[time-nuts] (no subject)
Thankyou to all those who responded to my question...Don. ___ 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] Reference source 1E10^8 only ...Ideas
I need a frequency reference for my frequency counters, it needs to be accurate to at least +or- 1 part in 10,000,000. !0MHz would be OK, but also 5, or 1. Due to technical improvements, the 4.43361875 MHz colour subcarrier which is available on the analogue TV system here in New Zealand, is no longer referenced to a Rubidium standard, and can be about +,- 1Hz in error. I have a communications receiver, and have been thinking of using this with Lyssajous figures on an oscilloscope, with the receiver tuned to WWVH in Hawaii, but a GPS might be a possability, if there is satellite coverage here in Invercargill, southern NZ. Bearing in mind I don`t need extreme accuracy, what is my best option, please?.Don. ___ 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] nubie querie
I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] If this is known, then it becomes easier to design low phase noise oscillators. I hope you enjoy these questions,.Don. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time-nuts Digest, Vol 47, Issue 6
Thankyou Bruce! It is god to know these things. Cheers,Don C. PS : My O key is defective - I am not trying to convert you. - Original Message - From: [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Tuesday, June 03, 2008 2:58 PM Subject: time-nuts Digest, Vol 47, Issue 6 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [EMAIL PROTECTED] You can reach the person managing the list at [EMAIL PROTECTED] When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: time-nuts Digest, Vol 47, Issue 5 (Don Collie jnr) 2. Re: PCB design questions thread II (John Miles) 3. Re: time-nuts Digest, Vol 47, Issue 5 (Bruce Griffiths) 4. Re: time-nuts Digest, Vol 47, Issue 5 (M. Warner Losh) 5. Re: PCB design questions thread II (Prologix) -- Message: 1 Date: Tue, 3 Jun 2008 14:21:27 +1200 From: Don Collie jnr [EMAIL PROTECTED] Subject: Re: [time-nuts] time-nuts Digest, Vol 47, Issue 5 To: time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; format=flowed; charset=iso-8859-1; reply-type=original I`m curious : What is a virgin teflon standoff, and does it have anything to do with the teflon Don? I don`t see much SMD, here, at the extreme edge of the known Universe, but I can see that the single sided approach would make tracing a circuit much easier,.. ...Don C. PS : Perhaps the double sided approach would be more suitable for Schitzophernics - a few of whome it has been my pleasure to meet. - Original Message - From: [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Tuesday, June 03, 2008 1:53 PM Subject: time-nuts Digest, Vol 47, Issue 5 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [EMAIL PROTECTED] You can reach the person managing the list at [EMAIL PROTECTED] When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: PCB design questions thread II (John Day) 2. Re: PCB design questions thread II (Bruce Griffiths) 3. Re: PCB design questions thread II (Matthew Smith) 4. Re: PCB design questions thread II (Bob Paddock) 5. Re: PCB design questions thread II (Matthew Smith) 6. Re: PCB design questions thread II (Bob Paddock) 7. Re: PCB design questions thread II (Chuck Harris) 8. Re: PCB design questions thread II (Bob Paddock) 9. Re: PCB design questions thread II (Keith Payea) 10. Re: PCB design questions (Didier Juges) -- Message: 1 Date: Mon, 02 Jun 2008 20:20:14 -0400 From: John Day [EMAIL PROTECTED] Subject: Re: [time-nuts] PCB design questions thread II To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=us-ascii; format=flowed At 08:04 PM 6/2/2008, you wrote: Personally I *hate* turning boards over and clipping leads. And I'd much rather layout SMD than T/H. A man after my own heart. 0.5mm and even 0.4mm pin pitch is fine, QFN is doable, but takes patience sadly BGA is a bit beyond the pale for me right now until I get some more gear. Until I started the job I have now I hadn't done any PTH in nearly 15 years - and now I know why! And now I know why we have technicians to assemble prototypes, but none of them can outdo me for speed and accuracy on an 0.5mm PQFP FPGA. If you are going to do a lot of SMT work by hand, then a good stereo microscope and a Metcal MX500 series iron are almost indispensable. John -- Message: 2 Date: Tue, 03 Jun 2008 12:20:26 +1200 From: Bruce Griffiths [EMAIL PROTECTED] Subject: Re: [time-nuts] PCB design questions thread II To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1; format=flowed christopher hoover wrote: John Miles wrote: For one-off PCBs, I've had good luck with www.batchpcb.com . I agree. I've used them once and have been happy with the results, you just can't be in any hurry. Unfortunately, there's no indication of how long it will take a priori. SMD is not hard to work with by hand, down to 0603 or thereabouts depending on eyesight and/or equipment. I find it easier to deal
Re: [time-nuts] time-nuts Digest, Vol 47, Issue 5
I`m curious : What is a virgin teflon standoff, and does it have anything to do with the teflon Don? I don`t see much SMD, here, at the extreme edge of the known Universe, but I can see that the single sided approach would make tracing a circuit much easier,.. ...Don C. PS : Perhaps the double sided approach would be more suitable for Schitzophernics - a few of whome it has been my pleasure to meet. - Original Message - From: [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Tuesday, June 03, 2008 1:53 PM Subject: time-nuts Digest, Vol 47, Issue 5 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [EMAIL PROTECTED] You can reach the person managing the list at [EMAIL PROTECTED] When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: PCB design questions thread II (John Day) 2. Re: PCB design questions thread II (Bruce Griffiths) 3. Re: PCB design questions thread II (Matthew Smith) 4. Re: PCB design questions thread II (Bob Paddock) 5. Re: PCB design questions thread II (Matthew Smith) 6. Re: PCB design questions thread II (Bob Paddock) 7. Re: PCB design questions thread II (Chuck Harris) 8. Re: PCB design questions thread II (Bob Paddock) 9. Re: PCB design questions thread II (Keith Payea) 10. Re: PCB design questions (Didier Juges) -- Message: 1 Date: Mon, 02 Jun 2008 20:20:14 -0400 From: John Day [EMAIL PROTECTED] Subject: Re: [time-nuts] PCB design questions thread II To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=us-ascii; format=flowed At 08:04 PM 6/2/2008, you wrote: Personally I *hate* turning boards over and clipping leads. And I'd much rather layout SMD than T/H. A man after my own heart. 0.5mm and even 0.4mm pin pitch is fine, QFN is doable, but takes patience sadly BGA is a bit beyond the pale for me right now until I get some more gear. Until I started the job I have now I hadn't done any PTH in nearly 15 years - and now I know why! And now I know why we have technicians to assemble prototypes, but none of them can outdo me for speed and accuracy on an 0.5mm PQFP FPGA. If you are going to do a lot of SMT work by hand, then a good stereo microscope and a Metcal MX500 series iron are almost indispensable. John -- Message: 2 Date: Tue, 03 Jun 2008 12:20:26 +1200 From: Bruce Griffiths [EMAIL PROTECTED] Subject: Re: [time-nuts] PCB design questions thread II To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1; format=flowed christopher hoover wrote: John Miles wrote: For one-off PCBs, I've had good luck with www.batchpcb.com . I agree. I've used them once and have been happy with the results, you just can't be in any hurry. Unfortunately, there's no indication of how long it will take a priori. SMD is not hard to work with by hand, down to 0603 or thereabouts depending on eyesight and/or equipment. I find it easier to deal with than through-hole, frankly. I agree with the first part, but I actually find SMD to be easier than T/H, if you stick with 0603 and larger for the passives. I find SMD not only easier but quite bit a faster. SMD IC packages are easy once you get the hang of them, but a microscope is needed for inspecting and fixing fine pitched parts. (I think this is a bit of surprise to some folks.) Personally I *hate* turning boards over and clipping leads. And I'd much rather layout SMD than T/H. -ch However for low frequency work the low thermal mass of resistors and opamps in smt packages can be problematic. Also SMT packages are more sensitive to board deflections and vibration. Using guard rings with some SMT parts is difficult to impossible. You no longer have the option of directly connecting a leakage sensitive lead to a virgin teflon standoff. Mixers and phase detectors with dc and low frequency isolated grounds for the IF and RF ports dont appear to be available in SMT packages. How do you cope with SMT parts (eg high frequency ADCs) with metal thermal transfer /ground connections under the package itself? Bruce -- Message: 3 Date: Tue, 03 Jun 2008 10:04:44 +0930 From: Matthew Smith [EMAIL PROTECTED] Subject: Re: [time-nuts] PCB design questions thread II To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type:
[time-nuts] Re : Favourite DC power Supply
Dave I managed to turn a couple of 5 Volt 100 Amp SMPS into 13.8 Volt 100 Amp ones, by reforming the output filter cap to 16 Volts, and increasing the duty cycle from 0.4 to 0.8. They were made by Pioneer Magnetics, and had the spare grunt to do their new job [or else I would have set the current limit to 50 Amps]. Only problem was they each needed a 5 Amp bleeder load, otherwise the switching frequency came down into the audible range. Tried putting both in parallel once, and connecting their output to Dads welding setup, but there wasn`t enough back EMF to strike an arc! :-).Don C. ___ 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] Barkhausen Effect
Hi Bruce, I`ll include this in the several MB of reading I hope to do on this subject! [I love succinctness! ],Don C. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] low noise in synthesisers
