Re: [time-nuts] Centering ocxo
ok.. So that may very well be true of this unit. Electrical tuning is 3E-7 0 - 5v (+/-). It also lists a digital tuning range of +- 3Hz at 10MHz. Correct me if I am wrong but that appears to mean 3Hz electrical and 6Hz digital tuning range. I am not doing digital tuning but thought I would throw that out there. I have been trying to optimize parameters on this Fury board but it seems my optimization has just been increasing the deviation. Running 1.8 ns sd overnight with an average TI of about 26ns (was with my optimized settings)...the original settings were giving me a much lower deviation...I didnt log it but looking at the graph of frequency in excel I would say probably between 0.1-0.6 ns. I just put it back on the original settings and am letting it settle now. Was adjusting Dampening, EFCSCALE and DAC gain. My observations reveal dampening makes it a bit slower to respond and perhaps settles it some, The efcscale seems to act as pure gain on top of the baseline dac gain which is essentially determined by the tuning range as you referred to. What I saw with a low efcscale is that the TI was higher but the SD lower... with efc scale higher the TI was lower but the SD suffered. Since my goal here is low noise and very good short term stability I prefer the lower efcscale (low gain with low SD). Let me know if I have any gross conceptual errors here or if I am looking at this properly. Doc KX0O On Tue, Oct 2, 2012 at 11:54 PM, Hal Murray hmur...@megapathdsl.net wrote: docdai...@gmail.com said: I am ok for awhile but how do you center the efc of an ocxo? I understand there is something (screw) to adjust the ocxo so it is approximately on freq with 2.5v efc. Specific oscillator datum-c. I have he datasheet but doesn't say coarse frequency adjust this screw or some such. There may not be a coarse adjustment. If the tuning range is big enough to cover the aging over your design life, you don't need one. There is a tradeoff between adjustment range and the number of bits you need in a DAC to get a required accuracy. Suppose I have an adjustment range of 1 Hz (peak to peak) on a 10 MHz oscillator. That's 1 part is 10^7. If I have a 10 bit DAC, I can adjust to 1 part is 10^10. A 20 bit DAC can get to 1 part is 10^13. But if the tuning range is 10 Hz, the same 20 bit DAC setup only gets you to 1 part is 10^12. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Doc Bill Dailey KXØO ___ time-nuts mailing 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] ThunderBolt Display
Hi all Another production run – the last - of the “ThunderBolt Display” is being done. Thought I would give it quick mention here, in case any ThunderBolt owners were interested, as some TimeNuts subscribers obtained a display last in the first production run. For details, pictures, video and information see: http://www.vklogger.com/forum/viewtopic.php?f=71t=10282 If you are looking for a display to monitor your ThunderBolt, without the need for a laptop, this is it! In the last post in that topic I link to above, you will find the Order Form doc. Should you wish to purchase a display, simply download that, and follow the instructions. Outside of Australia, I accept PayPal. You will also find a downloadable pdf User Guide if you want to know more about what this display does. A lot of people who wasted their money on the cheap and nasty $30 Chinese eBay display are now extremely satisfied with one of these. PCBs are being ordered THIS Friday night, so the deadline to order a completed ThunderBolt Display unit is Friday – in 2 days time. I don’t normally monitor this email list, so any enquiries should be made on the forum, or direct to me via the email address found in the topic. Cheers, Adam, VK4GHZ ___ time-nuts mailing 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] GPS Jammer
It is not that hard to transmit broad band noise over the entire GPS channel and clobber it entirely. Didier Sent from my Droid Razr 4G LTE wireless tracker. -Original Message- From: johncr...@aol.com To: time-nuts@febo.com Sent: Tue, 02 Oct 2012 9:33 PM Subject: Re: [time-nuts] GPS Jammer In considering the effect of a simple jammer on a GPS receiver, a simple link analysis is insufficient. What must also be considered is the anti-jam capability of the receiver which due to spread spectrum processing gain will reject any simple jamming signal even though is it 10's of dB stronger than the desired signal. 73 -john k6iql ___ time-nuts mailing 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] RFX GPSDO - Anybody played with one of these?
On 10/2/12 10:35 PM, b...@lysator.liu.se wrote: On 10/2/12 2:36 PM, saidj...@aol.com wrote: Hello Paul, thanks much for the feedback! Yes, we think we have identified a nice combination of oscillators, GPS, and firmware that seems to work pretty well. The GPSTCXO units cannot be compared to a lower cost $150 Thunderbolt in terms of phase noise or stability of course, and they have CMOS 10MHz outputs, but then the TB's cost around $1500 new I guess. We think the GPSTCXO's and LC_XO type units will work quite well wherever standard OCXO's are used today, and power/size/weight are an issue. Intriguing.. Can it handle the Doppler, etc., for a cubesat in LEO? (7km/s) The total Doppler isn't usually the issue (the GPS satellites are moving faster, after all), but the receiver may not work for high velocities, high altitudes? GPS SVs moves at around 4km/s, but nevertheless there are still COCOM limits implemented in nearly all receivers (never break both 504m/s and 18km height) Doh. of course. higher is slower In any case, though, nothing stops Jackson Labs from selling one that is export controlled and has no restrictions. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
Of course, that only works when you actually need a GPSDO, but what is the point of a GPS timing receiver if not to discipline a high quality oscillator? Didier KO4BB Sent from my Droid Razr 4G LTE wireless tracker. -Original Message- From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Tue, 02 Oct 2012 9:34 PM Subject: Re: [time-nuts] Best counter setting for ADEV? On 10/2/12 7:00 PM, shali...@gmail.com wrote: The Thunderbolt is a special case that does not provide sawtooth correction because it does not need it. It uses the OCXO as the clock for the processor while disciplining it to GPS so there is no nominal timing error between where the 1PPS is versus where it should be. The processor is able to bring the PPS edge exactly where it wants it, instead of the typical 25 to 40 ns granularity of most other GPS receivers that operate on a separate clock. Pretty simple and elegant solution. But it does depend on having a good oscillator that can be shoved around. That costs money and power. ___ time-nuts mailing 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] Oscillator frequency?
