Re: [time-nuts] Realistic Tbolt phase noise
You'll need somwhat more than +14V for a generic 7812 to regulate correctly. Also, remember the local (to the regulators) decoupling caps, or some of them make quite good HF oscilators! See the data sheets for the particular regulators used for exact details. Dave B. -Original Message- -- The supply provided by TAPR is a pretty basic unit. It would not surprise me if some were better than others. They also may work better on US mains voltage than they do on international voltages. I would rig up another supply and see what happens. That would at least rule out the supply as an issue. In a previous post the idea of putting a 7805 and 7812 regulator on the TBolt came up. If you have +14 available that seems like the best thing to try. Bob ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 5370A vs 5370B
Mark Sims wrote: 99.95 ns is a typical number for the period reading at minimum gate time. Set the gate time to 1 sec. My 5370A shows 99.999 999 9650 +/- 50 at 1 sec gate time. Measuring it's own time-base is expected to give value not exactly on-beat. Internal cross-talk with the internal distribution of time-base scews the response somewhat. Also, differences in start and stop channels is achieved, and since those deviation patterns relate to the time-base it will be a particular point that will be viewed statically rather than being smoothed out over time. Fiddle with the trigger levels can remove the bias. It is also worth looking at the RMS jitter number. Ultra-sensitive fingers and a big bag of patience can find down into the valeys of the jitter numbers. A trigger voltage offset difference between start and stop channels will crunch out as a time-difference on the slopes of the waveform. The number of events (edges) or alternatively the overall time will control how bit error contribution it effects to. From my experience it can take at least a couple of months of continuous operation for the oscillator in an unused 5370 to stabilize its drift rate. Once stabilized, the 10544A's in the 5370A seem to be much LESS drifty than the 10811's in the 5370B. This is of importance only if you rely on the internal OCXO for your measurements. If the basic plan is to have it hooked to an external source, then the OCXO is muxed out and is unused. The SR-620 chooses the PLL approach instead. There are three mods that I do to all the 5370s that cross my path. First I replace the fan with a 12V 120 ma brushless DC fan driven by the 10V supply. What is the rational for doing that? Is your goal only to get a quieter fan? Second I drill a hole in the top of the case over the oscillator tuning control. To maintain the thermal conditions while tuning it's frequency I presume. This is meaningful if you intend to use the internal OCXO as reference and care about the calibration, then it is a very good idea. If always externally fed, then skip this step. Third, I add a switch to the oscillator buffer board to disable that STUPID oscillation detected LED that spew put 5 MHz noise all over creation. Very annoying indeed. I was happy that I discovered that one myself. I don't know if others found it and approached it before me, but a spectrum analyser on the 10 MHz output gave me a surprise. Why is there spurs inbetween the 10 MHz and overtones? Look at the schematic... think.. oh no... A switch or as in my case... just solder a blob once and for all. The really bad thing was that the detector is built in ECL with all the extra UMPF in the risetime that causes a true EMI/SI issue. Well built isn't always a good thing. I also disassemble and clean those slide switches on the front panel. Sounds like a good idea. I fail to do that... I guess I am lazy. 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] HP 5372A Fan
At 12:44 AM 3/10/2010, Ed Palmer wrote... It would seem to make more sense to have the fan blowing hot air out the back and drawing the hot inside air over the temperature sensor. The reason to have a fan blow in is so you can put a filter on it. It also creates more turbulence inside the box, for more effective heat removal. ___ time-nuts mailing 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] 5370A vs 5370B
Hi Yes indeed, the period was measured with the two channels in the com mode and the reference into one of them. I hadn't considered the trigger offset issues and was expecting something sub-100 ps rather than 500 ps. Obviously I need to spend some quality time with this beast. Now I gotta figure out how to change the gate time :}.. It sounds like my oscillator buffer board is going to get butchered pretty soon. Bob On Mar 9, 2010, at 11:30 PM, Mark Sims wrote: 99.95 ns is a typical number for the period reading at minimum gate time. Set the gate time to 1 sec. My 5370A shows 99.999 999 9650 +/- 50 at 1 sec gate time. From my experience it can take at least a couple of months of continuous operation for the oscillator in an unused 5370 to stabilize its drift rate. Once stabilized, the 10544A's in the 5370A seem to be much LESS drifty than the 10811's in the 5370B.There are three mods that I do to all the 5370s that cross my path. First I replace the fan with a 12V 120 ma brushless DC fan driven by the 10V supply. Second I drill a hole in the top of the case over the oscillator tuning control. Third, I add a switch to the oscillator buffer board to disable that STUPID oscillation detected LED that spew put 5 MHz noise all over creation. I also disassemble and clean those slide switches on the front panel. _ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. http://clk.atdmt.com/GBL/go/201469226/direct/01/ ___ time-nuts mailing 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] HP 5372A Fan
Good point about the filter, but it doesn't appear that the 5371a or 5372a ever had a filter. Unless it was just done out of habit because other HP units did have a filter. Ed Mike S wrote: At 12:44 AM 3/10/2010, Ed Palmer wrote... It would seem to make more sense to have the fan blowing hot air out the back and drawing the hot inside air over the temperature sensor. The reason to have a fan blow in is so you can put a filter on it. It also creates more turbulence inside the box, for more effective heat removal. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 5372A Fan
Mike S wrote: At 12:44 AM 3/10/2010, Ed Palmer wrote... It would seem to make more sense to have the fan blowing hot air out the back and drawing the hot inside air over the temperature sensor. The reason to have a fan blow in is so you can put a filter on it. It also creates more turbulence inside the box, for more effective heat removal. You want to collect dust before it comes into the electronics, yes. I have never had a problem with hot air blowing at me in front of a HP5372A, and I have spent many ours in front of one. The HP5372A has many good places for venting air, even if the air-tunnel effect is far from optimum, but kind of typical for its age. I have yet not found an instrument that fully replaces it either even if several outperform it in resolution (200 ps) and memory-depth (8192 time-stamps can be stored). 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.
[time-nuts] HP 5370A
Hi everyone, Keep on having that HP 5370A/B conversation! I just purchased a 5370A and will take possession this weekend. Will probably have questions next week. Thanks, Bert, VE2ZAZ __ The new Internet Explorer® 8 - Faster, safer, easier. Optimized for Yahoo! Get it Now for Free! at http://downloads.yahoo.com/ca/internetexplorer/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 5372A Fan
Ed Palmer wrote: Good point about the filter, but it doesn't appear that the 5371a or 5372a ever had a filter. Unless it was just done out of habit because other HP units did have a filter. If you want to toss a filter on it because your environment isn't exactly clean, it is trivial. Maybe that is part of their rational. I am by no means a fan and air-flow expert, but I seem to recall something about it being easier to push air into a box than pulling it out of it. Higher pressure air should also have a slightly higher ability to remove heat (more molecules to heat), but I guess heating-gurus can tell me it is of marginal effect. 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] 5370A vs 5370B
Bob Camp wrote: Hi Yes indeed, the period was measured with the two channels in the com mode and the reference into one of them. I hadn't considered the trigger offset issues and was expecting something sub-100 ps rather than 500 ps. Obviously I need to spend some quality time with this beast. Now I gotta figure out how to change the gate time :}.. If you do not fiddle with trigger levels, you _will_ loose accuracy. It is a systematic error. It sounds like my oscillator buffer board is going to get butchered pretty soon. I hope you mean modified. Applying a short at the right point improves the situation, but you don't need that to get started. It is a refinement that could wait for a little while. 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] ADF4002 phase noise - in FireFly-IIA-100MHz
John and Said, from my limited understanding of things I would have guessed that the ADF4001/2 PFD's ability to produce very short pulses in the locked condition puts a lot of energy into higher harmonics of the PFD's output, making it more easy for the loop filter to remove them. In contrast to that the simple rectangle from an XOR has most of its energy in the lower harmonics. That is why I have believed AD's claims to have a real low noise PFD in these devices. Is the theory all that wrong or do you expect other factors to be responsible for the not superiour performance? Let me put forward the question in another way: Had you to lock a 100 MHz VCXO to a 10 MHz reference, what other chip had you used that you believe is the better performer? Please no injection locking or even stranger, just plain PLL. I am in the state of constructiong a 10 to 100 MHz multiplier and your advice is highly appreciated, until now I have been thinking the ADF4002 could be an improvement against my usual AD9901 cover design in an FPGA or CPLD. Best regards Ulrich -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von saidj...@aol.com Gesendet: Mittwoch, 10. Marz 2010 00:28 An: time-nuts@febo.com Betreff: [time-nuts] ADF4002 phase noise - in FireFly-IIA-100MHz Hi John, we have a new 100MHz board (FireFly-IIA-100MHz) that uses an ADF4002 to generate 100MHz from the 10MHz internal OCXO. The VCXO we use is rated at better than 100dBc at 100Hz. The 10MHz reference achieves typ. -148 dBc at 100Hz. We measured -115dBc/Hz at 100MHz at 100Hz offset in a couple of sample units using the TSC5125A. This is in-line with your measurement at 80MHz. Loop BW is ~30Hz, so the 100Hz offset is slightly outside of the ADF4002 loop BW. Note that we get ~15dB better performance at 100Hz offset than the VCXO datasheet would let us expect. bye, Said In a message dated 3/9/2010 14:00:16 Pacific Standard Time, jmi...@pop.net writes: I haven't exhaustively tested the ADF4107 but I have played with the ADF4002 recently. I haven't been able to come within several dBc/Hz of its rated noise level. In one test, at 100 Hz from an 80 MHz carrier, I've seen about -118 dBc/Hz from the ADF4002 when fed by 10 MHz with -145 dBc/Hz at 100 Hz (which would become about -127 dBc/Hz in an ideal 80 MHz multiplier.) The figure-of-merit equation suggests that -222 + 20*log(8) + 10*log(10 MHz) = -134 dBc/Hz would be achievable, well below the -127 dBc/Hz limit imposed by the reference. ___ time-nuts mailing 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] Advice on TRACOR 527E
