[time-nuts] Fwd: Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html I said that thermistors have been obsolete for 40 years not themocouples. (With a FEW rare exceptions) I do not consider platinum wire to be a thermistor. I own a 100 Ω platinum wire thermometer for the DVM in my 2236 Tekronix. It is not worth much without a Kelvin connection. From 0° C to to 100° C it changes 40 Ω and uses banana plugs. Those are unstable by ~ 0.2Ω. This is 0.5° C of error and intermittent. It is worthless for designing ovens. I use thermocouples in my Fluke 52 stereo thermometers all the time. They will work at nearly red heat and are stable. They are hard to use because they only produce 40 μV/C° and require a cold junction comparison. The cold junction is easily calibrated by an ice bath however. Thermistors depend on the cauldron in which they were stirred by the witches at manufacture. In the range of -55° C to 150° C, I don't think anything can match the AD590 or equivalent for repeatability, accuracy, stability, linearity or convenience. They are not affected by lead resistance and can use tiny wires. It will tolerate 3,000 Ω of lead resistance and can be multiplexed. The chip itself is 52 mils by 42 mils or comparable to a thermocouple bead. I figured out that two of them can be driven back to back by a square wave and two temperatures monitored at once with the same pair of wires. An Analog Devices product engineer split a $100 prize with me for my invention. πθ°μΩω±√·Γλ WB0KV -- Forwarded message -- From: Attila Kinali Date: Sun, Jun 4, 2017 at 4:59 PM Subject: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies) To: Discussion of precise time and frequency measurement Moin, This discussion is kind of getting heated. Let's put some facts in, to steer it away from opinion based discussion. On Sun, 4 Jun 2017 08:44:33 -0700 "Donald E. Pauly" wrote: > I stand by my remark that thermistors have been obsolete for over 40 > years. The only exception that I know of is cesium beam tubes that > must withstand a 350° C bakeout. Thermistors are unstable and > manufactured with a witches brew straight out of MacBeth. Their > output voltages are tiny and are they inconvenient to use at different > temperatures. If you really mean thermistors, and not, as Bob suggested thermocouples, then I have to disagree. The most stable temperature sensors are platinum wire sensors. The standards class PRT's are the gold standard when it comes to temperature measurement, for a quite wide range (-260°C to +960°C) and are considered very stable. They offer (absolute) accuracies in the order of 10mK in the temperature range below 400°C. Even industrial grade PRT sensors give you an absolute accuracy better than 0.1K up to 200-300°C. The "cheap" PT100 are more of the order of 1-10°C accuracy... all numbers just using a two-point calibration. For more information on this see [1] chapter 6 and [2] for industrial sensors. NTC sensors have a higher variablity of their parameters in production and are usually specified in % of temperature relative to their reference point, which is usually 25°C. Typical values are 0.1% to 5%. Additionally there is a deviation from the reference point, specified in °C, which is usually in the order of 0.1°C to 1°C. The NTC sensors are less accurate than PT sensors, but offer the advantage of higher resistance (thus lower self-heating), higher slope (thus better precision). Biggest disadvantage is their non-linear curve. Their price is also a fraction of PT sensors and due to that you can have them in many different forms, from the 0201 SMD resistor, to a large stainless steal pipe that goes into a chemical tank. NTCs are the workhorse in todays temperature measurement and control designs. The next category are band-gap sensors like the AD590. Their biggest advantage is that their 0 point is fix at 0K (and very accurately so). Ie they can be used with single point calibration and achieve 1°C accuracy this way. Their biggest drawback their large thermal mass and large insulating case, because they are basically an standard, analog IC. Ie their main use is in devices where there is a lot of convection and slow temperature change. Due to their simple and and quite linear characteristics, they are often used in purely analog temperature control circuits, or where a linearization is not feasible. But only if price isn't an issue (they cost 10-1000 times as much as an PTC). Their biggest disadvantage, beside their slow thermal raction time, is their large noise uncorrelated to the supply voltage, and thus cannot be compensated by ratiometric measurement. They are also more suceptible to mechanical stress than NTC's and PT's, due to their construction. Similar to voltage references (which they actually are), their aging is quite substantial and cannot be neglect
[time-nuts] TAPR GPS Experimenters Kit
We are finishing a pair of HP5061B cesium standards which we have up and running. We would like to acquire a GPS disciplined oscillator with 5 or 10 mc output for comparison with the cesium clocks. 1 pulse per second would be nice but is not mandatory. A roof antenna with preamp that could drive 100 feet or so of foam RG-58 is required. Does anyone have such a device that needs a new home? If not, what should we look for on eBay? πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Dave Mallery Date: Sun, Jun 4, 2017 at 8:54 AM Subject: Re: [time-nuts] TAPR GPS Experimenters Kit To: Discussion of precise time and frequency measurement hi I have been having great results with my M12 and Lady H. I (foolish me) had tried to cobble up a Perl program at first... just browse through some of the 400+ pages of heathgps.cpp to see why that was a bad idea! Both my M12 and my Tbolt are controlled by Heather running on two PI3s. Now, i would like to get a Lucent RFTG-u REV-0 to run using the PPS from the M12. there is a nice PPS interrupt driven arduino sketch on the Sync Channel Blog. I'd love to hear from anyone who is also trying this. 73 dave mallery, k5en On Sun, Jun 4, 2017 at 7:03 AM, Gregory Beat wrote: > Mark - > Yes, it does. :-) > The "S" and "!" menus are the most frequent menus I use with LH. > > Jerry is using SynTAC. > After a few e-mail exchanges, off-list, problem was antenna location. > > gb > === > So does Lady Heather... the "S" menu control things like self-surveys, > entering fixed position coordinates, and the receiver operating mode. SN > will put it in Navigation (3D) mode. SH will put it in position Hold mode > (timing mode). > > Sent from iPad Air > ___ > 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. > -- Dave Mallery, K5EN (ubuntu linux 16-10) PO Box 15 Ophir, OR 97464 linux counter #64628 (since 1997) ___ 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] HP5061B Versus HP5071 Cesium Line Frequencies
I own several Fluke 52 stereo thermometers with K themocouples. They run 40 μV/C°. All thermistors have tiny outputs without op amps. They also suffer from self heating. AD590 sensors give AT LEAST 15 mV/C° without op amps. If a regulated 3,000V supply is available they can give 2 V/C° into a 1 Watt 10 Meg resistor. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Sun, Jun 4, 2017 at 11:46 AM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement Cc: "rwa...@aol.com" , "Donald E. Pauly" Hi I think you have thermistors and thermocouples a bit mixed up. You can get quite substantial output voltages from a thermistor bridge…. Bob > On Jun 4, 2017, at 11:44 AM, Donald E. Pauly wrote: > > I stand by my remark that thermistors have been obsolete for over 40 > years. The only exception that I know of is cesium beam tubes that > must withstand a 350° C bakeout. Thermistors are unstable and > manufactured with a witches brew straight out of MacBeth. Their > output voltages are tiny and are they inconvenient to use at different > temperatures. > > Where did you get the idea to use a 1 k load for an AD590? If you run > it from a -5 V supply you can use a 15 k load to a +5V supply. This > gives 15 V/C° output. If you drive it from a 10 Meg impedance current > source, you get 30,000 V/ C°. If I remember correctly, I drove a > power MOSFET heater gate directly in my prototype oven 20 years ago. > It would go from full off to full on in 1/15 ° C. Noise is 1/25,000 ° > C in a 1 cycle bandwidth. > > The room temperature coefficient of an AT crystal is -100 ppb per > reference cut angle in minutes. (-600 ppb/C° for standard crystal) > The practical limit in a crystal designed for room temperature is > about 0.1' cut accuracy or ±10 ppb/C°. If you have access to an > atomic standard, you can use feed forward to get ±1 ppb/C°. If the > temperature can be held to ±0.001° C, this is ±1 part per trillion. > This kind of accuracy has never been heard of. Feed forward also > allows you to incorporate the components of the oscillator into the > thermal behavior. It does no good to have a perfect crystal if the > oscillator components drift. > > πθ°μΩω±√·Γλ > WB0KVV > > -- Forwarded message -- > From: jimlux > Date: Sun, Jun 4, 2017 at 4:47 AM > Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies > To: time-nuts@febo.com > > > On 6/3/17 9:56 PM, Donald E. Pauly wrote: > >> It was only in the early 70s that Analog Devices invented the AD590 >> solid state temperature sensor. It made thermister bridges obsolete. > > > There is a difference between something like a platinum resistance > thermometer (PRT or RTD) and a thermistor, but they both are "measure > resistance to measure temperature" devices. > > Yes, the AD590 is a useful part (I've got some in a device being > launched in August), but PRTs,thermistors, and thermocouples are still > widely used. > > I don't know that the inherent precision (at room temperature)of the > various techniques is wildly different. A 1mV/K signal (AD590 into a > 1k resistor) has to be measured to 0.1mV for 0.1 degree accuracy. > That's out of 300mV, so 1 part in 3000 > > A type E thermocouple is 1.495 mV at 25C and 1.801 at 30C, so about > 0.06 mV/K slope. Measure 0.006mV for 0.1 degree (plus the "cold > junction" issue). 1 part in 250 measurement. > > Modern RTDs all are 0.00385 ohm/ohm/degree at 25C. Typically, you > have a 100 ohm device (although there are Pt1000s), so it's changing > 0.385 ohm/degree. 1 part in 3000 > > Checking the Omega catalog.. A 44007 has nominal 5k at 25C, and is > 4787 at 26C, so 1 part in 24. > > Especially these days, with computers to deal with nonlinear > calibration curves, there's an awful lot of TCs and Thermistors in > use. The big advantage of the AD590 and PRT is that they are basically > linear over a convenient temperature range. > > In a variety applications, other aspects of the measurement device are > important - ESD sensitivity, tolerance to wildly out of spec > temperature without damage, radiation effects etc. Not an issue here, > but I'll note that the thermistor, PRT, and thermocouple are > essentially ESD immune. The AD590 most certainly is not. > > If you go out and buy cheap industrial PID temperature controller it > will have input modes for various thermocouples and PRTs. I suppose > there's probably some that take 1uA/K, but it's not something I would > expect. > > So I wouldn't say thermistor bridges (or other
[time-nuts] Fwd: Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
