Re: [time-nuts] GPS W/10KHz
You're looking for the older Rockwell/Conexant/Navman Jupiter-T ones. Some default in Motorola binary compatibility mode, with only 8 channels visible. Due to scarcity they are getting way to pricey... You might be better off with the newer uBlox NEO/LEA-6T, with configurable output(s). On 2/8/2014 6:10 AM, Perry Sandeen wrote: List, Wrote: where is a good source of GPS receiver modules I need one which has 10kHz output to phase lock a quartz oscillator. Fluke.1 Motorola ONCORE M12+T timing gps receiver 1pps 100hz eBay item number:290656401551 Also RDR There is another china seller that has them(10KHz) with leads for $90 but is almost impossible to find. Last time I searched it took me a hour. But he has a wide assortment. I forgot to bookmark his site. Regards, Perrier ___ time-nuts mailing 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] Thunderbolt tuning DAC theory of operation
On a later version, the Trimble/Nortel 45k, there are a few obvious HW differences (lousy Rx, bigger FPGA - XC5204, second Flash EEPROM). The PWM is generated differentially (better CMR) in the FPGA (output on pins 12, 13) registered, synchronously with the squared OCXO output signal to reduce jitter, in the 74AC174 on D0, and D1 (input on pins 3, 4), which is being supplied with a stabilized voltage from the LT1021-5 reference through one section of the quad Op Amp LT1014, and a series transistor. Those operations (jitter minimization and clean supply voltage) are crucial to the quality of the PWM signal. While the operation is obviously by PWM modulating the 102.4us period (10MHz/2^10) signal by the 10MSBs, the processing of the 10LSBs is less so. The PWM signal is dithered, by a ripple minimizing pattern, with a periodicity of 1024 pulses (104.8576ms = 1/10MHz/10^20), giving the DAC a full 20bit monotonic resolution. On 11/2/2013 10:41 AM, Stewart Cobb wrote: While poking around the Thunderbolt to determine whether -5V could be used in place of -12V, I discovered how the OCXO tuning DAC works. Apologies if this is old news, but I haven't seen it documented before. The 10MHz sine wave from the OCXO is squared up and used to clock the Xilinx 5200 CPLD (U22) and a 74AC174 hex D flip-flop (U14). Inside the CPLD (apparently) the 10 MHz clock is divided by 1024, giving a square wave with a period of 102.4 us (about 9.7 kHz). The duty cycle of that square wave is modulated by the 10 MSBs of the commanded DAC value. The LSBs are used to offset the falling edge of the square wave one clock cycle (100 ns) later, during a fraction of the 9.7 kHz square waves proportional to the LSBs value. On a modern digital scope, you can zoom in on the falling edge of the square wave, set the display to average, and see that the averaged height of that clock cycle is proportional to the DAC LSBs. There appear to be at least 8 LSBs, perhaps as many as 10, giving a total DAC resolution of 18 to 20 bits. (If the DAC value is averaged over one second, there are 10^7 clock cycles which can be controlled, giving a theoretical maximum resolution of 23+ bits. Trimble may have chosen a shorter averaging time and fewer bits.) The PWM square wave travels from pin 13 of the CPLD (U22) to pin 4, the D1 input of the 74AC174 (U14). The flip-flops in this chip are also clocked by the squared-up 10 MHz from the OCXO. The Q1 output, pin 5 of U14, goes to one side of R83 in the circuitry around the LT1014 op-amp. The other five inputs and outputs of U14 are constantly high or low. They may also be fed to the op-amp circuits, to help it handle the square wave in a purely ratiometric manner. The inputs and outputs of the Xilinx CPLD can be programmed for many different I/O standards. Unfortunately, this makes their output pin drivers far from ideal. The purpose of the 74AC174 is presumably to drive the analog circuitry with a input that is as close as possible to a mathematically ideal digital signal. Outputs in the 74AC logic family can source or sink 24 mA and have relatively balanced raise and fall times. This was probably the most ideal digital output available to the Thunderbolt's designers in the late '90s. This DAC implementation is guaranteed monotonic, an important consideration. There is exactly one rising edge and one falling edge per cycle, so that any difference between rise and fall times will have a constant effect which can be tuned out. Unlike a sigma-delta DAC, this PWM DAC produces strong spectral lines at multiples of the 9.7 kHz square wave frequency. On the one hand, it is comparatively easy to design filters to remove a single frequency (and its harmonics). On the other hand, this signal is strong enough that it may appear in phase noise plots anyway. If you want to view the 9.7 kHz square wave for yourself, it appears on a small square test point next to the silkscreen designator for C78, very close to the 6-pin power input jack. This test point is part of the connection from the Xilinx CPLD to the hex D flip-flop. Probing it does not affect the OCXO tuning. Hope this helps. Cheers! --Stu ___ time-nuts mailing 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] SDR Radio Opinion- Next Question
It depends what you mean under professional... an individual that pushes buttons for a wage, having no clue about what's actually happening underneath, or an individual that knows his business in, and out? The definition in my book is the second one, and I met many amateurs (aka hobbyists, with a passion for a certain domain, with deep knowledge, but not necessarily their main income source) which outclassed most professionals. If you appreciate more the point and click features to program something rapidly, without any control of the generated code, you're better served with the nicely integrated toys for windumb co. Ever wondered why low latency audio is working nicely on linux (eventually with the appropriate kernel settings, if you intend to load the system heavily), and is such a nightmare on windoze? Or why microsuxx castrated the network bandwidth usage (btw, a very professional solution) when a multimedia application is running under Vista 1, 2 (aka 7), or 3 (aka 8)? On 8/7/2013 12:03 AM, Alberto di Bene wrote: On 8/6/2013 5:12 AM, Chris Albertson wrote: /It depends of it you want to be the kind of ham who understands radios and can build and design them or the kind who would have never remove the cover off his commercial built radio. Linux is the best OS for developers and those who like to build gear. Windows is better for the appliance user crowd./ When I developed Winrad and my other SDR programs, a few years ago, I examined which were the tools available to a serious developer. My conclusion was that under Windows you could find professional tools, geared towards professional developments. What was available under Linux were little more than toys, meant for the hobbyists and the tinkerers. For example, at the time I was unable to find under Linux a development environment with the features and the power of the Embarcadero Rad Studio, which is what I use. This made me to choose Windows as my main platform. 73 Alberto I2PHD ___ time-nuts mailing 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] Heads up: Mark C. Stephens...
Good luck delisting a DNSBL listed IP (block) from those crusaders... Back some time there was a piss contest between some of those blacklists on which one would blacklist the whole internet faster. In the mean time different security providers bought up some of those rabid blacklists to power their antispam offerings, usually bundled with a security appliance. If you get caught in their web, you'll have a tough time to get delisted, usually denied with some puerile pretext, from obtuse criteria up to pure blackmail. On 8/5/2013 12:29 PM, John Miles wrote: Mark, I'm having trouble replying to your email, as your ISP is using a spam blacklist (SORBS) that blocks the SMTP servers used by the largest American cable ISP. Do you have another ISP you can use to receive email? -- john, KE5FX Miles Design LLC ___ time-nuts mailing 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] Re: Heads up: Mark C. Stephens...
While I'll agree on Spamhaus' decent services, SORBS has definitely a very shoddy history (the internet is full of beneficiaries's stories). Besides being very trigger happy, and unresponsive on requests, the owners at least used to force a fine, err. donation for delisting. Since it has been sold, a few years ago, I guess the latter practice was discontinued. Thanks for the suggestions, but even if I'm running/administering mail servers since last century, I still had encounters with some donkey-brained DNSBLs, one even trying to blackmail me, conditioning delisting with forcing my ISP, through me, to contact them to solve some unfinished business they had... Cases of blacklisting all IP blocks of certain ISPs as a retaliatory measure are not unknown of, if the DNSBL's master felt so... Not one of those brain-dead DNSBLs could provide a single example of spam originating at one of the MXs's addresses, but offered a lot of hot air about their intelligent algorithms. In the case of a DNSBL acquired by m$, they justified the blacklisting for sending over 50% spam after supposedly getting _one_ offending message... which they of course couldn't/wouldn't provide. You have to trust their word! It's usually just a waste of time, and nerves, to try to reason with those DNSBLs. It's faster to convince the admin of the partner's domain to whitelist the IP(s) directly. BTW, most viruses, and other malwares usually don't use the victim's ISP MXs, but send the spam/malware directly to the world. I've more seen spoofing compromised generic (web)mail provider's accounts (especially yahoo). Windumb, and computer illiterate lusers are the main source of spam/malware dissemination. Blocking SMTP connections except to the own MX (with appropriate filtering before relaying) is current practice. On 8/5/2013 2:46 PM, James Harrison wrote: On 05/08/13 11:42, MailLists wrote: Good luck delisting a DNSBL listed IP (block) from those crusaders... Back some time there was a piss contest between some of those blacklists on which one would blacklist the whole internet faster. In the mean time different security providers bought up some of those rabid blacklists to power their antispam offerings, usually bundled with a security appliance. If you get caught in their web, you'll have a tough time to get delisted, usually denied with some puerile pretext, from obtuse criteria up to pure blackmail. In fairness, SORBS and Spamhaus are some of the better candidates, and ISP-bundled mail servers typically are _full_ of spam because their customers get viruses that proceed to use their email accounts for spamming all the time. If you want to get your email delivered reliably and receive email reliably, run your own mailserver or get someone who knows what they're doing to run one for you. ___ time-nuts mailing 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] Re: Heads up: Mark C. Stephens...