Hello Group members, I need some help interpreting Lady Heather software results like the colours and chart results for My Tibold GPS Receiver, any help would be appreciated as I am new at this. Best regards, Sal C. Cornacchia Electronic RF Microwave Engineer (Ret.) From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sun, March 7, 2010 8:05:25 AM Subject: Re: [time-nuts] Advice on TRACOR 527E Hi On the site - also grab the 527A manual. It's the one with the schematics in it. It also has a complete listing of the FSCM numbers as of 1967. Useful for figuring out who made that questions when repairing military surplus gear . One thing you will run into on the 527 - They originally came out in the era of 5 MHz standards. The specs on the boxes only list 100KHz, 1 MHz, and 5 MHz as valid inputs. In reality, they will accept anything that's an integer sub-multiple of 5 MHz as an input (2.5 MHz, 1.6 MHz, 500 KHz ...). The front end is an injection locked multivibrator. Check to see how happy yours is with a 10 MHz input. Most will run with 10 MHz and some multiples of 5 MHz sub multiples (like 5/2 x 3 = 7.5 MHz). If enough people have them, we can start a thread on correctly computing the Alan Variance from 100 foot long strip chart's. So much fun, ink all over the place Bob On Mar 7, 2010, at 6:32 AM, olivier MEHEUT wrote: Thank you so much for all replies. Good reading for this sunday. 73, Olivier F6HGQ Le 7 mars 10 à 12:05, gandal...@aol.com a écrit : In a message dated 07/03/2010 10:17:54 GMT Standard Time, f6...@wanadoo.fr writes: Could not locate any OM manual on the web for this equipement can somebody help ? - Once again Didier saves the day:-). _http://www.ko4bb.com/cgi-bin/manuals.pl?dir=09%29_Misc_Test_Equipment_ (http://www.ko4bb.com/cgi-bin/manuals.pl?dir=09)_Misc_Test_Equipment) Look towards the bottom of the page, no diagrams in the 527E manual unfortunately but the 527A manual that's also there does have diagrams so that might help, and much other interesting stuff to keep you distracted too:-) regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] nubie querie
Hi Jim, jimlux wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Has recently been done by German amateurs in Bochum: http://www.southgatearc.org/news/march2009/eve.htm We've done Moonbounce with 3mW (Hobart - Dwingeloo) in JT65 - but a 26m and a 25m dish is stretching 'amateur' a bit again. So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? For Camras, I do now have to point out that the dish had been unused for 13 years, and apart from the construction itself, nothing was really in a serviceable state anymore. This means that we installed new engines and the hardware/software to drive them, gearbox modifications, new antennas, preamps, receivers, backends, pulsar-processing, computing, networking and much more. It's not as if we were handed the key to a working telescope - in fact, the first work was mucking out the dirt and dead animals that had gathered inside... So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. Singlehandedly is a poor discriminator, as doing things like this in a group is great fun, Fabrication seems more relevant - but in the end, what's really the point of drawing such an arbitrary line, as long as we're having a great time and accomplish things? The great equalizer here is simply the ongoing rapid technological progress. Hobby-prized access to fun toys like Rubidiums (does anyone have an H-maser to spare though? ;-), FPGAs and fast A/D converters make things possible for amateurs nowadays that were out of reach for professionals just a decade ago. Working on a dish that is more than 50 years old really puts this in perspective, and we as amateurs have already improved its performance in some aspects beyond what it could do in its 'professional' life (thanks of course to this 13 year gap). Regards, Paul Boven. ___ time-nuts mailing 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] 5370A vs 5370B
Yes, I replace the standard HP fan with a MUCH quieter one. I get mine from a local surplus shop. It is made by AAVID. it draws 120 mA at 12V and I run it off the 10V supply (which is somewhat over 10V). I don't have one handy to get the part number. They also have a 160 mA model part number 148A233. (Hint, fan noise correlates greatly with power drawn). There is also a Panasonic model that is particularly quiet (but the store owner keeps them for himself). Just about any fan that fits will work. It is VERY difficult to get one of the fan screws back in without stripping the machine... I leave it out. Before getting all whiny about overheating, careful HP engineers putting that obnoxious hurricane in for a reason, etc... know that I put several thermocouples all over the guts of the machine and found no significant changes in cooling. I have had modified machines running continuously for many years. I usually use an external reference, but like being able to use the internal one. Hence the tweaker hole above the OSC (also do that on the 5371 and 5372). It is a royal pain to set that slug anywhere near close enough. Basically you tweak it randomly enough until one gets close enough (I try to get the freq display to under 10.000 000 005 0) Another dumb aspect of the 5370 design is that the CPU is clocked by the 10 MHz oscillator. Switch the timebase while it is running and the thing crashes... Those slide switches on the front panel are actually a nice design... except they are located where the fan deposits all that rust, dust, bits of fluff, cat hair, cheerios, smutz. You would not beleive the hairballs that I have pulled out of that area. The switches are sliding contacts over a gold plated PCB. The support frame of the switch leaves the contacts open to the air. Easy enough to clean, but a royal PITA. Also note that when modifying the reference buffer board that the LED does not turn off after you do the mod, it just gets a little dimmer. _ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. http://clk.atdmt.com/GBL/go/201469226/direct/01/ ___ time-nuts mailing 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] 5370A vs 5370B
At 4:10 PM + 3/10/10, Mark Sims wrote: Yes, I replace the standard HP fan with a MUCH quieter one. I get mine from a local surplus shop. It is made by AAVID. it draws 120 mA at 12V and I run it off the 10V supply (which is somewhat over 10V). Before getting all whiny about overheating, careful HP engineers putting that obnoxious hurricane in for a reason, etc... know that I put several thermocouples all over the guts of the machine and found no significant changes in cooling. I have had modified machines running continuously for many years. It's reasonable to assume that HP engineers put in twice as much fan as needed by 95% of their customers, to prevent problems with that last 5% that run the thing in an extreme environment. If the counter's spec sheet says it will run at 50C, then it's gotta be able to run for a couple years at 50C without failure. So your 25C office can use a much quieter fan. Our telescope at 3500m altitude, on the other hand, needs all the fan noise it can get since the thin air is only 50% as effective at cooling as sea-level air is. -- --David Forbes, Tucson, AZ http://www.cathodecorner.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.
Re: [time-nuts] HP 5372A Fan
Ed, From your description of the fan noise, I have one concern. If the fan speed seems to increase without a good cleaning or change in the supply voltage, then it's likely that the airflow has been decreased, an obvious speed up is not good news. Pete Rawson On Mar 9, 2010, at 10:44 PM, Ed Palmer wrote: I have a question for owners of the HP 5372A (and probably 5371A) Time Interval Analyzer. Is the fan on the back blowing out or sucking in? I was looking at mine to see about replacing the fan with a quieter one and I was surprised to see that mine is sucking in. This doesn't make sense to me for two reasons: 1. It blows hot air out the front and bottom straight at the operator. Uncomfortable on a hot day. 2. Just inside the unit at the back on the motherboard there's a temperature sensor that controls the fan speed. Why would you blow cool outside air over the temperature sensor? It would seem to make more sense to have the fan blowing hot air out the back and drawing the hot inside air over the temperature sensor. I experimented with this configuration and found that the noise level went up because the fan was turning faster - no big surprise there. I can't find any info in the manual (service or operating) about this. Ed ___ time-nuts mailing 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] The WWVB Atomic Clock Kit #7
Hi Tom: I've built it and it works great. See: http://www.prc68.com/I/Loop.shtml#K5JHF Next is to develop a better loop antenna based on the Russian Ferrite rods. ---and--- The subject of my prior post, add thermal mass and insulation to the 32768 crystal. Have Fun, Next This not your father's WWVB clock. Many CW output features and even Westminster chimes have been added. In fact we have 22 selectable parameters for those who like pushing buttons. Since it is very difficult to maintain a 60Khz RF link to WWVB during the day the Atomic Clock indicates when it was last synced to WWVB. This will allow you to experiment with various VLF antennas to see which is best. Antenna orientation is also important and you can experiment there. I've been using some larger ferrite rods (off eBay) with great success. Also tried some Litz wire antennas. Great fun. The best way to describe all of it's features is to walk through the setup process. Power: The Atomic Clock draws 0.22 mA running current, and 1.08 mA beeping current. To reduce power consumption the microcontroller hunts for the correct WWVB signal during the first 10 minutes of every hour. Two AA batteries should last a long time. Construction: A diagram is located on the schematic page. Components on the back are shown in mirror image. Mount a 2pin header on the CMMR-6P-60 for antenna attachment and experimentation. Remember this is “H” field, locate the ferrite rod away from metal and at right angles to Ft Collins CO, WWVB for best reception….mostly in the late evening and very early morning hours. Use: Step forward through the Modes by pushing the Mode button. Backup by holding in the Mode button until you hear the first half second tick. You can repeat this. If you hold the Mode button in for two half second ticks you go back to the “clock”. All data is immediately stored in flash memory at the time you change it. Clean display (no prefix) means you are “set” to WWVB, otherwise U,S,E,L is displayed for Unsynced (no sync detected), Second sync detected (it requires two good sync pulses before updating the time data with WWVB), Error (noise), or Loss of any signal. The microcontroller wll attempt to detect WWVB and sync up during the first 10 minutes of the hour (drawing ~1mA) it will then revert to 0.22mA for the remaining 50 minutes whether synced or not to conserve the battery. You can use #22 (below) to determine antenna effectiveness. Modes/Parameters: Initial default is Clock shown as “HH – MM – SS” with; Offset = -6, Interval = 1min, Beeper On, Call On, Tick On, and Westminster On Offset ….GMT offset selectable from -12 to 12 Beeper On/Off ….One mode provides all sound On/Off for quiet running (wife's request) Beeper Tone …. Frequency selectable from 294 Hz to 2093 Hz Beeper Speed …. Morse WPM selectable from 3 WPM to 40 WPM Beeper Interval …..Selectable output interval of #14 and/or #15 from 1 to 60 minutes. Test mode output including everything for “0” interval Call 1 …. Callsign entry (saved) by number A-Z = 1 - 26, 1234567890 = 27-36 Call 2 ….same as #6 Call 3 ….same as #6 Call 4 ….same as #6 Call 5 ….same as #6 Call 6 ….same as #6 Call 7 ….same as #6 Call 8 ….same as #6 Call On/Off ….Send Morse Code call sign de Callsign Callsign up to 8 characters for output to Beeper, LED, and Key output for rig Time On/Off …. Send Morse Code Time to Beeper, LED, and Key output for rig Westminster On/Off …. Westminster Chimes on Quarter Hour with Hour(s) “Gong” on the Hour Tick On/Off ….One second tick RS232 9600/4800 Baud ….9600 or 4800 Baud selectable for $GPZDA time data RS-232 output Display 12Hr/24Hr …. 