I stand by my remark that thermistors have been obsolete for over 40 years. The only exception that I know of is cesium beam tubes that must withstand a 350° C bakeout. Thermistors are unstable and manufactured with a witches brew straight out of MacBeth. Their output voltages are tiny and are they inconvenient to use at different temperatures. Where did you get the idea to use a 1 k load for an AD590? If you run it from a -5 V supply you can use a 15 k load to a +5V supply. This gives 15 V/C° output. If you drive it from a 10 Meg impedance current source, you get 30,000 V/ C°. If I remember correctly, I drove a power MOSFET heater gate directly in my prototype oven 20 years ago. It would go from full off to full on in 1/15 ° C. Noise is 1/25,000 ° C in a 1 cycle bandwidth. The room temperature coefficient of an AT crystal is -100 ppb per reference cut angle in minutes. (-600 ppb/C° for standard crystal) The practical limit in a crystal designed for room temperature is about 0.1' cut accuracy or ±10 ppb/C°. If you have access to an atomic standard, you can use feed forward to get ±1 ppb/C°. If the temperature can be held to ±0.001° C, this is ±1 part per trillion. This kind of accuracy has never been heard of. Feed forward also allows you to incorporate the components of the oscillator into the thermal behavior. It does no good to have a perfect crystal if the oscillator components drift. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: jimlux Date: Sun, Jun 4, 2017 at 4:47 AM Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies To: time-nuts@febo.com On 6/3/17 9:56 PM, Donald E. Pauly wrote: > It was only in the early 70s that Analog Devices invented the AD590 > solid state temperature sensor. It made thermister bridges obsolete. There is a difference between something like a platinum resistance thermometer (PRT or RTD) and a thermistor, but they both are "measure resistance to measure temperature" devices. Yes, the AD590 is a useful part (I've got some in a device being launched in August), but PRTs,thermistors, and thermocouples are still widely used. I don't know that the inherent precision (at room temperature)of the various techniques is wildly different. A 1mV/K signal (AD590 into a 1k resistor) has to be measured to 0.1mV for 0.1 degree accuracy. That's out of 300mV, so 1 part in 3000 A type E thermocouple is 1.495 mV at 25C and 1.801 at 30C, so about 0.06 mV/K slope. Measure 0.006mV for 0.1 degree (plus the "cold junction" issue). 1 part in 250 measurement. Modern RTDs all are 0.00385 ohm/ohm/degree at 25C. Typically, you have a 100 ohm device (although there are Pt1000s), so it's changing 0.385 ohm/degree. 1 part in 3000 Checking the Omega catalog.. A 44007 has nominal 5k at 25C, and is 4787 at 26C, so 1 part in 24. Especially these days, with computers to deal with nonlinear calibration curves, there's an awful lot of TCs and Thermistors in use. The big advantage of the AD590 and PRT is that they are basically linear over a convenient temperature range. In a variety applications, other aspects of the measurement device are important - ESD sensitivity, tolerance to wildly out of spec temperature without damage, radiation effects etc. Not an issue here, but I'll note that the thermistor, PRT, and thermocouple are essentially ESD immune. The AD590 most certainly is not. If you go out and buy cheap industrial PID temperature controller it will have input modes for various thermocouples and PRTs. I suppose there's probably some that take 1uA/K, but it's not something I would expect. So I wouldn't say thermistor bridges (or other temperature measurements) are obsolete. ___ 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] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
I've bought dozens of them over the years and talked to crystal engineers for tens of hours. I watched them plated and tuned at a crystal filter company in Phoenix. I own Virgil Bottom's book on the subject and understood half of it. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Sun, Jun 4, 2017 at 5:15 AM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement Cc: "rwa...@aol.com" , "Donald E. Pauly" Hi Have you ever tried to actually *buy* a crystal built to a specification? There is a tolerance on them. That has a profound impact on what you can *buy*. 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] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
You have a fundamental misunderstanding of the AT curve family. See my QBASIC plot at http://gonascent.com/papers/hp/hp5061/photos/newxtl.jpg . The commonly described AT cut is shown as the largest sine wave in the blue rectangle. The left side of the rectangle is -55°C, the center is 25° C and the right side is 105° C. The bottom of the rectangle is -16 ppm and the top is +16 ppm. Main Cut Temp Freq -55° C -16 ppm -15° C +16 ppm +25° C ±0 ppm +65° C -16 ppm 105° C +16 ppm You can get a lower turnover point of 24° C and an upper turnover point of 26° C. Their amplitude would be °±0.250 ppb. As the turnover points approach each other, their amplitude approaches zero. The line joining all the turnover points is y= -8·x^3. The zero temperature for 25° is y=4·x^3. Practical tolerance these days is on the order of 0.1 minutes of arc. This is within the width of the traces in the graph. You are way off on your 0° to 50° C crystal. ["Umm …. errr … it’s quite easy to get a +/- 2 ppm 0-50C AT cut *including* the tolerance on the cut angle."] Temp Freq 0° C -0.488 ppb (lower limit) 12.5° C +0.488 ppb (lower turning point) 25° C ±0 37.5° C -0.488 ppb (upper turning point) 50° C +0.488 ppb (upper limit) As I claimed, a Thermal Electric Cooler has never been used to build a crystal oscillator. In the 50s, TEC efficiencies were on the order of 1% and were useless. The Soviets made coolers more practical in the 70s with better materials. I saw one used at Telemation that was able to measure dew point by condensing water vapor on a mirror. It looks like efficiencies have now improved to 33% or so. It was only in the early 70s that Analog Devices invented the AD590 solid state temperature sensor. It made thermister bridges obsolete. Switching amplifiers are required to drive thermal coolers if you want to preserve efficiency. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Fri, Jun 2, 2017 at 12:22 PM Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies To: "Donald E. Pauly" Cc: "rwa...@aol.com" , time-nuts Hi Any real crystal you buy will have a tolerance on the angle. In the case of a crystal cut for turn the temperature will be a bit different and you will match your oven to it. If you attempt a zero angle cut, you will never really hit it and there is no way to compensate for the problem. Bob On Jun 2, 2017, at 3:19 PM, Donald E. Pauly wrote: A cut at that angle has no turn over temperature. The zero temperature coefficient point is 25°. Its temperature coefficient everywhere else is positive. On Friday, June 2, 2017, Bob kb8tq wrote: > > Hi > > If you are going to use an oven, it’s better to run it at the turn > temperature of > the crystal. That would put you above 50C for an AT and a bit higher still > for an SC. > > 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] Fwd: Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-June/date.html I am familiar with this effect. My specialty is switching amplifiers and I wrote the classic paper for Motorola on the subject, see http://gonascent.com/papers/an1042.pdf . Ripple in the dc from a switching amplifier is less than a part per thousand. These thermal coolers have about a 10% efficiency which means it takes 10 Watts to pump a Watt. That is a tiny switching amplifier. Ovens also require several Watts if operated at -55° C. Thermo coolers/heaters require little power when operated close to room temperature. Highest power is required at high ambient temperatures. πθ°μΩω±√·Γ WB0KVV https://www.febo.com/pipermail/time-nuts/2017-June/date.html -- Forwarded message -- From: Bruce Griffiths Date: Fri, Jun 2, 2017 at 4:34 PM Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies To: jimlux , Discussion of precise time and frequency measurement Thermomechanical fatigue can significantly reduce the lifetime of Peltier devices if the ripple current flowing in the Peltier device is too high. This can become an issue with switchmode drive to a Peltier cooler. Bruce > > On 03 June 2017 at 11:02 jimlux wrote: > > On 6/2/17 2:51 PM, Donald E. Pauly wrote: > > > > > > This is an improvement of 476 to 1. You apparently have not thought > > thru what improvements are possible with thermal coolers/heaters. > > Among these is near instant warm up and greatly reduced power for > > thermal management. > > > > > > without getting into the whole crystal issue, one of the advantages of a > heater is that it can be VERY simple (and hence reliable, just on a > parts count basis). With a decent package, once it's hot, the power > required to keep it hot can be quite low. > > With a heat/cool, you need to be able to have a bipolar supply to the > peltier device, and they're not particularly efficient (that is, to > extract 1 Watt of heat, you're putting in significantly more than 1 watt > of DC, and rejecting 1+X watts to the outside world. > > And then, if you use a linear power supply/amplifier to drive the > device, that is probably a class A device, and somewhat lossy. A > switcher would be more efficient, but then you have the problem of > switching noise, in close proximity to the crystal. You could put a big > low pass filter in, but now you're adding even more components. > > There are undoubtedly some cases where the thermoelectric scheme would > work better - for instance, you have a system with a TCXO and it's > really set up for the TCXO to be at 25C, and you want to regulate that. > > ___ > 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] Fwd: HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-Jun/date.html We finally got in the Panasonic thermal fuses for the HP10811 and have a few extra. They will either plug in or solder. Contact me if you need one. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Van Horn, David Date: Thu, May 11, 2017 at 7:01 PM Subject: Re: [time-nuts] HP10811 Oscillator Thermal Fuse To: Discussion of precise time and frequency measurement The original article was from Kodiak consulting. Good thing I saved a copy. Thanks for the link to this one. ___ 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] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html Electronic thermal coolers did not exist then so it could not be done. Electronic temperature sensors did not exist either. That crystal cut has been known since the 1940's at least. It has been neglected because of limited temperature range. It yields ±1 ppm over a range of ±20° C from 25° C. A slightly different angle of cut can yield ±250 ppb over that range. (4:1 improvement) Contrast that with a normal AT cut which yields ±9 ppm over that range. I built an oven with an Analog Devices temperature sensor 20 years ago. I did not have time to incorporate foam insulation. The heater power was not available to run it at 65° C without insulation. It had to run at 40° C and it would hold about 1 ppb over a few hours. It would hold the crystal within 0.01° or so but it was far away from the turnover temperature. Convection currents cause problems. It convinced me that ovens were headaches. Thermal coolers remove most of these. πθ°μΩω±√·Γ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Fri, Jun 2, 2017 at 3:50 PM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement Cc: "rwa...@aol.com" , "Donald E. Pauly" Hi Have you checked out the papers from the 1950 and `1960’s where they actually tried what you propose with essentially the same parts you are looking at using? Bob > On Jun 2, 2017, at 5:51 PM, Donald E. Pauly wrote: > > # 2 is not true. A cut has either two turning points or zero. Where > both turning points exist there are two temperatures at which the > temperature coefficient of frequency is zero. Cut 0 on figure 6 at > https://coloradocrystal.com/applications has no turnover point. It is > neither fish nor fowl. Cut 6 is the normal AT curve with extremes of > ±16 ppm for -55° C thru +105° C. All curves normally intersect at 25° > C rather than the 27° C shown. 25° C is half way between -55° C thru > +105° C. Curve 6 is the Tchebychev polynomial y=4x^3-3x and curve 0 > is y=4x^3. > > Consider the standard AT cut which has turnover points at -15° C and > 65° C. The lower turnover would ordinarily not be used in ovens. A > set point error of ±1° C in the upper turnover point at 65° C results > in a frequency error of +14.875·10^-9. For cut 0, that same ±1° error > in room temperature results in a frequency error of ±31.25·10^-12. > This is an improvement of 476 to 1. You apparently have not thought > thru what improvements are possible with thermal coolers/heaters. > Among these is near instant warm up and greatly reduced power for > thermal management. > > πθ°μΩω±√·Γ > WB0KVV > > On Friday, June 2, 2017, Bob kb8tq wrote: >> >> Hi >> >> Any real crystal you buy will have a tolerance on the angle. In the case of >> a crystal cut for turn >> the temperature will be a bit different and you will match your oven to it. >> If you attempt a zero >> angle cut, you will never really hit it and there is no way to compensate >> for the problem. >> >> 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.