Hi, I have a tcxo that I recovered from a very old, suitcase-sized gps receiver some years ago. The oscillator is marked ERC Eros-750-MA110, with an output frequency of 5.119155MHz. I have tried to think of a use for for it but failed. I played with the numbers but could not find anything useful, so I thought I would try the collective wisdom of the list to see if anyone could come up with a use for such an oddball frequency. As an aside, it was fascinating to see a gps in discrete components, lots of mixers (I recovered no less than 10, MCL ASK1 mixers and there are still several left on the boards) on something like 7 or 8 , 200mm square, gold-plated plug-in boards on a very nice card frame with many, many interconnecting small-diameter coaxes with gold-plated connectors. Pity I wasn't interested in time-nuttery at the time, it probably worked before I reduced it to component parts! Thanks, Ken www.vk7krj.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] Oscillator frequency?
Boy have to say no clue and not a very useful frequency. Would it make a nice bookend? Paper weight. Glue a watch to it and you have at least time. ;-) Regards Paul WB8TSL On Wed, Oct 3, 2012 at 9:07 AM, ken johnson bats...@gmail.com wrote: Hi, I have a tcxo that I recovered from a very old, suitcase-sized gps receiver some years ago. The oscillator is marked ERC Eros-750-MA110, with an output frequency of 5.119155MHz. I have tried to think of a use for for it but failed. I played with the numbers but could not find anything useful, so I thought I would try the collective wisdom of the list to see if anyone could come up with a use for such an oddball frequency. As an aside, it was fascinating to see a gps in discrete components, lots of mixers (I recovered no less than 10, MCL ASK1 mixers and there are still several left on the boards) on something like 7 or 8 , 200mm square, gold-plated plug-in boards on a very nice card frame with many, many interconnecting small-diameter coaxes with gold-plated connectors. Pity I wasn't interested in time-nuttery at the time, it probably worked before I reduced it to component parts! Thanks, Ken www.vk7krj.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS Jammer
One of fine units from Hong Kong delivered +32dBm of wide-band FM noise centered on 1575MHz!!! Just a tad more range than 10m I would expect. -Brian, WA1ZMS (sent from my over-priced iPad3) On Oct 3, 2012, at 8:44 AM, shali...@gmail.com wrote: It is not that hard to transmit broad band noise over the entire GPS channel and clobber it entirely. Didier Sent from my Droid Razr 4G LTE wireless tracker. -Original Message- From: johncr...@aol.com To: time-nuts@febo.com Sent: Tue, 02 Oct 2012 9:33 PM Subject: Re: [time-nuts] GPS Jammer In considering the effect of a simple jammer on a GPS receiver, a simple link analysis is insufficient. What must also be considered is the anti-jam capability of the receiver which due to spread spectrum processing gain will reject any simple jamming signal even though is it 10's of dB stronger than the desired signal. 73 -john k6iql ___ time-nuts mailing 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] GPS Modulation and 10 MHz Delay Lock
I think it was this thread. But the actual chip rates derive from a 10.2299543 clock. We call it 1.023 Mhz but its not. In time-nuttery it matters. Doesn't that make the use of the signal a bit messy? Regards Paul WB8TSL On Tue, Oct 2, 2012 at 10:30 PM, Jim Lux jim...@earthlink.net wrote: On 10/2/12 3:39 PM, johncr...@aol.com wrote: Hello All - Here is a link that describes the GPS modulation. You do not need the 1 pps to lock the 10 MHz oscillator to the atomic clock in the satellites. http://www.kowoma.de/en/gps/**signals.htmhttp://www.kowoma.de/en/gps/signals.htm If you look at the block diagram you see PN code modulates the carrier at the 1.023 MHz chip rate. This is done by BPSK modulation of the carrier with the PN code. It can be done simply with a double balanced mixer. This spreads the signal with PSK at the chip( i.e. code clock) rate. Note also the modulo - 2 addition of the data to the code sequence. This called code inversion modulation. After de-spread of the code in the receiver - the signal is then simple BPSK and may be demodulated by a Costas or Squaring Loop to get at the data message. The obtain precision frequency needed I believe the T bolt simply locks to the chipping rate using some form of Delay Lock Loop. It is NOT at PLL. There is no need what ever to deal with the 1 pps using this method. The internal 10 MHz oscillator is controlled by this locking circuit and is part of the code correlation loop. That's not quite how it works.. It would work for terrestrial links where there is no Doppler, but in the GPS case, there is significant Doppler shift on all the signals. Since the carrier and the chips are generated from a common source on the spacecraft (the carrier frequency is a multiple of the chip rate, in fact), you can recover carrier and chips at the same time. But.. most receivers these days don't actually have an analog tracking loop at all. They digitize the input signal (1 bit quantizer) at a rate that makes the carrier alias down to something convenient (a few hundred kHz is typical.. you want it far enough away from zero that Doppler never makes it go negative). In the experimental receiver in SCaN Testbed flying on ISS it's about 39 MHz sample rate. Once you've got your one bit samples, you do some sort of combined Doppler/Code phase acquisition (these days, often using an FFT), then track both together digitally using some form of NCO. The tracking loops for all the satellite signals aren't necessarily independent and might be part of a Kalman filter that estimates all the observables together. Finally, from all that, you have an estimate of your local clock offset and timing offset, and from that you can generate your 1pps, typically with another NCO (with granularity of your clock rate). Since it's unlikely that your clock is EXACTLY an even number of cycles per second, at each second, a bit of error accumulates, until you have an whole cycle's worth leading to the familiar sawtooth error. That sawtooth error is predictable, of course, so you can generate a time error estimate for each 1pps pulse (or, even, control a variable delay to line it up). The important thing is that in modern receivers, nowhere is there a signal at the GPS carrier frequency, nor is there a signal at the chip rate. There *is* probably a signal (with low precision) at the code epoch (every millisecond), but it's different for each satellite signal, of course. __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] GPS Jammer
On Tue, Oct 2, 2012 at 9:40 PM, Ron Ward n6idl...@comcast.net wrote: Hi: Other than a terrorist, who would want to jam GPS? A delivery truck driver. His boss installs a GPS tracker on the truck and the driver wants to take a three hour lunch break. This is a pretty common scenario and likely the way most GPS jammers are used. I'd call it self jamming where you jam your own receiver so other people will not know where you are. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Oscillator frequency?