12Hr or 24Hr mode shown on the LCD Set Hour …. Manual setting of Hours and Minutes if necessary Set Minute …. Manual setting of Hours and Minutes if necessary Tells you when the last successful setting to WWVB occurred, format: YYMMDDHHMMSS The price for the WWVB Atomic Clock Kit #7 (without the CMMR-6P-60) is $20 plus $2 postage in the USA and $5 postage for DX. The CMMR-6P-60 is available for $10 with no additional postage if ordered with the kit. We did that since several local people already have this WWVB receiver and the other worldwide time standards require different receivers and microcode (which is TBD). ___ time-nuts mailing 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] HP 5372A Fan
Are you sure that it has a variable speed fan? My 5372A has a pretty quiet fan and I have never tried to change it. I am assuming that it uses the same 117V fan as the 5371A. That thermal switch may be a power supply shutdown. I have a couple of 5371A's that are a different matter. Utterly obnoxious fans. I put in much quieter 12V fans. I powered them with a separate wall wart module mounted inside the box with velcro. I used Nidec Beta V TA450DC fans rated at 250 mA. Again, I checked the before/after thermal environment and found no changes. I have some even quieter NMB Smartfans with a thermal sensor. They draw around 150 mA until the temp reaches 35C, then they kick in at 750 mA and scream bloody murder. _ Hotmail: Trusted email with powerful SPAM protection. http://clk.atdmt.com/GBL/go/201469227/direct/01/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 5372A Fan
Yes, the fan is variable speed and it's 12V DC. It's described in the motherboard section of the service manual on page 11-4 (pdf page 503). That's why I thought it was so odd that the fan is blowing cool outside air over the thermal sensor on the motherboard. I guess they could have calibrated the system to work on the basis of ambient temperature variations, but it seems backwards to me. Ed Mark Sims wrote: Are you sure that it has a variable speed fan? My 5372A has a pretty quiet fan and I have never tried to change it. I am assuming that it uses the same 117V fan as the 5371A. That thermal switch may be a power supply shutdown. I have a couple of 5371A's that are a different matter. Utterly obnoxious fans. I put in much quieter 12V fans. I powered them with a separate wall wart module mounted inside the box with velcro. I used Nidec Beta V TA450DC fans rated at 250 mA. Again, I checked the before/after thermal environment and found no changes. I have some even quieter NMB Smartfans with a thermal sensor. They draw around 150 mA until the temp reaches 35C, then they kick in at 750 mA and scream bloody murder. _ Hotmail: Trusted email with powerful SPAM protection. http://clk.atdmt.com/GBL/go/201469227/direct/01/ ___ time-nuts mailing 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] 5370A vs 5370B
Hi Right now my main concern is if the gizmo is broken beyond repair. Setting trigger levels manually will be possible on the two main inputs. Not so much on the external arm input. Going through a full calibration on the interpolators - pretty major effort. First up on the project list is getting the display rate pot set to something rational. The external arm pot seems to be set to somewhere I can trigger it. That moves it down the list. Fan wise the noise is nowhere near as bad as a 5335 I have sitting here. Maybe I got lucky on the fan. The 5370 is packed pretty loose by modern standards. Lots of room for the air to move around inside. OCXO is right in back by the fan so it can be kept nice and cool Is there anything special / unique about the 10811 in the 5370B? It's got a unique part number, but that may not mean much. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Wednesday, March 10, 2010 7:48 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 5370A vs 5370B Bob Camp wrote: Hi Yes indeed, the period was measured with the two channels in the com mode and the reference into one of them. I hadn't considered the trigger offset issues and was expecting something sub-100 ps rather than 500 ps. Obviously I need to spend some quality time with this beast. Now I gotta figure out how to change the gate time :}.. If you do not fiddle with trigger levels, you _will_ loose accuracy. It is a systematic error. It sounds like my oscillator buffer board is going to get butchered pretty soon. I hope you mean modified. Applying a short at the right point improves the situation, but you don't need that to get started. It is a refinement that could wait for a little while. 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. ___ time-nuts mailing 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] 5370A vs 5370B
Ed Palmer wrote: One trick I always use to quiet down a rowdy fan is to replace the mounting screws with rubber mounts. This isolates the fan's mechanical vibrations from the chassis. The difference is audible - even with a good fan. I salvaged some mounts from IBM machines that work great. Most of the big online computer retailers have something along these lines. The same trick works very well for hard-disks. Modern quiet computer chassis is very very quiet while using a multitude of very simple and straightforward tricks like this. Recently built a server with 8 hard-disks this way. The DVD-player is the noisiest part... by far. However, we will never really use it after initial booting, so it is OK. * rubber suspension of fans * rubber suspension of hard-disks * damping on flat surfaces We got a pair of extra large (and quiet) fans to ensure air-flow. Slightly more expensive than the standard chassis. Quieter when in the terminal room than the computer-hall with closed door. 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] 5370A vs 5370B
Hi Fanless Atom motherboard / solid state disk / wall wart power supply ... DVD is still the main source of noise. Of course the bean grinder in the single cup Cappuccino machine drowns out the DVD pretty effectively. Looks like a 5370B with an intact front panel and some sort of internal issue(s) just showed up at auction. Hmmm. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Wednesday, March 10, 2010 12:31 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 5370A vs 5370B Ed Palmer wrote: One trick I always use to quiet down a rowdy fan is to replace the mounting screws with rubber mounts. This isolates the fan's mechanical vibrations from the chassis. The difference is audible - even with a good fan. I salvaged some mounts from IBM machines that work great. Most of the big online computer retailers have something along these lines. The same trick works very well for hard-disks. Modern quiet computer chassis is very very quiet while using a multitude of very simple and straightforward tricks like this. Recently built a server with 8 hard-disks this way. The DVD-player is the noisiest part... by far. However, we will never really use it after initial booting, so it is OK. * rubber suspension of fans * rubber suspension of hard-disks * damping on flat surfaces We got a pair of extra large (and quiet) fans to ensure air-flow. Slightly more expensive than the standard chassis. Quieter when in the terminal room than the computer-hall with closed door. 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. ___ time-nuts mailing 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] 5370A vs 5370B
back to the original issue front panel One thing I have had success with is emailing some of the bigger EBay instrument sellers and asking if they have a parts unit. It helps of you are/were a regular customer. I repaired a 3325A that needed some buttons, a bottom panel etc. I asked and was offered a mechanically clean one minus the power supply and oscillator for $10 and something like $10 for shipping since I didn't need it FIPed. Another was I have a 8660D that the handles were broken off and was someday just going to grind down the remaining sharp edges. When I won an instrument/lot I asked of they had any HP gear the same generation, height, and depth and told them why. When I got the item I won in the box were also two side panels and a bag of screws. I sent them a $10 Starbucks gift card. just a thought ... -pete ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ADF4002 phase noise - in FireFly-IIA-100MHz
Hi Ulrich, I think in our design the spec is limited by the ~-100dBc noise at 100Hz offset of the 100MHz VCXO. Please note that the ADF4002 actually improves that noise by about 15dB from the datasheet spec (or the unit we tested was that much better than the one shown in the datasheet). Also, the ADF4002 allows different Current settings for the PFD, this affects phase noise as well. Fine-tuning of these settings and the loop filter reduced the noise further. We use a 10MHz PFD output, so that should be optimal for phase noise. So in short, we improve the inherent close-in PN performance of the VCXO significantly. Would an Exor gate have resulted in better performance? Maybe. But the 10MHz spur on the VCXO EFC pin from the EXOR output may cause much higher spur levels at 10, 20, 30MHz etc on the VCXO output. And you would have to contend with counter noise (10:1 divider), and there would not have been flexibility in frequency, as well as a PLL Lock indicator.. bye, Said In a message dated 3/10/2010 07:19:14 Pacific Standard Time, df...@ulrich-bangert.de writes: Let me put forward the question in another way: Had you to lock a 100 MHz VCXO to a 10 MHz reference, what other chip had you used that you believe is the better performer? Please no injection locking or even stranger, just plain PLL. ___ time-nuts mailing 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] 5370A vs 5370B
Bob Camp wrote: Hi Fanless Atom motherboard / solid state disk / wall wart power supply ... DVD is still the main source of noise. This was far from that. It is a AMD PHENOM II X4 90SE 2,5GHz CPU with 8 SAMSUNG ECOGREEN F2 1,5TB SATA disks is certainly not tailored in such a fashion. The Fractal Design chassi has a fair bit to do with noise reduction. Of course the bean grinder in the single cup Cappuccino machine drowns out the DVD pretty effectively. True. I think the computer club will not invest in one for that purpose. Looks like a 5370B with an intact front panel and some sort of internal issue(s) just showed up at auction. Hmmm. Hmm 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.