[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html Tell us more about the RF leakage problems in the 5061. I thought that the 5071 used the same beam tube. How does the electricity leak out and at what frequencies?My method costs a tenth as much and has higher spectral purity performance to the beam tube. I admit that I hadn't thought about the electricity leaking out. Can the leak be plugged? BTW these are not strictly Diophantine equations. No exact solution is possible if C field is to be used. Can you tell us the magic numbers? πθ°μΩω±√·Γλ WB0KV -- Forwarded message -- From: Richard (Rick) Karlquist Date: Fri, Jun 2, 2017 at 12:10 PM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement , "Donald E. Pauly" , "rwa...@aol.com" I said no *manufacturer* does it this way. NBS is not a manufacturer. In a one-off money-is-no-object non-portable standard, you can make direct multiplication work. It will not work well in a 5061, because of RF leakage issues specific to the 5061 that are well documented. Bolting on a different synthesizer does nothing to change that. The decision not to use direct multiplication has nothing to do with not being able to figure out how to synthesize the correct frequency. Certainly by the time we did the 5071A, we were already using DDS, and it wouldn't have been any problem to synthesize for direct multiplication if we had wanted to do that. You seem to be doing it the hard way (pre DDS) involving Diophantine equations. So it's easier to do direct multiply than it used to be, but that doesn't necessarily mean you should do it that way. 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] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
# 2 is not true. A cut has either two turning points or zero. Where both turning points exist there are two temperatures at which the temperature coefficient of frequency is zero. Cut 0 on figure 6 at https://coloradocrystal.com/applications has no turnover point. It is neither fish nor fowl. Cut 6 is the normal AT curve with extremes of ±16 ppm for -55° C thru +105° C. All curves normally intersect at 25° C rather than the 27° C shown. 25° C is half way between -55° C thru +105° C. Curve 6 is the Tchebychev polynomial y=4x^3-3x and curve 0 is y=4x^3. Consider the standard AT cut which has turnover points at -15° C and 65° C. The lower turnover would ordinarily not be used in ovens. A set point error of ±1° C in the upper turnover point at 65° C results in a frequency error of +14.875·10^-9. For cut 0, that same ±1° error in room temperature results in a frequency error of ±31.25·10^-12. This is an improvement of 476 to 1. You apparently have not thought thru what improvements are possible with thermal coolers/heaters. Among these is near instant warm up and greatly reduced power for thermal management. πθ°μΩω±√·Γ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Fri, Jun 2, 2017 at 12:43 PM Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies To: "Donald E. Pauly" Hi Which statement is not true: 1) That there is a tolerance on the cut angle of a crystal? 2) That true zero temperature coefficient only happens at the turn? 3) That heater based controllers are impossible to build? Bob On Jun 2, 2017, at 3:40 PM, Donald E. Pauly wrote: That is not true. I say that thermal coolers have made ovens obsolete. A zero temperature coefficient at room temperature is easier to hit than a zero temperature at the upper turnover point when such a thing exists. See curve 0 in Figure 6 at https://coloradocrystal.com/applications/ . πθ°μΩω±√·Γ WB0KVV On Friday, June 2, 2017, Bob kb8tq wrote: > > Hi > > Any real crystal you buy will have a tolerance on the angle. In the case of a > crystal cut for turn > the temperature will be a bit different and you will match your oven to it. > If you attempt a zero > angle cut, you will never really hit it and there is no way to compensate for > the problem. > > 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] HP5061B Versus HP5071 Cesium Line Frequencies
That is not true. I say that thermal coolers have made ovens obsolete. A zero temperature coefficient at room temperature is easier to hit than a zero temperature at the upper turnover point when such a thing exists. See curve 0 in Figure 6 at https://coloradocrystal.com/applications/ . πθ°μΩω±√·Γ WB0KVV On Friday, June 2, 2017, Bob kb8tq > wrote: > Hi > > Any real crystal you buy will have a tolerance on the angle. In the case > of a crystal cut for turn > the temperature will be a bit different and you will match your oven to > it. If you attempt a zero > angle cut, you will never really hit it and there is no way to compensate > for the problem. > > Bob > > On Jun 2, 2017, at 3:19 PM, Donald E. Pauly > wrote: > > A cut at that angle has no turn over temperature. The zero temperature > coefficient point is 25°. Its temperature coefficient everywhere else is > positive. > > On Friday, June 2, 2017, Bob kb8tq wrote: > >> Hi >> >> If you are going to use an oven, it’s better to run it at the turn >> temperature of >> the crystal. That would put you above 50C for an AT and a bit higher >> still for an SC. >> >> 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] HP5061B Versus HP5071 Cesium Line Frequencies
A cut at that angle has no turn over temperature. The zero temperature coefficient point is 25°. Its temperature coefficient everywhere else is positive. On Friday, June 2, 2017, Bob kb8tq wrote: > Hi > > If you are going to use an oven, it’s better to run it at the turn > temperature of > the crystal. That would put you above 50C for an AT and a bit higher still > for an SC. > > Bob > > > On Jun 2, 2017, at 2:09 PM, Donald E. Pauly > wrote: > > > > https://www.febo.com/pipermail/time-nuts/2017-May/105566.html > > > > If we build this circuit it would be a bench model not designed to be > > inside a hot chassis. It would be able to lock ± 5° C of 25° C. My > > idea of an oven is to keep the crystal and oscillator at 25° C ±0.001 > > °C with 60 second warm up/cool down time. > > > > πθ°μΩω±√·Γλ > > WB0KVV > > > > -- Forwarded message -- > > From: Bob kb8tq > > > Date: Fri, Jun 2, 2017 at 5:57 AM > > Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies > > To: Discussion of precise time and frequency measurement < > time-nuts@febo.com > > > > > Hi > > > > I would suggest you check a few real crystals over the 20 to 40C range …. > > With all the “stuff” in a 5061, it will change (rise) at least 10C > > after turn on. > > > > 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.
[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html If we build this circuit it would be a bench model not designed to be inside a hot chassis. It would be able to lock ± 5° C of 25° C. My idea of an oven is to keep the crystal and oscillator at 25° C ±0.001 °C with 60 second warm up/cool down time. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Fri, Jun 2, 2017 at 5:57 AM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement Hi I would suggest you check a few real crystals over the 20 to 40C range …. With all the “stuff” in a 5061, it will change (rise) at least 10C after turn on. 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] HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html A guy by the name of David W. Allan used direct multiplication to build NBS-4 and NBS-5, see http://tf.nist.gov/general/pdf/65.pdf . He didn't see anything wrong with it. He used a commercial frequency standard modified from 5 mc to 5.006880 mc. That in turn was multiplied by 1836. This was a multiplier chain of 2·2·3·3·3·17. When multiplied to 9192 mc, this is 90 cycles low so the standard would be forced high by 0.05 cps.. They measured the locked frequency standard to determine the actual frequency of the cesium line. I propose NO multiplier chain. What are the supposed problems in using a direct submultiple of the cesium resonance? It seems to me that all other techniques result in more phase noise there. I found the relationship 91.92631770 mc·(137,075/126,008)=99,999,999.98992 cps=100,000.000--0.01008 cps. It is low by 0.1 ppb and therefore cannot be adjusted by C field current. The C field can only lower the frequency. There is another relationship that gives a higher frequency of a fraction of a part per billion which is easily adjustable. Perhaps HP was unaware that such a frequency exists. πθ°μΩω±√·Γλ WB0KV -- Forwarded message -- From: Richard (Rick) Karlquist Date: Thu, Jun 1, 2017 at 10:01 PM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement , "Donald E. Pauly" , "rwa...@aol.com" Direct multiplication to 9192 MHz isn't used by any manufacturer of any atomic clock that I know of, due to its well known disadvantages. I can state for a fact that it was summarily rejected by the designers of the 5060/5061 (Cutler, et al). In the 5071, I (being the RF designer) also summarily rejected it. The architecture that is instead used is indeed complex and expensive as you say. It is also ACCURATE. Rick On 6/1/2017 7:04 PM, Donald E. Pauly wrote: > > https://www.febo.com/pipermail/time-nuts/2017-May/105566.html > > The lock system on the HP5071 is complex and expensive. My plan to > improve the HP5061B is to to use a pair of third overtone crystals > running at 91.9 mc and 100 mc. I have come up with the magic numbers > to lock them together. This eliminates all multipliers with the > exception of the A4 board. The 12.61 mc synthesizer input presently > wastes half the microwave power produced by the 90 mc input in the > unused lower sideband. Therefore only half the 91.9 mc drive is > required. > > Eight bit ECL dividers in one package are available to perform the > necessary lock. When multiplied by 100 to the cesium resonance line, > the 91.9 mc frequency is a few cycles high so that C field currents > are reasonable. With crystal cuts for zero temperature coefficient at > 25°C, it is possible to get along without an oven. Room temperature > performance at 25°C±5°C is ±15·10^-9. Oscillator warm up time would > be measured in seconds. > > Square wave modulation of variable frequency and amplitude shows > promise for reducing the noise effects of the beam tube. You can > smoothly change the lock time constant, deviation and frequency. This > would avoid the big disturbance of the HP5061B when you switch from > OPR to LTC. (OPR=operate with 1 second time constant, LTC=operate with > 100 second time constant) > > πθ°μΩω±√·Γλ > WB0KV > ___ > 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] HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html The lock system on the HP5071 is complex and expensive. My plan to improve the HP5061B is to to use a pair of third overtone crystals running at 91.9 mc and 100 mc. I have come up with the magic numbers to lock them together. This eliminates all multipliers with the exception of the A4 board. The 12.61 mc synthesizer input presently wastes half the microwave power produced by the 90 mc input in the unused lower sideband. Therefore only half the 91.9 mc drive is required. Eight bit ECL dividers in one package are available to perform the necessary lock. When multiplied by 100 to the cesium resonance line, the 91.9 mc frequency is a few cycles high so that C field currents are reasonable. With crystal cuts for zero temperature coefficient at 25°C, it is possible to get along without an oven. Room temperature performance at 25°C±5°C is ±15·10^-9. Oscillator warm up time would be measured in seconds. Square wave modulation of variable frequency and amplitude shows promise for reducing the noise effects of the beam tube. You can smoothly change the lock time constant, deviation and frequency. This would avoid the big disturbance of the HP5061B when you switch from OPR to LTC. (OPR=operate with 1 second time constant, LTC=operate with 100 second time constant) πθ°μΩω±√·Γλ WB0KV ___ 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] HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105554.html Our attempt to measure the low frequency noise to determine the possible lock improvement was a failure. We will have to get access to the Loop Gain pot to get a flat signal at low impedance. Beware of low frequency roll off. I found out that the feedback amplifier on the A7 board causes the electron multiplier output to roll off above 19 cps. It places an 8,200 pFd condenser across the 1 M load resistor which causes the roll off. Here is a linear sweep up to 8 kc. http://gonascent.com/papers/hp/hp5061/waveform/wideswee.jpg It shows the 274 cps second harmonic as well as the 16 cps roll off. Our previous posts involving various modulation schemes were correct because we drove the scope directly from the electron multiplier. While the meter driver is a convenient amplifier, you have to disconnect C1 to prevent the low frequency roll off. The feedback amplifier has a gain proportional to frequency. This restores flatness above 19 cps for the loop gain pot. I got a gain of 141 at 137 cps with a lagging phase angle of 90°. R10 is loaded by C1 which drops the level at that frequency by 7:1. Effective gain is about 20:1 on the Loop Gain pot in the hi gain position of S1. Gain is about 7 in the low gain position. In both positions low frequency roll off is about 19 cps. πθ°μΩω±√·Γλ WB0KV ___ 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] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105500.html We recently did a partial alignment of the lock servo on our #2 HP5061B after replacing the beam tube. The previous owner had tried to fix it by turning adjustments. This made a big improvement in the lock. KB7APQ got the idea to use the audio spectrum analyzer in his I Phone to measure the noise output of the beam tube. We used the Beam I meter driver emitter follower for an audio source. It provides about 0.4 Volts per 25 uA on the meter. A 100 ohm safety resistor was in series with Q6 emitter on the A7 board. It was followed by a 100 nFd condenser into the 100 k input impedance of the I phone. Low frequency cutoff is about 16 cps. See http://gonascent.com/papers/hp/hp5061/waveform/spectrum.jpg . Start frequency is 4 cps and each bin is 8 cps wide. Center frequency of each bin is 8 cps higher than the one before it. Frequency and amplitude are both logarithmic. Amplitude is 12 db per division. The first three bands show the low frequency rolloff of the coupling condenser. Five harmonics of the 137 cps modulation frequency can be seen. For unknown reasons, a sharp null in the noise of about 2 db at 137 cps is seen. The servo nulls the 137 cps there but I can't see how the noise could be nulled. The prominent second harmonic at 274 cps is normal. It measures -74 db below reference. I calculated it at about 0.15 V pp or 53 mV rms. The third harmonic at 411 cps again shows up as a 2 db noise null for unknown reasons.The fourth harmonic at 548 cps cannot be seen. The fifth harmonic at 685 cps barely breaks thru the lower limit of the spectrum analyzer. It looks like rectifier pulse harmonics can be seen at 120 cps. They may be getting thru the mu metal shields of the beam tube. That frequency is right on the border of two bins. 360 cps third harmonic of rectifier pulses can be seen. It appears in the middle of a bin. An unknown signal is seen at 564 cps. This could be the +3500 power supply frequency. 1 cps bandwidth noise in the 50 to 100 cps area seems to be about 20 db below the 274 cps second harmonic. This will determine the possible lock improvement with improved modulation methods. πθ°μΩω±√·Γλ WB0KV -- Forwarded message -- From: Bob kb8tq Date: Sat, May 27, 2017 at 6:01 PM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement Hi Having run a 5071A with a *very* good 10811 in it, the OCXO does dictate what happens at 0.1 seconds. Once you get past that, you are headed into a bit of a gray zone. You are partly looking at the Cs and partly looking at the OCXO. Pushing out the crossover between the two could help you at 1 second. The gotcha is that the “hump” will still be there, just a bit further out. The net effect at (say) 100 seconds could easily be worse with the “fix”. 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] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
