Re: [time-nuts] 5060A question
Dave Carlson wrote: > Hello, > > Since the source of the noise is the vibration of the Hot Wire Ionizer > ribbon inside the CBT it will require using something other than pressure on > the outer container to snuff it out. The outer steel of the CBT is rigid. > > Dave > > Which is why it transmits the sound so well. Its not the pressure but the acoustic damping. However material which has high acoustic damping also tends to be a good thermal insulator, so care must be taken to avoid overheating components. The idea isnt so much to stop the ribbon vibrating but attenuate the transmission of the vibration to the surrounding structures and ultimately the air. A correctly sized and located acoustic resonator with appropriate internal damping can help by absorbing the sound caused by the vibration. 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] 5060A question
Hello, Since the source of the noise is the vibration of the Hot Wire Ionizer ribbon inside the CBT it will require using something other than pressure on the outer container to snuff it out. The outer steel of the CBT is rigid. Dave - Original Message - From: "Bruce Griffiths" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" Sent: Monday, January 07, 2008 9:58 PM Subject: Re: [time-nuts] 5060A question Magnus Danielson wrote: >> Hej Magnus >> >> Do you mean an active noise cancellation system?? >> > > No, you could do that too, but I was basically refering to a simple box > tuned > in size to cancel at 2 kHz. Toss in a thick cloth for additional resistive > damping. > > You could even go Helmholtz if you want. > > Simple passive cancelation. Classical acoustical approach. For 2 kHz it is > in > reasnoble sizes. > > Another thing is to put heavy lead-rubber on the metal faces to make them > less > of a resonator/radiator. That mod can be done inside the box. > > There are a whole bunch of other tricks. Pressing on the surfaces of the > whining chamber will make it stiffer and provide a higher acoustical > impedance. > Pressing using rubber blocks, from say silicon rubber, is known to work. > > Cheers, > Magnus > > Hej Magnus Its a pity that the old rho-c impedance matched high dissipation rubber method only works under water. 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] 5060A question
Magnus Danielson wrote: >> Hej Magnus >> >> Do you mean an active noise cancellation system?? >> > > No, you could do that too, but I was basically refering to a simple box tuned > in size to cancel at 2 kHz. Toss in a thick cloth for additional resistive > damping. > > You could even go Helmholtz if you want. > > Simple passive cancelation. Classical acoustical approach. For 2 kHz it is in > reasnoble sizes. > > Another thing is to put heavy lead-rubber on the metal faces to make them less > of a resonator/radiator. That mod can be done inside the box. > > There are a whole bunch of other tricks. Pressing on the surfaces of the > whining chamber will make it stiffer and provide a higher acoustical > impedance. > Pressing using rubber blocks, from say silicon rubber, is known to work. > > Cheers, > Magnus > > Hej Magnus Its a pity that the old rho-c impedance matched high dissipation rubber method only works under water. 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] 5060A question
From: Bruce Griffiths <[EMAIL PROTECTED]> Subject: Re: [time-nuts] 5060A question Date: Tue, 08 Jan 2008 15:31:17 +1300 Message-ID: <[EMAIL PROTECTED]> Hej Bruce, > > Maybe set up a tuned box around it to cancel whine. > > > > MVH > > Magnus > > > > > Hej Magnus > > Do you mean an active noise cancellation system?? No, you could do that too, but I was basically refering to a simple box tuned in size to cancel at 2 kHz. Toss in a thick cloth for additional resistive damping. You could even go Helmholtz if you want. Simple passive cancelation. Classical acoustical approach. For 2 kHz it is in reasnoble sizes. Another thing is to put heavy lead-rubber on the metal faces to make them less of a resonator/radiator. That mod can be done inside the box. There are a whole bunch of other tricks. Pressing on the surfaces of the whining chamber will make it stiffer and provide a higher acoustical impedance. Pressing using rubber blocks, from say silicon rubber, is known to work. Cheers, Magnus ___ time-nuts mailing 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] 5060A question