Thanks for the comments guys!,..Don C. ___ 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] phase noise/jitter
Hello Bruce and all, OK, now I think I understand : the more phase noise on the VCO, the more jitter on the output of the divide by N. This output spectrum comprises *only* the PRF+ close-in noise sidebands [plus harmonics, and their noise sidebands]. Since the lowest frequency [ignoring close-in noise sidebands for a moment] present in the divide by N logic is equal to its output frequency anyway, there are no frequencies present in the output that are below this, and because the loop rolls off at a frequency that is much less than this, the VCO is not modulated by any signal comming from the reference, or the divide by N logic ..The loop filter filters these signals out.This is how a PLL can clean up jittery signals. So I guess one way to improve PLL phase noise is to have as high a frequency going to the phase detector as possible, and to have as low a loop bandwidth as possible, [and put up with a long lock - in time].Having now filtered out most of the jitter, the problem becomes one of designing a VCO [or variable reluctance oscillator, as in a YIG], that produces little phase noise of itself. This must be where the designers get crafty! Facinating stuff !,Don C. ___ 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] Phase Noise/Jitter/SNR/N to Slope ratio etc
So to summarise : To make a synthesiser`s phase noise low :
- Apply the KIS principle [Keep It Simple]
- Use high speed [non-saturating?] logic rather than low
- The logic supplies should be well regulated, distributed
and decoupled.
- Make the PRF to the P/F detector as high as possible.
- The loop filter should have a sharp rolloff
and maintain loop stability ;-)
- The loop BW should be as low as possible.
[ ie loop filter should rolloff at the lowest frequency
tolerable]
- The reference frequency should have the highest slope to
noise ratio possible Since slope is proportional to
amplitude if frequency is constant, then this ratio
equates to a high SNR - and we all might as well
go shoot ourselves if the reference frequency
changes - eh guys ;-).
- Use quality, low noise, components in the VCO including
the active device.
- Employ great craftiness in the choice of circuit
configuration for the VCO.
- The VCO resonant circuit should be of the highest
Q possible - Why?
- Use a YIG in preference to Varicaps, and use back-to-
back matched varicaps if possible.
- Use great care with PSU, and earth returns between the
digital [phase detector] circuits, and analogue
circuits [ VCO].
-The VCO supply Voltage needs to be very clean, and
stable.
- Minimise the tuning range of the VCO where possible
to minimise the effect of any jitter that *does*
reach the VCO through the loop filter.
- Keep the RF Voltage across the varicaps small
[class A oscillator?/crafty design]
- Maximise the VCO output voltage to maximise SNR
or output amplitude to phase noise amplitude.
Some of these are at odds with each other, but can anyone
constructively criticise or refute these points, or add more, or expand on any
of them, please?
Again, thankyou for your thoughts,...Don C.
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[time-nuts] How do you minimise jitter?
I`ve been puzzling over the reasons why one synthesised signal generator produces more close-in noise than another, and thought that one of the reasons for this noise would be jitter on the digital signals applied to the phase detector producing FM sidebands from the VCO. What then are the causes of jitter in digital circuits? A poorly regulated PSU to the logic might cause the hi/lo decision Voltage to vary, and this, combined with finite rise, and fall times, could cause jitter, but what are the things a designer can do to keep jitter to a minimum? Could the group comment please. ...Don C. PS : I apologise if this question is a bit off topic, but minimising jitter is also important to precise time and frequency measurement [as is reducing close-in VCO sideband noise]. ___ 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] (no subject)
ssSsSs ssSsSSstestSSSssSs ___ 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] (no subject)
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.
Re: [time-nuts] phase noise questions
Hi Steve!, I know this is off topic, but I would be facinated to know why you are called Steve the knife [Please don`t tell me if it is anything illegal] Yours in extremely low noise,Don. - Original Message - From: steve the knife [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Wednesday, January 23, 2008 1:22 PM Subject: [time-nuts] phase noise questions Hello, I followed with some interest a discussion about a NIST doubler circuit using matched FET's and I was wondering if you could get similar results using an analog multiplier chip from Analog Devices. It would seem that they take some care about device matching and have parts that work up to pretty high frequencies. Of course there would need to be some filtering employed. Oh, and I think those parts do pretty well with temperature. Also, when using a doubler that is rated in dBc how do you apply that number to get an expectation from a given starting dBc oscillator. So if my 10 MHz clock is -125dBc and I use the NIST circuit, what would I see at 20 MHz in dBc? thanks in advance, steve ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] phase noise questions
Just to let you all know that Steve the knife did reply to me off group - it is a facinating story. Very, Very low noise to you all,Don C. - Original Message - From: Don Collie [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, January 23, 2008 5:04 PM Subject: Re: [time-nuts] phase noise questions Hi Steve!, I know this is off topic, but I would be facinated to know why you are called Steve the knife [Please don`t tell me if it is anything illegal] Yours in extremely low noise,Don. - Original Message - From: steve the knife [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Wednesday, January 23, 2008 1:22 PM Subject: [time-nuts] phase noise questions Hello, I followed with some interest a discussion about a NIST doubler circuit using matched FET's and I was wondering if you could get similar results using an analog multiplier chip from Analog Devices. It would seem that they take some care about device matching and have parts that work up to pretty high frequencies. Of course there would need to be some filtering employed. Oh, and I think those parts do pretty well with temperature. Also, when using a doubler that is rated in dBc how do you apply that number to get an expectation from a given starting dBc oscillator. So if my 10 MHz clock is -125dBc and I use the NIST circuit, what would I see at 20 MHz in dBc? thanks in advance, steve ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How to measure regulator noise?
I`d just hang an AC millivoltmeter[or microvoltmeter] across the regulator`s output. I use my H/P 400H, which will give readings down to about 50uV. If your regulator produces less noise than this [say a 723, with 2uV], then you`ll need a more sensitive meter. It might be wise to short the input wires of the meter, to check the inherent noise in the measurement setup - for meaningful results this should be, perhaps, no more than a tenth of the expected reading [depending on how riggerus you want to be]. Bear in mind that most analogue meters are average responding, and calibrated for a sinewave - so to get the RMS value for white noise [or whatever] a correction factor should be applied [depending also on what sort of accuracy you need/want]. If you want to *look* at the noise, I understand that one of the Tek 7000 series plug-ins is able to display very small amplitudes of this order. Again, because you may be dealing with comparitively small voltages [compared with those which might be induced due to hum fields etc], it would be wise to check the residual noise by shorting the probe[s] at the regulator. This is valid since the output impedance of the regulator is nearly zero. Go to it!,..Don C. - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, January 08, 2008 10:03 AM Subject: Re: [time-nuts] How to measure regulator noise? Poul-Henning Kamp wrote: In message [EMAIL PROTECTED], Dave Brown writes: John You won't need much of a cap for DC blocking as inputs are hi-Ztoo big and the chargeup may well trigger the overrange condition. You need to put a shunt resistor after the capacitor if the input is hi-Z but an even better way is to offset the gnd clip with a couple of fresh batteries so that you can avoid the capacitor. Batteries have very low, but not zero noise, so what you do is: Put six fresh 1.5 volt batteries in series, so that three of them is the wrong way and the resultant voltage is zero and then you measure their noise. Then you put three of them the wrong way on your 5v supply, so that the output voltage is only .5V and then you measure the noise. That worked fine for me using a HP6885B This technique only offsets the voltage to within 3/4V of zero when measuring an arbitrary voltage regulator output. With a discrete regulator it is usually easy enough for test purposes to adjust the regulator output so that it is within a few tens of millivolts of the battery stack voltage. A low noise preamp with perhaps 40-60dB gain is still required before the spectrum analyser. Even residual dc voltages of a few tens of millivolts may saturate such an amplifier. A simple dc servo can be used to remove the residual offset (1V) without using electrolytic capacitors with their attendant leakage and noise. A low frequency cutoff well below 1Hz is possible without adding significant noise. Alternatively for measurements in the 10Hz to 100kHz range a preamp like that used in Linear Technology's AN83: http://www.linear.com/pc/downloadDocument.do?id=4172 may be useful. It uses electrolytic coupling capacitors together with low value resistors. For ultralow (milliHertz) frequency noise measurement AC coupling is best avoided altogether, if possible. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How to measure regulator noise?