Tom: The Greek letters are my pallet for common electronic letters. I transposed two items in my last post and here they are corrected. Note that the √(frequency error)=ratio of Zeeman frequencies as well as ratio of C fields. model/freq error cps/Zeeman freq kc/C field/(milliGauss) 5061A 1.59 42.82 61 mG 5061B 2.50 53.53 76 mG 5062C 4.30 70.40 (100 mG?) I am investigating the total redesign of the HP5061B lock system for vastly improved performance. It looks like the performance of the HP5071A can be beaten by 10 to 1 for averaging times on the order of a few seconds. πθ°μΩω±√·Γλ WB0KV -- Forwarded message -- From: Tom Van Baak Date: Fri, May 26, 2017 at 5:36 PM Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies To: "Donald E. Pauly" Donald, I'm enjoying many of your 5061 posts the past few months. Fun isn't is? Thanks for taking the time sharing them with the group. Question... > πθ°μΩω±√·Γλ What's that Greek mean (70 3F B0 B5 4F 3F B1 76 B7 47 3F)? Thanks, /tvb Moderator, http://leapsecond.com/time-nuts.htm ___ 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] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html Those were interesting links. C field levels are a small fraction of the earth's field of 700 milliGauss. The C field winding is a few turns inside the beam tube. They are driven by several different possible currents depending upon the desired frequency correction. For the HP5061B it is 24.5 mA for the standard tube at 100%. At the 0% point of the C field, the cesium resonance is unaffected. At the 50% point, it is shifted upward by the amount of error in the microwave frequency. This varies depending on synthesizer design. At the 100% point, the error is reversed to give a reverse adjustment range equal to the original error. An electron orbits in a magnetic field with frequency f=qB/(2πm). (q=charge, B=field strength, m=electron mass) The Zeeman frequency is the same as the frequency of an electron orbit in a field equal to 25% of C field listed. The square of the C field gives the frequency shift in the cesium line. I saw 90 mG listed for the 5062C but I think that it should be 100 mG. There is a test for the beam tube when the rf drive is removed and the LF coil is driven with a frequency equal to half the Zeeman frequency. It induces a peak that checks the operation of the tube without rf. Does anyone know what is actually going on then? We had a bad beam tube that failed this test. model|freq error cps|Zeeman freq kc|C field|(milliGauss) 5061A 2.50 53.53 76 mG 5061B 1.59 42.82 61 mG 5062C 4.30 70.40 (100 mG?) πθ°μΩω±√·Γλ WB0KV -- Forwarded message -- From: Tom Van Baak Date: Thu, May 25, 2017 at 9:23 PM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement Donald, You're familiar with the 9,192,631,770 Hz definition of the SI second; but that's only for an "unperturbed" atom. The bad news is that in order to make the cesium beam operate at the central resonance peak one actually has to violate the SI definition and perturb it -- by applying a magnetic field (the so-called C-field), as well as other factors. This cannot be avoided. The good news is that the shift can be calculated. In other words, because a magnetic field must be applied the actual cesium resonance frequency is not 9192.631770 MHz. The synthesizer locks to the peak, but the peak is at a slightly higher frequency than the nominal book value. This detailed note from hp may help: http://leapsecond.com/museum/hp5062c/theory.htm Different model beam tubes use different field strength / Zeeman frequency. Search the archives for lots of good postings about all these magic frequencies -- google: site:febo.com zeeman If you want to see what the resonance peaks (all 7 of them) actually look after the C-field is applied see: http://leapsecond.com/pages/cspeak/ and (poster size): http://leapsecond.com/pages/cfield/ See also John's version: http://www.ke5fx.com/cs.htm One final comment -- the perturbed vs. unperturbed issue is far more complex than a single correction. To get an idea of the math and physics complexity of a laboratory Cs beam standard read some of these: http://tf.nist.gov/general/pdf/1497.pdf http://tf.nist.gov/general/pdf/65.pdf http://tf.boulder.nist.gov/general/pdf/101.pdf /tvb - Original Message - From: "Donald E. Pauly" To: "time-nuts" ; "Donald E. Pauly" Sent: Thursday, May 25, 2017 7:55 PM Subject: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies https://www.febo.com/pipermail/time-nuts/2017-May/105298.html The synthesizer in the HP5061B generates a frequency of about 9,192,631,772.5 cps when the 5 mc oscillator is exactly on frequency. First the 5 mc oscillator is multiplied by 18 to 90 mc on the A1 board. That in turn is multiplied by 102 in the A4 board to give 9,180 mc. The 5 mc is also divided by 4079 to produce 1,225.790635 cps. That in turn is multiplied by 10,305 to produce 12,631,772.5 cps. This is added to the 9180 mc in the A4 mixer to produce the final frequency of 9,192,631,772.5 cps approximately. This is higher than the defined frequency of 9,192,631,770 cps by about 2.5 cps or 271·10^-12. If I figured it right, the C field adjustment only has a range of 40·10^-12. This seems to be insufficient to put the standard on frequency. Can anyone explain these mysteries? Does anyone know why this frequency was chosen? Does anyone know the choice for the frequency of the HP5071 cesium? πθ°μΩω±√·Γλ WB0KV 4,079=prime 10,305=5x9x229 ___ 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] HP5061B Versus HP5071 Cesium Line Frequencies
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html The synthesizer in the HP5061B generates a frequency of about 9,192,631,772.5 cps when the 5 mc oscillator is exactly on frequency. First the 5 mc oscillator is multiplied by 18 to 90 mc on the A1 board. That in turn is multiplied by 102 in the A4 board to give 9,180 mc. The 5 mc is also divided by 4079 to produce 1,225.790635 cps. That in turn is multiplied by 10,305 to produce 12,631,772.5 cps. This is added to the 9180 mc in the A4 mixer to produce the final frequency of 9,192,631,772.5 cps approximately. This is higher than the defined frequency of 9,192,631,770 cps by about 2.5 cps or 271·10^-12. If I figured it right, the C field adjustment only has a range of 40·10^-12. This seems to be insufficient to put the standard on frequency. Can anyone explain these mysteries? Does anyone know why this frequency was chosen? Does anyone know the choice for the frequency of the HP5071 cesium? πθ°μΩω±√·Γλ WB0KV 4,079=prime 10,305=5x9x229 ___ 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] HP5061B Modulation Adjustment
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html The first time that we worked with this HP10514A mixer we had an HP105 oscillator to provide the 5mc comparison against our #1 cesium clock. Stability was not good enough to get closer than a few hundred picoseconds. We expected some diode drift but not at that level. We could not see a hot finger on a diode in the mixer. One millivolt out of the mixer is about 31 picoseconds phase change near quadrature at the drive levels used then. (±1 V peak dc) The theoretical dc output is sin θ where θ is the phase angle between inputs. Two volts pp of 10 mc rides on that dc. We were operating unterminated on the output of the mixer. As long as the diode drops are stable, we can still see phase changes to a fraction of a picosecond. A picosecond is the delay in an 8 mil length of RG58 cable. (1,500 ps per foot) We have one DVM with a resolution of 1 μ V dc. The data sheet on the mixer is at http://gonascent.com/papers/hp/hp10514a.pdf . We would appreciate anyone who has experience on diode drift on these types of mixers to post accordingly. We built a 400 kc five pole low pass Butterworth filter yesterday that removes the 10 mc from the mixer output. (CLCLC) Attenuation is about 10 million to one at 10 mc which reduces the rf to about 0.1 μV peak to peak. We can now see phase changes on the oscilloscope of a few picoseconds at 1 mV per division. The modulation deviation is hard to see at 5 mc and there is no handy output there to drive a mixer. We therefore drove our mixer with the 90 mc outputs of each HP5061B. We used 6 db 50 Ω attenuators ahead of the L and R inputs to avoid mixer overload. In phase dc out was about 0.5 V and 180° out of phase was about -0.5 V dc and was terminated in 50 by the low pass filter and the scope. We ran both HP5061B's in open loop with modulation on one of them on and the other one off. See http://gonascent.com/papers/hp/hp5061/waveform/90mcmod.jpg . This shows the 137 cps modulation. Note that there is a fair amount of noise present. This contributes to noise in the final lock. Modulation from cesium #2 was 16.9 mV pp and #1 was 13.9 mV pp. The #2 is about ±0.968° lead and lag or ±29.8 ps at 90 mc. Modulation is at 137 cps. Phase change in a half cycle of the modulation is 2x 29.8 ps in 1/274 sec or 16.3 parts per billion average rate of phase change. Average phase change for a half cycle of a sine wave is 2/π (0.636) times peak phase change. Peak phase change is therefore ±25.7 ppb or ± 2.31 cps at 90 mc. The 90 mc is multiplied in the A4 mixer by 102 to 9180 mc. At that frequency the deviation becomes ± 236 cps or 472 cps peak to peak. This is roughly the 550 cps distance between the cesium atomic resonance at 9,192,631,770 cps and the valley either side of it. We have not disturbed the modulation adjustment on our #1 machine which is 82% of the deviation of #2. We will correlate the HP modulation adjustment method with our measurements. It seems to me that over deviation of the modulator will increase the noise of the system. Has anyone experimented with lower modulation and higher gain on A7 board? We can easily see any improvement with our mixer. We are familiar with the 2nd harmonic gain pot but have decided that the instrument needs a complete alignment after the beam tube change. We do not know how many knobs were turned trying to get it to work with a bad beam tube. It needs an alignment like it would have gotten after it was built in the factory. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Wed, May 17, 2017 at 4:05 AM Subject: Re: [time-nuts] HP5061B Modulation Adjustment To: Discussion of precise time and frequency measurement Cc: "rwa...@aol.com" , "Donald E. Pauly" Hi Keep in mind that the mixer has millivolt level offsets and millivolt level drift (over a wide range). There is a gain pot that “sets” the second harmonic. It can be low and the device will still lock. Bo ___ 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] HP5061B Modulation Adjustment
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html We recently got our second HP5061B to lock after changing the beam tube. We did no alignment with the exception of changing the gain on Beam current. Ion current dropped from 14 to 1 with only a few hours of operation of the instrument. We obtained momentary lock but lost it after a couple of minutes. The trouble was a blown themal fuse on the HP10811 oscillator which shut down the oven. We have TEMPORARILY jumpered it while the correct fuse is on order. We aligned the C Field on #1 but have not done that alignment on #2 yet. The 5 mc output of our #1 instrument was compared to the 5mc output of #2 with an HP10514A balanced mixer. Two input ports L and R are multiplied by internal Shottky diodes to produce an X output which can be terminated in 50 Ω. Maximum input current on both the L and R port is 40 mA or 2 V rms. One instrument was put in Open Loop and the fine frequency adjusted to approach quadrature. It was then returned to OPR and steered to final quadrature with the C Field. We used a digital voltmeter with a resolution of 10 uV dc to measure the X output of the mixer with the L and R inputs in near quadrature. The mixer output contains a large 10 mc component of about 2 V peak of peak which rides on the dc representing the phase difference. The dc output for in phase and out of phase inputs is about +1 and -1 Volts. Our calculated sensitivity was 31 uV per picosecond of error when within a few degrees of quadrature. Lock within a few picoseconds was obtained by adjusting C field on #2. It had to be continuously manually steered. We could not look at the X output on the scope because of the large rf level present. Our digital meter might have been experiencing rf overload causing inaccuracy at low dc voltages. Continuous lock was lost a few times on #2 which we attributed to it needing a complete alignment. Second harmonic was only 22. The procedure in 5-217 g for modulation adjustment is not very scientific. It calls for adjusting modulation for maximum 137 cps out of the AC amplifier board when the beam tube is driven at 5x10^-9 below the resonance line. Modulation is then to be reduced by 5%. This affects all other adjustments. We decided to directly measure this deviation with precision. The phase noise of the 90 mc output of the A3 multiplier board was measured as well as the modulation. The spectral width of our function generators at 5 mc was compared to the HP5061B 5 mc output. Our adventures with this project will be covered in a separate post. πθ°μΩω±√·Γλ WB0KVV ___ 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] HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-May/date.html While I find traces of your article quoted, it seems to have vanished. It lead me to this interesting article of 16 pages on electronic fires by a fire investigator. There is a lot here for designers when it comes to preventing fires from your products. I would never have dreamed of some of the ways that fires can start. http://dri.org/docs/default-source/dri-online/course-materials/2016/fire-science/08-dangerous-things-come-in-small-packages.pdf πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Van Horn, David Date: Thu, May 11, 2017 at 4:31 PM Subject: Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse To: Discussion of precise time and frequency measurement There's an excellent article out there on the web called "Low Voltage, the incompetent ignition source" I highly recommend a read. I dealt with a case like this a couple years ago. Failed fet in an H bridge caused a fault which the brick SMPS picked up as a short, and went into "hiccup" mode on. The energy delivered in "hiccup" mode was about 1W average, and that was enough, after several hours, to cause ignition and sustained flame on the PCB. ___ 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] Fwd: time.gov