I would appreciate it, if you would read more carefully... It's about abusive DNSBLs. I don't know from where you got the funny idea that SORBS has something to do with Spamhaus... Look up Michelle (ex-Matthew) Sullivan to learn a bit about SORBS' history... in the mean time bought by GFI, and now landed at Proofpoint. PS: I don't have any problems with not receiving messages. On 8/5/2013 9:34 PM, Paul wrote: Date: Mon, 05 Aug 2013 17:17:37 +0300 From: MailListsli...@medesign.ro While I'll agree on Spamhaus' decent services, SORBS has definitely a very shoddy history (the internet is full of beneficiaries's stories). You have the roles reversed. If you have a problem with a BL the resolution is with your SMTP provider not the BL and not the sender. The system using the block list can either stop using it or whitelist you. If they don't care about you losing legitimate mail you should change mail service providers. I do mai for a living -- we use SpamCop, SpamHaus (SORBS) and Sophos and have no prolems (that we can't resolve) with them. ___ time-nuts mailing 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] GPDSO is working
Historically U(S)ARTs had the data signals in positive logic, and the control ones active low - after inversion in the level translators, signals are in mark (-12V) condition for an inactive interface. The threshold being slightly positive in modern EIA-232 receivers, is a fail-safe measure to unambiguously interpret the signals as mark in case the line is interrupted. If the standard thresholds would be used, in case of a line failure the line receiver would memorize the last state. The 75154 is one of the line receivers which can be configured in both modes (even so the thresholds are not symmetrically around GND, but the hysteresis is much larger). Also the ubiquitous 1489 could have the thresholds adjusted using the response-control pin. For experimenting, an USB-serial adapter like the FTDI MM232R could be used. It has the possibility to invert the logic signals (configurable on-chip), and to adjust the logic levels 1.8-5V (5V TTL or 3.3V LVTTL with the internal regulator), to adapt it to most logic level circuits. Even a lower power load up to ~400mA (eg. GPSRx) could be powered directly (5V), or through an external (adjustable) regulator, through the USB bus (available on most computers, unlike a real COM interface)... On 7/14/2013 12:25 AM, Chris Albertson wrote: On Sat, Jul 13, 2013 at 6:52 AM, Chuck Harriscfhar...@erols.com wrote: If a TTL signal does just work with your RS232 receiver, you have a faulty receiver. The receiver is supposed to have a dead zone from +3V to -3V. You are 100% correct, almost all modern RS-232 receivers are faultily as you describe and will work with TTL level signals ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How dangerous if a Rb lamp broken?
7. RbOs show up on ebay military black market (TM), an ATF sting operation, hugely overpriced... 8. The war on Rb goes on, hunting for the evil terrorists which purchased, and intend to use RbOs. 9. Time-n... err. terrorists get a drone visit, with some Hellfires placed through their chimney. 10. The MII complex is happily counting their profits, while the world is getting a safer place point 1 correction - it's DHS... not TSA. The TSA goons have still some time to wait until getting armed. For now they have to please themselves only with naked pictures, and groping genitalia, of the sheeple. On 7/10/2013 8:20 AM, Perry Sandeen wrote: Hui and all, You have absolutely NOTHING to fear. Here is why: If in the USA it was found that it MIGHT possibly hurt something on the endangered species list [Humans might count also in some situations.] The following would happen. 1. A Transportation Security Agency [1.6 Billion bullets and counting] heavily armed and masked SWAT team would appear at Rb owners houses. They know where we are thanks to NSA wire taps and the fact that every piece of mail in the US mail system is photocopied on each side and stored. 2. The rubidiums would be seized. Next: A. The owner would be fined for having an unregistered WMD. B. The owners name would go on a WMD offenders list. Offenders would have to report to the police wherever they live and would be barred from contact of anyone below the age of 18 and could not reside within one mile of a school. 3. The administration branch of our US government would declare that: The War On Dangerous Rb’s Has Been Won and the US citizens are now safer. 4. Bonus’s will be awarded. 5. Congressional oversight committees will ask the TSA what has been done with seized rubidiums. The TSA will not tell congress who authorized the seizer and where the Rubidiums are. Any TSA leaders subpoenaed will take the 5th amendment. Congress will get really, really mad and stop their feet. Nothing more will happen. It will fade away as the administration spokesman will say: “It is old news and really doesn’t matter compared to what I tell you today”. 6. Magically, as no one knows anything, the Rubidiums will end up in a third world country without environmental law to be salvaged and the sold to mainland China. See, it really is simple. Regards, Perrier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How dangerous if Rb lamp broken?
In those tough times, since the General Electric reactors melted down at Fukushima, and still spewing lots of radiation after more than two years, a radioactive particle detector is a must have - at least for gamma radiation. As for beta particles, you can try visual detection. If you don't see the blue glow in dielectrics (aka Cherenkov radiation) there's still some hope... On 7/9/2013 7:07 AM, Hui Zhang wrote: Dear Group: I have four compact Rb Stanard, but I am worried about what if my Rb lamp broken in accident someday? How dangerous of this situration? Is Rb87 came out from Rb lamp will be a disaster? You know I haven't any beta rays detect instrument. Hui ___ time-nuts mailing 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] Nortel Trimble thunderbolt
The cable is a straight DTE-DCE one. BR is 9600 (8O1). The yellow LED won't go off until it's communicating with the base station through the rear 110-pin connector. Is it connected to an on board COM or through an USB adapter? On COM1 LH 3.10 starts straight without any command line switches or other fiddlings (just a warning message about no COM1 data seen, which disappears quickly). On 7/5/2013 10:55 PM, Jim Sanford wrote: All: I have my new Nortel unit powered up. I have been unsuccessful at getting it to communicate with Lady Heather. I have tried both 19K2, 7, O 1 and 9K6, 8, N, 1 on the serial port to no avail. I tried the command line switch to wake up Nortel units wit both sets of serial parameters, to no avail. The instance of Lady Heather which goes out to KE5FX site works, so I presume I have a correct installation of Lady Heather. The Nortel appears to go through normal power up display on power up. Then it lights the yellow no communication LED. Once I hooked up an antenna, within a few minutes, the green LOCK LED came on. It appears that the Nortel is working. Is there something I'm missing about making these two play nicely together?? Thanks 73, Jim wb4...@amsat.org ___ time-nuts mailing 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] Glonass Payload lost... (Rob Kimberley)
Actually it's a US-Russian private enterprise (ILS) which is driving the modernization (read cost-cuttings) of the Proton-M... as they have the exclusive commercial launch rights. Failures started to add up since 2007. Guantanamo would be more fitting today. On 7/2/2013 7:26 PM, brent evers wrote: No kidding. Talk about embarrassing. I guess in the good old days, that project manager would be packing his teacup to go spilt rocks in siberia for the rest of his life, if he got off that lucky. Brent On Tue, Jul 2, 2013 at 12:03 PM, Dan Kemppainend...@irtelemetrics.comwrote: Note to self, Not getting on any Russian made rockets any time soon. At least the rockets were unmanned, and hopefully no one on the ground was hurt! Sounds like this isn't the first time this happened, and it isn't the first time they lost three Glonass birds. Wonder how much money was lost in just the 6 satellites blown up thus far. It may be a while before I start looking for any glonass receiver hardware. Dan On 7/2/2013 10:27 AM, time-nuts-requ...@febo.com wrote: http://www.bbc.co.uk/news/science-environment-23140665 Rob ___ time-nuts mailing 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] Answers to regulator choices comments
At higher (load) currents, thermal, and parasitic resistance effects are getting more prevalent, to the limits of monolithic IC technology. Why don't consider a more classical approach with external pass transistor (a much larger selection available), if a linear regulator is really necessary? Also look up the old Unitrode UCx83y family, for example... A mixed bag of IC regulator technologies were mentioned... the LDOs (usually with series p-device for positive voltage ones) are much more picky about load conditions, and tougher to stabilize, let alone working in parallel configurations. To equally share the load current, the paralleled regulators should tightly track each other over load, and ambient conditions... don't consider it to be guaranteed over all operating conditions. The 3 terminal regulators were designed for convenience, not highest performance. note: LM338 is not a LDO like LT1084 (as TI proudly classifies it) On 6/30/2013 7:19 AM, Perry Sandeen wrote: Wrote: If you are in the US (maybe elsewhere) you can request two free samples. That might work for projects on and two, but what about projects three and onward? Wrote: I suppose that the same philosophy [paralleled regulators] would apply to getting more power with a 7805 farm. It does however with the general output rating of 1 to 1.5 amps for each regulator it wouldn’t be very practical. It’s much cheaper and simpler to use ones in the 3 amp plus range. Wrote: A regulator needs to be specifically designed for parallel operation. If it's not designed that way you will have a very hard time with it. I’ve never heard of any three terminal regulator designed for parallel operation. I believe that all three terminal regulators use a pass transistor. When one uses them in parallel they need a slight resistance added to each pass transistor to prevent current hogging