[time-nuts] Lady Heather software help
Hello Group members, I need some help interpreting Lady Heather software results like the colours and chart results for My Tbold GPS Receiver, any help would be appreciated as I am new at this. Best regards, Sal C. Cornacchia Electronic RF Microwave Engineer (Ret.) ___ time-nuts mailing 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] Thermal Time Constant
Hi Mathew: There are a bunch of them, but I like the DS3231 because it has a software frequency tweak and I2C interface. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4627/t/al http://datasheets.maxim-ic.com/en/ds/DS3231.pdf Hi Bruce: Do you have a value for the thermal resistance of Styrofoam? Have Fun, Brooke Clarke http://www.PRC68.com Matthew Smith wrote: Quoth Brooke Clarke at 10/03/10 10:22... ...like a Dallas 32khz, or one of the newer Maxim units... There's a Maxim part to supersede the DS32kHz? I know that my regular vendors [Farnell, Soanar, Futurlec] in Australia don't stock the DS32kHz, which makes them mega-expensive to acquire. ___ time-nuts mailing 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] Thermal Time Constant
Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Bruce Griffiths wrote: Brooke Clarke wrote: Hi: For some time I've considered surrounding a free running 32678 Hz oscillator (like a Dallas 32khz, or one of the newer Maxim units) with thermal mass and insulation in order to get the time constant into the range of some days. To get a feel for it a simple experiment shows that a half inch diameter brass rod 3.75 long (102 grams) has a thermal time constant of about 6 min 35 seconds when wrapped lightly in a towel. Is there a way to calculate the amount of aluminum and Styrofoam needed to get a time constant of say 100 hours? This came up in relation to WWVB clocks that free run for most of the time. When you compare WWVB clocks it's not uncommon to see tens of seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC Start with the maximum thermal resistance the application can withstand (determined by internal dissipation and acceptable temperature rise above ambient). If for example the dissipation is 10mW and acceptable temperature rise 10C then thermal resistance will be about 1000C/W. The thermal capacity required can then be calculated from the time constant: C= 3.6E5/1E3 = 360 J/C requires about 7.2 kg of aluminium. The required thickness of styrofoam can then be calculated from the surface area of the aluminium block. Achieving a thermal resistance of 1000C/W may be a little difficult without using radiation shields. Bruce Oops, the specific heat of Alum9inium is about 0.2Cal/gm/C or 0.8371 J/gm/C so the mass of Aluminium required would be 430gm if the thermal resistance to ambient were 1000K/W. With a thermal resistance of 100C/W you need 4.3Kg of aluminium 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] Thermal Time Constant
~3.3E-2 W/mK. If, as I suspect, its transparent to 10-20um infrared then adding intermediate aluminium foil radiation shields may be useful. Some styrofoam insulating panels include carbon black to inhibit infrared transmission: http://www.glasscellisofab.com/sheets/polystyrene/data_sheets/STYROFOAM%20PANELMATE.pdf Foam glass is also black for the same reason and its cells are filled with sulphur dioxide (at least it smalls like that when you cut it). Aerogel foam is also good (not sure about its infrared transparency). Bruce Brooke Clarke wrote: Hi Mathew: There are a bunch of them, but I like the DS3231 because it has a software frequency tweak and I2C interface. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4627/t/al http://datasheets.maxim-ic.com/en/ds/DS3231.pdf Hi Bruce: Do you have a value for the thermal resistance of Styrofoam? Have Fun, Brooke Clarke http://www.PRC68.com Matthew Smith wrote: Quoth Brooke Clarke at 10/03/10 10:22... ...like a Dallas 32khz, or one of the newer Maxim units... There's a Maxim part to supersede the DS32kHz? I know that my regular vendors [Farnell, Soanar, Futurlec] in Australia don't stock the DS32kHz, which makes them mega-expensive to acquire. ___ time-nuts mailing 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] Thermal Time Constant
Thermal resistance is measured in degrees (C or K or ..) per watt. Its inversely proportional to area and proportional to thickness. I think the clueless clown who created that table means that for a 1 square meter panel of the specified thickness the thermal resistance is the tabulated value measured in Kelvin/Watt. Bruce Brooke Clarke wrote: Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Bruce Griffiths wrote: Brooke Clarke wrote: Hi: For some time I've considered surrounding a free running 32678 Hz oscillator (like a Dallas 32khz, or one of the newer Maxim units) with thermal mass and insulation in order to get the time constant into the range of some days. To get a feel for it a simple experiment shows that a half inch diameter brass rod 3.75 long (102 grams) has a thermal time constant of about 6 min 35 seconds when wrapped lightly in a towel. Is there a way to calculate the amount of aluminum and Styrofoam needed to get a time constant of say 100 hours? This came up in relation to WWVB clocks that free run for most of the time. When you compare WWVB clocks it's not uncommon to see tens of seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC Start with the maximum thermal resistance the application can withstand (determined by internal dissipation and acceptable temperature rise above ambient). If for example the dissipation is 10mW and acceptable temperature rise 10C then thermal resistance will be about 1000C/W. The thermal capacity required can then be calculated from the time constant: C= 3.6E5/1E3 = 360 J/C requires about 7.2 kg of aluminium. The required thickness of styrofoam can then be calculated from the surface area of the aluminium block. Achieving a thermal resistance of 1000C/W may be a little difficult without using radiation shields. Bruce Oops, the specific heat of Alum9inium is about 0.2Cal/gm/C or 0.8371 J/gm/C so the mass of Aluminium required would be 430gm if the thermal resistance to ambient were 1000K/W. With a thermal resistance of 100C/W you need 4.3Kg of aluminium 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 mailing 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] nubie querie
This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? I think the traditional test for an amateur is do you get paid for it. (Yes, it helps to be independently wealthy.) Even if you build your own antenna, there is the question of where do you start. Is it OK to buy a dish if I build the mount? Can I buy steel pipe or do I have to start from iron ore? I suspect if you look at other amateur activities (say sports), there are examples equivalent to scrounging time on Arecibo. My 2 cents... You get credit for the part that you do. Anything goes as long as you are honest about what you do. If you buy the electronics and build the antenna, you get credit for building the antenna. If you build the electronics and buy (or scrounge) the antenna, then you get credit for the electronics. ... Some people are really good at scrounging. -- 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.
Re: [time-nuts] Thermal Time Constant
Hi Bruce: If a square meter of Styrofoam is 1.5 deg C/W then a cubic inch would be 39.37 * 39.37 * 1.5 or 2,325 deg C/W The DS3231 dissipates about 1 mw when running. I'm not sure how to come up with an allowable temp increase, but suspect it's based on not exceeding the max allowed operating temp. But for this part the Temp vs. freq curve is flattest at room temp so best to minimize the temp rise. So: (1 deg C) / (0.001 W) = 1000 deg C/W, the same number you had. That requires 185 g of Aluminum or about 69 cc volume or 4.25 cubic inches. That's a block about 1.62 on a side. How does that look? Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Thermal resistance is measured in degrees (C or K or ..) per watt. Its inversely proportional to area and proportional to thickness. I think the clueless clown who created that table means that for a 1 square meter panel of the specified thickness the thermal resistance is the tabulated value measured in Kelvin/Watt. Bruce Brooke Clarke wrote: Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Bruce Griffiths wrote: Brooke Clarke wrote: Hi: For some time I've considered surrounding a free running 32678 Hz oscillator (like a Dallas 32khz, or one of the newer Maxim units) with thermal mass and insulation in order to get the time constant into the range of some days. To get a feel for it a simple experiment shows that a half inch diameter brass rod 3.75 long (102 grams) has a thermal time constant of about 6 min 35 seconds when wrapped lightly in a towel. Is there a way to calculate the amount of aluminum and Styrofoam needed to get a time constant of say 100 hours? This came up in relation to WWVB clocks that free run for most of the time. When you compare WWVB clocks it's not uncommon to see tens of seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC Start with the maximum thermal resistance the application can withstand (determined by internal dissipation and acceptable temperature rise above ambient). If for example the dissipation is 10mW and acceptable temperature rise 10C then thermal resistance will be about 1000C/W. The thermal capacity required can then be calculated from the time constant: C= 3.6E5/1E3 = 360 J/C requires about 7.2 kg of aluminium. The required thickness of styrofoam can then be calculated from the surface area of the aluminium block. Achieving a thermal resistance of 1000C/W may be a little difficult without using radiation shields. Bruce Oops, the specific heat of Alum9inium is about 0.2Cal/gm/C or 0.8371 J/gm/C so the mass of Aluminium required would be 430gm if the thermal resistance to ambient were 1000K/W. With a thermal resistance of 100C/W you need 4.3Kg of aluminium 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 mailing 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] nubie querie
Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? Marconi claimed credit for the first transatlantic communication by sending the letter S in Morse code. That sounds like a fine standard - one byte of data. It's statistically significant. With regard to the restoration and use of a derelict radio telescope for amateur radio, that's a fine example of amateurs putting themselves to a big task and succeeding. I work on radio telescopes, so I know how big a task that is. --David Forbes ___ time-nuts mailing 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] Thermal Time Constant
Hi If a square meter of foam 2 thick is 1.5 C/W then a 1 square inch piece (also 2 thick) would be ~40^2 times better. Your cube has ~2 square inches on a side and six sides. (divide by ~12) The outer cube after you put 2 of foam on it has surfaces 5.6 on a side. That's a surface area of 25 square inches. The 10:1 increase in area needs to be considered.(divide by X in addition). 2325/12 = 193.75 193.76 / (5) = 38.75 C/W The block is going to get a *lot* bigger. Consider using steel instead of aluminum. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Brooke Clarke Sent: Wednesday, March 10, 2010 4:28 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thermal Time Constant Hi Bruce: If a square meter of Styrofoam is 1.5 deg C/W then a cubic inch would be 39.37 * 39.37 * 1.5 or 2,325 deg C/W The DS3231 dissipates about 1 mw when running. I'm not sure how to come up with an allowable temp increase, but suspect it's based on not exceeding the max allowed operating temp. But for this part the Temp vs. freq curve is flattest at room temp so best to minimize the temp rise. So: (1 deg C) / (0.001 W) = 1000 deg C/W, the same number you had. That requires 185 g of Aluminum or about 69 cc volume or 4.25 cubic inches. That's a block about 1.62 on a side. How does that look? Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Thermal resistance is measured in degrees (C or K or ..) per watt. Its inversely proportional to area and proportional to thickness. I think the clueless clown who created that table means that for a 1 square meter panel of the specified thickness the thermal resistance is the tabulated value measured in Kelvin/Watt. Bruce Brooke Clarke wrote: Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Bruce Griffiths wrote: Brooke Clarke wrote: Hi: For some time I've considered surrounding a free running 32678 Hz oscillator (like a Dallas 32khz, or one of the newer Maxim units) with thermal mass and insulation in order to get the time constant into the range of some days. To get a feel for it a simple experiment shows that a half inch diameter brass rod 3.75 long (102 grams) has a thermal time constant of about 6 min 35 seconds when wrapped lightly in a towel. Is there a way to calculate the amount of aluminum and Styrofoam needed to get a time constant of say 100 hours? This came up in relation to WWVB clocks that free run for most of the time. When you compare WWVB clocks it's not uncommon to see tens of seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC Start with the maximum thermal resistance the application can withstand (determined by internal dissipation and acceptable temperature rise above ambient). If for example the dissipation is 10mW and acceptable temperature rise 10C then thermal resistance will be about 1000C/W. The thermal capacity required can then be calculated from the time constant: C= 3.6E5/1E3 = 360 J/C requires about 7.2 kg of aluminium. The required thickness of styrofoam can then be calculated from the surface area of the aluminium block. Achieving a thermal resistance of 1000C/W may be a little difficult without using radiation shields. Bruce Oops, the specific heat of Alum9inium is about 0.2Cal/gm/C or 0.8371 J/gm/C so the mass of Aluminium required would be 430gm if the thermal resistance to ambient were 1000K/W. With a thermal resistance of 100C/W you need 4.3Kg of aluminium 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 mailing 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] nubie querie