Be sure to post your result. Five years ago I regularly checked my Casio LED watch which was holding 0.3 seconds per week. It always worked properly. Perhaps we should report this to Trump so he can fire the head of NIST. -- Forwarded message -- From: Jerry Hancock Date: Thu, May 11, 2017 at 4:52 PM Subject: Re: [time-nuts] time.gov To: Discussion of precise time and frequency measurement Cc: "Donald E. Pauly" I checked it on two different computers and again just now, all were counting 5+ seconds slow. I then downloaded their flash app which as an option I never had to do and that was correct. Both of the apps claim to be adjusted for network delay. This was around 14:00Pacific. I just checked again and both apps are now correct. I’ll have to dig into the issue. > On May 11, 2017, at 3:09 PM, Donald E. Pauly wrote: > > https://www.febo.com/pipermail/time-nuts/2017-May/date.html > > About 10 years ago, I checked my WWVB time code receiver that I built > against time.gov and it was within 0.1 seconds. That was as close as > the eyeball can tell. You report a huge error and if confirmed, you > should complain. I would double check against WWV since WWVB is now > worthless for time comparison. That webpage is supposed to be > compensated for network delay within 0.1 second. > > Just now at 15:00:00 MST I checked my phone with time.gov on wireless > versus a full size computer also on wireless. I momentarily saw the > phone 65 seconds ahead of the computer. After hitting refresh and > going off wireless and directly to my carrier, the phone matched the > computer. I had a witness but cannot get the problem to reappear. I > don't know exactly why the problem went away. Some servers may cache > web pages so refresh may be necessary. > > πθ°μΩω±√·Γλ > WB0KVV > > -- Forwarded message -- > From: Jerry Hancock > Date: Thu, May 11, 2017 at 2:36 PM > Subject: [time-nuts] time.gov > To: Discussion of precise time and frequency measurement > > > I went to time.gov today as I was sitting away from my lab when a new > watch arrived. Finally got the 25yr watch from the company that laid > me off a week later… > > Anyway, I set the seconds rollover to 00 when time.gov reset and then > walked down to my lab and noticed the watch is now 6 seconds slow. So > I checked again with another computer, same problem, www.time.gov is 6 > seconds slow. Never say this happen, usually it is right on the money > give or take about .2 seconds. > > Jerry > ___ > 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] HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-May/date.html These oscillators sold for $800 in 1985 or so. They are on eBay all working for $250 or more. Where are all the ones with blown thermal fuses for $25? I want to buy. It would be interesting to have the HP warranty data for nuisance blows. The three reported fire preventions would have paid for the labor on all of the reported nuisance blows. This is not to excuse the HP design error of picking a thermal fuse temperature too close to the operating temperature. Smoke damage could do thousands of dollars of damage to a HP5061B or and expensive microwave instrument. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Thu, May 11, 2017 at 4:28 PM Subject: Re: [time-nuts] HP10811 Oscillator Thermal Fuse To: Discussion of precise time and frequency measurement Hi A bit in jest:… that compares to 3,957 incidences of open fuses that had nothing to do with a thermal runaway. Of those, the majority 3,721 resulted in the 10811 being tossed in the garbage as “another junker”……(yes, those are estimates, but I’d bet they are close based on the number of 10811’s made and how flakey those fuses are). 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.
Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-May/date.html This is the third report of an open thermistor which would have resulted in a fire in an HP10811 oven. There are a dozen other problems that could cause such a fire. See http://gonascent.com/papers/hp/hp10811/thermal.jpg . The leads are long enough that they can be soldered quickly without a heat sink if the socket is to be replaced for better reliability. A hemostat can also be used to heatsink the leads one at a time. We have the 108° C fuse which is prone to nuisance blows. HP has superceded it with a 125° C version. Panasonic seems to make a direct replacement. It is stocked by Digikey for under a dollar. I can find no reports of a nuisance blow of the 125° version of the thermal fuse in a HP10811. All nuisance blows seem to be in the 108° version. In the 1970s, many consumer electronic products with 60 cps power transformers had a thermal fuse inside them. I bought a Sony real to real stereo tape deck which was not working with that problem. It was a nuisance blow since no problems existed in the tape deck. I installed a fine gauge piece of solder since the fuse was close to 180° C. I used it for over two years with no problems. Later model switching power supplies have windings of several volts per turn. Shorts in these transformers will blow the fuse or destroy the switching transistors. A 60 cps transformer operates at a small fraction of a volt per turn. A few shorted turns in a will not draw an excessive primary current but merely causes a hot spot. The hot spot will grow as additional turns short. Line current will not be greatly excessive even as the transformer heats up. It can catch fire well before the fuse blows. I saw a living room that caught fire because of a 60 cps transformer in a stereo receiver. The line breaker never tripped. But for the grace of G-d, the house would have burnt down. A thermal fuse in the transformer would have prevented several thousand dollars of damage. That would have paid for over a thousand thermal fuses. πθ°μΩω±√·Γλ WB0KVV Forwarded message -- From: David G. McGaw Date: Wed, May 10, 2017 at 8:20 PM Subject: Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse To: Discussion of precise time and frequency measurement I too have had a fuse open up due to a failed thermistor in a HP10811. David N1HAC ___ 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] time.gov
https://www.febo.com/pipermail/time-nuts/2017-May/date.html About 10 years ago, I checked my WWVB time code receiver that I built against time.gov and it was within 0.1 seconds. That was as close as the eyeball can tell. You report a huge error and if confirmed, you should complain. I would double check against WWV since WWVB is now worthless for time comparison. That webpage is supposed to be compensated for network delay within 0.1 second. Just now at 15:00:00 MST I checked my phone with time.gov on wireless versus a full size computer also on wireless. I momentarily saw the phone 65 seconds ahead of the computer. After hitting refresh and going off wireless and directly to my carrier, the phone matched the computer. I had a witness but cannot get the problem to reappear. I don't know exactly why the problem went away. Some servers may cache web pages so refresh may be necessary. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Jerry Hancock Date: Thu, May 11, 2017 at 2:36 PM Subject: [time-nuts] time.gov To: Discussion of precise time and frequency measurement I went to time.gov today as I was sitting away from my lab when a new watch arrived. Finally got the 25yr watch from the company that laid me off a week later… Anyway, I set the seconds rollover to 00 when time.gov reset and then walked down to my lab and noticed the watch is now 6 seconds slow. So I checked again with another computer, same problem, www.time.gov is 6 seconds slow. Never say this happen, usually it is right on the money give or take about .2 seconds. Jerry ___ 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] Fwd: Fwd: HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-May/date.html In order to have a runaway trophy, the thermal fuse would have to have been jumpered and then an oven control failure would have to have occurred. The rated temperature of 125° C is well above operating temperature of 82°C. The thermal fuse can easily be soldered in by heat sinking the leads where they enter the fuse. The leads are plenty long enough. I have done this dozens of times on Amana microwave ovens in the late 70s. The venerable HP105 oscillator contains a thermal fuse in both the fast warmup heater and the proportional heater. "3-8 Each heater circuit contains a thermal fuse to prevent damage to components within the oven due to overheating." I hadn't thought about smoking the styrofoam which melts at 240° C. https://en.wikipedia.org/wiki/Polystyrene#Extruded_polystyrene_foam I calculate that the oven could reach at least 208° C at the rated 71° C ambient.Solder melts at 180° C. Each power transistor has around 10 Volts across it and might even reach 300° C without destruction. Many oscillators are operated above 20 Volts for the heater supply. We have two reports of open thermistors in which disaster was avoided by the thermal fuse blowing. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Richard (Rick) Karlquist Date: Wed, May 10, 2017 at 5:34 PM Subject: Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse To: Discussion of precise time and frequency measurement The view from inside HP when I worked with the people who designed and built the 10811 some 35-40 years ago was that: 1. 10811 ovens rarely fail. 2. When they do fail, it is rarely because the oven runs away. I know I have never encountered a runaway. No one at HP had a "trophy" on their desk of a runaway 10811. People tend to collect stuff like that. One engineer did have a 10811 with a 45 caliber bullet fired through it (long story). 3. From a business perspective, a failure is a failure and so there is no business reason to have a fuse. 4. Because the fuse could not be soldered in, it had to be socketed, and the socket failures exceeded any oven runaways by a good margin. Therefore, it made the "failure rate" worse. That is all that matters to the bean counters. 5. The one and only reason it was in there at all was the concern about toxic gases being released from the foam. Even without a runaway, foams tend to have a "slow burn" and outgas "stuff" all the time. Various foams were evaluated to balance that issue with thermal resistance and with the big issue with foam which is mechanical fatigue. This is similar to the wear out of foam mattresses. What should have been done with the thermal fuse would have been to put crimp lugs on the leads and attach the crimp lugs with screws. However, there was no space for all that stuff. 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] Fwd: HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-May/date.html The poster at http://www.simonsdialogs.com/2016/09/a-thermal-fuse-and-hp-10811-60111-repair/ reported that the thermal fuse saved an oscillator from destruction when a thermistor opened. HP made thousands of these which sold for $800. If a large portion failed it would have been addressed. They raised the temperature of the thermal fuse to reduce nuisance blows. I say that nuisance blows equal to real blows are worth the trouble. You may be getting oscillators on the surplus market or eBay which have a higher proportion of nuisance blows. πθ°μΩω±√·Γλ WB0KVV From: Mike Feher Date: Tue, May 9, 2017 at 9:10 PM Subject: Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse To: Discussion of precise time and frequency measurement Respectfully I disagree. I have totally shorted out numerous oscillator’s fuses with no problems. The design of those thermal fuses makes them vulnerable to opening just due to years of use without problem, in any of the electronics. My shorted out oscillators still work. Ideally, if handy, it is easy enough to replace them if one is available. They just plug in. If there is a thermal runaway, that caused the opening, to me that implies that there are other issues. Regards – Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 848-245-9115 ___ 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] Fwd: HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-May/date.html I disagree about permanently jumpering the thermal fuse. The oscillator is rated down to -55° C and the oven can maintain 82° C at that temperature. This is a 137° C rise. It is likely capable of more heat than that. At 25° C, it would therefore be able to reach at least 25+137=162° C. This is near solder melting temperature and would quickly cook the components. It is rated to work at 71° which would give a temperature of 208° C and do serious damage. That thermal fuse is very important. There are a dozen failures which could result in a thermal runaway. This web page discusses the fact that a thermal fuse should be 30° C above normal operating temperature to prevent nuisance blows. http://www.simonsdialogs.com/2016/09/a-thermal-fuse-and-hp-10811-60111-repair/ HP originally used a 26° C margin and later changed it to a 33° margin. This explains the frequent failures. This poster used the wrong type of fuse but the correct type is commercially available. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: Bob kb8tq Date: Mon, May 8, 2017 at 6:07 PM Subject: Re: [time-nuts] HP10811 Oscillator Thermal Fuse To: Discussion of precise time and frequency measurement Cc: "Donald E. Pauly" Hi You will get a lot of diversity of opinion on the topic of the thermal fuse on the 10811. My feeling is that they are a nuisance and contribute very little to the design. I’d just short it out and move on. In the era of failure prone heater transistors or faulty thermistors, the fuse may have made sense. That era ended before the 10811 went into production. 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] HP10811 Oscillator Thermal Fuse