Hi Bruce and Henk, Your point about Bandwidth is a valid one, and as you say, it depends on the application. The 400H has corner frequencies of about 10Hz, and 4Mhz, so the noise BW is a bit wider than this [Y/N?]. This setup can`t measure noise at very low Frequencies, or Frequencies much greater than the [nominal] 4Mhz, because the noise frequency components simply can`t get through. For my purposes the setup I described is adequate - I mainly want to compare one regulator with another [although it would be nice to be able to do so over the frequencies 0Hz to infinity]. I suggest that if a regulator proves itself quieter over a restricted BW such as I described, it is *probably* quieter at other frequencies too. Take that Bruce! ;-)..Don. - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, January 09, 2008 9:26 AM Subject: Re: [time-nuts] How to measure regulator noise? Henk ten Pierick wrote: On Jan 8, 2008, at 12:50, Don Collie wrote: I`d just hang an AC millivoltmeter[or microvoltmeter] across the regulator`s output. I use my H/P 400H, which will give readings down to about 50uV. If your regulator produces less noise than this [say a 723, with 2uV], then you`ll need a more sensitive meter. Electronic voltmeters or microvoltmeters have a noise bandwidth which is larger than the bandwidth on the front panel. The front panel bandwidth is related to accuracy and is not the -3dB bandwidth. The noise bandwidth is nearly always range setting dependent and can vary very much. I have seen a factor of four in noise bandwidth between adjacent range settings. The only way to have a good indication on noise is in a known and constant bandwidth. The noise bandwidth of a filter is not the same as the 3dB bandwidth and dependent of the filter order and shape. It is always more. Henk Thus if one is to make useful comparative measurements with an AC voltmeter, an external filter which has a significantly narrower bandpass than that of the AC voltmeter is useful. A spectrum analyser with the capability of averaging cross power spectra has the added advantage (over an AC voltmeter) of being able to make meaningful measurements of noise below the noise of its input amplifiers (or the noise of external preamplifiers). Since its difficult to build a preamp with noise much below 10nV/rtHz whilst ensuring that the preamp input will survive worst case transients etc when connected to a power supply of 10V or more, such a capability is useful for measuring the noise of ultra low noise regulators which may have high frequency noise of 20nV/rtHz or less. For example the preamp used in Linear technologies AN83 is virtually guaranteed to be damaged by connecting its input to a powered up 20V supply. Off course, connecting it to the power supply before powering up the supply will (if the regulator output slew rate is sufficiently low) allow it to be used to measure the noise of higher voltage supplies (at least if higher voltage 330uF OSCON caps were available). However accidents/mistakes do happen (as do faulty regulators) and eventually the preamp input opamp will be destroyed. Using standard electrolytics for the input coupling capacitor for testing higher voltage supplies isnt particularly useful as they have increased leakage current and associated noise. Schemes such as using a relatively high resistance in series with the preamp input which is shorted out after the coupling capacitor has charged are not foolproof and eventually a mistake will lead to destruction of the preamp input stage. For circuit schematics of preamps with input protection schemes that allow power supplies with outputs greater than 5V to be tested see: http://www.ko4bb.com/~bruce/LNPS.html http://www.ko4bb.com/%7Ebruce/LNPS.html Bruce ___ 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] New years apology
Dear all, [especially Bruce] I would like to formally and sincerely apologise for all offence caused, mistakes made, clangers dropped, annoyance , and general carelessness in what I have said, both on and off groups, to one and all, for the year ending 11th January 2008 [11-33pm]. I undertake to endevour to try to minimise the above [offence, etc], in the ensuing year, and wish all who read this all happiness and joy for the new year, and for the future. Cheers!...Don Collie jnr. ___ 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] OT? - Irish Submariners
Has anybody heard the one about the Irish Submariner who was previously a Mathematician? He would add the number of times the sub decended to the number of times it had surfaced, and divide the total by two - if there was one left over, he didn`t open the hatch. Cheers!...Don C. - Original Message - From: John Miles [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, January 06, 2008 4:59 PM Subject: Re: [time-nuts] 35601A as stand-in for 11848A ? John Miles wrote: I have a 35601A, although I've never done anything with it. Did you happen to spot any service/calibration manuals for the 35601A? I haven't found anything online yet, but one of the manual dealers I checked lists a hard copy. I do have a hardcopy manual for the 35601A but am not sure if I have a .PDF of it or not. Will check tomorrow and let you know. I can probably scan it easily enough if not, 11x17 foldouts excepted. I've never used the older 3047a, but the impression I have from the catalog info I've found so far is that the 3048a updated to the newer 3561a for narrowband analysis and added more internal sources to the 11848a for convenience; I'm hoping that much of the basic signal path for calibration and quadrature lock was left alone. The 11729B/C plus an 8662A (or even an 8640B) has everything most people will ever need for PN measurement. I need to measure things that are lower close in than the 11729/8662a combo noise floor; i.e. OCXO, direct synthesis from OCXO, amp/divider residual noise floors, down to 1-10 Hz offsets. Keep in mind, though, that without the 11848A's internal sources, you're going to have to supply some kind of reference source at the same frequency as the DUT. At that point, all the 35601A, 11848A, *or* 11729B/C is doing for you is providing a mixer, an LNA, and a quadrature-locking PLL in one box. They can all be used to compare two external sources directly if you want, with no 8662A required. Of those models, only the 11729B/C is really meant for standalone use (meaning, without a GPIB controller.) The 35601A doesn't have buttons on the front panel to let you change PLL bandwidths, override the default loop capture range, or anything else, and I don't believe the 11848A does, either. You either need a 3047A/3048A system, or some custom software that you'll have to write yourself. I can't speak from experience, but I don't know of any magical reason why the 35601A's or 11848A's noise floor will be much lower than the 11729's. See http://www.ke5fx.com/regen.htm for a case where the 11729C goes up against the TSC-5120A in a low-noise measurement scenario and gives a reasonable accounting of itself. If the 11848A has an advantage, it probably comes at offsets 1 kHz, where the 11729C doesn't do so well. Note that HP is careless with the 11729's noise-floor specs in some places, in that they report what is really the system noise floor, limited by the 8662A they assume (hope) you are using. One caveat: to use the 11729 to measure carriers below about 20 MHz, you *will* have to add an LPF prior to its LNA. Otherwise the upper sideband from the phase-detector mixer will enter the LNA and saturate it. Not the end of the world, but the additional LPF wouldn't be necessary with the 11848A, and I assume not with the 35601A either, because they have more internal filter options. (Which, again, have to be selected via GPIB.) Analyzer-wise, the fact that you need to look at offsets down to 1 Hz is a complication. You cannot use a conventional spectrum analyzer for that unless you have a new/fancy model with sub-1 Hz resolution. An FFT analyzer would be needed, and like Bruce suggests, a sound card may be the best way to go there. (I don't currently support sound-card input in my noise-measurement app, but I probably ought to. If someone needed that capability and wanted to help test it, it wouldn't be out of the question.) Renting/buying a E5052A or TSC5120A does get to be expensive How many significant digits are there in a 5120A price quote? $2.0*10^4, last I heard. :) -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] xtal oscillator phase noise
Bruce, do you get out much?Don. - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, December 30, 2007 3:42 PM Subject: Re: [time-nuts] xtal oscillator phase noise Henk The 30dB/decade phase noise slope could be the result of the effect of low pass filtering a power supply or reference source that has significant flicker noise. Lack of local RF feedback and /or high dc gain from base to collector in BJT buffer stages can produce significant flicker phase noise. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] EFC Input pin impedance for the HP 10544Aand10811-6011