just as one had to do when paralleling power transistors in other high amperage circuits. Wrote: It may be a bit more complicated than that. You need some way to share the load and you also need to make sure things are stable. The TI/National data sheet doesn't show anything about paralleling regulators. The AD data sheet shows 2 ft of #18 wire between each regulator and the load. I'm not enough of an analog guru to reverse engineer that setup and figure out the stability constraints and transfer them to 78xx type devices. I stand corrected about the LM 1084 showing paralleled regulators. However the data sheet says it is pin compatible with the LM 317. So we get to the paralleled regulator circuits by a bit of a circuitous route. If we go to National Semiconductor Linear Brief 51 March 1981 titled “Add Kelvin Sensing and Parallel Capability To 3-Terminal Regulators” it shows how to parallel two or more three terminal LM 338 regulators. The stability problem is solved for us by the Nation Semiconductor engineers. The 2 ft. of #18 wire for each regulator provides the load balancing resistance needed. One could use an ordinary resistor instead if it had the value of 30 mili-ohms. The operation of all 3 terminal regulators are the same. The internal circuitry looks at the relationship between the output voltage and the *ground* terminal. As the data sheets show, if we change that relationship with resistor combinations we can manipulate the output voltage to our needs. For most low voltage applications one can usually find a three terminal regulator that will fit the current needs, My original point was that the LM 1084 [$14] IMNSHO is very expensive for what it does. By paralleling two far cheaper of the LM 338 family one gets a larger ampacity of 10 amps instead of 7.5 amps for $3 to $5 instead depending on one’s scrounging abilities. In the end you pays your money and you make your choices. Regards, Perrier ___ time-nuts mailing 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] wwvb 60 khz tuning fork crystals Some insights
Especially as the inverting gates have independent source and/or drain connections - series resistors can be used to lower even more the consumption when biased in the linear region... On 6/28/2013 7:20 AM, Don Latham wrote: Maybe the old 4007 cmos would be better... Don paul swed Yes it makes a very fine 35 Mhz oscillator and reasonably stable. Been there and done that. Hey the systems done. May remod it one day but bigger fish to fry with the d-psk-r Regards Paul WB8TSL On Thu, Jun 27, 2013 at 6:41 PM, David McGaw n1...@alum.dartmouth.orgwrote: Lower gain is better as long as it oscillates. The 74HCU04 is unlikely to drive spurious responses. The 74HC04 is OK as long as you keep the feedback gain low - sometimes a series resistor from the output to the resonant circuit is required. A 74HC14 is the WRONG part for the job as it can and will oscillate without the crystal controlling it - just try it with a resistor for feedback and a capacitor to ground at the input, no crystal. David N1HAC On 6/27/13 6:30 PM, paul swed wrote: I will say the fact is the 74hc14 is a bit of a power pig we are talking 12 ma. The rcvr is something much less like 100 ua. At least for the moment it all works but 12 ma is a pig. Especially when you take the signal out and knock it down to 100-200 uv. Regards Paul. On Thu, Jun 27, 2013 at 5:37 PM, ed breyae...@telight.com wrote: Still having email problems - here we go again. This is second try, please excuse if both show up. Hal Murray said: They make 74xU04 for many values of x. The U is for Unbuffered. They have lower gain in the linear region. I thought they were intended to be used for things like this, but I don't understand that area. Can anybody give me a quick lesson or point me at a good URL? I always thought the unbuffered U versions were preferred for ring oscillators mostly to save power - you don't want the high-drive output stages to be cooking away in linear mode if not needed. The propagation delay can also be less since the U ones have only one stage instead of three (the building block is the totem-pole inverter stage), but they can't drive very much load anyway. I think that most MSI and LSI parts that have built-in ring/crystal oscillator sections use the U topology, but I don't think there's anything special about it - it's the simplest thing that works. I've made quite a few CD4000 and 74HC oscillators, and never worried too much about U versions or not, except for battery-run items where power is critical (or you can run the oscillator at lower voltage). Often they are made from inverting gates that are part of a shared package, where you wouldn't want puny drive capability in the other gates anyway. They are relative power hogs though, whenever linear biasing is needed. Except in the 4000 series, I don't know if U versions are available in anything but the '04 hex inverter, but I suppose it's possible. I think the Schmitt-trigger types like HC14 are necessarily buffered, so have three stages, since you need a non-inverted version of the signal for the positive feedback to the input. I've never tried making one in 74AC - I don't know if it's even possible to bias one up that way without it burning up. I'm working on some related circuits now, so maybe I'll set up an experiment to see how much current it would take for one inverter - I've often wondered about this. I read about this years ago in various CMOS application notes, so I may be missing some key points - there should be plenty of info online. The older generation (when CMOS was fairly new) info may provide more detail about the guts than that related to the newer, higher performance families. Ed ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshtt**ps://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-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-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. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
Re: [time-nuts] OT Prototype Boards
In the eastern block the customary pitch was exactly 2.5mm. At least SSSR and DDR ICs were made so. For DIP40s it was a little of a stretch (read pin bending) job to get them fit on .1 spaced boards... On 6/25/2013 5:09 PM, J. Forster wrote: It's not 'industry'. It's the international standards agency, whatever it's called. The folks that define a meter as some number of wavelengths of light in vacuo and so on. There are some early perf boards that have holes on 1/16 centers, for use w/flea clips'. -John === OK, I see in the wiki that 0.1 is by definition 2.54mm. I was taught it was 2.54001, but that's not right, either. But, if industry says that they're defined as the same, then I'm the one out of date. =) I wonder what was with that old prototype board. I can't find it, so it must be in a landfill, but it was just exactly the wrong size to fit a chip. You could get the first few pins in, but then the differences would be enough that no more would fit. Bob - Original Message - From: Orin Emanorin.e...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: Sent: Monday, June 24, 2013 11:35 PM Subject: Re: [time-nuts] OT Prototype Boards 0.1 is 2.54mm by definition these days. See: http://en.wikipedia.org/wiki/International_yard_and_pound Now whether the board really is 2.54mm is an entirely different matter... if it is, you should be fine with 0.1 pitch chips. Orin. On Mon, Jun 24, 2013 at 9:10 PM, Bob Stewartb...@evoria.net wrote: I need to get some largish prototype boards for my project. Has the industry standardized on a 0.10 pitch for hole spacing? IOW, if the ad says 2.54mm pitch will I get a board that will fit American chips, or will I just get something metric sized for the landfill? I ask, because I've got a prototype board sitting around here someplace that is unusable because the pitch isn't quite right. Needless to say, I'm ordering this from ebay from a seller in China or Hong Kong or someplace, points East. Bob - AE6RV ___ time-nuts mailing 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] HP and other equipment failure
In the classical (transformer -) [bridge] rectifier - storage capacitor configuration, the capacitor charge current is creating short high peaks on the current waveform (and therefor truncate the peaks of the voltage waveform, the distribution circuit resistance being finite), due to the nonlinear load. The negative effects are much more due to high current harmonics than (slightly) capacitive cos fi, and increase the losses in the distribution circuits. On 6/16/2013 12:57 AM, Azelio Boriani wrote: Although off-topic here, the PFC (or power factor correction) is a switching mode front-end used to correct the cos-phi of the otherwise capacitive load that every switching mode power supply is for the mains. On Sat, Jun 15, 2013 at 11:52 PM, J. L. Tranthamjlt...@att.net wrote: Sorry for the interruption but what is 'PFC'? Thanks. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Saturday, June 15, 2013 4:09 PM To: Robert Atkinson; Discussion of precise time and frequency measurement Cc: Perry Sandeen Subject: Re: [time-nuts] HP and other equipment failure In message1371329221.83869.yahoomail...@web171902.mail.ir2.yahoo.com, Robert Atkinson writes: While I agree with everything else you say, you CAN have too much filter capacitance. At least where dc rectifier / filter (smoothing) circuits are concerned. Increasing C causes increased ripple current [...] And ripple current can be a major source of power-line frequency noise in all electronics. The main reason why switchmode power-supplies today (can) outperform linear power supplies with respect to noise, is because the legally mandated PFC correction eliminates the bridge-rectifier ripple harmonics. I would not hessitate to use a good quality switchmode to replace the linear supply in a HP5370B. I did some experiments a couple of years ago, with an audio-amplifier: I put a standard PFC corrector chip on the secondary side of the trafo. The overall result was not satisfactory, but the 50 Hz sneer we all know and hate was absent, and the Tzoing! power-on mechanical shock from the trafo was also eliminated, as was the consequent dimming of the lights ;-) The main reason not to do this, is that you need some physically gargantuan coils for a 10A+ PFC-switcher. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] Why are 1PPS signals so skinny?