On 3/10/10, David Forbes dfor...@dakotacom.net wrote: With regard to the restoration and use of a derelict radio telescope for amateur radio, that's a fine example of amateurs putting themselves to a big task and succeeding. I work on radio telescopes, so I know how big a task that is. Here in Italy, radio telescopes, brand new ones like the Sardinia Radio Telescope, get abandoned just a minute after they've been built (or a minute before maybe). I whish radio amateurs could have any role in rescuing such a great tool for research and science (64m dish). Government looks not so interested in science here. Frank IZ8DWF (IS0FKQ some years ago) ___ time-nuts mailing 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] Thermal Time Constant
Surely you meant 1 square inch of styrofoam with the specified thickness?? For a 100 hour (3.6E5 seconds) time constant and 1000 deg C/W thermal resistance you need a thermal capacitance of 3.6E5/1E3 = 360 J/C or 360/0.8371 = 430 gm of Aluminium which has a volume of 430/2.7 = 159 cc. You still have the thermal radiation coupling problem through the infrared transparent insulator. Gold plating the aluminium will help. Even if you solve the thermal radiation problem, the thermal conductance of any leads bringing power or signals to or from the clock will be an major problem even if you use constantan or austenetic stainless steel leads. Bruce Brooke Clarke wrote: Hi Bruce: If a square meter of Styrofoam is 1.5 deg C/W then a cubic inch would be 39.37 * 39.37 * 1.5 or 2,325 deg C/W The DS3231 dissipates about 1 mw when running. I'm not sure how to come up with an allowable temp increase, but suspect it's based on not exceeding the max allowed operating temp. But for this part the Temp vs. freq curve is flattest at room temp so best to minimize the temp rise. So: (1 deg C) / (0.001 W) = 1000 deg C/W, the same number you had. That requires 185 g of Aluminum or about 69 cc volume or 4.25 cubic inches. That's a block about 1.62 on a side. How does that look? Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Thermal resistance is measured in degrees (C or K or ..) per watt. Its inversely proportional to area and proportional to thickness. I think the clueless clown who created that table means that for a 1 square meter panel of the specified thickness the thermal resistance is the tabulated value measured in Kelvin/Watt. Bruce Brooke Clarke wrote: Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Bruce Griffiths wrote: Brooke Clarke wrote: Hi: For some time I've considered surrounding a free running 32678 Hz oscillator (like a Dallas 32khz, or one of the newer Maxim units) with thermal mass and insulation in order to get the time constant into the range of some days. To get a feel for it a simple experiment shows that a half inch diameter brass rod 3.75 long (102 grams) has a thermal time constant of about 6 min 35 seconds when wrapped lightly in a towel. Is there a way to calculate the amount of aluminum and Styrofoam needed to get a time constant of say 100 hours? This came up in relation to WWVB clocks that free run for most of the time. When you compare WWVB clocks it's not uncommon to see tens of seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC Start with the maximum thermal resistance the application can withstand (determined by internal dissipation and acceptable temperature rise above ambient). If for example the dissipation is 10mW and acceptable temperature rise 10C then thermal resistance will be about 1000C/W. The thermal capacity required can then be calculated from the time constant: C= 3.6E5/1E3 = 360 J/C requires about 7.2 kg of aluminium. The required thickness of styrofoam can then be calculated from the surface area of the aluminium block. Achieving a thermal resistance of 1000C/W may be a little difficult without using radiation shields. Bruce Oops, the specific heat of Alum9inium is about 0.2Cal/gm/C or 0.8371 J/gm/C so the mass of Aluminium required would be 430gm if the thermal resistance to ambient were 1000K/W. With a thermal resistance of 100C/W you need 4.3Kg of aluminium 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 mailing 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] nubie querie
This thread mentioned puilsars and the best clocks. Here are some comments from those really in the know: == Latest Al+ clock comparision at NIST is at better than 10^-17 level see. http://arxiv.org/abs/0911.4527 == rich...@karlquist.com said: I vaguely remember reading that pulsars have some fantastic stability like 1E-20. [snip] Pulsars decelerate due to electrodynamic drag -- the reaction torque from the pulsar's external magnetic field trying to spin the plasma surrounding the pulsar, and generating MHD waves in this plasma. Because the plasma density varies randomly, the drag torque varies randomly. Some pulsars are subject to other torques, for example because they have close binary companions. Even in the absence of external torque, some pulsars change angular velocity abruptly because their moments of inertia change when starquakes (like earthquakes, but in the neutron crystalline solid body of the star) occur. In early 1969, shortly after the Crab Nebula pulsar (the first so- called millisecond pulsar, with a rotation rate of of about 30 revs per second) had been discovered, and (IIRC) before a starquake had been observed, we began observing this pulsar at Arecibo Observatory in Puerto Rico. In one daily observation that involved about an hour of averaging, we could determine the pulsar's rotation phase angle with precision of about 50 microradians. (This was after removing the time-varying propagation group-delay due to plasma between us and the pulsar. To distinguish the plasma delay, we observed the pulsar concurrently at radio frequencies ranging from 40 MHz to 430 or 611 MHz.) Within a few months, we found that the pulsar was a rotten clock relative to the Observatory's H-P Cesium-beam- referenced clock, which we checked daily against the Loran-C ground- wave (over sea water, actually) signal from Jupiter, FL. Since then, other pulsars have turned out to be more stable (and others less so). AFAIK, none has yet beaten a good atomic clock. Pulsar PSR1937+21, discovered in 1982, attracted attention because its rotation rate was about 600 revs per second. (So it was more deserving of the title, millisecond pulsar.) In its first two years of being observed, it did not have a glitch or starquake. In two years, about 2 x 10^11 rotations were observed, and the rotation phase had been determined within about about 1/160th of a revolution, so the average spin rate was known within about a part in 10^13. However, in the next twenty-five years, its spin rate on a time-scale of about one year turned out to be no more stable than about 1 in 10^13. AFAIK. It's been a few years since I read anything about this pulsar. Millisecond pulsars are more stable than slower pulsars, and hope has been expressed that, when thousands or tens of thousands of these pulsars have been discovered and can be observed nearly continuously, the ensemble of this many pulsars will allow establishment of a pulsar- based standard of time having stability, on a time-scale of about one year, of a few parts in 10^15. AFAIK, such a standard remains a dream, not a reality. ___ time-nuts mailing 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] Thermal time constant
Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil ___ time-nuts mailing 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] Thermal time constant
Hi The gotcha is that you are interested in the amount of heat per cubic foot rather than the amount of heat per pound. You need to take the standard heat per weight numbers and convert them to heat per volume numbers. Of the things you can easily get, copper is good. Steel is not as good as copper, but better than aluminum. Bob On Mar 10, 2010, at 5:52 PM, p...@pseng.org.uk wrote: Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil ___ time-nuts mailing 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] Thermal time constant
A better metric may be stored heat for a dollar's worth of material. Scrap iron is pretty cheap. From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Date: 03/10/2010 06:03 PM Subject: Re: [time-nuts] Thermal time constant Sent by: time-nuts-boun...@febo.com Hi The gotcha is that you are interested in the amount of heat per cubic foot rather than the amount of heat per pound. You need to take the standard heat per weight numbers and convert them to heat per volume numbers. Of the things you can easily get, copper is good. Steel is not as good as copper, but better than aluminum. Bob On Mar 10, 2010, at 5:52 PM, p...@pseng.org.uk wrote: Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil ___ time-nuts mailing 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] Thermal time constant
p...@pseng.org.uk wrote: Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil Actually in this application minimising the volume of the metal block rather than its weight is probably better so one should use specific heat*density as a figure of merit. METALSpecific heat*density (W/J/cubic cm) Aluminium 2.46 Beryllium3.29 Copper 3.49 Silver 2.41 Iron3.87 Thus copper and iron are better choices than Beryllium they also poses fewer machining diffculties 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] Thermal time constant
Just in case anyone finds a beryllium brick somewhere and tries to use it: Beryllium is very very poisonous. cheers, Neville Michie On 11/03/2010, at 10:08 AM, Bruce Griffiths wrote: p...@pseng.org.uk wrote: Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil Actually in this application minimising the volume of the metal block rather than its weight is probably better so one should use specific heat*density as a figure of merit. METALSpecific heat*density (W/J/cubic cm) Aluminium 2.46 Beryllium3.29 Copper 3.49 Silver 2.41 Iron3.87 Thus copper and iron are better choices than Beryllium they also poses fewer machining diffculties 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] Thermal time constant
There's at least one known case where someone attempted to grind a beryllium mirror substrate using conventional methods without proper control of dust resulting in his death. Bruce Neville Michie wrote: Just in case anyone finds a beryllium brick somewhere and tries to use it: Beryllium is very very poisonous. cheers, Neville Michie On 11/03/2010, at 10:08 AM, Bruce Griffiths wrote: p...@pseng.org.uk wrote: Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil Actually in this application minimising the volume of the metal block rather than its weight is probably better so one should use specific heat*density as a figure of merit. METALSpecific heat*density (W/J/cubic cm) Aluminium 2.46 Beryllium3.29 Copper 3.49 Silver 2.41 Iron3.87 Thus copper and iron are better choices than Beryllium they also poses fewer machining diffculties 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 mailing 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] Thermal time constant
Hi The same caution applies to the beryllium in beryllium oxide heat spreaders. You find them in old RF transistors and some RF tubes. Bob On Mar 10, 2010, at 6:45 PM, Bruce Griffiths wrote: There's at least one known case where someone attempted to grind a beryllium mirror substrate using conventional methods without proper control of dust resulting in his death. Bruce Neville Michie wrote: Just in case anyone finds a beryllium brick somewhere and tries to use it: Beryllium is very very poisonous. cheers, Neville Michie On 11/03/2010, at 10:08 AM, Bruce Griffiths wrote: p...@pseng.org.uk wrote: Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil Actually in this application minimising the volume of the metal block rather than its weight is probably better so one should use specific heat*density as a figure of merit. METALSpecific heat*density (W/J/cubic cm) Aluminium 2.46 Beryllium3.29 Copper 3.49 Silver 2.41 Iron3.87 Thus copper and iron are better choices than Beryllium they also poses fewer machining diffculties 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 mailing 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] Thermal time constant
Beryllium copper parts are also an issue although the beryllium content is only 0.3%-0.5% by weight. Bruce Bob Camp wrote: Hi The same caution applies to the beryllium in beryllium oxide heat spreaders. You find them in old RF transistors and some RF tubes. Bob On Mar 10, 2010, at 6:45 PM, Bruce Griffiths wrote: There's at least one known case where someone attempted to grind a beryllium mirror substrate using conventional methods without proper control of dust resulting in his death. Bruce Neville Michie wrote: Just in case anyone finds a beryllium brick somewhere and tries to use it: Beryllium is very very poisonous. cheers, Neville Michie On 11/03/2010, at 10:08 AM, Bruce Griffiths wrote: p...@pseng.org.uk wrote: Looking at the specific heat of metals: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html Wouldn't Beryllium be better instead of aluminium? I could foresee a few problems though eg machining holes at home, never mind where to get a block from. Phil Actually in this application minimising the volume of the metal block rather than its weight is probably better so one should use specific heat*density as a figure of merit. METALSpecific heat*density (W/J/cubic cm) Aluminium 2.46 Beryllium3.29 Copper 3.49 Silver 2.41 Iron3.87 Thus copper and iron are better choices than Beryllium they also poses fewer machining diffculties 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 mailing 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] Thermal Time Constant