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Surely the only impedance we`re concerned with is that at DC, since it`s only an adjustment. The input would look like 200K, in series with a constant voltage source [zero resistance ] of 6.4 Volts. Cheers!,..Don C. - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Don Collie [EMAIL PROTECTED]; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, October 29, 2007 9:01 PM Subject: Re: [time-nuts] EFC Input pin impedance for the HP 10544Aand10811-6011 Don Collie wrote: So, what *is* the input impedance? Cheers,...Don. It depends on the frequency. Network is complex 20k in series with 100-200pF plus another 20K to signal ground plus a few pF shunt C from the varicap to ground (a few pF) for the 10544A as a first approximation. For the 10811 100K in series with the 100pF varicap plus a few pF in paralle with 100K to signal ground. Bruce ___ 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] Parallel voltage regulators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Surely there will be an improvement in oven temparature regulation, by using a regulated supply, but whether or not this improvment is marginal or significant would have to be determined either by experiment [my favourite], or calculation. As you say Chuck : it`s eliminating [or reducing the effect of] one variable in the equation. Cheers,Don. - Original Message - From: Chuck Harris [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, October 26, 2007 12:29 PM Subject: Re: [time-nuts] Parallel voltage regulators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The simple answer is if the heater supply in unregulated, and the supply changes, it will take a little while before the heater control loop can compensate. While this is happening, the oven temperature will be slightly wrong, and the crystal frequency will be offset. Voltage regulation adds one more level of isolation to the oven temperature from changes in raw supply voltage. -Chuck Harris Matt Ettus wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY This may be a bit late in this [strangely contentious] discussion, but I have to ask why you need to regulate the heater voltage? If the voltage varies, the control loops will adjust accordingly. Unless the input voltage is higher than some safe range for the heater circuitry. Matt ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Parallel voltage regulators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, October 26, 2007 12:36 PM Subject: Re: [time-nuts] Parallel voltage regulators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Magnus Danielson wrote: From: Bruce Griffiths [EMAIL PROTECTED] Subject: Re: [time-nuts] Parallel voltage regulators Date: Thu, 25 Oct 2007 17:42:51 +1300 Message-ID: [EMAIL PROTECTED] Don Collie wrote: Hi Tom, If you really want to regulate the oven`s supply voltage, my National Voltage Regulator handbook shows that the LM317T will supply over 2 Amps, with an input/output differential of between 5, and 12.5 Volts. A single one of these should do the job OK. Cheers!,.Don Collie jnr. Never rely on typical specs always use the minimum spec which is 1.5A not quite enough. You want design-margin. Some of that toll will be in less than optimum heating, some will be in less heating in the first place (compared to upper limit) and for a power regulating aspect, headroom allows better regulations. In one design we had to parallel the regulators since the regulator the designer put in just barely was able to regulate the CPU core voltage. It worked, but at just rebooted at some vauge point an the memory tests. What actually happend was that as soon as it started to actually do anything, the regulator was running at its limit and output voltage dropped as the current was rising and the voltage supervision pulled the RESET. That's what you get from reading the typical reading on the CPU current and match that with the maximum rating of the power regulator. A no margin design. That designer had a few more flaws which was creeping around in that design, but let's not bring that can of worms open here. :) The 5A LM338 will be just fine. Infact, you can pull 8A out of it under certain conditions. Cheers, Magnus Hej Magnus The LM338 thermal design is also much easier (it has a much lower junction to case thermal resistance than an LM317) especially if the circuit is intended to operate over wide temperature (0 -40C or more) and mains voltage ranges (+-10% or more). The alleged problem with the high short circuit current is easily solved by using diodes with adequate current ratings in conjunction with a fuse to protect the transformer if it isnt rated to produce an 8A dc output. The startup current of the load (rubidium standard) may also vary with temperature and /or input voltage. Either find the manufacturers specifications or allow adequate margins. Worst case design is desirable even for one off circuits especially if the circuit is published. When the design is publicly available one is in effect transferring the production run problems associated with a marginal design to many individuals rather than a single factory or production line. Bruce I don`t think the higher current created when a fuse is used instead of near-instantaneous current limiting is alleged, but rather a real problem that can cause damage further down the line. Fast acting current limiting is preferable to all but the fastest fuses that are designed to protect semiconductors. Current limiting plus thermal shutdown in the regulator will protect both load, and regulator [and resovior capacitor, and diodes, and transformer] Commonly available fuses won`t give much protection to the load - especially the delay types often necessary with large filter capacitors. A precision, proven, high performance, low noise regulator like the 723 using an external pass transistor [or preferably a darlington], to avoid chip heating, and a well bypassed reference would be a lovely solution. Cheers!,Don C. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-triggerable Monostable?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Grant, What`s wrong with a diode and a capacitor?.Don C. - Original Message - From: Grant Hodgson [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, October 26, 2007 4:41 AM Subject: [time-nuts] Re-triggerable Monostable? ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I'm working on a synth. project which can take either an external 10MHz reference input or use an internal TCXO. It would be nice if the presence (or more importantly, failure) of the external 10MHz ref. could be detected automatically, and signaled to the user. There are, of course, a number of ways to do this. One is to use a level detecting circuit; simply AM detect the ext. ref. input and apply to a comparator. Lots of circuits to do this, no problem - but requires a number of components, unless there is some magic IC that will do it that I'm not aware of - I suppose a dual op-amp is all that's needed, plus a handful of discretes. Another option might be to use a re-triggerable monostable, which is constantly looking for the presence of (say) a falling edge every 100nS on the ext. ref. input line. It would seem that conceptually, this would be the easiest way, possibly using less components. Does anybody have any favourite circuits for this; or are there any caveats that are not mentioned in the plethora of monostable circuits that are mentioned on the 'web? Mnay (older) test equipments have an int/ext switch on the back, with an indicator on the front, but some newer ones detect the ext. ref. and switch automatically. I suppose that's not a problem on a box, which this synth. is not. The output would simply be a high/low digital line, the ext. ref. input will of course be buffered; I can cope with switching the 10MHz signals. Any ideas appreciated. regards Grant ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Parallel voltage regulators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Great idea!!,Don C. - Original Message - From: Max Robinson [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, October 27, 2007 10:07 AM Subject: Re: [time-nuts] Parallel voltage regulators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I do have some experience with temperature controlled ovens. I found that a long term plot of the temperature while using an unregulated supply on the oven heater showed small random variations due to voltage variations. When the oven heater was put on a regulated supply the line became flat. The problem here seems to be during the heat up cycle. The voltage doesn't need to be regulated during that time. You might try sensing the error signal and when it is outside of the linear control range you could switch in a parallel transistor and resistor to handle the warm-up current and it would switch out when the oven has stabilized at the lower current. Regards. Max. K 4 O D S. Email: [EMAIL PROTECTED] Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with tubes group send an email to, [EMAIL PROTECTED] - Original Message - From: Bill Hawkins [EMAIL PROTECTED] To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Friday, October 26, 2007 1:21 AM Subject: Re: [time-nuts] Parallel voltage regulators There is a concept in temperature control called feed-forward. In this case you would sample the supply line with an inverting amplifier and use it to increase the oven drive signal as the line voltage decreases. The goal is to keep the integral term from changing as the line voltage changes. It is not as easy as it sounds. Bill Hawkins ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.15.11/1094 - Release Date: 10/26/2007 8:50 AM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Parallel voltage regulators
I`ve always wondered about noise from batteries - please tell us more Bruce!! [also wondered about noise from the electrolytic action of aluminium, and tantalum electrolytic capacitors, and wondered if the reference bypass capacitor in a 723 should be a plastic dielectric type, rather than electrolytic]. ...Don C. - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, October 27, 2007 1:57 PM Subject: Re: [time-nuts] Parallel voltage regulators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Tom Clifton wrote: This has been a fascinating and educational thread! I have always been aware of noise coming from switching regulators - just have Argo or Speclab look at your laptop's sound card with no input signal and there is plenty to look at until you go to battery power. I had never considered diode switching noise in linear supplies, nor birdies from an assortment of logic devices - though I am a believer in healthy distribution of bypass capacitors... Now if Sears only sold Diehard batteries that put out 3.3 volts... Even batteries have noise, some types have more than others. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Parallel voltage regulators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Don Collie [EMAIL PROTECTED]; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, October 25, 2007 7:20 PM Subject: Re: [time-nuts] Parallel voltage regulators Don Collie wrote: Bollocs, Bruce! If National say it will do it, you can bet that it will. An LM338K will do the job too, but in my opinion it`s overkill, and in the event of a short circuit on the output of the regulator the current for the LM338 will only be limited to [...he gets the book..] 8 Amps [Typ], as against 2.2 Amp [Typ] for the LM317T. This would probably be too much for the transformer, rectifiers, and smoothing capacitor, effectively meaning that you would have no current limiting. If the input/output differential was kept in the range of 5 to 10 Volts, while the oven was stabilising, and the LM317 had an adequate heatsink, it would do the job nicely [and cheaper too!] Actually, it wouldn`t matter if the oven supply went unregulated while the temperature was stabilising, because you wouldn`t be using it for measurements during this time anyway - or is that a bit radical!? All the best!,..Don. - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Don Collie [EMAIL PROTECTED]; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, October 25, 2007 5:42 PM Subject: Re: [time-nuts] Parallel voltage regulators Show me where that is actually guaranteed on the datasheet. Only the inexperienced and the gullible fall into the trap of assuming every regulator (or any other device) will meet its typical specs. The designer of this particular regulator actually cautions against this cavalier approach to design. If you worried about the transformer a simple fuse (resettable or otherwise) will surely cure that problem. Bruce Hi Bruce, I`ve got the National Semiconductor Corporation Voltage Regulator Handbook [1982]. On page 3-3, the leftmost graph shows the LM117/217/317 as having its current limit, with a junction temperature of 125 degrees Centigrade, at 2.25 Amps over the input/output differential of 5 to 10 Volts. The point being, that if you use a higher current regulator, you loose the advantage of the regulator`s current limiting, and perhaps, its thermal shutdown protection as well. A fuse *might* protect the semi`s down the line, but often it`s the semi`s that fail before the fuse, and the peak current that might flow before the fuse blows might be many times the current limit of the regulator [which is nearly instantaneous], and if so, damaging, so it is wise to run these regulators near their current limit, just as you would set the current limit on a bench supply to just above the working current. I find your use of the emotive words inexperienced, gullible, and cavalier saddening. Wishing you well,Don. ___ 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] Parallel voltage regulators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Tom, If you really want to regulate the oven`s supply voltage, my National Voltage Regulator handbook shows that the LM317T will supply over 2 Amps, with an input/output differential of between 5, and 12.5 Volts. A single one of these should do the job OK. Cheers!,.Don Collie jnr. - Original Message - From: Tom Clifton [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Thursday, October 25, 2007 12:33 PM Subject: [time-nuts] Parallel voltage regulators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY A question for those that might know (or have an opinion)... I have in hand an LPRO rubidium reference that requires 1.7 amps at 24 volts while the oven warms, dropping to 500ma while it runs. Can I parallel three or four 7824 TO220 style 1 amp regulators with a quarter ohm half watt equalizing resistor on the output of each one? At maximum load there would be a quarter volt drop across the resistors and the LPRO is stated to be ok running on 16 to 32 volts. Tom __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Parallel voltage regulators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Bollocs, Bruce! If National say it will do it, you can bet that it will. An LM338K will do the job too, but in my opinion it`s overkill, and in the event of a short circuit on the output of the regulator the current for the LM338 will only be limited to [...he gets the book..] 8 Amps [Typ], as against 2.2 Amp [Typ] for the LM317T. This would probably be too much for the transformer, rectifiers, and smoothing capacitor, effectively meaning that you would have no current limiting. If the input/output differential was kept in the range of 5 to 10 Volts, while the oven was stabilising, and the LM317 had an adequate heatsink, it would do the job nicely [and cheaper too!] Actually, it wouldn`t matter if the oven supply went unregulated while the temperature was stabilising, because you wouldn`t be using it for measurements during this time anyway - or is that a bit radical!? All the best!,..Don. - Original Message - From: Bruce Griffiths [EMAIL PROTECTED] To: Don Collie [EMAIL PROTECTED]; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, October 25, 2007 5:42 PM Subject: Re: [time-nuts] Parallel voltage regulators Don Collie wrote: Hi Tom, If you really want to regulate the oven`s supply voltage, my National Voltage Regulator handbook shows that the LM317T will supply over 2 Amps, with an input/output differential of between 5, and 12.5 Volts. A single one of these should do the job OK. Cheers!,.Don Collie jnr. Never rely on typical specs always use the minimum spec which is 1.5A not quite enough. Bruce ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Don Collie wrote: Gidday Bruce, Yes, the temperature sensor [a diode or thermistor, etc] would be placed in thermal contact with [the plate attached to] the cold side of the pile [there would be a finned heatsink attached to the hot side, and an expanded polystyrene sheet between the two sides, as much as possible]. The voltage developed across the sensor would be fed to one input of a comparitor [or what have you - PID controller etc]. There would be a voltage reference applied to the other input so as to make a conventional negative feedback control loop. If the loop gain was high enough, the system would operate in switch mode to maintain the cold side at a constant temperature. If the gain is lower the loop will operate in linear mode [ie : non oscillatory, but sluggish]. The advantage of a high gain loop is that there is no setting up necessary [self adjusting] - the thing will find the right temperature, and then cycle on/off to maintain it. [providing the temps involved are within the compliance of the system [Peltier, ambient temp.,etc]] Does a PID control loop *always* out-perform an oscilliatory loop? [or does that depend on?] Another way to reduce the change of temperature at the crystal [and circuitry], would be to put a substance with thermal resistance between the plate [cold side], and a mass of copper or aluminium, which housed the crystal etc. This oven would have to be lagged. Please correct me if I`m wrong, but as the comparitor gain is increased, both the frequency of the temperature variation [at the sensor], and its amplitude are reduced. A PID controller would be the *quickest* way to stabilise the temperature, but this is a secondary concideration : the primary concideration would be temperature stability - it wouldn`t really matter if it took an hour or two to stabilise]. If the object of the exercise is to make a *single* oven, The current supplied to the Peltier by the comparitor could be arranged to be reversable, depending on whether the temp at the sensor was more, or less than the set temp. Thus it would be possible to maintain the 25 degree temp, as the ambient temp changed from [say] 0 to 70 degrees. Not quite sure what to do about the [diode-like] barrier voltage of the Peltier pile. Do crystals do better/last longer/less ageing at lower temperatures? - you would think so. Cheers,..Don. A temperature control system without an integral term will always have an offset from the desired setpoint. The offset will depend on the ambient temperature and the gain. Depending on the amount of heat being pumped a convection cooled heatsink will probably be inadequate. At least a blown heatsink (or better yet a water cooled heatsink) may be necessary if the heat being pumped is substantial. For example, try using a 70Watt single stage Peltier module on an convection cooled heatsink to cool the to surface to below freezing. At first ice forms on the cold plate, but gradually as the heatsink warms up the ice melts and the cold plate becomes fairly warm. It may be possible to use a cpu heatsink with integral heatpipes, at least some of these allow a reasonable thickness of insulation to be used. The usual technique is to actually sense and control the Peltier device current. Either a high frequency switchmode current controller with an output filter to reduce the Peltier ripple current or an analog driver can be used. Surely the oscillation frequency depends primarily on the thermal transport delays within the system? If self oscillating temperature controllers are so effective why are they no longer used for precision temperature control? If the control loop responds too slowly then it wont effectively correct the effects of ambient temperature changes. Placing a large thermal resistance between the cold plate and the oven mass is somewhat counterproductive. The oscillator will dissipate power that has to be removed, limiting the maximum usable oven mass to ambient thermal resistance. If this thermal resistance is too large most of the heat flow will be via the oven thermal insulation at which point temperature control tends to be somewhat ineffective. Crystals operating at cryogenic temperatures were at one time found to age very slowly. However the effect of temperature on aging depends on the aging mechanism(s) involved. Peltier devices used to regulate the temperature of large baseplates typically achieve a temperature stability of around 0.1C. When used to control the temperature of smaller objects like laser diodes a baseplate temperature stability of 0.001-0.002C has been achieved. Objects of intermediate size like some ECDLs routinely achieve a stability of 0.01C or better when a Peltier cooler is used. Bruce - Original Message - From
[time-nuts] Delusions
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Dear Bruce, This is Donalds wife can you please explain to me the last sentince of your email to my husband. Cause to me it sounds like your giving him a hardtime. I hope your feeling alright your self. Meriam ___ 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] Peltier cooled double crystal oven