As most PSs for digital circuitry include a regulator, it's output impedance at 1Hz is low enough to filter most out of it - see the load transient response diagram of the used regulator - as the open loop gain of the regulator's internal error amplifier at such a low frequency is practically equal to that of DC gain. While the 1Hz component is of no concern (power consumption left aside), the fast edges pose a higher demand on proper decoupling. On 5/15/2012 9:45 PM, shali...@gmail.com wrote: The narrow pulses are easily filtered by the power supply because the frequency distribution of the power consumption has a much smaller component at 1Hz. At 1Hz, the power supply filters nothing. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Mike Smi...@flatsurface.com Sender: time-nuts-boun...@febo.com Date: Mon, 14 May 2012 20:44:04 To:time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Why are 1PPS signals so skinny? On 5/14/2012 8:21 PM, Tom Van Baak wrote: one day during an experiment where I was comparing a large set of clocks I noticed my lab's digital AC power meter was jumping by tens of watts every second. The last thing you want in a precision timing lab is to load your AC line down exactly once a second. How does a short pulse help? It's still tens of watts every second, but instead of lasting 0.5 seconds, it lasts 0.5 seconds. Less power used overall, but still the same sudden change on the second. ___ time-nuts mailing 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] Clocks for Audio gear
Ashihara's tests were with music/voice, taking into account psychoacoustics, for an average group of music savvy listeners, and even music professionals. As uncorrelated jitter is practically raising the noise floor, most of it was masked by the signal, making it more difficult to detect. Benjamin and Gannon used sinusoidal jitter, which isn't appearing normally in signal chains (badly designed ones excepted). In a real case, with higher probability (added) jitter would be correlated with the digital content transmitted over a path - S/PDIF, and AES/EBU are prone to jitter induced by the signal path characteristics, ISI - PSUs, and even external noise sources. A more realistic simulation would take those into account. OTOH there where tests on pure sine tones, with sine jitter, detectable by trained ears at even lower levels of jitter, which might indicate the lowest threshold of hearing, but using artificial conditions. Who would listen to pure sine tones? On 5/10/2012 8:25 PM, Heinzmann, Stefan (ALC NetworX GmbH) wrote: Chris Albertson wrote: If we are to believe the above paper,then those guys who claim to hear pS jitter are wrong. Note that the jitter spectrum matters for its audibility. Ashihara et.al. used random jitter, and it is not very suprising that the sensitivity for random jitter is lower than for jitter that has specially been shaped to improve detectability by human ears. Thus the results by Ashihara are credible, but they are not the lower limit on jitter audibility. Benjamin and Gannon, the first reference in Ashihara's paper, come to lower figures for sinusoidal jitter with carefully selected frequencies relative to the main signal, which is also sinusoidal. Their results reach down to the single figure nanosecond range, and that can be regarded as the real limit of audibility. Of course, that still leaves those who claim to hear jitter in the picoseconds range out in fairy-tale land. And jitter of just a few nanoseconds is still quite easy to achieve with crystal oscillators. No need for special and expensive parts, then. Normal developer diligence is enough. Cheers Stefan ___ time-nuts mailing 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] Clocks for Audio gear
Hearing tests showed the ability to discern jitter above a few hundred nanoseconds rms. http://amorgignitamorem.nl/Audio/Jitter/Detection%20threshold%20for%20distortions%20due%20to%20jitter%20on%20digital%20audio%2026_50.pdf Others claim the ability to detect jitter in the picoseconds range... It would be a conservative assumption that jitter in the range of tens-hundreds of picoseconds will be practically not discernible. Usually integrated oscillators are composed of the classical inverting gate oscillator, with external CQC, and selfbiasing R, which has practically no rejection (~6dB) of the power supply noise. As it's usually on the same die with noisy digital circuitry, the gate threshold will jump around, producing timing errors, also the slew-rate is quite low, which just worsens the situation. As most digital circuitry is less affected by jitter, the best solution is to place a clean oscillator near the D/A conversion, where the most critical timing point is, and through buffers clock the rest of the digital circuits - eventually galvanic isolation might be implemented, to pollute less the analog part with digital noise. To minimize jitter, digital clock inputs should be driven by fast slew-rate circuitry. On 5/10/2012 12:25 AM, Hal Murray wrote: was Subject: Re: [time-nuts] Faster than light of a different type (Probably my fault.) act...@hotmail.com said: What I found funny was that the Audiophlie and light thread drew such attacks when it hit home to me as exactly what the Time-Nuts mission is about. The Audio thread touched on some real world time and freq research ... I too enjoyed the technical discussions. Thanks for your contributions. It's the audiophool bashing that people are complaining about. Sure, it's fun, but only at the right time and it gets old quickly. The problem is that with large groups, there are different opinions of when and how much is appropriate. The long tail on opinions of reasonable can annoy a lot of people. --- Back to technical stuff... As a practical matter, is clock jitter or phase noise from a typical low cost crystal and decent board layout a significant problem in audio gear? How hard is it to measure? Is clock accuracy a practical problem? How good are people with perfect pitch? It wouldn't surprise me if there are a few that are much much better than others, but how good is that relative to 50 PPM which I can get in a low cost crystal? Video geeks solved their clock distribution problems by using frame buffers. Is there a similar trick for audio? Is there a need for it? I know clocking is a serious problem in fancy DSP systems. For example, modern radar has gone digital. In that context, clock jitter can be important. Standard procedure is don't run your clock through a FPGA because it will add jitter. Part of the problem is that they are doing magic down conversion in the ADC. (I can't think of the term.) Suppose you have a 100 MHz signal with a 1 MHz bandwidth. You don't have to sample at 200 MHz. You can sample at 2 MHz and your signal will alias down. It's turning what is normally a bug into a feature. The catch is that the errors/noise due to clock jitter happens at the high frequency, in this case multiplying the noise by 100. (Your sample/hold at the front end has to work at the high frequency and your anti-aliasing filter gets more interesting.) There has been an interesting change in the specs for ADCs and DACs over the past 20(?) years. They used to be specified using terms like DNL and INL and No-missing-codes. Modern high-speed ADCs are specified with terms like ENOB and SFDR. Data sheets often include several plots of a batch of samples run through a DFT so you can see the noise floor and such. Here is a reasonable glossary: http://pdfserv.maxim-ic.com/en/an/AN641.pdf I don't remember comments/specs about clock jitter in the data sheets but I haven't looked at one in a few years. I'll have to keep an eye out the next time I'm browsing. ___ time-nuts mailing 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] Oh dear
Let's expect the ultimate portable MP3 player with atomic clock reference... :] Also funny are the offerings with RbO CD-clocks... usually tweaked FE-5680s, which are not exactly famous for a clean jitter/spurious free output signal... The only reason is the easiness of output frequency adjustment (for the DDS models) to that of the standard CD clock, which promptly places a premium on the price tag. A good XO is way better and cheaper, with the notable exception of temperature, and long term stability - still waiting for the golden ears capable of hearing that one... On 5/7/2012 12:20 PM, Attila Kinali wrote: On Mon, 07 May 2012 13:40:15 +0530 Rajvu2...@gmail.com wrote: I once did a test with a audio expert and compared a CD and a digital copy. He confirmed that the copy was the original and when I showed him which was which he still refused to believe.. I know a local guy who gold plated the PCBs for his home brewed amp! Well.. there is lots of bogus information going around in the audiophile scene... Probably mostly because todays audio technology is so advanced, that Clarke's 3rd Law applies... But to bring this back to time nutty topics, have a look at http://www.colorfly.eu/product.html It's an MP3 player with high precision timing. It does not only use two TCXOs with5ps Jitter.. No! It also employes a technique known as Jitter Kill for the ultimate mobile sound experience! :-) Attila Kinali ___ time-nuts mailing 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] Oh dear