https://www.febo.com/pipermail/time-nuts/2017-May/date.html We got a new beam tube for our #2 HP5061B cesium clock. When the tube was changed, it momentary locked for a couple of minutes but then unlocked. The oscillator had been set on frequency with our #1 HP5061B a while back but it was suddenly 100 cycles low at 5 mc. Oscillator oven current was normal at 38. This oscillator is used on many other HP instruments such as counters. KB7APQ tore apart the HP10811 oscillator and found that the thermal fuse was open in the oven heater. We think that it was a nuisance blow. Does anyone have any experience on this thermal fuse? Digikey seems to have one that will work for under a dollar at https://www.digikey.com/product-detail/en/panasonic-electronic-components/EYP-05BE115/P10907-ND/295803 . We temporarily jumpered the fuse, the oscillator came right up on frequency and we got our first lock. We watched the actual oven current go down when it reached operating temperature. The oscillator oven current indication is useless on the HP meter since it is not actual oven current. I found this post: [https://groups.google.com/forum/#!msg/rec.radio.amateur.homebrew/g3Up39Wljak/DGr8OeLdz2gJ I dug out my notes to find out the specifics. My counter is an HP 5334B with Option 1, the high stability oscillator. The oscillator is one of the HP 10811 series. The original thermal fuse, F1, was rated for 108 degrees C. HP revised the part to one rated for 115 degrees C, part number 2110-0617 (10811-80003). The Radio Shack thermal fuse was 270-1322A, rated for 128 degrees C. There is also an NTE Electronics NTE8115, "Thermal Cut-Off", rated for 117 degrees C. Either is larger than the HP part, and is a tight fit. I wrapped them in electrical tape to protect against short circuits. When soldering to the high-value resistors, I clamped the fuse leads in a pair of pliers held with rubber bands. Of course this may not apply to your counter if it doesn't have the crystal oven! Fred K4DII] Does anyone have any experience on this thermal fuse or words of wisdom? πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Cesium Tube Resonance
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html Yesterday we swept our HP5061B thru the cesium resonance curve. As far as I know this is the first time that the curves have been published. The original phase modulation is a very unlinear sine wave frequency sweep. We built a 100 ms time constant integrator for the 20 cps triangle from the function generator. When a triangle is integrated, the result looks much like a sine wave but it is not. It is really back to back parabolas as shown in http://gonascent.com/papers/hp/hp5061/waveform/dblepara.jpg . The waveform is actually inverted in the display. Note that it appears a bit squashed. That small difference results in a linear triangle frequency sweep. We drove J1 on the A3 board with the output of the integrator and turned R20 the Mod Level pot all the way up. The phase modulation differentiates the output of the integrator to restore linear sweep. We ran the electron multiplier output J1 which went into the A7 board into scope channel two see http://gonascent.com/papers/hp/hp5061/waveform/csweep.jpg Vertical was 5 millivolts per division inverted. Ground is shown by the yellow 1 arrow and the scope amplifier was providing the 1 MΩ termination. The corresponding peak beam current is 20 nA or 20 on the HP meter. Because of the varactor polarity, the frequency sweep is inverted and is from -1,200 cps below resonance to +1,200 cps above resonance. The center of the negative going sweep of the triangle is the peak response of the cesium tube while being swept from low to high frequency. At -550 cps below it and +550 cps above it are seen the two valleys of the main resonance peak. The center of the positive going sweep of the triangle is also the peak response of the cesium tube while being sweep from high to low frequency. The valleys either side of the main peak are seen again along with partial false peaks. As you approach the positive peak of the triangle the lower false peak is seen. As you approach the negative peak of the triangle, the upper false peak is seen. Integrator limitations kept us from having enough drive levels to see the complete lower and upper false peaks. Remember that the sweep is reversed at both peaks of the triangle, low to high and high to low. See the artists depiction at Figure 4-43 in the manual. πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Square Wave Modulation Evalukation
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html We did some testing to evaluate the advantages of square wave modulation instead of sine waves for locking to the atomic resonance peak. We drove J1 on the A3 board with a 2.8 Volt peak to peak triangle at 20 cps from a signal generator. The crystal oscillator fine frequency was adjusted downward for below resonance. See http://gonascent.com/papers/hp/hp5061/waveform/sqrmod.jpg . The frequency out of the phase modulator is proportional to the derivative of the varicap voltage drive. For the triangle rising slope, the varicap is linearly increasing in capacitance with an constantly increasing phase lag. For the falling slope it is linearly decreasing in capacitance and a constantly increasing phase lead. This results in a lower and higher frequency for the positive and negative slope of the triangle respectively. The frequency shifts suddenly from about 300 cps below resonance to about 100 cps above resonance. We performed the same measurements with the fine frequency centered and above resonance but did not photograph them. Back of the envelope calculations predict a 10:1 improvement in jitter with square wave lock for average measurement times of 1 second. Beam current was injected directly into the scope with its 1 Meg resistance being the load for the electron multiplier. The scope was inverted to give a positive appearing beam current of 5 nA per division. Peak beam current is about 22 nA. (nA=Beam I meter reading) Note that the beam current is slightly delayed from the triangle and contains positive spikes at both transitions. This originates from the 1 millisecond or so travel time of the beam from the start of the microwave path to its end. During the rising portion of the triangle, the frequency out of the phase modulator is lowest and slightly below resonance. During the falling portion, it is the highest and slightly above resonance. When the frequency suddenly shifts, the beam cannot react instantly because it is only traveling at the speed of sound and must travel a foot or so in the microwave path. This takes on the order of a millisecond. A positive spike is created as the frequency passes thru the resonance peak at 22 nA. This occurs at both the low to high transition and the high to low transition. The frequency changes so fast that the voltage cannot reach 22 nA. As the center frequency is reduced, the negative half of the square wave becomes more negative and the positive half becomes more positive. As the center frequency is increased the square wave negative half becomes less negative and the positive half becomes less positive. When the center frequency is at the resonance of the cesium line the square wave disappears except for the spikes. Above center frequency, it reverses phase and gradually gets bigger. This type of lock is nearly 100% efficient and should be far lower noise. πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Cold Start
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html We performed an experiment with our working HP5061B which had been cold overnight. This was to better determine lock time from cold ovens. We found that the crystal oscillator oven heats up about twice as fast as does the cesium oven. Therefore the lock time is not much different whether the crystal oscillator was cold or hot. Our crystal oven has been running 34 when hot. The cesium oven has been running about 14 when hot. Here is our data as a function of measurement time in minutes versus meter readings. "+" denotes a pegged meter. The instrument was powered on at 0 minutes except for the cesium heater. The cesium heater was turned on at 13 minutes. The crystal oven had nearly stabilized by that time. Oscillator heater current was stable 15 minutes after power up and undershoots a bit at about 23 minutes. Note that first signs of beam current occur 7 minutes after cesium oven was powered up. First signs of 2nd harmonic occurred 9 minutes after cesium oven was on. We conclude that lock is feasible 23 minutes after a cold start. If the crystal oven is left on, lock can likely be achieved 20 minutes after the cesium oven is powered up. The ion pump preserves beam tube vacuum if the crystal oven is left on. If it is left off for long periods, high ion pump current may delay the application of power to the cesium oven until the vacuum is pumped down. For those who only occasionally need the stability of a cesium clock, you can have full performance 23 minutes after a cold start, or 20 minutes if the crystal and the ion pump are hot. If you use cesium for an hour a day, tube lifetime will be extended by 24 to 1 over continuous operation. If a beam tube lasted five years in continuous operation, it will last 120 years if used an hour per day. A similar benefit will occur if you use it continually for 2 weeks once a year. It does no good to waste cesium unless you are using the instrument. Time Ces Osc Beam 2nd 0 + 0 0 0 7 + 0 0 0 11 55 0 0 0 13 40 + 0 0 15 42 34 0 0 20 42 34 2 0 22 42 32 6 2 23 25 32 10 5 no lock 24 19 32 12 9 lock (free run back to OPR) 28 19 34 20 34 normal beam current ___ 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] Fwd: HP5061B High Ion Current/Tubes Out of Cesium
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html We did not attempt to achieve lock because we saw absolutely no beam current with the beam adjust all the way up. We were running the oven above 150° C which is more than 65° above normal oven temperatures. Cesium pressure should have been about 30 times normal. A photo of the A11 Cesium controller board is posted at http://gonascent.com/papers/hp/hp5061/photos/cesiheat.jpg taken by KB7APQ. Note that there are no electrolytics but tantulums installed instead. They must have been very costly 30 years ago. This also prevents hard to find problems with high ESR electrolytics with age. We have found open 47 μFd electrolytics inside two of our four HV power supplies. That is a place for tantalums if there ever was one. We are working on our HP5061B's from 500 miles apart so photographs of boards and waveforms help greatly. The cesium oven servo is underdamped. It overshoots and rings down at a 10 second time interval during temperature steps. You can see the R12 that we shorted out to get 150° oven temperatures for troubleshooting our suspected bad tube. I think that a website should be started with the collected wisdom of this list. I will host it if someone will maintain it. Corby's photo graphs of dismantled beam tube parts should be on a nice web page. If anyone has a high ion current 05061-6077 beam tube that they can part with please contact me. One of our beam tubes is completely out of cesium. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: paul swed Date: Thu, Apr 6, 2017 at 5:09 PM Subject: Re: [time-nuts] HP5061B High Ion Current/Tubes Out of Cesium To: Discussion of precise time and frequency measurement Donald running higher temperatures on a a normal tube may indeed give you a bit more life. Thats exactly how Frankenstein works. Its a hand me down tube that normally showed as dead. Believe me it doesn't even move the current meter and its working. My firm belief is that option 004 tubes do not have anything left to give. But yet with the higher temp (10-15 higher as I recall) it locks all on its own after a good warmup period. Serious fumes. Its been operating this way for some 4 years now. I don't run it all of the time and I actually recently found what was wrong that always gave it a slight offset. So a very good conversation running here with everyone sharing really good insights and pictures of detail I had only read about and generally without any pictures. The entire thread should be gathered up, cleaned up, and presented as the dummys guide to the care and feeding of old 5061s. Regards Paul. ___ 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] HP5061B High Ion Current/Tubes Out of Cesium
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html I spoke to Corby on the phone a few days ago about our first HP5061B that locks fine but has ion current on the order of 76 μA. It has not gone down significantly in two months of pump operation. He mentioned that the electrodes in the pump are made from titanium and that sharp whiskers can form on the electrodes from metal migration. They apparently cause corona and keep the ion current high indefinitely. According to Corby, the vacuum in the tube may be fine and the leakage current make it appear otherwise. We performed an experiment using our second HP5061B that we suspect of being out of cesium. When we first got it, we had about 10 μA of ion current and within a day it went down to nearly zero. Today we jumpered R12 on the cesium oven board to raise the oven temperature. We previously had checked all waveforms for normal operation on the board. This includes measuring cold resistance of the cesium heater at 2.6 Ω and hot wire ionizer of 0.1 Ω. Power to each was close to the nominal 2.6 Watts and 4 Watts respectively. We bumped oven heater voltage up to 11 Volts with the short on R12. This could have put up to 48 Watts into the oven heater unless its resistance went up significantly. After a couple of minutes the oven 150° C overtemp circuit shut down the switching regulator. We saw no increase of beam current even though normal oven temperature is 85° according to the tube data plate. We let the tube cool down and repeated the experiment several times. We had turned the beam current adjust all the way up to -2,880 V. On our good instrument we can get 20 μA beam current with only -1,700 V or so out of the -2,500 V supply. We therefore concluded that the beam tube was hopeless and decided on the risky experiment. We removed the +3,500 V supply on the suspected bad tube from the ion pump and connected the -2,500 V supply to the pump. We left the -2,500 supply on the electron multiplier as well. We saw no drop in its -2,880 Voltage. We would easily have seen 200 M Ω worth of leakage on the ion pump. Therefore the ion pump will work with either polarity of voltage. We have decided to take the risk of reversing the diodes on the +3,500 V supply on our good instrument and watch the ion current. We hope that the reverse polarity will burn out the whiskers or other leakage caused by long application of positive voltage. We have devised a test that will show up to 1,000 M Ω of any resistive leakage on the tube before we apply reverse voltage to it. πθ°μΩω±√·Γλ WB0KVV ___ 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] Hot Wire Ionizers