Hi So getting back to the original idea. Taking the other extreme - if you go for ~20 C / W on the insulation: The mass of the block will be ~50X what it was before. 1.6 on a side goes to ~5 on a side. Surface area goes up ~10X. 200 C/W with 2 foam goes to 20 C/W Outer surface area goes to ~1.6X the inner surface area Go to 4 of foam and you are pretty close. Go to 8 of foam and you have some room left for things like wires and the like. Resulting block is a bit under 2 feet on a side Bob On Mar 10, 2010, at 4:48 PM, Bruce Griffiths wrote: Surely you meant 1 square inch of styrofoam with the specified thickness?? For a 100 hour (3.6E5 seconds) time constant and 1000 deg C/W thermal resistance you need a thermal capacitance of 3.6E5/1E3 = 360 J/C or 360/0.8371 = 430 gm of Aluminium which has a volume of 430/2.7 = 159 cc. You still have the thermal radiation coupling problem through the infrared transparent insulator. Gold plating the aluminium will help. Even if you solve the thermal radiation problem, the thermal conductance of any leads bringing power or signals to or from the clock will be an major problem even if you use constantan or austenetic stainless steel leads. Bruce Brooke Clarke wrote: Hi Bruce: If a square meter of Styrofoam is 1.5 deg C/W then a cubic inch would be 39.37 * 39.37 * 1.5 or 2,325 deg C/W The DS3231 dissipates about 1 mw when running. I'm not sure how to come up with an allowable temp increase, but suspect it's based on not exceeding the max allowed operating temp. But for this part the Temp vs. freq curve is flattest at room temp so best to minimize the temp rise. So: (1 deg C) / (0.001 W) = 1000 deg C/W, the same number you had. That requires 185 g of Aluminum or about 69 cc volume or 4.25 cubic inches. That's a block about 1.62 on a side. How does that look? Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Thermal resistance is measured in degrees (C or K or ..) per watt. Its inversely proportional to area and proportional to thickness. I think the clueless clown who created that table means that for a 1 square meter panel of the specified thickness the thermal resistance is the tabulated value measured in Kelvin/Watt. Bruce Brooke Clarke wrote: Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Bruce Griffiths wrote: Brooke Clarke wrote: Hi: For some time I've considered surrounding a free running 32678 Hz oscillator (like a Dallas 32khz, or one of the newer Maxim units) with thermal mass and insulation in order to get the time constant into the range of some days. To get a feel for it a simple experiment shows that a half inch diameter brass rod 3.75 long (102 grams) has a thermal time constant of about 6 min 35 seconds when wrapped lightly in a towel. Is there a way to calculate the amount of aluminum and Styrofoam needed to get a time constant of say 100 hours? This came up in relation to WWVB clocks that free run for most of the time. When you compare WWVB clocks it's not uncommon to see tens of seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC Start with the maximum thermal resistance the application can withstand (determined by internal dissipation and acceptable temperature rise above ambient). If for example the dissipation is 10mW and acceptable temperature rise 10C then thermal resistance will be about 1000C/W. The thermal capacity required can then be calculated from the time constant: C= 3.6E5/1E3 = 360 J/C requires about 7.2 kg of aluminium. The required thickness of styrofoam can then be calculated from the surface area of the aluminium block. Achieving a thermal resistance of 1000C/W may be a little difficult without using radiation shields. Bruce Oops, the specific heat of Alum9inium is about 0.2Cal/gm/C or 0.8371 J/gm/C so the mass of Aluminium required would be 430gm if the thermal resistance to ambient were 1000K/W. With a thermal resistance of 100C/W you need 4.3Kg of aluminium 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 mailing 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] Thermal time constant
The suggestion of beryllium was somewhat tongue-in-cheek ie not to be taken seriously, I did mention there would be a few problems, death being somewhat a terminal one. I agree with Bruce that specific heat*density is what is really required (I'd forgotten how light beryllium is. I don't seem to have much laying around to be familiar with it) As an aside, cuts from copper swarf can take a long time to heal. Sorry if I've lowered the tone of a good list. Phil ___ time-nuts mailing 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] Thermal Time Constant
Hi Bob: I like the idea of a six inch on a side cube. An outer aluminum box, styrofoam insulation, and a block of (copper, Aluminum, etc.) in the center. A DS3231 or similar RTC and a PIC with a DB-9 connector on one face. Have Fun, Brooke Clarke http://www.PRC68.com Bob Camp wrote: Hi So getting back to the original idea. Taking the other extreme - if you go for ~20 C / W on the insulation: The mass of the block will be ~50X what it was before. 1.6 on a side goes to ~5 on a side. Surface area goes up ~10X. 200 C/W with 2 foam goes to 20 C/W Outer surface area goes to ~1.6X the inner surface area Go to 4 of foam and you are pretty close. Go to 8 of foam and you have some room left for things like wires and the like. Resulting block is a bit under 2 feet on a side Bob On Mar 10, 2010, at 4:48 PM, Bruce Griffiths wrote: Surely you meant 1 square inch of styrofoam with the specified thickness?? For a 100 hour (3.6E5 seconds) time constant and 1000 deg C/W thermal resistance you need a thermal capacitance of 3.6E5/1E3 = 360 J/C or 360/0.8371 = 430 gm of Aluminium which has a volume of 430/2.7 = 159 cc. You still have the thermal radiation coupling problem through the infrared transparent insulator. Gold plating the aluminium will help. Even if you solve the thermal radiation problem, the thermal conductance of any leads bringing power or signals to or from the clock will be an major problem even if you use constantan or austenetic stainless steel leads. Bruce Brooke Clarke wrote: Hi Bruce: If a square meter of Styrofoam is 1.5 deg C/W then a cubic inch would be 39.37 * 39.37 * 1.5 or 2,325 deg C/W The DS3231 dissipates about 1 mw when running. I'm not sure how to come up with an allowable temp increase, but suspect it's based on not exceeding the max allowed operating temp. But for this part the Temp vs. freq curve is flattest at room temp so best to minimize the temp rise. So: (1 deg C) / (0.001 W) = 1000 deg C/W, the same number you had. That requires 185 g of Aluminum or about 69 cc volume or 4.25 cubic inches. That's a block about 1.62 on a side. How does that look? Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Thermal resistance is measured in degrees (C or K or ..) per watt. Its inversely proportional to area and proportional to thickness. I think the clueless clown who created that table means that for a 1 square meter panel of the specified thickness the thermal resistance is the tabulated value measured in Kelvin/Watt. Bruce Brooke Clarke wrote: Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. Have Fun, Brooke Clarke http://www.PRC68.com Bruce Griffiths wrote: Bruce Griffiths wrote: Brooke Clarke wrote: Hi: For some time I've considered surrounding a free running 32678 Hz oscillator (like a Dallas 32khz, or one of the newer Maxim units) with thermal mass and insulation in order to get the time constant into the range of some days. To get a feel for it a simple experiment shows that a half inch diameter brass rod 3.75 long (102 grams) has a thermal time constant of about 6 min 35 seconds when wrapped lightly in a towel. Is there a way to calculate the amount of aluminum and Styrofoam needed to get a time constant of say 100 hours? This came up in relation to WWVB clocks that free run for most of the time. When you compare WWVB clocks it's not uncommon to see tens of seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC Start with the maximum thermal resistance the application can withstand (determined by internal dissipation and acceptable temperature rise above ambient). If for example the dissipation is 10mW and acceptable temperature rise 10C then thermal resistance will be about 1000C/W. The thermal capacity required can then be calculated from the time constant: C= 3.6E5/1E3 = 360 J/C requires about 7.2 kg of aluminium. The required thickness of styrofoam can then be calculated from the surface area of the aluminium block. Achieving a thermal resistance of 1000C/W may be a little difficult without using radiation shields. Bruce Oops, the specific heat of Alum9inium is about 0.2Cal/gm/C or 0.8371 J/gm/C so the mass of Aluminium required would be 430gm if the thermal resistance to ambient were 1000K/W. With a thermal resistance of 100C/W you need 4.3Kg of aluminium 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
Re: [time-nuts] Thermal time constant
I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing 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] Thermal time constant
Hi That raises the interesting question of weather radiant transfer is already included in the rated thermal resistance. My guess is that the 8 of foam is enough to cover any radiation issues and still get you above 20 C / W. Since you are probably starting with 1 or 2 slabs, including the aluminum foil would be pretty easy. It can't hurt and it might help. Bob On Mar 10, 2010, at 7:29 PM, Neville Michie wrote: I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing 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] Thermal time constant
Radiative heat transfer (for a surface with an emissivity of 1) is around 150uW/square cm /degreeC at 300K. That's equivalent to about 10cm of styrofoam. It seems unlikely that the radiative heat transfer component is included in the thermal resistance rating for Styrofoam. The radiative component is independent of insulation thickness where the insulation doesnt absorb in the 10-30um infrared region. Adding carbon black to the foam appears to increase the thermal resistance of 25mm thick foam by about 10%. Bruce Bob Camp wrote: Hi That raises the interesting question of weather radiant transfer is already included in the rated thermal resistance. My guess is that the 8 of foam is enough to cover any radiation issues and still get you above 20 C / W. Since you are probably starting with 1 or 2 slabs, including the aluminum foil would be pretty easy. It can't hurt and it might help. Bob On Mar 10, 2010, at 7:29 PM, Neville Michie wrote: I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing 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] Thermal time constant
Oops forgot a factor of 4 Radiative heat transfer for surface with an emissivity of 1 at 300K is about 612uW/square cm/degree C which is equivalent to about 25mm of styrofoam. Which raises the question what's the emissivity of the isothermal surface used when measuring the thermal resistance of a slab of styrofoam? Bruce Bruce Griffiths wrote: Radiative heat transfer (for a surface with an emissivity of 1) is around 150uW/square cm /degreeC at 300K. That's equivalent to about 10cm of styrofoam. It seems unlikely that the radiative heat transfer component is included in the thermal resistance rating for Styrofoam. The radiative component is independent of insulation thickness where the insulation doesnt absorb in the 10-30um infrared region. Adding carbon black to the foam appears to increase the thermal resistance of 25mm thick foam by about 10%. Bruce Bob Camp wrote: Hi That raises the interesting question of weather radiant transfer is already included in the rated thermal resistance. My guess is that the 8 of foam is enough to cover any radiation issues and still get you above 20 C / W. Since you are probably starting with 1 or 2 slabs, including the aluminum foil would be pretty easy. It can't hurt and it might help. Bob On Mar 10, 2010, at 7:29 PM, Neville Michie wrote: I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Thermal time constant
Hi Since styrofoam is being rated as a building insulation, it's reasonable to believe that the material on both sides is up around 1. I highly doubt that somebody tossing styrofoam in walls is going to add a radiation factor ... In our application we're talking about a metal block inside a metal enclosure, polishing the surfaces could drop the emissivity by 10X. If the budget allows, you could gold plate the surfaces in addition to polishing them . Bob On Mar 10, 2010, at 8:01 PM, Bruce Griffiths wrote: Oops forgot a factor of 4 Radiative heat transfer for surface with an emissivity of 1 at 300K is about 612uW/square cm/degree C which is equivalent to about 25mm of styrofoam. Which raises the question what's the emissivity of the isothermal surface used when measuring the thermal resistance of a slab of styrofoam? Bruce Bruce Griffiths wrote: Radiative heat transfer (for a surface with an emissivity of 1) is around 150uW/square cm /degreeC at 300K. That's equivalent to about 10cm of styrofoam. It seems unlikely that the radiative heat transfer component is included in the thermal resistance rating for Styrofoam. The radiative component is independent of insulation thickness where the insulation doesnt absorb in the 10-30um infrared region. Adding carbon black to the foam appears to increase the thermal resistance of 25mm thick foam by about 10%. Bruce Bob Camp wrote: Hi That raises the interesting question of weather radiant transfer is already included in the rated thermal resistance. My guess is that the 8 of foam is enough to cover any radiation issues and still get you above 20 C / W. Since you are probably starting with 1 or 2 slabs, including the aluminum foil would be pretty easy. It can't hurt and it might help. Bob On Mar 10, 2010, at 7:29 PM, Neville Michie wrote: I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Thermal time constant