If you take into consideration that the best currently available DACs, also true for analog circuits, have a dynamic range about 120-126dB, the last 3-4 bits are quite irrelevant (random noise mostly)... a good 20bit DAC already pushes the limits. The marketingdroids swarming for the newest 32 bitters is even more ludicrous. On the other side, the dynamic range of the ear (if you care the least for the future of your hearing), and of the quietest available listening spaces, hardly gets to 100dB... Of course, for the DSPs involved in the signal chain, 32bits integer math might not be enough, due to rounding errors. On 5/7/2012 7:02 PM, Tom Knox wrote: Actually the numbers are quite real, play with the math, a small amount of jitter in a DAC (X) can have a large difference (Y) when sampling a complex wave form especially in the audiophile world where the sound of 24bit dac 16,777,216 discrete levels is clearly superior to older 16 bit dac 65,536 possible levels in 44.1 KHz to 192 KHz formats. Thomas Knox Date: Mon, 7 May 2012 17:59:04 +0200 From: att...@kinali.ch To: time-nuts@febo.com Subject: Re: [time-nuts] Oh dear On Mon, 07 May 2012 08:20:55 -0700 Dan Raedan...@verizon.net wrote: I see nothing odd about wanting to get the best possible source for the Master Clock for your master recordings. My son does run a small studio and for him I was able to make a version of that unit, for a lot less money of course. If he says it improves the sound of the recordings, and his customers agree, I am inclined to believe him. The thing is, that an Rb is good for one thing: Have a long term stable and accurate frequency source that is better than 1 to some billions for measurement or other stuff that take more than a few hours or have to be repeated exactly in a couple of weeks. For audio, you need a frequency source that is stable over a couple of hours (probably a working day) and shows low jitter. Where as low jitter is quite high in time-nuts terms and stable not stable at all. A cycle-to-cylcle jitter of a couple of ns is not audioable at all, but any Rb will have a much lower jitter. Or to have a different look at it, you want to have very low phase noise, as this phase noise is mixed in over the ADCs into your signal. But as we know, the phase noise of an Rb is not defined by the Rb physics package, but by the OCXO they use. (yes i know that the close in phase noise is defined by the reference and not by the OCXO, but the base level is the OCXO, not the reference) As for stability. You want the instruments to sound the same over an recording. Ie the human ear has to preceive the recorded sound as the same. The frequency resolution of the human ear is somewhere around 3Hz. This makes for 150ppm (at 20kHz). Even a 32kHz tuning fork crystal achieves an absolute accuracy that is better than this. Its stability is much better than this Of course, you want to have enought headroom for other non ideal components. So, lets say, go for a factor of 10, then we are at 15ppm. For absolute accuracy, that's already a good XO. For stability, still most XO should do that. Or to say it differently: Using some good OCXO with low or very low phase noise would be more than enough for even the most high end audio equipment. You don't even have to discipline it, as a even quite bad OCXO has variations much lower than 1ppm, which is definitly not something anyone can hear. IMHO getting a 20-50USD OCXO from ebay, some good, low noise power supply (audio power supplies with low noise in the40kHz region), some distribution amplifier with low noise figure and you are set. All in all probably at a cost of 200-300USD including rack mount. If you want to have high fidelity you can use an GPSDO to get your OCXO within a couple mHz. To summarize: Nobody here does want to insult anyone who does professional audio recordings. But having the knowledge of what the stability and accuracy numbers for an ordinary Rb mean, and being able to put that into perspective with the not so good capabilties of the human sensory systems, one wonders why people spend an awfull lot of money for something that has no audiable effect over something a lot cheaper. Not to mention that other things have a much higher impact on audio quality than the reference oscillator: Like temperature and humidity during recording (do you control them as well to the ppm level?), or the tuning of the instruments which wanders quite a bit during use. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long 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. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe,
Re: [time-nuts] Oh dear
That was a big problem with the dynamic range of tape recorders, which had to be solved with noise reduction circuits. Even good 16 bit ADCs have a higher DR than the SNR of most instruments in quiet recording studios. With the mixing of multiple dubs, the main problem is the summed background noise, not that of the ADCs. When doing the mix digitally, a DAW with higher bit depth is needed, to conserve the DR: 16 tracks need another 4 bits. The downmix can then be truncated to the final media bit depth (eventually with some dither added, if not self-dithered due to noise). The main problem with the old CD format wasn't actually the DR, the SR was chosen too low. One of the famous audiophile studios (Chesky Records) expressly avoids overdubbing, and postprocessing, and puts accent on the microphone placement. That's real art, unlike some sound engineer using heavy processing, and turning up the compression control, for a louder sound. Modern AD/DA-Cs are mostly sigma-delta for technological, and cost reasons. The better ones are also multi-bit... On 5/7/2012 7:59 PM, li...@lazygranch.com wrote: Nearly all modern recordings are multiple mono. One microphone per instrument if not more. Multiple overdubs. If high ticket artists are collaborating, they may be recorded at different times. (Bruce Springsteen and Rosanne Cash duet for example.) They want a high bit depth so the final product doesn't have a high background noise. The classic back of the envelope calculation regarding clock jitter is based on 44.1KHz sampling and a 20KHz sine wave. Take the maximum slew rate of the sine wave and the timing uncertainty (jitter), then compare to a LSB. It doesn't take much jitter even at 16 bits to be significant. Modern ADCs are MASH. I don't know the analog to the argument for that technology. -Original Message- From: MailListsli...@medesign.ro Sender: time-nuts-boun...@febo.com Date: Mon, 07 May 2012 19:31:10 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Oh dear If you take into consideration that the best currently available DACs, also true for analog circuits, have a dynamic range about 120-126dB, the last 3-4 bits are quite irrelevant (random noise mostly)... a good 20bit DAC already pushes the limits. The marketingdroids swarming for the newest 32 bitters is even more ludicrous. On the other side, the dynamic range of the ear (if you care the least for the future of your hearing), and of the quietest available listening spaces, hardly gets to 100dB... Of course, for the DSPs involved in the signal chain, 32bits integer math might not be enough, due to rounding errors. On 5/7/2012 7:02 PM, Tom Knox wrote: Actually the numbers are quite real, play with the math, a small amount of jitter in a DAC (X) can have a large difference (Y) when sampling a complex wave form especially in the audiophile world where the sound of 24bit dac 16,777,216 discrete levels is clearly superior to older 16 bit dac 65,536 possible levels in 44.1 KHz to 192 KHz formats. Thomas Knox Date: Mon, 7 May 2012 17:59:04 +0200 From: att...@kinali.ch To: time-nuts@febo.com Subject: Re: [time-nuts] Oh dear On Mon, 07 May 2012 08:20:55 -0700 Dan Raedan...@verizon.net wrote: I see nothing odd about wanting to get the best possible source for the Master Clock for your master recordings. My son does run a small studio and for him I was able to make a version of that unit, for a lot less money of course. If he says it improves the sound of the recordings, and his customers agree, I am inclined to believe him. The thing is, that an Rb is good for one thing: Have a long term stable and accurate frequency source that is better than 1 to some billions for measurement or other stuff that take more than a few hours or have to be repeated exactly in a couple of weeks. For audio, you need a frequency source that is stable over a couple of hours (probably a working day) and shows low jitter. Where as low jitter is quite high in time-nuts terms and stable not stable at all. A cycle-to-cylcle jitter of a couple of ns is not audioable at all, but any Rb will have a much lower jitter. Or to have a different look at it, you want to have very low phase noise, as this phase noise is mixed in over the ADCs into your signal. But as we know, the phase noise of an Rb is not defined by the Rb physics package, but by the OCXO they use. (yes i know that the close in phase noise is defined by the reference and not by the OCXO, but the base level is the OCXO, not the reference) As for stability. You want the instruments to sound the same over an recording. Ie the human ear has to preceive the recorded sound as the same. The frequency resolution of the human ear is somewhere around 3Hz. This makes for 150ppm (at 20kHz). Even a 32kHz tuning fork crystal achieves an absolute
Re: [time-nuts] PICTIC II ready-made?
There was also the short lived XPLA2 PZ/XCR3320,3960 (Ph/X) SRAM CPLD family, which had to be configured from an external memory... just another exception which confirms the rule. ftp://ftp.xilinx.com/pub/coolpld/isp/960_conf.pdf The even older intel FLEXlogic, bought by Altera, and rebranded FLASHlogic, with the odd CFB/SRAM architecture, had also internal SRAM/Flash configuration memory. In XAPP440 the power-up configuration transfer of Xilinx CPLDs is very briefly mentioned, and in XAPP388 more details for CR-II are provided. Such often overlooked details cold be sometimes crucial... On 4/28/2012 11:46 PM, Bruce Griffiths wrote: Yes, I should have been more specific. The details about the state machine clock behaviour aren't on the datasheet and were obtained by asking Xilinx. The reason for using CMOS RAM to controll the CPLD interconnections is to reduce the static power consumption well below that possible when using EEPROM cells directly. As long as the state machine clock is turned off during normal operation then it will not be a source of timing jitter. I had intended the post as a warning that chip implementation details not necessarily given on the datasheet can be critical for such applications. Bruce MailLists wrote: I guess you wanted to refer to the old XPLA PZ3k/5k CoolRunner series bought from Philips, renamed XCR3k/5k, and later enhanced to XPLA3/XCR3kXL, not the antique FPGA family XC3k... (C)PLDs don't need an external memory for configuration storing, it's internal. There are also some Lattice, ACTEL, and even Xilinx FPGAs with internal non-volatile configuration memory. On 4/28/2012 3:12 PM, Azelio Boriani wrote: configuration is loaded from EEPROM to RAM on power up For every kind of logic? Even for the simplest XC3000 series (and the Altera equivalent EPM3000 series) small EEPROM CPLD? On Sat, Apr 28, 2012 at 9:04 AM, cfoxne...@luna.dyndns.dk wrote: On Fri, 27 Apr 2012 12:03:20 -0700, Jerry Mulchin wrote: You might want to take a look at the Atmel XMEGA parts. Far more capabilities than the ATMega parts. Watch out . If using an Xmega make sure to select the U ... Usb ones. Most of the non U parts have an errata list longer than the datasheet , and in the analog domain they have serious flaws. But going there (smd only) i'd select an arm instead. CFO ___ time-nuts mailing 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] PICTIC II ready-made?