Hi Enrico, I accidently deleted your message to me, would you please re-send it to me. Also, I would like to respond to the points you raise on the group, please, so could I please have your permission to do this? Thankingyou,Don C. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Hal, I was thinking of attaching a temparature sensor [AKA Star Treck] to the cold side of a Peltier [what`s the other type? Are they available/better?] pile. and driving the pile from the output of some sort of servo loop to maintain a temparature of ,say , 0 Degree C. If you wanted a double oven, you could heatsink a small oven, containing the crystal, the oscillator, and buffer[s] to this, and use a second servo loop to raise the temparature of this to 25 Degrees C working against the Peltier. In this way, you could maintain the crystal, and circuitry at 25 Deg C., over an ambient temparature of 0 to ,say 70 Deg C. Yes, you can cut a crystal to have an inversion temp at 25Deg C. [well certainly with an AT cut - I`m not sure about the SC cut.] Cheers,Don C. - Original Message - From: Hal Murray [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 16, 2007 5:49 AM Subject: Re: [time-nuts] Improving the stability of crystal oscillators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The resonator inversion temperature occurs at 70-80 degrees Celsius, depending on the cut angles. Is there something magic about quartz that has a turnover in the region that just happens to be handy for OCXOs? Or is it the other way around: people chose the cut angle to get a temperature that works well for ovens? Could I cut a crystal with a temperature at (say) 0C or something handy for Peltiers? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.488 / Virus Database: 269.14.12/1072 - Release Date: 10/15/2007 5:55 PM ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Has anyone concidered using a small Peltier pile to maintain the crystal`s temparature. I understand that these devices will heat or cool, so it would be possible to maintain the crystal temparature at , say, 25 degrees celcius, over a range of ambient temparatures [perhaps 0 to 70 degrees]. There would be several advantages in this approach. Cheers!,Don Collie jnr. ___ 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] Improving the stability of crystal oscillators
Thanks for that John. I`ve always wanted to play arround with one of these [Peltier] modules. They can now be bought quite cheaply. I envisage a double oven, with the inner oven heated [to 25 degrees], by conventional means, while the Peltier pile cools the inner oven. This way you could use a precision temparature regulator for the inner oven, while the outer oven would only have to cool. You wouldn`t be talking too many pumped watts, here. FWIW etc.,...Don C. - Original Message - From: Neon John [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, October 14, 2007 11:19 AM Subject: Re: [time-nuts] Improving the stability of crystal oscillators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Nah, not for this application. A Peltier module typically has a COP of 1. That is, it moves a watt of energy for each watt consumed. Thus, for each watt moved, two watts have to be dissipated to air. I can't imagine a well-insulated quartz oscillator needing more than a watt or two of cooling at the most. A heat sink capable of handling 4-5 watts should do the job just fine. Don: I've seen peltier-controlled ambient ovens before but I can't recall the details. I'm fairly sure one was a Fluke precision voltage transfer standard in which the zener reference diode was controlled to a constant temperature. The advantage of using room temperature, e.g., 70 deg F, is that under most conditions, the peltier module is doing little to nothing, perhaps just ridding the ovenized unit of the few milliwatts dissipated in the circuit itself. I've used multiple cascaded modules to cool a nuclear detector (Silicon surface barrier diode) to reduce its noise. Not as good as LN2 but much cheaper to operate. John On Sat, 13 Oct 2007 13:26:52 -0700, Brooke Clarke [EMAIL PROTECTED] wrote: Hi Don: They are very inefficient to the point that a system that's supposed to cool something may heat it because of all the heat generated by the module. It takes a huge amount of heat sinking or liquid cooling to get them to work. Don Collie wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Has anyone concidered using a small Peltier pile to maintain the crystal`s temparature. I understand that these devices will heat or cool, so it would be possible to maintain the crystal temparature at , say, 25 degrees celcius, over a range of ambient temparatures [perhaps 0 to 70 degrees]. There would be several advantages in this approach. -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com -- best little blog on the net! Tellico Plains, Occupied TN I like you ... you remind me of me when I was young and stupid. ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.488 / Virus Database: 269.14.9/1069 - Release Date: 10/13/2007 7:26 PM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: You know your getting old when...
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Don` you mean: (-: aixlsyd ? - Original Message - From: Didier Juges [EMAIL PROTECTED] To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Friday, September 07, 2007 11:04 AM Subject: Re: [time-nuts] OT: You know your getting old when... Sure sign of dyslexia :-) Didier -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Harris Sent: Thursday, September 06, 2007 5:35 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] OT: You know your getting old when... Geeze! What if you do both? -Chuck Harris ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.485 / Virus Database: 269.13.8/993 - Release Date: 9/6/2007 3:18 PM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Time may not exist
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Look, If time does not exist, then this group is gonna look a little sick. Let`s speak no more of this...Don C. - Original Message - From: Tim Shoppa [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Sunday, July 29, 2007 2:50 AM Subject: Re: [time-nuts] Time may not exist ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Didier Juges [EMAIL PROTECTED] wrote: I think what is proposed is that time, while real, would not be a fundamental dimension of the universe, it would be a dimension of convenience, due to our lack of understanding of the underlying principles. It is interesting considering that a lot of people in the last half century or so have tried to do the opposite: relate everything to time simply because time is what we can measure most accurately, at least at the macro scale. I am an engineer, so this makes no difference to me, but I find it fascinating. Maybe I should have been a physicist... I was a physicist. After hearing way too many years about super-string theory, coordinate-free notation, etc. I quit, and now my day job consists of building/maintaining a supervisory control system that hurtles metal subway trains 450 to 600 feet long from a stop to 60 MPH and back again every minute or two, 4 times a day. To say that I quit is one interpretation, an equally valid interpretation would be that I completely flamed out in my first post-doc :-). I am so much happier now that I get to use coordinates again :-). It is increasingly frustrating that the several thousand clocks around the railroad are never synchronized, though! Tim. ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.23/924 - Release Date: 7/28/2007 3:50 PM ___ 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] Homebrew primary standard?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Sorry, I forgot three of these : ;-)..Don C. - Original Message - From: Don Collie [EMAIL PROTECTED] To: Tom Van Baak [EMAIL PROTECTED]; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 28, 2007 1:00 PM Subject: Re: [time-nuts] Homebrew primary standard? ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] It is possible to build a standard, of very good long term stability, by amplifying the radiation produced by a simple incandesent light bulb. The frequency produced is well within the capabilities of present technology..Don C. - Original Message - From: Tom Van Baak [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 28, 2007 5:59 AM Subject: Re: [time-nuts] Homebrew primary standard? ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Has there been any attempts (or successes) at someone outside of a national laboratory, and commercial RD groups to build a primary frequency/time standard? Two attempts to build hydrogen masers that I know of; little or no progress. I am not sure if there is anything that would prevent an individual from building a cesium standard of the quality seen in early models from NPL and NIST, or an industrial style (compact Ramsey cavity) standard. -Michael Yes, it would be possible. I know that several of us have considered it, for a few minutes at least. It would require some expertise in physics, electronics, glass and metal fabrication, vacuum systems, magnet design, electron multipliers, and who knows that else. You'd go through many prototypes. To see if it's working you might want another one in-house. You'd learn a great deal. It would be an amazing story. In the end, you'd end up with a standard accurate to one part in ten to the 10th or 11th that would work for hours or even days at a time. The reason no one has tried it, I believe, is that you can get the same or better accuracy with a simple $75 GPS receiver today. It would seem motivation for the project would be the biggest problem. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.22/923 - Release Date: 7/27/2007 6:01 PM ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.22/923 - Release Date: 7/27/2007 6:01 PM ___ 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] Why Cesium and Rubidium only
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Please excuse my ignorance [I marvel/wonder at some of the essotevric comments on this group], but why are atomic clocks reliant on these two rare elements? - why not mercury, or water vapor, they are a lot easier to find. Ignorantly yours,...Don Collie jnr. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Time may not exist
Money *does* exist, although not in large enough quantaties to be of much practical use, usually...Don C. - Original Message - From: [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 28, 2007 8:39 AM Subject: Re: [time-nuts] Time may not exist ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Interesting article. But I see implications to the idea of time=money. -Brian, WA1ZMS -- Original message -- From: WB6BNQ [EMAIL PROTECTED] Tom, Very interesting concept ! But I do not think the business world is going to buy it. BillWB6BNQ Tom Clifton wrote: Just to stir the pot a little - I'm providing a link to Discover magazine - a tome of great repute and a source of information on scientific discoveries of epic magnitude... Enjoy... http://discovermagazine.com/2007/jun/in-no-time Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos more. http://mobile.yahoo.com/go?refer=1GNXIC ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.22/923 - Release Date: 7/27/2007 6:01 PM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Time may not exist