Yes, it would be interesting to run such a GPS receiver: maybe there are numbers of points to follow the signal processing. On Wed, Oct 3, 2012 at 3:12 PM, paul swed paulsw...@gmail.com wrote: Boy have to say no clue and not a very useful frequency. Would it make a nice bookend? Paper weight. Glue a watch to it and you have at least time. ;-) Regards Paul WB8TSL On Wed, Oct 3, 2012 at 9:07 AM, ken johnson bats...@gmail.com wrote: Hi, I have a tcxo that I recovered from a very old, suitcase-sized gps receiver some years ago. The oscillator is marked ERC Eros-750-MA110, with an output frequency of 5.119155MHz. I have tried to think of a use for for it but failed. I played with the numbers but could not find anything useful, so I thought I would try the collective wisdom of the list to see if anyone could come up with a use for such an oddball frequency. As an aside, it was fascinating to see a gps in discrete components, lots of mixers (I recovered no less than 10, MCL ASK1 mixers and there are still several left on the boards) on something like 7 or 8 , 200mm square, gold-plated plug-in boards on a very nice card frame with many, many interconnecting small-diameter coaxes with gold-plated connectors. Pity I wasn't interested in time-nuttery at the time, it probably worked before I reduced it to component parts! Thanks, Ken www.vk7krj.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] GPS Modulation and 10 MHz Delay Lock (Jim Lux) (Jim Lux)
for Jim Lux -- Thanks for the comments - Yes, if the receiver is linear (e.g. say you do a sliding code correlator and slide until you get the peak, with the correlator using a multiplier)... That is how the system I did worked. It could defeat an on-frequency jammer that was 20 db stronger than the signal while holding a 1e -6 BER. So considering the BPSK demod required a 10 db CNR, the total AJ processing gain was about 30 dB, which is what was expected. But since most (inexpensive) receivers have hard limiters/1 bit quantizers in front of the correlator, what goes into the correlator is a square wave at the jammer frequency, and you can slide your PN code all day and not get a peak. Yep - a hard limiter would kill any processing gain and simplify the design. There's some analysis out there that tells you how many bits you need for a given Jammer/Signal ratio, but in general, if the jammer is 20 dB over the signal, you need 3-4 bits. Back in the day, when bits were very expensive, that's why narrow band excisers were popular.. basically you'd run something like a PLL to recover the tone jammer, and subtract it out. We were not that good in 1976. But going above 20 GHz and antennas with a 2 degree beam width hid the signal and provided considerable immunity. Anyhow - thanks for the information on more modern techniques! -73 john k6iql ___ time-nuts mailing 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] GPS Jammer
Some 20 to 25 years ago a law enforcement agency in California was experimenting with GPS in its patrol cars. It required that the officer press key to report his/her location. It also had a pinging capability that the officers didn't know about. Through pinging, it was discovered that a number of the officers an interesting habit. Towards the end of their shift, their cars would be found stationary off the street in industrial areas. While they were close enough to their assigned patrol routes to quickly respond to calls, they avoided coming upon situations they would have to handle that might involve a lot of paperwork or otherwise might hold them past the end of shift. They also used the time to finish accumulated paperwork. I imagine that they would have liked a GPS jammer after they figured out that they were being watched. FWBRAY Sent from my CP/M machine. On Oct 2, 2012, at 21:40, Ron Ward n6idl...@comcast.net wrote: Hi: Other than a terrorist, who would want to jam GPS? Ron -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, October 02, 2012 2:28 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPS Jammer On 10/02/2012 11:05 PM, John Lofgren wrote: The 0.5 W and + 10 dBm numbers in the specs don't work out. +10 dBm is 10 mW. I suspect that the 1/2 watt is really the DC input power. Now, that makes sense. And, I'd agree about the range. +10 dBm into a dipole at 10 meters gets you about -44 dBm at the receiver antenna in a free-space model. That's really loud compared to the nominal -130 to -140 dBm you'd hear from the satellites. Indeed. Even for 10 mW it was not reasonable. No wonders that 1-10 m jammers cause such grief to DHS. Serious overkill. 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 mailing 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] Centering ocxo
Doc, You are on the right track, efc scale affects SD as you can see. The phaseco parameter is used to push down the average TI to 0ns. Higher values push faster. If your ocxo is still drifting (aging and or retrace) it will take about 48 hours for the aging measurement and correction to kick in, and bring the offset down to 0ns. Bye Said Sent From iPhone On Oct 3, 2012, at 3:46, Bill Dailey docdai...