There's a small problem with my calculation and the published figures for the thermal resistance of styrofoam. If the measurements include radiative transfers the thermal resistance per unit area of a styrofoam slab should reach a limiting value (when the radiative transfer component dominates) as the thickness is increased. Possibilities 1) My calculation is incorrect. 2) Infrared absorption in thick styrofoam slabs is significant. 3) The tabulated figures for the thermal resistance of styrofoam are merely scaled up from the values measured with thin sheets. This gives misleading values for thick sheets if the tabulated values include radiative transfer. Bruce Bob Camp wrote: Hi Since styrofoam is being rated as a building insulation, it's reasonable to believe that the material on both sides is up around 1. I highly doubt that somebody tossing styrofoam in walls is going to add a radiation factor ... In our application we're talking about a metal block inside a metal enclosure, polishing the surfaces could drop the emissivity by10X. If the budget allows, you could gold plate the surfaces in addition to polishing them . Bob On Mar 10, 2010, at 8:01 PM, Bruce Griffiths wrote: Oops forgot a factor of 4 Radiative heat transfer for surface with an emissivity of 1 at 300K is about 612uW/square cm/degree C which is equivalent to about 25mm of styrofoam. Which raises the question what's the emissivity of the isothermal surface used when measuring the thermal resistance of a slab of styrofoam? Bruce Bruce Griffiths wrote: Radiative heat transfer (for a surface with an emissivity of 1) is around 150uW/square cm /degreeC at 300K. That's equivalent to about 10cm of styrofoam. It seems unlikely that the radiative heat transfer component is included in the thermal resistance rating for Styrofoam. The radiative component is independent of insulation thickness where the insulation doesnt absorb in the 10-30um infrared region. Adding carbon black to the foam appears to increase the thermal resistance of 25mm thick foam by about 10%. Bruce Bob Camp wrote: Hi That raises the interesting question of weather radiant transfer is already included in the rated thermal resistance. My guess is that the 8 of foam is enough to cover any radiation issues and still get you above 20 C / W. Since you are probably starting with 1 or 2 slabs, including the aluminum foil would be pretty easy. It can't hurt and it might help. Bob On Mar 10, 2010, at 7:29 PM, Neville Michie wrote: I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] Thermal time constant
Hi Low density (1 or 2 lb / cu ft) urethane foam is going to be a better insulator than styrofoam. I believe it's reasonably opaque at IR. Bob On Mar 10, 2010, at 8:23 PM, Bruce Griffiths wrote: There's a small problem with my calculation and the published figures for the thermal resistance of styrofoam. If the measurements include radiative transfers the thermal resistance per unit area of a styrofoam slab should reach a limiting value (when the radiative transfer component dominates) as the thickness is increased. Possibilities 1) My calculation is incorrect. 2) Infrared absorption in thick styrofoam slabs is significant. 3) The tabulated figures for the thermal resistance of styrofoam are merely scaled up from the values measured with thin sheets. This gives misleading values for thick sheets if the tabulated values include radiative transfer. Bruce Bob Camp wrote: Hi Since styrofoam is being rated as a building insulation, it's reasonable to believe that the material on both sides is up around 1. I highly doubt that somebody tossing styrofoam in walls is going to add a radiation factor ... In our application we're talking about a metal block inside a metal enclosure, polishing the surfaces could drop the emissivity by10X. If the budget allows, you could gold plate the surfaces in addition to polishing them . Bob On Mar 10, 2010, at 8:01 PM, Bruce Griffiths wrote: Oops forgot a factor of 4 Radiative heat transfer for surface with an emissivity of 1 at 300K is about 612uW/square cm/degree C which is equivalent to about 25mm of styrofoam. Which raises the question what's the emissivity of the isothermal surface used when measuring the thermal resistance of a slab of styrofoam? Bruce Bruce Griffiths wrote: Radiative heat transfer (for a surface with an emissivity of 1) is around 150uW/square cm /degreeC at 300K. That's equivalent to about 10cm of styrofoam. It seems unlikely that the radiative heat transfer component is included in the thermal resistance rating for Styrofoam. The radiative component is independent of insulation thickness where the insulation doesnt absorb in the 10-30um infrared region. Adding carbon black to the foam appears to increase the thermal resistance of 25mm thick foam by about 10%. Bruce Bob Camp wrote: Hi That raises the interesting question of weather radiant transfer is already included in the rated thermal resistance. My guess is that the 8 of foam is enough to cover any radiation issues and still get you above 20 C / W. Since you are probably starting with 1 or 2 slabs, including the aluminum foil would be pretty easy. It can't hurt and it might help. Bob On Mar 10, 2010, at 7:29 PM, Neville Michie wrote: I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] Thermal time constant
Depends on the duration of the experiment. Urethanes arent well known for stability. The low thermal resistance of close cell urethanes is largely due to their better retention of the blowing agent which has lower thermal conductivity than air. Closed cell foam glass (however the sulphur dioxide released when a cell is broken may be an issue) is much more stable than plastic foams the thermal resistance of which slowly deteriorates due to gas diffusion (air diffuse in and blowing agent diffuses out). The gradual permeation of the plastic foam by water vapour can also have a significant effect. Foam glass is sometimes used to insulate very large cryogen tanks. Bruce Bob Camp wrote: Hi Low density (1 or 2 lb / cu ft) urethane foam is going to be a better insulator than styrofoam. I believe it's reasonably opaque at IR. Bob On Mar 10, 2010, at 8:23 PM, Bruce Griffiths wrote: There's a small problem with my calculation and the published figures for the thermal resistance of styrofoam. If the measurements include radiative transfers the thermal resistance per unit area of a styrofoam slab should reach a limiting value (when the radiative transfer component dominates) as the thickness is increased. Possibilities 1) My calculation is incorrect. 2) Infrared absorption in thick styrofoam slabs is significant. 3) The tabulated figures for the thermal resistance of styrofoam are merely scaled up from the values measured with thin sheets. This gives misleading values for thick sheets if the tabulated values include radiative transfer. Bruce Bob Camp wrote: Hi Since styrofoam is being rated as a building insulation, it's reasonable to believe that the material on both sides is up around 1. I highly doubt that somebody tossing styrofoam in walls is going to add a radiation factor ... In our application we're talking about a metal block inside a metal enclosure, polishing the surfaces could drop the emissivity by10X. If the budget allows, you could gold plate the surfaces in addition to polishing them . Bob On Mar 10, 2010, at 8:01 PM, Bruce Griffiths wrote: Oops forgot a factor of 4 Radiative heat transfer for surface with an emissivity of 1 at 300K is about 612uW/square cm/degree C which is equivalent to about 25mm of styrofoam. Which raises the question what's the emissivity of the isothermal surface used when measuring the thermal resistance of a slab of styrofoam? Bruce Bruce Griffiths wrote: Radiative heat transfer (for a surface with an emissivity of 1) is around 150uW/square cm /degreeC at 300K. That's equivalent to about 10cm of styrofoam. It seems unlikely that the radiative heat transfer component is included in the thermal resistance rating for Styrofoam. The radiative component is independent of insulation thickness where the insulation doesnt absorb in the 10-30um infrared region. Adding carbon black to the foam appears to increase the thermal resistance of 25mm thick foam by about 10%. Bruce Bob Camp wrote: Hi That raises the interesting question of weather radiant transfer is already included in the rated thermal resistance. My guess is that the 8 of foam is enough to cover any radiation issues and still get you above 20 C / W. Since you are probably starting with 1 or 2 slabs, including the aluminum foil would be pretty easy. It can't hurt and it might help. Bob On Mar 10, 2010, at 7:29 PM, Neville Michie wrote: I have been wondering about achieving the rated thermal resistance from plastic foam, the problem being that radiant transmission may be very strong through the foam. What happens if you interleave concentric sheets of foam plastic with aluminium foil? (taking care to keep the foil on isothermal surfaces) Will this stop the radiant transfer and leave only the thermal conduction of the plastic foam? cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and
[time-nuts] FE-5680A
Hi all -- I have the info for setting up the output freq. Has anyone managed to snag the info for the test points and adjustments in this beast? thanx! -ls- ___ time-nuts mailing 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] FE-5680A
Hi Like pretty much every other rubidium on the planet - no, not as far as I know. Most of the test points and adjustments are of the even if we told you, you aren't set up to use it nature. Put another way, they would have to provide a lot of proprietary information to enable you to do anything. A more cynical view would be if it breaks we want to sell you another one. My personal experience suggests that setting one up is indeed a black art known only to the select few. The high priest takes them into the back room and they magically come return in working order several days / weeks / what ever later. High priest goes on vacation - not much is going to ship Bob On Mar 10, 2010, at 9:23 PM, Larry Snyder wrote: Hi all -- I have the info for setting up the output freq. Has anyone managed to snag the info for the test points and adjustments in this beast? thanx! -ls- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] HP10811 taxonomy?
Has anyone compiled a taxonomy of the apparently numerous variants of 10811 OXOs? (Distinguishing features, rated performance, used in what instruments, etc.) Also, I found Mark's observation that 10544s may drift less than 10811s interesting. I own several 10544As and have experience with perhaps several dozen others, and think very highly of them, but haven't seen enough 10811s for a meaningful comparison (meaningful being a relative term, when the sample sizes are as low as dozens). What have others observed? Best regards, Charles ___ time-nuts mailing 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] Thermal Time Constant
Brooke Clarke wrote: Hi Bruce: What does m2K/W mean? See: http://building.dow.com/europe/uk/proddata/styrofoam/thermal.htm 50 mm it's about 1.5 and for 100 mm it's about 3. thermal resistance (you can tell because it's degrees/watt, as opposed to watts/degree which would be conductivity) square meter Kelvin/Watt. and doubling for a doubling in thickness makes perfect sense. ___ time-nuts mailing 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] nubie querie
Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? I think the traditional test for an amateur is do you get paid for it. (Yes, it helps to be independently wealthy.) Well, that's sort of the 18th/19th century model, certainly. Lavoisier wasn't paid to figure chemistry out. Neither did John Strutt, 3rd Baron Rayleigh. But is that an appropriate model for today? Even if you build your own antenna, there is the question of where do you start. Is it OK to buy a dish if I build the mount? Can I buy steel pipe or do I have to start from iron ore? I've always wanted to start with smelting, but my wife says no cupola furnace in the backyard (this after I was pointing out the books on this in the Lindsay Books catalog). I suspect if you look at other amateur activities (say sports), there are examples equivalent to scrounging time on Arecibo. Sure.. and the sponging off others has historical precedent, for DXpeditions and 8000 meter peak attempts alike. My 2 cents... You get credit for the part that you do. Anything goes as long as you are honest about what you do. If you buy the electronics and build the antenna, you get credit for building the antenna. If you build the electronics and buy (or scrounge) the antenna, then you get credit for the electronics. ... Some people are really good at scrounging. ___ time-nuts mailing 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] Thermal Time Constant
Brooke Clarke wrote: Hi Bruce: If a square meter of Styrofoam is 1.5 deg C/W then a cubic inch would be 39.37 * 39.37 * 1.5 or 2,325 deg C/W The DS3231 dissipates about 1 mw when running. I'm not sure how to come up with an allowable temp increase, but suspect it's based on not exceeding the max allowed operating temp. But for this part the Temp vs. freq curve is flattest at room temp so best to minimize the temp rise. So: (1 deg C) / (0.001 W) = 1000 deg C/W, the same number you had. That requires 185 g of Aluminum or about 69 cc volume or 4.25 cubic inches. That's a block about 1.62 on a side. How does that look? you can also use U.S. R-values.. BTU/hr/ft^2/deg F. ___ time-nuts mailing 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] HP10811 taxonomy?