I guess you wanted to refer to the old XPLA PZ3k/5k CoolRunner series bought from Philips, renamed XCR3k/5k, and later enhanced to XPLA3/XCR3kXL, not the antique FPGA family XC3k... (C)PLDs don't need an external memory for configuration storing, it's internal. There are also some Lattice, ACTEL, and even Xilinx FPGAs with internal non-volatile configuration memory. On 4/28/2012 3:12 PM, Azelio Boriani wrote: configuration is loaded from EEPROM to RAM on power up For every kind of logic? Even for the simplest XC3000 series (and the Altera equivalent EPM3000 series) small EEPROM CPLD? On Sat, Apr 28, 2012 at 9:04 AM, cfoxne...@luna.dyndns.dk wrote: On Fri, 27 Apr 2012 12:03:20 -0700, Jerry Mulchin wrote: You might want to take a look at the Atmel XMEGA parts. Far more capabilities than the ATMega parts. Watch out . If using an Xmega make sure to select the U ... Usb ones. Most of the non U parts have an errata list longer than the datasheet , and in the analog domain they have serious flaws. But going there (smd only) i'd select an arm instead. CFO ___ time-nuts mailing 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] Temex LPFRS-01
That would be the tougher part, as, with highest probability, the external analog adjustment is first AD converted in the MPU (AIN4) summed with the internally stored fine adjustment value, and then applied to the C-Field correction, through an external DAC8800. As both conversions are 8 bit, the obtained resolution of 1E-11 is insufficient to discipline the unit with enough accuracy, it was just meant to adjust the working frequency. In the last day of the easter holidays I opened one up, and now I'm trying to grasp the inner workings... time allowing. On 4/12/2012 7:50 PM, Azelio Boriani wrote: Interesting... have to check my LPFRS now: only tested for the lock indicator when received and then put aside to complete first the discipliner. On Thu, Apr 12, 2012 at 5:00 PM, MailListsli...@medesign.ro wrote: Well, the saga continues... A replacement part (for which a thorough check was specifically asked) has arrived. It boasts a Checked OK written with a marker pen on the label. Promising... With high expectations, the necessary connections were made, power applied, and after warming up it locks at precisely 9.999,817,1 MHz... bummer. Sometimes, for (yet) unknown reasons, it unlocks again, and, if the frequency adjustment trend is upwards, it locks again at ~10.000.000 MHz. The lock signal is active even at higher temperatures - that's quite better than the first unit, but after a power cycle the story repeats... mostly the wrong frequency comes out, but, on the brighter side, it's locked. On 3/18/2012 10:26 AM, MailLists wrote: Yes... Thank you, and the others, for the suggestions for cleaning/reviving the unit, but I can't recommend to my friend to keep a pile of rust (if water damage really is the problem) advertised as an used working item. Regards, bbg On 3/17/2012 4:10 PM, Azelio Boriani wrote: LPFRS from fluke.l? OK, then open it up and clean it, the LPFRS from fluke.l suffers from high humidity/water immersion and usually are very rusty inside. I have received one that was very bad but after cleaning with tetrachloroethylene (translated with google) it is working properly, maybe it will fail soon but now works. I complained with fluke.l and he refunded me without asking to ship back the LPFRS. TIP: handle with extreme care an opened LPFRS, there is a flexible PCB that holds the DB9 connector that can tear in the corners. On Sat, Mar 17, 2012 at 10:59 AM, MailListsli...@medesign.ro wrote: Hello all, a friend purchased from the bay asubj. in the LPRO configuration. After some problems encountered during the first power ups, he asked for help - I'm passing the questions further... After about 9 minutes of warm-up from room temperature (22°C) the lock signal goes low, but after a short time starts to switch low/high with decreasing low periods, until it remains high with short low pulses, spaced at about 2 seconds. After power-down, and sufficient cooling time, the cycle repeats. First step was to reapply the thermal interface to the integrated Al radiator, which helped a bit, the time during which the unit is locked growing slightly. Next step was forced cooling, which helped more, so the lock loss could be attributed with high probability to elevated operating temperatures. The temperature of the base plate (integrated Al radiator) at which lock gets lost is about 40°C, so for a reasonable operation it should not pass about 36°C, at which the power consumption raises to about 17W. That also means that for a 1°C/W heat sinking - obtainable with a larger passive HS or active cooling - operation above 30°C ambient gets practically impossible (except refrigeration, Peltier, etc.). Any further help or suggestions are welcome. Regards, bbg ___ time-nuts mailing 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] Temex LPFRS-01
The disadvantage of the digital adjustment is that it's meant to be permanent, the MPU also modifies it's internal EEPROM cell that stores the new value. Too many adjustments bear the risk of the used EEPROM cell wearing out, which would be inevitable in a disciplining process, and an unknown reaction of the firmware to such an event. Initially, I thought too it would be more convenient to use the serial interface for disciplining (this being one of the criteria favoring the LPFRS) but after a detailed reading of the specs it's clearly unusable as such. A dual pronged approach, with the external analog input rerouted to the C-Field adjustment circuit (with a narrower control range, equivalent to that of a few digital steps), and the digital fine adjustment used just when the analog range exhausts, should be the right one. Did your lock output test succeed? On 4/18/2012 1:25 PM, Azelio Boriani wrote: I'm not using the analog input but the serial port, yes, this doesn't improve the 1E-11 step but at least I skip the first A/D conversion. The direct access to the C-field control seems necessary but I like to have my stuff in the original state. My LPFRS is very rusty so I can drop my keep it original rule. On Wed, Apr 18, 2012 at 10:29 AM, MailListsli...@medesign.ro wrote: That would be the tougher part, as, with highest probability, the external analog adjustment is first AD converted in the MPU (AIN4) summed with the internally stored fine adjustment value, and then applied to the C-Field correction, through an external DAC8800. As both conversions are 8 bit, the obtained resolution of 1E-11 is insufficient to discipline the unit with enough accuracy, it was just meant to adjust the working frequency. In the last day of the easter holidays I opened one up, and now I'm trying to grasp the inner workings... time allowing. On 4/12/2012 7:50 PM, Azelio Boriani wrote: Interesting... have to check my LPFRS now: only tested for the lock indicator when received and then put aside to complete first the discipliner. On Thu, Apr 12, 2012 at 5:00 PM, MailListsli...@medesign.ro wrote: Well, the saga continues... A replacement part (for which a thorough check was specifically asked) has arrived. It boasts a Checked OK written with a marker pen on the label. Promising... With high expectations, the necessary connections were made, power applied, and after warming up it locks at precisely 9.999,817,1 MHz... bummer. Sometimes, for (yet) unknown reasons, it unlocks again, and, if the frequency adjustment trend is upwards, it locks again at ~10.000.000 MHz. The lock signal is active even at higher temperatures - that's quite better than the first unit, but after a power cycle the story repeats... mostly the wrong frequency comes out, but, on the brighter side, it's locked. On 3/18/2012 10:26 AM, MailLists wrote: Yes... Thank you, and the others, for the suggestions for cleaning/reviving the unit, but I can't recommend to my friend to keep a pile of rust (if water damage really is the problem) advertised as an used working item. Regards, bbg On 3/17/2012 4:10 PM, Azelio Boriani wrote: LPFRS from fluke.l? OK, then open it up and clean it, the LPFRS from fluke.l suffers from high humidity/water immersion and usually are very rusty inside. I have received one that was very bad but after cleaning with tetrachloroethylene (translated with google) it is working properly, maybe it will fail soon but now works. I complained with fluke.l and he refunded me without asking to ship back the LPFRS. TIP: handle with extreme care an opened LPFRS, there is a flexible PCB that holds the DB9 connector that can tear in the corners. On Sat, Mar 17, 2012 at 10:59 AM, MailListsli...@medesign.ro wrote: Hello all, a friend purchased from the bay asubj. in the LPRO configuration. After some problems encountered during the first power ups, he asked for help - I'm passing the questions further... After about 9 minutes of warm-up from room temperature (22°C) the lock signal goes low, but after a short time starts to switch low/high with decreasing low periods, until it remains high with short low pulses, spaced at about 2 seconds. After power-down, and sufficient cooling time, the cycle repeats. First step was to reapply the thermal interface to the integrated Al radiator, which helped a bit, the time during which the unit is locked growing slightly. Next step was forced cooling, which helped more, so the lock loss could be attributed with high probability to elevated operating temperatures. The temperature of the base plate (integrated Al radiator) at which lock gets lost is about 40°C, so for a reasonable operation it should not pass about 36°C, at which the power consumption raises to about 17W. That also means that for a 1°C/W heat sinking - obtainable with a larger passive HS or active cooling - operation above 30°C ambient gets practically impossible (except refrigeration, Peltier, etc.). Any
Re: [time-nuts] Re-radiating a GPS signal...??
GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Thoughts on lightning protection measures....
Only if it's not part of the sacrificial ritual... On the more serious part, while the lightning processes, and effects are scientifically researched for ages, an efficient lighting protection still borders black magic. On 4/12/2012 5:01 PM, ewkeh...@aol.com wrote: True if you do not include the cost of the burned down house which is a possibility. Bert Kehren In a message dated 4/12/2012 9:59:08 A.M. Eastern Daylight Time, jim...@earthlink.net writes: On 4/12/12 6:22 AM, Michael Baker wrote: Time-nutters-- Around here (N. Central Flori-DUH) it is not uncommon for near-by lightning strikes to damage underground cables and wiring. This is why buried wiring to things like driveway gate-openers are often placed in conduit rather than done with direct-burial wiring so that if lightning damages the wiring a new cable can be pulled through the conduit without having to re-dig the burial trench. Some years ago I had occasion to hold some long discussions with Martin Uman, one of the worlds most distinguished and eminent lightning researchers. He commented that even with the most extraordinary and costly efforts to install protection measures, that-- sooner or later-- there was a good chance that lightning would find a way to damage things. Dr. Uman (and his colleague Dr. Rakov) probably know about lightning and effects than any other humans alive. He's making an excellent point: at some point, the cost to replace the gear (or the cost of being off the air) is smaller than the cost of the protection scheme. Sometimes, you're better off having a sacrificial element, and a spare in the closet for speedy repair. His lightning research laboratory was located here in N.Central Florida because it is in the heart of the most dense strike area in N. America. ___ time-nuts mailing 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] Thoughts on lightning protection measures....