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Furthermore : If time=money, and money is in short supply, then there`s never enough time [to get things done]. This is verifiable empirricly, and may be the reason why rich people live longer, and why not so productive workers are paid less. Other conclusiond can be drawn, but I thought of these ones, myself.Don Collie jnr. - Original Message - From: [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 28, 2007 8:39 AM Subject: Re: [time-nuts] Time may not exist ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Interesting article. But I see implications to the idea of time=money. -Brian, WA1ZMS -- Original message -- From: WB6BNQ [EMAIL PROTECTED] Tom, Very interesting concept ! But I do not think the business world is going to buy it. BillWB6BNQ Tom Clifton wrote: Just to stir the pot a little - I'm providing a link to Discover magazine - a tome of great repute and a source of information on scientific discoveries of epic magnitude... Enjoy... http://discovermagazine.com/2007/jun/in-no-time Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos more. http://mobile.yahoo.com/go?refer=1GNXIC ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.22/923 - Release Date: 7/27/2007 6:01 PM ___ 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] Homebrew primary standard?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] It is possible to build a standard, of very good long term stability, by amplifying the radiation produced by a simple incandesent light bulb. The frequency produced is well within the capabilities of present technology..Don C. - Original Message - From: Tom Van Baak [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 28, 2007 5:59 AM Subject: Re: [time-nuts] Homebrew primary standard? ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Has there been any attempts (or successes) at someone outside of a national laboratory, and commercial RD groups to build a primary frequency/time standard? Two attempts to build hydrogen masers that I know of; little or no progress. I am not sure if there is anything that would prevent an individual from building a cesium standard of the quality seen in early models from NPL and NIST, or an industrial style (compact Ramsey cavity) standard. -Michael Yes, it would be possible. I know that several of us have considered it, for a few minutes at least. It would require some expertise in physics, electronics, glass and metal fabrication, vacuum systems, magnet design, electron multipliers, and who knows that else. You'd go through many prototypes. To see if it's working you might want another one in-house. You'd learn a great deal. It would be an amazing story. In the end, you'd end up with a standard accurate to one part in ten to the 10th or 11th that would work for hours or even days at a time. The reason no one has tried it, I believe, is that you can get the same or better accuracy with a simple $75 GPS receiver today. It would seem motivation for the project would be the biggest problem. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.22/923 - Release Date: 7/27/2007 6:01 PM ___ 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] Building a DC Block Thingy....
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] 3Tr`s can be very noisy - if the current drawn is constant, perhaps a decoupled resistor would be better..Don C. - Original Message - From: Rob Kimberley [EMAIL PROTECTED] To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Saturday, July 28, 2007 7:33 AM Subject: Re: [time-nuts] Building a DC Block Thingy ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] My first thought here would be to use a small 3 pin 5V regulator to drop the DC down, and then capacitively couple in and out to let the RF through. Interesting to see what other comments you get. Rob K -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jason Rabel Sent: 27 July 2007 20:12 To: 'Discussion of precise time and frequency measurement' Subject: [time-nuts] Building a DC Block Thingy ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] om I have a NTS-200 on the way, but one thing about them is their GPS power output is 12V instead of the usual 5V. I really didn't want to modify the board any in an irreversible fashion so I was hoping to build an inline coupler that I could block / sink the 12V current. I have a Symmetricom SmartSplitter, and I know that *should* do the job as long as a lower numbered port is supplying power, but I really don't want to take the accidental risk of sending 12V to my antenna. Doing the math to sink 25ma of current would require a 480 ohm resistor... That should make the receiver happy and think all is well. But that's as far as my knowledge goes. What size capacitor would I need to use? Do I need to add an inductor in series with the resistor? Jason ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.22/923 - Release Date: 7/27/2007 6:01 PM ___ 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] FW: Pendulums Atomic Clocks Gravity
It`s just like the fly in the glass jar scenarmino : Just imagine a glass jar [with a lid] with a fly flying around inside the jar. The jar is being accelerated towards it`s inevitable demise when it hits the sun. Does the fly stay in the same position in the jar, or is it pushed towards the end of the jar furtheest from the sun. Now I don`t know the answer to this one..but I sure wouldn`t like to bee the fly. Affectionately yours,...Don Collie jnr. - Original Message - From: Dr Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, May 30, 2007 12:49 PM Subject: Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity Bill Beam wrote: Not true. Very simple experiments will show occupants of the satellite that they are in a non-inertial reference frame. (Release a few test masses about the cabin and you will observe that they move/accelerate for no apparent reason, unless the satellite is in free fall which you'll know soon enough,) The experimenter must conclude that the satellite is undergoing acceleration due to the influence of an attractive (gravitational) field. Except when released at rest with respect to the satellites centre of mass the test masses will both drift towards the satellites centre of mass. The outermost test mass will have too slow an orbital speed to remain at the position it was released and the innermost test mass will have too large an orbital speed to remain at the position at which it was released. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.472 / Virus Database: 269.8.1/822 - Release Date: 5/28/2007 11:40 AM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] OT: eBay bidding question
Nothing worth having ever came easily...Don C. - Original Message - From: [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Sunday, April 29, 2007 11:17 AM Subject: Re: [time-nuts] OT: eBay bidding question In a message dated 4/28/2007 15:59:47 Pacific Daylight Time, [EMAIL PROTECTED] writes: I believe this is correct, that is where sniping does not work too well (manually or automatically). If you wait for the last second, and your bid is below the reserve, you may not even realize until after the auction is over. It actually still works the way I want it to. I bid as high as I am willing to pay, and if it's too low, I don't get the item. Pretty simple. Frustrating, but simple :-) Well, you can also contact the seller after the auction and offer them to buy the item A) in a private auction B) outside of Ebay (against their rules I think, not sure if this counts for failed auctions as well), or tell them to relist it with a more realistic price. One would be surprised how many sellers are just itching to get rid of their items, even below their original reserve once they went through an unsuccessful listing... One just has to be a bit resourcefull. Also, a reserve if used successfully is a way to prevent having to sell an item well below a pain point to the seller. A reserve with a low initial bid is a way to get around human nature and make people start bidding, which - as said earlier by someone else - will make the flock go crazy once an initial (low) bid has been placed by someone. It's all about human nature. The most interesting experience about auction addiction (similar to gambling addiction in my opinion) is going to a real life Test Measurement auction, and seeing the unsuspecting crowd sit in front and the following happen: * Bidders bid against themselves. This happened so far in every auction I went to. The Auctioneer just loves these kinds of naive folks, and it makes for nice entertainment. * Bidders bid against an imaginary bidder, the auctioneer will call a bid from the back of the room that does not exist. Who can prove this happened. Thats why the professional bidders sit as far back in the room as possible. I have also witnessed this numerous times. * Bidders get into an adrenaline rush, and bid up items far beyond their new retail price. One would be surprised, this happens ALL the time, especially for high-desirability items such as laptops etc. * Bidders will buy sight-unseen. I went to a recent auction where there were about 12 Agilent Spectrum analyzers for sale. Most of them had stickers on them Repair etc. I tried them all, all of them broken in one way or another. Again human nature prevailed and folks bought them in a buying frenzy with no return right for outrageous prices (far above what one would pay on Ebay) - the pro's were just sitting back and asking themselves what in gods name is going on - LOL. Ebay is great if you have a good strategy on how to use it. No buyers premium, world-wide sourcing, $2K insurance, great prices if you wait long enough. I have so far found everything I needed on it at the price I wanted to pay. For one item (a 2GHz scope plug-in) this took me over two years to do, but in the end I got it :) bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.467 / Virus Database: 269.6.2/779 - Release Date: 4/28/2007 3:32 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] 10MHz to 32MHz?