Charles P. Steinmetz wrote: Has anyone compiled a taxonomy of the apparently numerous variants of 10811 OXOs? (Distinguishing features, rated performance, used in what instruments, etc.) Charles, if you have not already seen it there is a manual, I think on the Time Lord, TvB's site that has an appendix listing all the varieties of the 10811 and thus how they were selected, which makes interesting reading. Dan ___ time-nuts mailing 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] nubie querie
If you like starting from scratch, get a copy of Procedures in Experimental Physics by John Strong. -John === Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? I think the traditional test for an amateur is do you get paid for it. (Yes, it helps to be independently wealthy.) Well, that's sort of the 18th/19th century model, certainly. Lavoisier wasn't paid to figure chemistry out. Neither did John Strutt, 3rd Baron Rayleigh. But is that an appropriate model for today? Even if you build your own antenna, there is the question of where do you start. Is it OK to buy a dish if I build the mount? Can I buy steel pipe or do I have to start from iron ore? I've always wanted to start with smelting, but my wife says no cupola furnace in the backyard (this after I was pointing out the books on this in the Lindsay Books catalog). I suspect if you look at other amateur activities (say sports), there are examples equivalent to scrounging time on Arecibo. Sure.. and the sponging off others has historical precedent, for DXpeditions and 8000 meter peak attempts alike. My 2 cents... You get credit for the part that you do. Anything goes as long as you are honest about what you do. If you buy the electronics and build the antenna, you get credit for building the antenna. If you build the electronics and buy (or scrounge) the antenna, then you get credit for the electronics. ... Some people are really good at scrounging. ___ time-nuts mailing 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] Thermal time constant
Bob Camp wrote: Hi The gotcha is that you are interested in the amount of heat per cubic foot rather than the amount of heat per pound. You need to take the standard heat per weight numbers and convert them to heat per volume numbers. Of the things you can easily get, copper is good. Steel is not as good as copper, but better than aluminum. Bob Gold is your friend. Mercury has convective losses because it's a liquid. Platinum or Osmium would also be ok. You might want something that is dense but lower conductivity.. lead? Depleted Uranium? (DU is available very cheaply if you can take 80,000 pound lots) ___ time-nuts mailing 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] FE-5680A
Bob Camp wrote: Hi Like pretty much every other rubidium on the planet - no, not as far as I know. Most of the test points and adjustments are of the even if we told you, you aren't set up to use it nature. Put another way, they would have to provide a lot of proprietary information to enable you to do anything. A more cynical view would be if it breaks we want to sell you another one. My personal experience suggests that setting one up is indeed a black art known only to the select few. The high priest takes them into the back room and they magically come return in working order several days / weeks / what ever later. High priest goes on vacation - not much is going to ship Bob On Mar 10, 2010, at 9:23 PM, Larry Snyder wrote: Hi all -- I have the info for setting up the output freq. Has anyone managed to snag the info for the test points and adjustments in this beast? thanx! -ls- Well, I agree to a point. I had some documentation on a Ball Efratom rubidium that had detailed theory sections and guidance on how to align the oscillator to the cell signal. It even had schematics of all the boards. So not every rubidium manufacturer was always guarding all the information. On the other hand, in my experience, FEI is not a company that is willing to share anything unless big bags of money and a contract are involved. Some of the information I have seen is bits of general documentation saved by those in the loop long ago. The majority of other helpful information seems to have been dug out by determined reverse engineering or experimentation of a few determined individuals. Documentation on most of the HP or Spectracom GPS or atomic stuff seems to be pretty sketchy too. ___ time-nuts mailing 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] Thermal time constant
Gawd, tell me about it... I just got through rebuilding the drive roller in half a dozen Tektronix YT-1 and YT-1S chart recorders for the 1502B/1520C/1503B/1503C TDR's. The recorders were built by AstroMed and the roller was made of a black urethane that reverts back to its primordial goo. It turns to an incredibly sticky spooge that flows over the circuit board and coats the print head. And then there is the drive roller in the HP65/67/97 calculator card readers. Not to mention the platen in the electrostatic 9120A printer for the 9100A and 9100B calculators. -- Urethanes arent well known for stability. _ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. http://clk.atdmt.com/GBL/go/201469229/direct/01/ ___ time-nuts mailing 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] FE-5680A
Bob Camp wrote: My personal experience suggests that setting one up is indeed a black art known only to the select few. The high priest takes them into the back room and they magically come return in working order several days / weeks / what ever later. High priest goes on vacation - not much is going to ship Bob There are still many high-tech products which fit in this general description. Adjusting tunable filters, Focusing TWTs using permanent magnets, etc. at lunch today, someone was talking about a guy from RS Microwave commenting that they had fooled with automatic filter tuning by computer, but a good tech could beat it every time. the machine tuning worked great for a specific filter, so if you had a big production run, it was ok, but if you're building just a few of each filter. (I rummaged in Google and found http://www.ee.ntu.edu.tw/news/96-Snyder-Filter-Development.pdf ) ___ time-nuts mailing 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] nubie querie
J. Forster wrote: If you like starting from scratch, get a copy of Procedures in Experimental Physics by John Strong. -John And, relevant to the thermal time constant discussion.. That book has a great section on thermal diffusion and conductivity, along with a chart of material properties. A newer book is building scientific apparatus by Moore, et al. There's a whole section on precision temperature control (where precision means milliKelvin).. But not as much fundamentals stuff as in Strong. e.g. Moore assumes you can buy a vacuum pump, Strong tells you how to build one..what a difference 60 years makes. But even Strong doesn't tell you how to make cast iron from ore. Lindsay Books is your friend, then. ___ time-nuts mailing 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] nubie querie
jimlux wrote: J. Forster wrote: If you like starting from scratch, get a copy of Procedures in Experimental Physics by John Strong. -John And, relevant to the thermal time constant discussion.. That book has a great section on thermal diffusion and conductivity, along with a chart of material properties. A newer book is building scientific apparatus by Moore, et al. There's a whole section on precision temperature control (where precision means milliKelvin).. Yes, it was coauthored by my thesis adviser, CC Davis. I was working for him while he was writing his sections. Never noticed anything of mine in it, though. -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.
Re: [time-nuts] Thermal time constant
water is pretty good, too and cheap. Coupling to it is easy as well. Don - Original Message - From: jimlux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, March 10, 2010 9:35 PM Subject: Re: [time-nuts] Thermal time constant Bob Camp wrote: Hi The gotcha is that you are interested in the amount of heat per cubic foot rather than the amount of heat per pound. You need to take the standard heat per weight numbers and convert them to heat per volume numbers. Of the things you can easily get, copper is good. Steel is not as good as copper, but better than aluminum. Bob Gold is your friend. Mercury has convective losses because it's a liquid. Platinum or Osmium would also be ok. You might want something that is dense but lower conductivity.. lead? Depleted Uranium? (DU is available very cheaply if you can take 80,000 pound lots) ___ time-nuts mailing 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] Lady Heather software help
That's a common question; rest assured you are not alone in your confusion. One of us -- Mark or myself or some other doughty volunteer -- *will* eventually write a user guide of some sort... but the software itself is still undergoing too many tweaks. It's a bit too soon to nail down the UI by writing documentation for it. I usually run the 3.00 beta with the /ga /go /gm /x=100 switches, to help keep the graph area uncluttered and bring up the PPI-style satellite view. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of SAL CORNACCHIA Sent: Wednesday, March 10, 2010 10:54 AM To: time-nuts@febo.com Subject: [time-nuts] Lady Heather software help Hello Group members, I need some help interpreting Lady Heather software results like the colours and chart results for My Tbold GPS Receiver, any help would be appreciated as I am new at this. Best regards, Sal C. Cornacchia Electronic RF Microwave Engineer (Ret.) ___ time-nuts mailing 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] Thermal time constant
How well depleted it really is? Uranium separation is not perfect. Some radioactivity is still left. I don't think it is healthy to have it beside You for a long time. Certainly not 8 pounds :)) At 05:35 11.3.2010, you wrote: Bob Camp wrote: Hi The gotcha is that you are interested in the amount of heat per cubic foot rather than the amount of heat per pound. You need to take the standard heat per weight numbers and convert them to heat per volume numbers. Of the things you can easily get, copper is good. Steel is not as good as copper, but better than aluminum. Bob Gold is your friend. Mercury has convective losses because it's a liquid. Platinum or Osmium would also be ok. You might want something that is dense but lower conductivity.. lead? Depleted Uranium? (DU is available very cheaply if you can take 80,000 pound lots) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. __ Information from ESET NOD32 Antivirus, version of virus signature database 4933 (20100310) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.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.
Re: [time-nuts] HP10811 taxonomy?
Hi Charles, See http://www.leapsecond.com/museum/10811a/90027-1.pdf for details of the 10811D/E versions and options. It's been appended to this copy of the A/B manual http://www.hparchive.com/Manuals/HP-10811AB-Manual.pdf Hope this helps. Robert G8RPI. --- On Thu, 11/3/10, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: [time-nuts] HP10811 taxonomy? To: Discussion of precise time and frequency measurement time-nuts@febo.com Date: Thursday, 11 March, 2010, 4:07 Has anyone compiled a taxonomy of the apparently numerous variants of 10811 OXOs? (Distinguishing features, rated performance, used in what instruments, etc.) Also, I found Mark's observation that 10544s may drift less than 10811s interesting. I own several 10544As and have experience with perhaps several dozen others, and think very highly of them, but haven't seen enough 10811s for a meaningful comparison (meaningful being a relative term, when the sample sizes are as low as dozens). What have others observed? Best regards, Charles ___ time-nuts mailing 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.