@gmail.com wrote: ok.. So that may very well be true of this unit. Electrical tuning is 3E-7 0 - 5v (+/-). It also lists a digital tuning range of +- 3Hz at 10MHz. Correct me if I am wrong but that appears to mean 3Hz electrical and 6Hz digital tuning range. I am not doing digital tuning but thought I would throw that out there. I have been trying to optimize parameters on this Fury board but it seems my optimization has just been increasing the deviation. Running 1.8 ns sd overnight with an average TI of about 26ns (was with my optimized settings)...the original settings were giving me a much lower deviation...I didnt log it but looking at the graph of frequency in excel I would say probably between 0.1-0.6 ns. I just put it back on the original settings and am letting it settle now. Was adjusting Dampening, EFCSCALE and DAC gain. My observations reveal dampening makes it a bit slower to respond and perhaps settles it some, The efcscale seems to act as pure gain on top of the baseline dac gain which is essentially determined by the tuning range as you referred to. What I saw with a low efcscale is that the TI was higher but the SD lower... with efc scale higher the TI was lower but the SD suffered. Since my goal here is low noise and very good short term stability I prefer the lower efcscale (low gain with low SD). Let me know if I have any gross conceptual errors here or if I am looking at this properly. Doc KX0O On Tue, Oct 2, 2012 at 11:54 PM, Hal Murray hmur...@megapathdsl.net wrote: docdai...@gmail.com said: I am ok for awhile but how do you center the efc of an ocxo? I understand there is something (screw) to adjust the ocxo so it is approximately on freq with 2.5v efc. Specific oscillator datum-c. I have he datasheet but doesn't say coarse frequency adjust this screw or some such. There may not be a coarse adjustment. If the tuning range is big enough to cover the aging over your design life, you don't need one. There is a tradeoff between adjustment range and the number of bits you need in a DAC to get a required accuracy. Suppose I have an adjustment range of 1 Hz (peak to peak) on a 10 MHz oscillator. That's 1 part is 10^7. If I have a 10 bit DAC, I can adjust to 1 part is 10^10. A 20 bit DAC can get to 1 part is 10^13. But if the tuning range is 10 Hz, the same 20 bit DAC setup only gets you to 1 part is 10^12. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Doc Bill Dailey KXØO ___ time-nuts mailing 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] OT question about liquid cooling
Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
On Oct 2, 2012, at 1:39 PM, saidj...@aol.com wrote: 1) calibrate the internal 100MHz vectron OCXO using a small screwdriver, this is not really critical though as the unit does not really function as a frequency counter. 2) Calibrate the power supplies for proper voltages if necessary with same screwdriver, I found that is really not necessary usually Thanks for those two steps. I've found a copy of the user and GPIB manuals, but not a service manual. Do you have a service manual that you could forward to me. Also, I was interested in the VISI software, but talking with Wavecrest a few years ago they said that it was no longer supported. Do you know to get an orphaned copy? Many thanks and for all of your help thoughts over the years. I'll look forward to the day and I can afford a GPS disciplined CSAC. Best, Kevin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
Many thanks and for all of your help thoughts over the years. I'll look forward to the day and I can afford a GPS disciplined CSAC. Best, Kevin The CSAC is cheap compared to the reference you need to measure it... http://www.leapsecond.com/pages/csac/log96872v.gif /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS Jammer
Let me just say that that's flea power! I saw some 80watt jammers being sold for movie theaters and churches. There is some very black market items from China, via Hong Kong and can arrive at your doorstep in just 4 days via DHL! What's out there would scare you. Been dealing with the fall out from such items in my day job. -Brian On Oct 2, 2012, at 4:43 PM, J. Forster j...@quikus.com wrote: Take a look at the specs of this unit: http://www.mobilephonejammer.com.au/covert-gps-jammer-portable-p-119.html The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT question about liquid cooling
5KW of power but that is only 1/4 of the spec. What temperature will the loads operate at? It is quite hard to cool anything to ambient with water. The cooler the operating point the larger the heat sink. Using a very oversize heat exchanger s not unreasonable of you want a relative low temperature. The other side of the loop matters LOT also. How will you cool the water? Do you have chilled water that can run open loop or do you need to chill and re-cycle the water in a closed loop system. Then again temperature matters. What is the inlet temperature? How much flow rate can your system provide. If you don't wnt to learn a loot about this the easy solultion it to simply over-spec the components by a large factor. This also gives you some margin for accients like a plumbing leak or a pump failure. Do plan for these practical issues.When a pump fails the 5KW load can boil water in the heat exchanger quickly and then your plumbing comes apart. To prevent that use enough water volume and thermal mass. Again an over sized heat exchanger is good. As is a thermal shutdown switch. These are cheap and work just like a fuse. They open the AC mains power at a set temperature, you bolt them to the heat sink. They are common in high power audio amplifiers. I don't have experience with a system like you need. Mine is with water cooling that involved TEC (thermo electric, or Peltier devices.) But I know that you do need to plan for mechanical failures, water leaks and so on.Just like with a domestic hot water heaters you place a basin and drain under them. On Wed, Oct 3, 2012 at 9:01 AM, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing 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] RFX GPSDO - Anybody played with one of these?