A very efficient solution would be to get the signal/power conducting cables out of the lightning path - that means a GPS receiver near the antenna, with a local power supply (photo cell panels / buffer accumulator) and signal transmission over optical fiber. Quite feasible, as a GPS Rx has low power requirements. If the delay from receiver to the disciplined oscillator is critical, or too high, a compensation scheme comes to mind - 2 identical optical paths in a loop, with the sent pps signal phase adjusted so that the received GPS pps is centered between the sent and the looped one. Regarding the TBs, even if they are the only ones directly connected to the antenna, the cable is already punching through the house Faraday cage, and chances are quite high that the lightning discharge won't stop at them. On 4/12/2012 5:03 PM, Azelio Boriani wrote: I have 2 TBolts but now I'm thinking to buy others to save them from the sacrifice... On Thu, Apr 12, 2012 at 3:58 PM, Jim Luxjim...@earthlink.net wrote: On 4/12/12 6:22 AM, Michael Baker wrote: Time-nutters-- Around here (N. Central Flori-DUH) it is not uncommon for near-by lightning strikes to damage underground cables and wiring. This is why buried wiring to things like driveway gate-openers are often placed in conduit rather than done with direct-burial wiring so that if lightning damages the wiring a new cable can be pulled through the conduit without having to re-dig the burial trench. Some years ago I had occasion to hold some long discussions with Martin Uman, one of the worlds most distinguished and eminent lightning researchers. He commented that even with the most extraordinary and costly efforts to install protection measures, that-- sooner or later-- there was a good chance that lightning would find a way to damage things. Dr. Uman (and his colleague Dr. Rakov) probably know about lightning and effects than any other humans alive. He's making an excellent point: at some point, the cost to replace the gear (or the cost of being off the air) is smaller than the cost of the protection scheme. Sometimes, you're better off having a sacrificial element, and a spare in the closet for speedy repair. His lightning research laboratory was located here in N.Central Florida because it is in the heart of the most dense strike area in N. America. ___ time-nuts mailing 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] Temex LPFRS-01
Well, the saga continues... A replacement part (for which a thorough check was specifically asked) has arrived. It boasts a Checked OK written with a marker pen on the label. Promising... With high expectations, the necessary connections were made, power applied, and after warming up it locks at precisely 9.999,817,1 MHz... bummer. Sometimes, for (yet) unknown reasons, it unlocks again, and, if the frequency adjustment trend is upwards, it locks again at ~10.000.000 MHz. The lock signal is active even at higher temperatures - that's quite better than the first unit, but after a power cycle the story repeats... mostly the wrong frequency comes out, but, on the brighter side, it's locked. On 3/18/2012 10:26 AM, MailLists wrote: Yes... Thank you, and the others, for the suggestions for cleaning/reviving the unit, but I can't recommend to my friend to keep a pile of rust (if water damage really is the problem) advertised as an used working item. Regards, bbg On 3/17/2012 4:10 PM, Azelio Boriani wrote: LPFRS from fluke.l? OK, then open it up and clean it, the LPFRS from fluke.l suffers from high humidity/water immersion and usually are very rusty inside. I have received one that was very bad but after cleaning with tetrachloroethylene (translated with google) it is working properly, maybe it will fail soon but now works. I complained with fluke.l and he refunded me without asking to ship back the LPFRS. TIP: handle with extreme care an opened LPFRS, there is a flexible PCB that holds the DB9 connector that can tear in the corners. On Sat, Mar 17, 2012 at 10:59 AM, MailListsli...@medesign.ro wrote: Hello all, a friend purchased from the bay asubj. in the LPRO configuration. After some problems encountered during the first power ups, he asked for help - I'm passing the questions further... After about 9 minutes of warm-up from room temperature (22°C) the lock signal goes low, but after a short time starts to switch low/high with decreasing low periods, until it remains high with short low pulses, spaced at about 2 seconds. After power-down, and sufficient cooling time, the cycle repeats. First step was to reapply the thermal interface to the integrated Al radiator, which helped a bit, the time during which the unit is locked growing slightly. Next step was forced cooling, which helped more, so the lock loss could be attributed with high probability to elevated operating temperatures. The temperature of the base plate (integrated Al radiator) at which lock gets lost is about 40°C, so for a reasonable operation it should not pass about 36°C, at which the power consumption raises to about 17W. That also means that for a 1°C/W heat sinking - obtainable with a larger passive HS or active cooling - operation above 30°C ambient gets practically impossible (except refrigeration, Peltier, etc.). Any further help or suggestions are welcome. Regards, bbg ___ time-nuts mailing 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] Thoughts on lightning protection measures....
You're right, but it's highly depending on the used construction materials... The building I live in, is quite like a Faraday cage - reinforced concrete. Even higher frequency radio signals have a tough time entering, mostly through the windows. What I wanted to underline is that, even if the house would be build like a Faraday cage, any conductor from the outside represents a potential dangerous ingress path. Of course, the generated fields would affect any sensitive equipment, but with the low impedance path of an antenna cable, even the less sensitive ones could suffer catastrophic failure. Not to neglect are all the other conductors entering from the outside - power lines, metallic pipes, etc. Full protection is quite difficult, almost impossible, to obtain, but an antenna cable is the preferred path. On 4/12/2012 6:02 PM, Attila Kinali wrote: On Thu, 12 Apr 2012 17:39:57 +0300 MailListsli...@medesign.ro wrote: Regarding the TBs, even if they are the only ones directly connected to the antenna, the cable is already punching through the house Faraday cage, and chances are quite high that the lightning discharge won't stop at them. A house isnt a faraday cage. Not by far. Unless you live in a box made out of solid 5mm steal plates. If a lightning hits your house directly and is going down the lightning rod down into earth there is a good chance that the electric and magnetic fields you have in the house will fry sensitive electronic equipment Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-radiating a GPS signal...??
Not quite, the delay of the antenna cable is affecting less the horizontal position (it depends also on the current received constellation geometry), but mostly the height ASL of the fix point, prolonging simultaneously all the paths from the satellites with a fixed value. Also, the propagation speed in a cable is significantly lower than in free space - the perceived delay increase is ~1.5 times for usual cables (~.67 velocity factor), and the computed fix point would have a lower height ASL than the real one. Those relaying systems are merely good for an approximate location fix, mostly for not loosing the GPS signal in covered areas so that the reacquire of the real signal is faster, with almost no perceived discontinuity. On 4/12/2012 6:11 PM, David McGaw wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes in a valley just below. The passive repeater consisted of an array of high-gain UHF yagis pointing to the 40 mile distant TV station tower. The yagi array was coupled to another set of high-gain yagi antennas pointing down to the homesites in the valley. I was told that it worked pretty well. Mike Baker -- ___ time-nuts mailing 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] Re-radiating a GPS signal...??
Purely geometrically, the fix solution is computed as the intersection point of spheres with the radii determined by the propagation time, and the centers by the positions of the satellites (practically not all spheres intersect in the same geometrical point, so an average is computed). If the GPS Rx would receive simultaneously all satellites, considered evenly distributed on a sphere, then the added path delays would mostly cancel out - but if only the visible satellites are accounted for, we will have an unbalanced system, approximated to an hemispehere, in which the horizontal error will be low, as the longer paths cancel mostly out, but for the vertical one it's not the case. Any GPS receiver will exhibit lower vertical precision than the horizontal one. The same phenomenon, of low precision, and biasing of position is evident if just a part of the constellation is used (an obstacle obscures a large part of the sky). The internal delays of the Rx are mostly fixed and known, so they can be accounted for, and compensated in the firmware fix solution, but the cable length is a variable (depending on the installation) factor, not accounted for. On 4/12/2012 7:15 PM, b...@lysator.liu.se wrote: Not at all! The (first) receiving antenna defines the position you get out of a long antenna cable or a reradiating system. The delays in LNA, filters, cables, rerad antenna, free air between rerad antenna and final receiving antenna ALL goed into the receiver clock error. This is clear both from a theoretical point, from most standard GPS texts and from practical experience from multiple installations I have used over the years. If you disagree, please provide evidence. -- Björn Not quite, the delay of the antenna cable is affecting less the horizontal position (it depends also on the current received constellation geometry), but mostly the height ASL of the fix point, prolonging simultaneously all the paths from the satellites with a fixed value. Also, the propagation speed in a cable is significantly lower than in free space - the perceived delay increase is ~1.5 times for usual cables (~.67 velocity factor), and the computed fix point would have a lower height ASL than the real one. Those relaying systems are merely good for an approximate location fix, mostly for not loosing the GPS signal in covered areas so that the reacquire of the real signal is faster, with almost no perceived discontinuity. On 4/12/2012 6:11 PM, David McGaw wrote: The time/position fix would be from the location of the receiving antenna of the repeater, degraded only by noise. This should work if both antennas have good back-side rejection (choke-rings are particularly good for this but perhaps any good timing antenna could meet this), the re-transmitting antenna is close to being directly under the receiving antenna, and the system gain is low enough. The problem I would see in a room that is not fully shielded is interference between the direct and retransmitted signals at the receiver under test. David N1HAC On 4/12/12 10:17 AM, MailLists wrote: GPS being extremely time-dependent, any delay introduced will affect positioning precision. Also, the signal is too weak for such an amplification/echo cancelling signal chain. Passive relaying, or using at most a simple amplifier with low enough gain, and short signal delay, remain the only feasible concepts. On 4/12/2012 4:48 PM, Azelio Boriani wrote: Passive UHF TV repeaters were in use in Italy too. Nowadays, for the DVB-T TV, active gap-fillers are used instead. Active gap-fillers are same-channel repeaters with the necessary, sophisticated echo suppression technique. We have developed our echo suppression signal processor on a Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS CDMA. On Thu, Apr 12, 2012 at 3:29 PM, Alan Meliaalan.me...@btinternet.comwrote: If the isolation is good and the clear view signal is reasonably strong, the passive system works well in hangers, metalclad warehouses, ferry lorry decks. The passive system in the UK used to be refered to as the Matlock Repeater. Alan G3NYK - Original Message - From: Michael Bakermp...@clanbaker.org To:time-nuts@febo.com Sent: Thursday, April 12, 2012 2:05 PM Subject: [time-nuts] Re-radiating a GPS signal...?? Time-nutters-- So-- How do GPS signal re-radiators work? How do you place a GPS antenna on top of a building, pick up the signal with an LNA, amplify it to re-transmit on an inside antenna without the amplified re-transmitted signal getting back into the roof-top receiving antenna? I can see circumstances where a huge metal building (aircraft hangar?) might provide enough isolation to prevent problems, but in many cases I wonder about it... As an aside note-- I recall seeing, many years ago, a totally passive TV signal repeater on top of a tall hill in mountainous territory relaying a TV station signal to some homes