Magnus Danielson wrote: > From: <[EMAIL PROTECTED]> > Subject: Re: [time-nuts] 5060A question > Date: Mon, 7 Jan 2008 20:43:55 -0500 > Message-ID: <[EMAIL PROTECTED]> > > >> Thanks to everyone who gave me feedback about the 2KHz whine >> from my HP-5060A. It appears to be the nature of the design >> and I'm not quite willing to try and re-design the oven controller >> to convert it from 2KHz AC to DC. >> >> I guess my 5060A will continue live in the back room where it's >> not heard much. >> > > Maybe set up a tuned box around it to cancel whine. > > MVH > Magnus > > Hej Magnus Do you mean an active noise cancellation system?? 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] 5060A question
From: <[EMAIL PROTECTED]> Subject: Re: [time-nuts] 5060A question Date: Mon, 7 Jan 2008 20:43:55 -0500 Message-ID: <[EMAIL PROTECTED]> > Thanks to everyone who gave me feedback about the 2KHz whine > from my HP-5060A. It appears to be the nature of the design > and I'm not quite willing to try and re-design the oven controller > to convert it from 2KHz AC to DC. > > I guess my 5060A will continue live in the back room where it's > not heard much. Maybe set up a tuned box around it to cancel whine. MVH Magnus ___ time-nuts mailing 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] 5060A question
Thanks to everyone who gave me feedback about the 2KHz whine from my HP-5060A. It appears to be the nature of the design and I'm not quite willing to try and re-design the oven controller to convert it from 2KHz AC to DC. I guess my 5060A will continue live in the back room where it's not heard much. -Brian, WA1ZMS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Frequency Standards & Services Sent: Wednesday, January 02, 2008 1:21 PM To: Time Nuts List Subject: Re: [time-nuts] 5060A question This was one of the reasons that HP eventually went to the DC oven controller. Even the early 5061A had this same problem. The 5060A and the early 5061As had an AC oven controller. When they changed to the DC controller, it probably saved a lot of people from insanity. some of the other reasons were the transformer taps that had to be changed when a new tube was installed, parts issues improved design, manufactureability, etc... Chuck Chuck Norton Frequency Standards & Services 2727 E. Palmer Park Blvd. Ste. 100 Colorado Springs, CO. 80909-5068 719-228-0540 Voice 719-228-9009 Fax ___ time-nuts mailing 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?
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] 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.
Re: [time-nuts] How to measure regulator noise?
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 -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing 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?
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. Been a while since I used a 3561A but can't the input tolerate up to 5 vdc? I may be thinking of something else. Great instruments - wish I still had access to one. There's a lot of good info in the support docs (not the 2 vol op-service manual) for the 3561A if you have any of that. For this particular task maybe one of the high resolution (16 bit) USB scopes might be appropriate? (in FFT mode) DaveB, NZ - Original Message - From: "John Ackermann N8UR" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" Sent: Monday, January 07, 2008 9:17 AM Subject: [time-nuts] How to measure regulator noise? > I'm experimenting with some low noise regulators, and want to do > some > meaningful measurements to compare them (and hopefully compare to > published specs). > > I have an HP 3561A FFT analyzer, which can probably be beaten these > days > by a sound card, but has the advantage of absolute calibration and > GPIB > to dump data. I also have a very low noise 40dB audio amplifier > that > covers <10 Hz to >100 kHz. > > I've tried just looking at the regulator output with the analyzer, > with > and without the amp, but am not sure what I'm seeing. In > particular, > even with a capacitor to block the DC, the analyzer indicates > "Overrange" at a reference level below -5 or so dBV. That puts most > of > the noise spectrum below the bottom of the screen. > > Any suggestions on an appropriate test configuration, and on how to > get > readings that directly relate to the root-Hertz value shown by > regulator > data sheets? > > Thanks, > > John > > ___ > time-nuts mailing 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: 7.5.516 / Virus Database: 269.17.13/1211 - Release Date: > 6/01/2008 11:57 > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