On 10/2/12 10:35 PM, b...@lysator.liu.se wrote: On 10/2/12 2:36 PM, saidj...@aol.com wrote: Hello Paul, thanks much for the feedback! Yes, we think we have identified a nice combination of oscillators, GPS, and firmware that seems to work pretty well. The GPSTCXO units cannot be compared to a lower cost $150 Thunderbolt in terms of phase noise or stability of course, and they have CMOS 10MHz outputs, but then the TB's cost around $1500 new I guess. We think the GPSTCXO's and LC_XO type units will work quite well wherever standard OCXO's are used today, and power/size/weight are an issue. Intriguing.. Can it handle the Doppler, etc., for a cubesat in LEO? (7km/s) The total Doppler isn't usually the issue (the GPS satellites are moving faster, after all), but the receiver may not work for high velocities, high altitudes? GPS SVs moves at around 4km/s, but nevertheless there are still COCOM limits implemented in nearly all receivers (never break both 504m/s and 18km height) Doh. of course. higher is slower In any case, though, nothing stops Jackson Labs from selling one that is export controlled and has no restrictions. Not more than some paperwork for Jackson Labs to source a no limit uBlox. And then checking that the uBlox actually performs as expected in that environment. Well, I am not sure the doppler search range is wide enough in a standard firmware. (+-4km/s vs +-11km/s relative vel.) On the black sheep Javad online shop they quote an extra $1k for this. -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
Hi NTP server? Time tagging remotely collected data? Large area industrial automation? Generally as you relax the timing requirement, the number of applications goes up quite a bit. If all you need is a few hundred ns (but under a few microseconds), a bare timing receiver is a fine thing. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of shali...@gmail.com Sent: Wednesday, October 03, 2012 8:46 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? Of course, that only works when you actually need a GPSDO, but what is the point of a GPS timing receiver if not to discipline a high quality oscillator? Didier KO4BB Sent from my Droid Razr 4G LTE wireless tracker. -Original Message- From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Tue, 02 Oct 2012 9:34 PM Subject: Re: [time-nuts] Best counter setting for ADEV? On 10/2/12 7:00 PM, shali...@gmail.com wrote: The Thunderbolt is a special case that does not provide sawtooth correction because it does not need it. It uses the OCXO as the clock for the processor while disciplining it to GPS so there is no nominal timing error between where the 1PPS is versus where it should be. The processor is able to bring the PPS edge exactly where it wants it, instead of the typical 25 to 40 ns granularity of most other GPS receivers that operate on a separate clock. Pretty simple and elegant solution. But it does depend on having a good oscillator that can be shoved around. That costs money and power. ___ time-nuts mailing 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] GPS Jammer
Who would want to jam GPS? Haven't heard this one: Fishing party boat captain - knows where to find the fishing spots after years of experience. Rotates use of the spots so as not to over-fish them. Arrives at his spots to find fishermen who had gone out with him and captured the GPS locations of his spots. Now tells his customers that any GPS receivers found will be float tested by throwing them overboard. Bill Hawkins -Original Message- From: Chris Albertson Sent: Wednesday, October 03, 2012 9:27 AM On Tue, Oct 2, 2012 at 9:40 PM, Ron Ward n6idl...@comcast.net wrote: Hi: Other than a terrorist, who would want to jam GPS? A delivery truck driver. His boss installs a GPS tracker on the truck and the driver wants to take a three hour lunch break. This is a pretty common scenario and likely the way most GPS jammers are used. I'd call it self jamming where you jam your own receiver so other people will not know where you are. ___ time-nuts mailing 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] Centering ocxo
Thanks Said. This is a learning experience but it is fun watching it settle down. I will stop fiddling with the settings and just let it do it's thing. I am watching the output with my qs1r direct digital to spectrumlab. This way I don't have to worry about any audio glitches. I have been recording frequency every minute the entire time to see what it is doing. Sent from mobile On Oct 3, 2012, at 10:39 AM, Said Jackson saidj...@aol.com wrote: Doc, You are on the right track, efc scale affects SD as you can see. The phaseco parameter is used to push down the average TI to 0ns. Higher values push faster. If your ocxo is still drifting (aging and or retrace) it will take about 48 hours for the aging measurement and correction to kick in, and bring the offset down to 0ns. Bye Said Sent From iPhone On Oct 3, 2012, at 3:46, Bill Dailey docdai...@gmail.com wrote: ok.. So that may very well be true of this unit. Electrical tuning is 3E-7 0 - 5v (+/-). It also lists a digital tuning range of +- 3Hz at 10MHz. Correct me if I am wrong but that appears to mean 3Hz electrical and 6Hz digital tuning range. I am not doing digital tuning but thought I would throw that out there. I have been trying to optimize parameters on this Fury board but it seems my optimization has just been increasing the deviation. Running 1.8 ns sd overnight with an average TI of about 26ns (was with my optimized settings)...the original settings were giving me a much lower deviation...I didnt log it but looking at the graph of frequency in excel I would say probably between 0.1-0.6 ns. I just put it back on the original settings and am letting it settle now. Was adjusting Dampening, EFCSCALE and DAC gain. My observations reveal dampening makes it a bit slower to respond and perhaps settles it some, The efcscale seems to act as pure gain on top of the baseline dac gain which is essentially determined by the tuning range as you referred to. What I saw with a low efcscale is that the TI was higher but the SD lower... with efc scale higher the TI was lower but the SD suffered. Since my goal here is low noise and very good short term stability I prefer the lower efcscale (low gain with low SD). Let me know if I have any gross conceptual errors here or if I am looking at this properly. Doc KX0O On Tue, Oct 2, 2012 at 11:54 PM, Hal Murray hmur...@megapathdsl.net wrote: docdai...@gmail.com said: I am ok for awhile but how do you center the efc of an ocxo? I understand there is something (screw) to adjust the ocxo so it is approximately on freq with 2.5v efc. Specific oscillator datum-c. I have he datasheet but doesn't say coarse frequency adjust this screw or some such. There may not be a coarse adjustment. If the tuning range is big enough to cover the aging over your design life, you don't need one. There is a tradeoff between adjustment range and the number of bits you need in a DAC to get a required accuracy. Suppose I have an adjustment range of 1 Hz (peak to peak) on a 10 MHz oscillator. That's 1 part is 10^7. If I have a 10 bit DAC, I can adjust to 1 part is 10^10. A 20 bit DAC can get to 1 part is 10^13. But if the tuning range is 10 Hz, the same 20 bit DAC setup only gets you to 1 part is 10^12. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Doc Bill Dailey KXØO ___ time-nuts mailing 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] Best counter setting for ADEV?
