to at least 100 Hz is entirely due to the crystal. An interesting aspect of flicker noise of frequency is that Allan deviation is independent of tau. Thus, just one number describes the crystal noise. Rick On 9/30/2012 4:44 AM, Bob Camp wrote: Hi Close in, it looks like it's pretty much the crystal and the loading of the bridge oscillator. Bob On Sep 29, 2012, at 11:46 PM, Richard (Rick) Karlquist rich...@karlquist.com wrote: The E1938A uses a crystal that is basically the same as the 10811 crystal except that it is in a reduced height package. However the phase noise is not as good as a 10811 due to broadband noise in the automatic frequency control circuit. By the time I discovered this, it was too late to try to fix it. Rick Karlquist N6RK E1938A designer ___ 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.