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html I posted this patent assigned to Frequency Control Corporation on hot wire ionizers at http://gonascent.com/papers/hp/hp5061/US3433944.pdf . They must have been an HP competitor in the 1960s. It discusses the physics of cesium ionization and should be of interest πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Peak to Valley Ratios
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html We did our first Zeeman frequency test on our good cesium 05061-6077 Tube with a 1 Meg scope probe and a 11 Meg Digital Voltmeter in parallel. KB7APQ used his digital generator for the variable frequency. See paragraph 3-16 on page 3-8. At 53.53 kc the level peaked at 3 V peak to peak which is close to the theoretical 1 V rms. I didn't have a program readily available to do a graph but you can see the main and upper and lower adjacent peaks. We can compare with Figure 4-43 (page 4-31) in the service manual for the HP5061B if anyone can graph this. We had the C field control at the factory setting of 453. Our actual maximum on main peak was 53.657 kc not 53.530 kc. We got 53.530 kc with a slightly different new C field setting of 463. Factor spec is within 100 cps and we were 127 cps off. This is probably not a bad drift for a 30 year old instrument. https://www.febo.com/pipermail/time-nuts/2017-April/104600.html kc beam (C Field set at 453) 55.03 27 54.93 27 54.83 27 54.73 28 54.63 30 54.53 32 54.43 33 54.33 31 54.23 28 54.13 25 54.03 22 53.93 22 53.83 24 53.73 29 53.63 35 53.53 32 53.43 39 53.33 34 53.23 28 53.13 24 53.03 22 52.93 23 52.83 25 52.73 28 52.63 31 52.53 32 52.43 31 52.33 29 52.23 27 52.13 27 52.03 26 We suspect a bad beam tube on our second instrument and therefore wanted to practice the Low Frequency Coil test on our known good beam tube. It allows the performance of the tube to be checked with no rf drive. See paragraph 5-175 (page 5-22) We used 26.765 kc and it also peaked out at 3 V pp. I discovered that this is half of the Zeeman frequency but it is not clear why this is so. We obtained a beam current of 23 with rf drive removed from the tube by pulling P2 on A4A1. I spoke to Corby Dawson last night. Among many things, he reported that you will be able to get 80% to 90% of this beam current in normal lock mode. We are getting 87% or 20. πθ°μΩω±√·Γλ WB0KVV ___ 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] Fwd: HP5061B Peak to Valley Ratios
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html Here is the plot on the Zeeman frequency data that we gathered this morning. It is close to Figure 4-43 (page 4-31) in the service manual for the HP5061B. Thanks to Jonathon for plotting this. http://gonascent.com/papers/hp/hp5061/waveform/zeeman.jpg πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Peak to Valley Ratios
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html We hooked up the oscilloscope directly to the electron multiplier in the beam tube with a 1 Meg termination. We were operating open loop and varying the fine crystal oscillator adjust for the different photos. Remember that higher beam current is downward in the photo. Currents listed in nA translate to beam current numbers on the HP5061B meter. First photo at http://gonascent.com/papers/hp/hp5061/waveform/centered.jpg is the frequency swept at a 137 cps rate around the peak of the cesium resonance. Ground is at the top of the screen and 5 mV (also 5 nA) per division. Horizonal is 4 ms per division.This corresponds to a peak beam current of -22 nA and a valley current of -17 nA. One valley current is below resonance and the other is above resonance. The waveform is 274 cps. Sequence is low to high and then high to low. No 137 cps is present. The fine frequency control was adjusted to produce a slight offset from center for the photo at http://gonascent.com/papers/hp/hp5061/waveform/smalloff.jpg . Note that the peak beam current is still -22 nA but two different valley currents exist. One is 17 nA and the other is -18 nA. Most of the signal is 274 cps but some asymmetry is present at 137 cps. One extreme of the sweep is slightly closer to center frequency than the other. Finally the frequency was adjusted to produce a severe offset with all of the sweep below resonance in the photo of http://gonascent.com/papers/hp/hp5061/waveform/largeoff.jpg . The peak is now slightly below resonance at -21 nA and the valley is far below resonance at 5 nA. The signal is all 137 cps with no 274 cps. See figures 4-43 and 4-44 on page 4-31 of the manual for further explanation. We will be finding out the effect on beam current of tests shortly on the Zeeman coil and LF coil. We think that the 55.53 kc Zeeman frequency introduces some AM into the beam frequency but no FM. What the LF coil has is unclear at this time. πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Peak to Valley Ratios
We are having trouble getting beam current on our #2 HP5061B. Ion current has gone down in a week from 10 to zero. It looks like the rf chain is working normally. Both HV power supplies had to repaired. Beam current is all the way up and which gives 2 on the meter. We are preparing to do the Low Frequency Coil test mentioned on page 5-22 section 5-175. I got this idea from that procedure. On our good #1 instrument we set the beam current at 20 with normal lock. The middle coax J2 which carries 12.631 mc to the harmonic generator was removed next. The beam current instantly dropped to 2. We set the beam current with the front panel control at 10 to 30 and all three settings dropped about 10 to one when the cable was pulled. This ratio seems to be a good indicator of beam tube quality. I don't see it in the manual, but the fine five turn pot oscillator control works much better than the course adjustment for setting peak beam current. It also works better for setting the control voltage to zero. The push to turn course frequency control slot has been chewed up by the previous owner. We are planning to get an oscilloscope display of the main and secondary lobes similar to page 4-31 Figure 4-43. If it works we will post it. It should show both the dc and ac parts of the beam current as the 137 cps sweep goes from one extreme to the other. Will anyone having any experience with the Low Frequency Coil test kindly post on the subject? This is NOT the Zeeman frequency test. ___ 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] HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html I posted another HP cesium beam tube patent at http://gonascent.com/papers/hp/hp5061/US3387130.pdf . It covers the formation of the cesium beam and should be of interest. We now have over a month of operation on our first HP5061B at ion currents over 50 μA with no lock problems. The uon pump voltage is 2,338 V at that current. We are still working for lock on our second HP5061B. Both of the HV power supplies had to be repaired and other problems remain. Anyone having supposedly unusable beam tubes with high ion current should contact me at trojancowboy at gmail .com. πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Cesium Oven Properties
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html The cesium oven acts as an evaporator for liquid cesium which melts at 28.5° C. One of our beam tubes has 83°C for its operating temperature. It also calls for a A11R11 and A11R12 of 3.83 K and 42.2K which is 3.51K. Oven power is specified at 2.2V and 0.9A or 1.98 W. Being in a vacuum allows less heater power. Oven temperature is very critical to provide enough cesium in the beam but at the same time not wasting it. A switching power supply runs the oven as well as providing 1.2V at 3.4A to the hot wire ionizer which is 4.08 Watts. It took 10 minutes from a cold start for the cesium oven current to drop from being pegged to its final value. After stabilizing, we connected a 470 Ω across the thermistor from the beam tube to shut off the heater. Here is the beam current versus time in minutes as the oven cooled off. Note that it took 17 minutes for the beam current to drop to half value. Continuous lock was maintained. time beam 0 20 3 18 5 17 8 16 9 15 1114 1412 1711 We then reapplied oven power and watched the beam current increase and oven current decrease. time beam oven 0 16 over 50 3 20missed 5 22missed 6 2115 8 20 15 10 20 14 Finally we applied oven power from a 35 minute cooldown and waited for lock. If the oscillator oven is stable, the cesium oven will achieve lock in only two minutes. There is no need to waste cesium if you do not need the instrument to be locked. time beam status 0 8 unlock 2 10 lock 3 12lock 4 18lock πθ°μΩω±√·Γλ WB0KVV ___ 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] Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html We continue troubleshooting our 2nd HP5061 acquisition. The 200 Meg resistor in the +3,500 V supply had gone way up in value and made it appear that the supply was half normal voltage. See the black resistor in http://gonascent.com/papers/hp/hp5061/3500top.jpg . We installed a temporary resistor. The ion current was pegged when we reinstalled the supply. This is not surprising since instrument has been stored for over a year. Here is the way that KB7APQ unsoldered the latest two high voltage supplies. See http://gonascent.com/papers/hp/hp5061/desolder.jpg . High Voltage Power Supply Unsoldering and Repair 1 - Suspend power supply on steel wires using 6-32 ground lugs and nuts. 2 - Heat solder joint evenly all the way around using a propane torch. Be careful to avoid too much heat on connections. Act as quickly as possible to avoid overheating components. 3 - Pull down firmly on outer can while wearing a welding glove. Rotate unit until can comes away from power supply. Cold solder on the inside of the can can prevent power supply from sliding all the way out. You may want to shake off some excess solder as it melts. 4 - When can slides off of the power supply turn it over and tap it on the floor to remove excess solder from the inside of the can. 5 - Mark can for mounting holes to be used to reattach outer can after repair. I used 0.970 inches from the can side and 0.100 inches from the open end. The off center 0.970 dimension is to avoid power supply screws from interfering with each other in the event both power supplies need this modification. 6 - Center punch where marked then insert power supply back into can. Note the orientation for the label on top. Using a number 50 drill bit, drill through both can and base. 7 - Tap holes in the base using a number 2-56 tap. 8 - Enlarge the holes in the outer can using a number 43 drill bit. 9 - Use 2-56 x 1/8" pan head screws to secure the outer can. πθ°μΩω±√·Γλ WB0KVV ___ 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] Fwd: Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html The -2500 supply is nearly identical to the +3500 supply. We will post some photos on the disassembly process. We also had to disassemble the +3,500 supply because the 200 Meg resistor had gone up in value. It showed only 1,900 V with no load when it should have shown 3,200 V. We replaced the 47 uFd electrolytic with a tantalum as a preventive measure. After we repaired the -2,500 supply we measured the output voltage versus beam current as set by front panel adjustment. Note that about a 10% increase in electron multiplier voltage will double beam current. beam current High Voltage 30 -1,755 20 -1,658 10 -1,507 On our freshly repaired HP5061B, we ran it four hours with no voltage on the ion pump. It maintained lock when voltage was reapplied. Ion current and voltage were unchanged at 76 uA and 2500 V. You apparently can operate for some time with no ion pump. Really good pix on the inside of the 3500V module. So the opening of the can is the typical lots of heat and pry it open approach right? How about a good pix of the 2500 Volt module? Thanks Paul WB8TSL ___ 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] Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html We continue to try to achieve lock on our latest HP5061B acquisition. We found that the -2,500 supply would only come up to -780 V under normal 55 Meg multiplier load. When we pulled off the HV lead to the beam tube, it came up to only about -1,500V. After another horrible desoldering job, Q2 collector waveforms were essentially normal. We found a near open C1 which is 47 μFd at 35 Volt electrolytic was open. This caused massive spikes on the bypassed +18.7 line. We replaced it with a tantalum. This brought it up to normal -2,700 V for full clockwise beam adjust on R7. Next we found that the +3,500 supply was only up to 1,000 V with normal ion current load. We expect to find the same problem on this supply. See http://gonascent.com/papers/hp/3500top.jpg. C1 cannot be seen in this photo. Ion current was only 15 μA because of the low supply voltage. I will have another post on what we found about electron multiplier voltages. DEP πθ°μΩω±√·Γλ WB0KVV ___ 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] Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html The design on the voltage and current limiter is complete but not breadboarded yet. We are getting a little more time on our HP5061B beam tube after beefing up the +3,500 Volt power supply. We have the frequency control R4 turned all