Very nice plot Tom! Did you thermally insulate the CSAC to get this kind of performance? bye, Said In a message dated 10/3/2012 09:24:54 Pacific Daylight Time, t...@leapsecond.com writes: Many thanks and for all of your help thoughts over the years. I'll look forward to the day and I can afford a GPS disciplined CSAC. Best, Kevin The CSAC is cheap compared to the reference you need to measure it... http://www.leapsecond.com/pages/csac/log96872v.gif /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Centering ocxo
Please don't adjust the dampening, you might find it floating... adjust the damping if you need to change the settling time. Yours in pedantry-one of my hot buttons :-) Don Bill Dailey ok.. So that may very well be true of this unit. Electrical tuning is 3E-7 0 - 5v (+/-). It also lists a digital tuning range of +- 3Hz at 10MHz. Correct me if I am wrong but that appears to mean 3Hz electrical and 6Hz digital tuning range. I am not doing digital tuning but thought I would throw that out there. I have been trying to optimize parameters on this Fury board but it seems my optimization has just been increasing the deviation. Running 1.8 ns sd overnight with an average TI of about 26ns (was with my optimized settings)...the original settings were giving me a much lower deviation...I didnt log it but looking at the graph of frequency in excel I would say probably between 0.1-0.6 ns. I just put it back on the original settings and am letting it settle now. Was adjusting Dampening, EFCSCALE and DAC gain. My observations reveal dampening makes it a bit slower to respond and perhaps settles it some, The efcscale seems to act as pure gain on top of the baseline dac gain which is essentially determined by the tuning range as you referred to. What I saw with a low efcscale is that the TI was higher but the SD lower... with efc scale higher the TI was lower but the SD suffered. Since my goal here is low noise and very good short term stability I prefer the lower efcscale (low gain with low SD). Let me know if I have any gross conceptual errors here or if I am looking at this properly. Doc KX0O On Tue, Oct 2, 2012 at 11:54 PM, Hal Murray hmur...@megapathdsl.net wrote: docdai...@gmail.com said: I am ok for awhile but how do you center the efc of an ocxo? I understand there is something (screw) to adjust the ocxo so it is approximately on freq with 2.5v efc. Specific oscillator datum-c. I have he datasheet but doesn't say coarse frequency adjust this screw or some such. There may not be a coarse adjustment. If the tuning range is big enough to cover the aging over your design life, you don't need one. There is a tradeoff between adjustment range and the number of bits you need in a DAC to get a required accuracy. Suppose I have an adjustment range of 1 Hz (peak to peak) on a 10 MHz oscillator. That's 1 part is 10^7. If I have a 10 bit DAC, I can adjust to 1 part is 10^10. A 20 bit DAC can get to 1 part is 10^13. But if the tuning range is 10 Hz, the same 20 bit DAC setup only gets you to 1 part is 10^12. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Doc Bill Dailey KXØO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] Oscillator frequency?
Hi Ken: I have two of these, and had the same problem some years ago (see archives time-nuts). Nothing seemed to need this frequency. Fast forward to present. I'm using an ICOM 260A 2m all-mode xceiver for if in a 13 cm moonbounce system. The xtal frequency for the basic synthesizer in these units is 5.12 MHz. I played around with the idea of separate better xtals, until one day I was cleaning out. DOH! I now have a use for those weird OCXO's! Soo... never throw anything away, and never dismay, for all weird stuff WILL be useful someday. There's a coarse adjustment of some kind on these units. 73, Don AJ7LL ken johnson Hi, I have a tcxo that I recovered from a very old, suitcase-sized gps receiver some years ago. The oscillator is marked ERC Eros-750-MA110, with an output frequency of 5.119155MHz. I have tried to think of a use for for it but failed. I played with the numbers but could not find anything useful, so I thought I would try the collective wisdom of the list to see if anyone could come up with a use for such an oddball frequency. As an aside, it was fascinating to see a gps in discrete components, lots of mixers (I recovered no less than 10, MCL ASK1 mixers and there are still several left on the boards) on something like 7 or 8 , 200mm square, gold-plated plug-in boards on a very nice card frame with many, many interconnecting small-diameter coaxes with gold-plated connectors. Pity I wasn't interested in time-nuttery at the time, it probably worked before I reduced it to component parts! Thanks, Ken www.vk7krj.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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] Oscillator frequency?