I have learned the hard way that the 4046 needs input signals whose risetimes [and falltimes?] are not too long , and It`s probably best to use the inhibit function, and avoid using the source follower. The output resistance can then be absorbed into the first resistor of the loop filter, outside the package. I`ve played around with the 4046B, and have built a synchroniser to overcome thermal drift in a signal generator that I own. Funny thing is, even a 15.625Hz [ie 15Hz approx] frequency at the phase detector is quite sufficient to practically eliminate thermal frequency drift, and with a long loop time constant, the output signal, when mixed with another steady frequency, sounds very clean. Lockup time is a couple of seconds or so. Lots of fun. The thing that puzzles me is: why is the plot of VCO voltage versus time different when locking from below to locking from the same initial frequency difference when locking from above. It`s a pity you can`t predict PLL lockup characteristics using linear algebra - or do you need a particular kind of phase [or frequency] detector that would enable you to do this? FWIW, Cheers!..Don C. To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, April 23, 2007 3:24 PM Subject: Re: [time-nuts] 10MHz to 32MHz? Hi John, talking about 4046 PLL's: we are looking for a better Spice model for the 4046 PLL, but only found an HC4046 model in Pspice. That part is too slow. Would you have a pointer to a better chip such as the 74HC4046 etc? thanks, Said Not sure; I've never used any SPICE other than LTSpice, and never tried to use a 4046 in it. I'll bet they have a model for it somewhere, though. I would think you could just play with the propagation delay values in the HC4046 model to make it work with any other logic family. I've built a ton of PLLs with the PLLatinum and Analog Devices chips, but only one with a 4046. -- john, KE5FX ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 269.5.9/773 - Release Date: 4/22/2007 8:18 p.m. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] OT: Knifephoolery
How much was the Chef?Don C. - Original Message - From: Rasputin Novgorod [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, April 22, 2007 3:34 PM Subject: Re: [time-nuts] OT: Knifephoolery Hmm. ...and I just bought a set of three Chef's knives for my kitchen for $500. /b --- Jack Hudler [EMAIL PROTECTED] wrote: Just please tell me they're not serrated, know how to use a steel, and you keep them holder or leather pouch. Hi Jack: I love cooking, as a hobby (and surprisingly, it's a chick magnet). I've always wanted a good set of knives but didn't know what to buy, so didn't. This summer I've signed up for a professional French chef class and we are required to own and bring a good set of four knives: Chef, Boning, Paring and Scalloped Slicer. They recommended several different makes and models, in different price ranges. mine came with a Knife carrying Case: 16 Slot, fake leather. My knives (S series Henkels): http://usa.jahenckels.com/index.php?subcategory=5 . 9 Chef Knife . 6 Boning Knife . 3.5 Paring Knife . 10 Scalloped Slicer . 10 Sharpening Steel . vegetable peeler . 7 Carving Fork We will spend three days on knives: 1) care, sharpening and then cutting vegetables. 2) cutting up and de-boning chickens. 3) cutting up fish. I've refrained from sharpening until the class, even though I'm a cabinetmaker and trained in sharpening chisels and plane blades, so know how to use a water stone. I've been using them for a few days, and what a joy they are to use. If you cook, get yourself a good set of knives; at least, spend $100 and get a good 9 chef's (french) knife. You'll have and use it for the rest of your life. /b __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 269.5.7/771 - Release Date: 4/21/2007 11:56 a.m. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Stepping up the output of an OCXO
Why not use an optocoupler as an isolation amplifier? - to the best of my knowledge it would provide infinite isolation. Cheers,...Don Collie - Original Message - From: Dr Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, February 03, 2007 12:29 PM Subject: Re: [time-nuts] Stepping up the output of an OCXO Ulrich Bangert wrote: Bruce and Didier, i had the opportunity to measure the output to output as well as the output to input isolation of a diy MAX477 based distribution amplifier very similar to the TADD-1 (but not identical). The output to output isolation was in the order of 75 dB while the output to input isolation was in the order of 90 dB. This is not too bad for this simple design and perhaps more than adequate for most of us time nuts. I have not been able to measure the increase in terms of noise figure but this statement must be read as: The increase in noise figure was less than the noise floor of my equipment. Nevertheless my statement of beliefs is the same as Bruce's one: A single transistor stage may be more easily optimized than a multi-transistor-design. Best regards Ulrich Bangert Ulrich Since the MAX477 has an input noise of around 5nV/rtHz at 10MHz compared to around 1nV/rtHz for a low noise bipolar transistor, the MAX477 may be expected to be have a phase noise floor of up to 14dB higher than that of an optimised discrete transistor amplifier. This however may not be a concern unless one has an OCXO with a phase noise floor approaching the state of the art (-180dBc/Hz). There are wideband opamps with lower noise than the MAX477 available. One could always use 4 MAX 477s inparallel to lower the phase noise floor by about 6dB. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.17.20/664 - Release Date: 2/2/2007 3:42 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Stepping up the output of an OCXO
I am depantsd, Dr Bruce ;-)Don. PS : How much reverse transconductance would a typical high speed opto have [ball park figure]? What sort of SNR is necessary to prevent an uncertaincy of 1part in 10^13? - Original Message - From: Dr Bruce Griffiths [EMAIL PROTECTED] To: Don Collie [EMAIL PROTECTED]; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, February 03, 2007 6:43 PM Subject: Re: [time-nuts] Stepping up the output of an OCXO Don Don Collie wrote: Why not use an optocoupler as an isolation amplifier? - to the best of my knowledge it would provide infinite isolation. Cheers,...Don Collie And lots of noise. You will need a cleanup PLL on the output side. Also optocoupler isolation isn't infinite, there is a finite capacitance between the closely spaced emitter and detector. Not all optoisolators are fast enough. The most effective way of using optical isolation is in fact to modulate a stabilised laser and then couple the output into a fibre. This technique is employed to distribute stable frequencies to Radio telescope antennas especially when a large number are employed in an array. A phase locked loo is used at the other end to cleanup the signal after the photodetector. Fibre has the advantage in this and other applications where long runs are involved that its propagation delay tempco is significantly lower than that of coax. It is also possible to use fibre stretchers and other techniques to actively compensate variations in the fibre propagation delay. Isolation becomes particularly important when one mixes a pair of signals a few Hz apart and then analyses the zero crossing times of the mixer output beat signal. It is easier to achieve a high isolation between RF frequencies than at frequencies of a few Hz, JPL found fibre optic isolation can be invaluable in this case. Bruce -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.17.20/664 - Release Date: 2/2/2007 3:42 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