the way up to 1900 cps with beam tube ion pump load. We have a shunt across the ammeter so it can measure 100 μA full scale instead of 50μA. We dare not disconnect the load because voltage limiting is not operational yet. Continuous lock light is lit. Note that lock is normal at over 3 times what the book said was normal cesium turn on point. If we could go to +3,500 Volts, the current would likely be 100 μA. I calculate that lock would be normal at 1 mA ion pump current. time μA voltage 08:46 56 3,620 09:46 70 3,400 11:25 72 3,360 12:58 76 3,300 We just got in our second HP5061B yesterday It's ion current was only 14 μA but we haven't checked the voltage on the +3,500 V supply yet. It appears to have a problem with the -2,500 V supply. πθ°μΩω±√·Γλ WB0KVV ___ 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] HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html The patent that I posted at http://gonascent.com/papers/hp/US3323008.pdf has many interesting facts about the cesium beam tube. It says that the temperature of the cesium oven is 65° C. I researched the vapor pressure of cesium at various temperatures. With a change of 30° C in the oven temperature, the cesium pressure goes up or down by 10 to 1. If the oven temperature goes up by 5°C, cesium use rate goes up by 1.46 to 1. If it goes down by 5°C, cesium consumption decreases by 1.46 to 1. Cesium oven temperature is quite critical to beam tube life. The HP5061A has a switch to reduce cesium oven temperature to increase beam tube life at a price of slightly worse short term stability. If the oven is shut off in CS OFF mode, pressure drops to 1.41x10^-6 Torr at 25 at temperatures about 25° C. This is 2.8 times more that the 5x10^-7 Torr that is considered a good vacuum for the tube. good vaccum is considered 2 μA on the ion pump. This would be 5.6 μA for the higher pressure. Therefore, the tube will get somewhat gassy if the instrument is not used. If it is stored at temperatures about 25° C while not in operation, the situation is worse. I don't know what is causing higher currents but it must be contaminants beside cesium. http://www.powerstream.com/vapor-pressure.htm C° log mm Hg -18° -8 2° -7 22° -6 47° -5 77 -4 109° -3 155° -2 207° -1 252° -0 πθ°μΩω±√·Γλ WB0KVV ___ 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] Fwd: Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html I have posted two HP patents on the cesium beam tube at http://gonascent.com/papers/hp/US3323008.pdf and http://gonascent.com/papers/hp/US3397310.pdf . Both are of academic interest. The first claims that the cesium oven operates at 60°-70° C. This is a tiny heating compared to a 1,000° filament on a power transmitting tube. I say that it can be cycled a million times with no problem of thermal cracking. πθ°μΩω±√·Γλ WB0KVV -- Forwarded message -- From: John Miles Date: Tue, Mar 21, 2017 at 5:41 PM Subject: Re: [time-nuts] Fwd: HP5061B Ion Current To: Discussion of precise time and frequency measurement , rwa...@aol.com That's some very nice work, Donald. Looking back, I have junked one or two Cs tubes that might have been usable if I'd thought through the problem of high ion pump current as you and KB7APQ seem to have done. Another good reason to raise the lockout threshold would be to cut down on the repetitive ionizer filament cycling that the tube will otherwise undergo when you first fire up the oven. That phenomenon always makes me rally nervous. -- john, KE5FX Miles Design LLC > -snip- > When we overrode the cesium lockout at 29 μA or so of ion current, we > needed only minor front panel adjustments for beam current of 20 μA. > (We shorted across A15 R-4.) Our last ion current before power supply > modifications at risen to 39 uA. Beam current has been stable. ___ 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] Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html You bring up an interesting point. As the cesium is used up over the years, it forms a cesium frost which deposits on everything inside the tube. If it gets thick enough it conducts or can arc between frost grains. A charged capacitor can blow some of this away. Cesium melts at 83° F. If you heated the beam tube up in a hot car or out in the hot sun, you could turn this frost into dew. The dew might run down hill into some cesium lakes where it was harmless. Those lakes would freeze when back at room temperature and might be even more harmless. I have seen two TV picture tubes that developed leakage between focus and screen electrodes. Adjusting focus changed the brightness and adjusting the screen changed the focus. I applied the high voltage between the two and the arc burnt out the high resistance leak. It saved both picture tubes. WB0KVV πθ°μΩω±√·Γλ If you cannot get the ion current below 50ua or so after a week at 5kV then you are out of luck. Most likely you have resistive deposits on the ion pump insulator. If you can get the tube to give a decent SN at those levels then you can run with the alarm circuit bypassed. I have run tubes a couple years this way (at <50ua) but if you let them sit cold you will have to manually cycle the ovens at turn on until the excess gas load is pumped. If you have a bad ion pump supply when you open it up to repair it I would suggest adding a 66K resistor across the 75K resistor. This will increase the alarm trip up to about 40-45ua. If it's the older one the oil capacitors will need changing as well as the 200Meg resistor. If the later one (in the 5061B) then the 47uf radial cap is open. both these units are interchangeable. One other trick is to use a spark discharge tester (miniature hand held tesla coil used in the neon sign industry) to ZAP the ion pump lead. This can blow out any whiskers that the ion pump has developed. You can also (carefully) with the HV on, remove and replace the ion pump connector a few times. Sometimes you will get a sharp discharge that blows out the whisker. I have used both methods with good success. Cheers, Corby ___ 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] HP5061B Ion Current
It looks like that there is about 10% hysteresis on the cesium trip off/on. That may not be enough to prevent cycling on and off. I may not have made it clear but instability in the +3,500 voltage makes a big difference in the threshold ion current required for activation. If it fades it can require a 10 uA smaller ion current to activate cesium. -- Forwarded message -- From: John Miles Date: Tue, Mar 21, 2017 at 5:41 PM Subject: Re: [time-nuts] Fwd: HP5061B Ion Current To: Discussion of precise time and frequency measurement , rwa...@aol.com That's some very nice work, Donald. Looking back, I have junked one or two Cs tubes that might have been usable if I'd thought through the problem of high ion pump current as you and KB7APQ seem to have done. Another good reason to raise the lockout threshold would be to cut down on the repetitive ionizer filament cycling that the tube will otherwise undergo when you first fire up the oven. That phenomenon always makes me rally nervous. -- john, KE5FX Miles Design LLC > -snip- > When we overrode the cesium lockout at 29 μA or so of ion current, we > needed only minor front panel adjustments for beam current of 20 μA. > (We shorted across A15 R-4.) Our last ion current before power supply > modifications at risen to 39 uA. Beam current has been stable. > ___ 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] Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html Paul: I don't think that I made myself clear. This power supply is a rare example of HP engineering incompetence. The transformer is EASILY capable of 10 Watts out at 3500 V. Instead they made it where it can't even put out 100 mW without sagging. This supply was designed in the middle 80s when IC technology was well developed. >From what I am able to determine about ion pumps, current is proportional to pressure and voltage is proportional to pumping rate. Paragraph 4-349 of the HP5061B manual states that 2 μA ion current corresponds to a pressure of 5x10^-7 Torr. At 760 Torr, the mean free path of an oxygen molecule is 93 nm. Assuming that a cesium atom is the same size, this gives it a mean free path of 141 meters. This means that there is a 50% chance of a collision in a 141 meter travel thru such a vacuum. At an ion current of 1 mA, the pressure would be 500 times greater and the mean free path 500 times less or 0.282 meters. This is 11" or about the length of travel for the beam in the tube. A beam current of 1 mA would only cause a loss of 50% in beam current and should still allow lock. That same paragraph claims that cesium is turned on at 40 μA. That was not true. Another place claims 20 μA (Appendix A-1 b) as well as 30 to 40 μA. The exact trip point depends on how much sag occurs in the HV supply and is very complex to calculate. It is stupid to have to wait for weeks for a reduction in ion current to allow the cesium to come on naturally. Lock can be achieved instantly. I think the final vacuum improvement can be achieved more quickly if the cesium oven is on. It should cook off cesium that has condensed on its outside. See page 8-51 schematic. We measured the properties of the power supply as it is. For 18.7 V supply, 357 μH and 20 μs, energy stored is in T1 primary is 108 μ Joules. Frequency can be adjusted from 524 to 2002 cps. Power supply with no load was set to 704 cps for +3,500V out with no load except for the internal 200 Meg bleeder. Input power was 76.3 mW and output power was 61.25 mW or 80% efficiency. At frequencies above 704 cps, output voltage increases above safe levels for no load. With gassy beam tube for load, voltage sags to 2296 V with 39 μA ion current 11.4 μA bleeder current. Total power is 115.9 mW. With frequency raised to 55 μA ion current, voltage was 2460 V or 165 mW power. With frequency turned all the way up to 2002 cps, voltage was 2562 V and 71.4 uA ion current or 215 mW power. We are working on a voltage regulator and current limiter that will provide at least 1 mA before voltage reduction from +3500V. This is an improvement of at least 20 to 1. Output power is limited by the 21 kc self resonance of the transformer due to secondary winding capacitance. We don't know its saturation current yet. We plan to use the two unused meter switch positions to monitor output voltage and current. It will likely mean that no external 3500 volt supply will ever be required for tubes that have been in long storage. I made a typo on WB4BPP's call in my first post but he reports using a 5,000V external supply. He didn't provide current figures or whether this voltage actually stayed there. I am concerned about arc over at the ion pump at that voltage. Ion pump manufacturers caution about overheating at high pump currents. HP claims in Appendix B A-2 h that +3500 V at 5 mA for no more than 15 minutes is permissible. This is 17.5 Watts which sounds like a lot for a small cathode. When we overrode the cesium lockout at 29 μA or so of ion current, we needed only minor front panel adjustments for beam current of 20 μA. (We shorted across A15 R-4.) Our last ion current before power supply modifications at risen to 39 uA. Beam current has been stable. WB0KVV πθ°μΩω±√·Γλ -- Forwarded message -- From: paul swed Date: Mon, Mar 20, 2017 at 7:08 PM Subject: Re: [time-nuts] HP5061B Ion Current To: Discussion of precise time and frequency measurement Donald welcome to the group. If a units been off a long time and it sure sounds like thats the case it may take quite a while like a month or so for the unit to remove all of the "Stuff" that has out gassed. So be patient and let the pump do its job. After it does lower and my fingers are crossed. Then you only need to run it about every 6 months. The fact that it actually locks and you found a simple fix is pretty good. What was the beam current?? That gives you a hint on the quality of the tube. Not sure I would run the defeat on the HV supply for to long. That may stress the supply if I had to guess. Regards Paul WB8TSL ___ 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] HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html I could not figure out why the A15 Ion Current monitor would not let the cesium oven turn on with ion current under 25 uA. At the time we had no way of measuring the +3,500 ion pump supply. We bought some 200 Meg resistors and made a crude HV meter to feed our 10 Meg Fluke 77. The supply had sagged to 2000 Volts with that load. This prevented the ion pump current monitor from energizing the cesium oven. KB7APQ unsoldered the can on the 3,500 Volt supply with suggestions from WB4BBP. It is a horrible design and we studied it. R4 is set at the factory to produce 3,500 Volts with no load. It runs at 704 pulses per second and sags badly with the slightest load. This prevents the ion pump from clearing the gas in the beam tube. The pot core transformer is plenty big that it appears that the supply can put out 5 mA at 3,500 volts. This allows it to replace the external supply recommended by HP for gassy tubes. It looks like that it can run at 10 kc with existing pot core transformer. The pulse width looks like it can be doubled as well. This allows for a 30 to 1 increase in output power. A small circuit board will regulate the voltage as well as limit the current. ___ 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] HP5061B Ion Current
This is my first post. I just bought a non-working HP5061B on eBay for $350. My old boss KB7APQ in Salt Lake City and I are working on it. It came in from the Philipines in October of 2015 and was diagnosed with a bad physics package in March 2016 by AllTest in New Jersey. We initially found an open R8 pot on the 5 mc oscillator A10A2 which was killing most of the output. Next we had ion current of about 25 uA which stayed up. The book seems to indicate that this was low enough to enable the cesium oven. The analysis of the theoretical ion current for cesium turn on was very difficult. We shorted the base emitter of Q6 on A15 board to override Cesium oven disable. The instrument then achieved lock with beam current of 20. Ion current rose to 35 after cesium oven warm up and lock. We have made great progress on the +3500V power supply analysis. We believe that many so called gassy tubes are perfectly functional up to 1 mA ion current. Mean free path is on the order of 142 mm in that case or the length of the beam. We will discuss our findings if there is interest. WB4BBP has been most helpful with our efforts. ___ 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.