5.12MHz is often used as the reference for PLL channelised radio receivers. Alan G3NYK - Original Message - From: Don Latham d...@montana.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, October 03, 2012 6:28 PM Subject: Re: [time-nuts] Oscillator frequency? Hi Ken: I have two of these, and had the same problem some years ago (see archives time-nuts). Nothing seemed to need this frequency. Fast forward to present. I'm using an ICOM 260A 2m all-mode xceiver for if in a 13 cm moonbounce system. The xtal frequency for the basic synthesizer in these units is 5.12 MHz. I played around with the idea of separate better xtals, until one day I was cleaning out. DOH! I now have a use for those weird OCXO's! Soo... never throw anything away, and never dismay, for all weird stuff WILL be useful someday. There's a coarse adjustment of some kind on these units. 73, Don AJ7LL ken johnson Hi, I have a tcxo that I recovered from a very old, suitcase-sized gps receiver some years ago. The oscillator is marked ERC Eros-750-MA110, with an output frequency of 5.119155MHz. I have tried to think of a use for for it but failed. I played with the numbers but could not find anything useful, so I thought I would try the collective wisdom of the list to see if anyone could come up with a use for such an oddball frequency. As an aside, it was fascinating to see a gps in discrete components, lots of mixers (I recovered no less than 10, MCL ASK1 mixers and there are still several left on the boards) on something like 7 or 8 , 200mm square, gold-plated plug-in boards on a very nice card frame with many, many interconnecting small-diameter coaxes with gold-plated connectors. Pity I wasn't interested in time-nuttery at the time, it probably worked before I reduced it to component parts! Thanks, Ken www.vk7krj.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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT question about liquid cooling
My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.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] OT question about liquid cooling
BWIWY (back when I was young) we needed a dummy load for a supercomputer (think Cray YMP size) that drew many many kw. Our test load was about 250' of 3/4 copper tubing coiled at about 12 dia and 1 spacing. The load was varied by changing where the + and - leads were bolted onto the coil with u bolts. The whole mess was cooled by running water through it. A hose barb on the input connected up to the cold water supply and the output was run into a drain. You had too little resistance dialed in when all thy came out the output end was steam. :) Anyway such a test load could be replicated using 1/4 ice machine copper tubing available at the hardware store, some hose clamps, and or hose barbs. Bob On Oct 3, 2012, at 19:35, Tom Harris celephi...@gmail.com wrote: My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT question about liquid cooling
It actually takes supprisingly little water flow to dissipate 5 kW. Very roughly 5 kW = 1250 cal/sec (4.18 J/cal) so, for a 1 C degree = 1.25 liters/sec at 50C degrees = 25 mL / sec. = 1.5 L/min. -John == BWIWY (back when I was young) we needed a dummy load for a supercomputer (think Cray YMP size) that drew many many kw. Our test load was about 250' of 3/4 copper tubing coiled at about 12 dia and 1 spacing. The load was varied by changing where the + and - leads were bolted onto the coil with u bolts. The whole mess was cooled by running water through it. A hose barb on the input connected up to the cold water supply and the output was run into a drain. You had too little resistance dialed in when all thy came out the output end was steam. :) Anyway such a test load could be replicated using 1/4 ice machine copper tubing available at the hardware store, some hose clamps, and or hose barbs. Bob On Oct 3, 2012, at 19:35, Tom Harris celephi...@gmail.com wrote: My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] GPS Modulation and 10 MHz Delay Lock
On 10/03/2012 03:38 PM, paul swed wrote: I think it was this thread. But the actual chip rates derive from a 10.2299543 clock. We call it 1.023 Mhz but its not. In time-nuttery it matters. Doesn't that make the use of the signal a bit messy? Nope. You missed the point of this off the mark is to compensate for the relativistic frequency shift that is occuring so the GPS clock at launch is at this rate, but when in orbit it will run a little faster, so this rate will match up better. Then, the remaining error is corrected for in the broadcast model so this first degree approximation will just get that decently into range. Check ICD GPS 200D. 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] OT question about liquid cooling
If you let the water boil, it takes even (much) less. Tom - Original Message - From: J. Forster j...@quikus.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, October 03, 2012 8:14 PM Subject: Re: [time-nuts] OT question about liquid cooling It actually takes supprisingly little water flow to dissipate 5 kW. Very roughly 5 kW = 1250 cal/sec (4.18 J/cal) so, for a 1 C degree = 1.25 liters/sec at 50C degrees = 25 mL / sec. = 1.5 L/min. -John == BWIWY (back when I was young) we needed a dummy load for a supercomputer (think Cray YMP size) that drew many many kw. Our test load was about 250' of 3/4 copper tubing coiled at about 12 dia and 1 spacing. The load was varied by changing where the + and - leads were bolted onto the coil with u bolts. The whole mess was cooled by running water through it. A hose barb on the input connected up to the cold water supply and the output was run into a drain. You had too little resistance dialed in when all thy came out the output end was steam. :) Anyway such a test load could be replicated using 1/4 ice machine copper tubing available at the hardware store, some hose clamps, and or hose barbs. Bob On Oct 3, 2012, at 19:35, Tom Harris celephi...@gmail.com wrote: My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT question about liquid cooling
Perhaps, but unless you plan on just draining the water, you need a liquid to air heat exchanger (LAHE) to cool the water in your loop. Perhaps for a lab it's no big deal, but if you intend to operate where it can get cold (needing glycol) or where there is very limited water supply (remote locations) this matters. I'm installing a 96.5% efficient 9 MVA inverter right now and it needs a minimum of 65 GPM through the LAHE of a 40% glycol solution (glycol moves less heat than water). The heat exchanger is *substantial*, much larger than the items + cold plates it's keeping cool. On 10/3/2012 8:14 PM, J. Forster wrote: It actually takes supprisingly little water flow to dissipate 5 kW. Very roughly 5 kW = 1250 cal/sec (4.18 J/cal) so, for a 1 C degree = 1.25 liters/sec at 50C degrees = 25 mL / sec. = 1.5 L/min. -John == BWIWY (back when I was young) we needed a dummy load for a supercomputer (think Cray YMP size) that drew many many kw. Our test load was about 250' of 3/4 copper tubing coiled at about 12 dia and 1 spacing. The load was varied by changing where the + and - leads were bolted onto the coil with u bolts. The whole mess was cooled by running water through it. A hose barb on the input connected up to the cold water supply and the output was run into a drain. You had too little resistance dialed in when all thy came out the output end was steam. :) Anyway such a test load could be replicated using 1/4 ice machine copper tubing available at the hardware store, some hose clamps, and or hose barbs. Bob On Oct 3, 2012, at 19:35, Tom Harris celephi...@gmail.com wrote: My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1427 / Virus Database: 2441/5308 - Release Date: 10/03/12 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Oscillator frequency?
Thanks Don and Allen, it's been that long since I played with radio I had forgotten- 5.12 is half of 10.240 used to downconvert from 10.7 if to 455. I had a look through the circuits for my rigs, and my Eddystone 770r boat anchor uses 5.12MHz to align the various if's, and multiples of it to align various other bits, so the ocxo may yet come in handy. Of course, that means I now need to look for yet another round tuit for that job- there never seems to be enough round tuits for the jobs currently on hand, let alone new ones.. On 2012-10-04 03:28, Don Latham wrote: Hi Ken: I have two of these, and had the same problem some years ago (see archives time-nuts). Nothing seemed to need this frequency. Fast forward to present. I'm using an ICOM 260A 2m all-mode xceiver for if in a 13 cm moonbounce system. The xtal frequency for the basic synthesizer in these units is 5.12 MHz. I played around with the idea of separate better xtals, until one day I was cleaning out. DOH! I now have a use for those weird OCXO's! Soo... never throw anything away, and never dismay, for all weird stuff WILL be useful someday. There's a coarse adjustment of some kind on these units. 73, Don AJ7LL Ken, vk7krj www.vk7krj.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] OT question about liquid cooling
9 MVA is somewhat bigger than 5 kW. I was assuming fairly short duration tests, perhaps a few hours, where open-cycle water is practical. If you are going to use a water loop, getting rid of the heat is certainly an issue. -John == Perhaps, but unless you plan on just draining the water, you need a liquid to air heat exchanger (LAHE) to cool the water in your loop. Perhaps for a lab it's no big deal, but if you intend to operate where it can get cold (needing glycol) or where there is very limited water supply (remote locations) this matters. I'm installing a 96.5% efficient 9 MVA inverter right now and it needs a minimum of 65 GPM through the LAHE of a 40% glycol solution (glycol moves less heat than water). The heat exchanger is *substantial*, much larger than the items + cold plates it's keeping cool. On 10/3/2012 8:14 PM, J. Forster wrote: It actually takes supprisingly little water flow to dissipate 5 kW. Very roughly 5 kW = 1250 cal/sec (4.18 J/cal) so, for a 1 C degree = 1.25 liters/sec at 50C degrees = 25 mL / sec. = 1.5 L/min. -John == BWIWY (back when I was young) we needed a dummy load for a supercomputer (think Cray YMP size) that drew many many kw. Our test load was about 250' of 3/4 copper tubing coiled at about 12 dia and 1 spacing. The load was varied by changing where the + and - leads were bolted onto the coil with u bolts. The whole mess was cooled by running water through it. A hose barb on the input connected up to the cold water supply and the output was run into a drain. You had too little resistance dialed in when all thy came out the output end was steam. :) Anyway such a test load could be replicated using 1/4 ice machine copper tubing available at the hardware store, some hose clamps, and or hose barbs. Bob On Oct 3, 2012, at 19:35, Tom Harris celephi...@gmail.com wrote: My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1427 / Virus Database: 2441/5308 - Release Date: 10/03/12 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
On Oct 3, 2012, at 11:15 AM, saidj...@aol.com wrote: The CSAC is cheap compared to the reference you need to measure it... http://www.leapsecond.com/pages/csac/log96872v.gif Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 seconds. Kevin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT question about liquid cooling
And the heat transfer to the fluid s better too. However, boiling has it's own serious issues. -John = If you let the water boil, it takes even (much) less. Tom - Original Message - From: J. Forster j...@quikus.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, October 03, 2012 8:14 PM Subject: Re: [time-nuts] OT question about liquid cooling It actually takes supprisingly little water flow to dissipate 5 kW. Very roughly 5 kW = 1250 cal/sec (4.18 J/cal) so, for a 1 C degree = 1.25 liters/sec at 50C degrees = 25 mL / sec. = 1.5 L/min. -John == BWIWY (back when I was young) we needed a dummy load for a supercomputer (think Cray YMP size) that drew many many kw. Our test load was about 250' of 3/4 copper tubing coiled at about 12 dia and 1 spacing. The load was varied by changing where the + and - leads were bolted onto the coil with u bolts. The whole mess was cooled by running water through it. A hose barb on the input connected up to the cold water supply and the output was run into a drain. You had too little resistance dialed in when all thy came out the output end was steam. :) Anyway such a test load could be replicated using 1/4 ice machine copper tubing available at the hardware store, some hose clamps, and or hose barbs. Bob On Oct 3, 2012, at 19:35, Tom Harris celephi...@gmail.com wrote: My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
On Oct 3, 2012, at 6:52 PM, Kevin Rosenberg ke...@rosenberg.net wrote: Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 seconds. Sorry, 1E-14 at 1E5. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
Hi A 1 ns resolution TI counter will do the measuring part just fine. Hitting the number, is where it gets a bit crazy. A *good* GPSDO might get near that. Bob On Oct 3, 2012, at 8:56 PM, Kevin Rosenberg ke...@rosenberg.net wrote: On Oct 3, 2012, at 6:52 PM, Kevin Rosenberg ke...@rosenberg.net wrote: Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 seconds. Sorry, 1E-14 at 1E5. ___ time-nuts mailing 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.