Re: [time-nuts] NTP jitter with Linux
Nice toy, but the question of the necessity of a fully fledged OS for most tasks thrown at such a small system still remains (integrated network connectivity is a plus). NTP isn't capable to improve the precision of a system's clock, as it works over a heterogeneous path, which is quite unpredictable (NTP being specifically optimized to compensate for such effects). It can only improve the long term accuracy, similarly to a GPSDO. If the internal clock of the system to get synchronized isn't precise enough, NTP won't help. While FPGAs excel at high throughput/parallel processing, the GPSDO process is mostly a quite slow one (with the notable exception of phase comparison - for which a CPLD is more than enough), so they would be overkill. A NTP server needs a network stack, and those are mostly included in full OSs - there are some small uC ones, but it's debatable if such a uC is capable of servicing more requests, and/or having a low enough and predictable processing overhead. There are a few implementations of linux systems in a FPGA, but a bigger uC/SoC would be enough for such a task, costs being another factor - that task would fit nicely a PI. On 4/5/2012 8:36 AM, Gmail wrote: Indeed, I'm looking forward to getting a few raspberry pis to play with. NTP is but one of the interesting time related projects possible with a $35(us) Linux platform. The system has a number of i/o pins directly exposed that will make interfacing interesting. On a side note, speaking of deterministic systems, why has no one built a GPSDO with an FPGA yet? Or an NTP server? :) Bob On Apr 5, 2012, at 1:15, MailListsli...@medesign.ro wrote: As a rule of thumb, any general purpose architecture will be less effective at a specific task than a specially designed one. That applies more and more to the modern way of solving tasks: software. The PC is one of the classical examples of GPA, and as such it is best to know its limitations, so as to not have exaggerated expectations. The first limitation, in that specific case, is the way the PPS source is connected to the system. LinuxPPS tries to optimize it. The serial port is far from being a precision path, the newer implementations being optimized for throughput (FIFOs) are even worse. Any additional layer (USB especially) makes things just more and more worse. As for linux itself, to increase predictability, any disturbing factor should be minimized, if not eliminated. That would mean especially laptop power consumption optimization gimmicks, which are useless in a high performance server/workstation environment (eco, green, and the other trendy marketingdroid buzzwords are lately more, and more abused for a few percent power consumption reduction). The suggested RTOS approach is workable, but it represents just another example of tweaking a GPA to a specific task, which for a server is usually not desired. The low latency patches are another example, used usually for DAWs, but with the reverse side of increased processor loading. First you must define what your goals, and necessities are, and then optimize your system for the desired task - here linux is your friend, with its almost unlimited tweaking options (no comparison to windumb.) Also, don't use a dumbed down distro, and (learn to) patch/compile your own special kernels (best stripped down of all useless ballast of a generic one). On 4/5/2012 1:22 AM, Mike S wrote: I asked this on an NTP list, got some guesses, but no knowledgeable responses. I've got a Trimble Thunderbolt PPS source for NTP, Linux 2.6.35, on a quad core CPU. PPS source is coming into a multiport serial card, which /proc/interrupts shows is sharing IRQ with some inactive USB ports (IRQ 17). It's a PCI-E card, so it would be using MSI interrupts. My understanding is that those aren't really shared, in the traditional sense, but IDK. The kernel clocksource is TSC, which is claimed to be core invariant on my processor (AMD Athlon II 610e). Changing to HPET doesn't help. Running normally, I'll get about +- 20 us ptp of jitter (as reported by ntpq -p, and in loopstats). If I load up the CPU (load average4 is swell), jitter will shrink to +- 1-2 us. I've played around with different cpufreq setting, thinking it might be related to the processor speed during an IRQ varying, but that seems to have minimal impact (performance vs. conservative vs. ondemand). I've also tried irqbalance, with no change in performance. So, running a process(es) which keep the CPU completely busy reduces the jitter. The busier, the better. Why? I'm guessing it has something to do with interrupt latency, but why does a busy CPU make it more consistent - I'd expect the opposite? The difference is very obvious. Is there something else I can do to keep the jitter low? Aside: Something which I believe was discussed here a few weeks ago - clocksource speeds changing between reboots. I patched the kernel to allow statically setting the
Re: [time-nuts] NTP jitter with Linux
As a rule of thumb, any general purpose architecture will be less effective at a specific task than a specially designed one. That applies more and more to the modern way of solving tasks: software. The PC is one of the classical examples of GPA, and as such it is best to know its limitations, so as to not have exaggerated expectations. The first limitation, in that specific case, is the way the PPS source is connected to the system. LinuxPPS tries to optimize it. The serial port is far from being a precision path, the newer implementations being optimized for throughput (FIFOs) are even worse. Any additional layer (USB especially) makes things just more and more worse. As for linux itself, to increase predictability, any disturbing factor should be minimized, if not eliminated. That would mean especially laptop power consumption optimization gimmicks, which are useless in a high performance server/workstation environment (eco, green, and the other trendy marketingdroid buzzwords are lately more, and more abused for a few percent power consumption reduction). The suggested RTOS approach is workable, but it represents just another example of tweaking a GPA to a specific task, which for a server is usually not desired. The low latency patches are another example, used usually for DAWs, but with the reverse side of increased processor loading. First you must define what your goals, and necessities are, and then optimize your system for the desired task - here linux is your friend, with its almost unlimited tweaking options (no comparison to windumb.) Also, don't use a dumbed down distro, and (learn to) patch/compile your own special kernels (best stripped down of all useless ballast of a generic one). On 4/5/2012 1:22 AM, Mike S wrote: I asked this on an NTP list, got some guesses, but no knowledgeable responses. I've got a Trimble Thunderbolt PPS source for NTP, Linux 2.6.35, on a quad core CPU. PPS source is coming into a multiport serial card, which /proc/interrupts shows is sharing IRQ with some inactive USB ports (IRQ 17). It's a PCI-E card, so it would be using MSI interrupts. My understanding is that those aren't really shared, in the traditional sense, but IDK. The kernel clocksource is TSC, which is claimed to be core invariant on my processor (AMD Athlon II 610e). Changing to HPET doesn't help. Running normally, I'll get about +- 20 us ptp of jitter (as reported by ntpq -p, and in loopstats). If I load up the CPU (load average 4 is swell), jitter will shrink to +- 1-2 us. I've played around with different cpufreq setting, thinking it might be related to the processor speed during an IRQ varying, but that seems to have minimal impact (performance vs. conservative vs. ondemand). I've also tried irqbalance, with no change in performance. So, running a process(es) which keep the CPU completely busy reduces the jitter. The busier, the better. Why? I'm guessing it has something to do with interrupt latency, but why does a busy CPU make it more consistent - I'd expect the opposite? The difference is very obvious. Is there something else I can do to keep the jitter low? Aside: Something which I believe was discussed here a few weeks ago - clocksource speeds changing between reboots. I patched the kernel to allow statically setting the TSC frequency ( http://old.nabble.com/-PATCH--tsc_khz%3D-boot-option-to-avoid-TSC-calibration-variance-td23494975.html ). This eliminates the semi-random, often 30-40 ppm change in frequency reported by NTP between reboots. After tweaking, it's now consistently 1 us, reboots be damned. This should be in the mainline kernel! This made no difference to the jitter mentioned above, although non was expected. ___ time-nuts mailing 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] Temex LPFRS-01
Yes... Thank you, and the others, for the suggestions for cleaning/reviving the unit, but I can't recommend to my friend to keep a pile of rust (if water damage really is the problem) advertised as an used working item. Regards, bbg On 3/17/2012 4:10 PM, Azelio Boriani wrote: LPFRS from fluke.l? OK, then open it up and clean it, the LPFRS from fluke.l suffers from high humidity/water immersion and usually are very rusty inside. I have received one that was very bad but after cleaning with tetrachloroethylene (translated with google) it is working properly, maybe it will fail soon but now works. I complained with fluke.l and he refunded me without asking to ship back the LPFRS. TIP: handle with extreme care an opened LPFRS, there is a flexible PCB that holds the DB9 connector that can tear in the corners. On Sat, Mar 17, 2012 at 10:59 AM, MailListsli...@medesign.ro wrote: Hello all, a friend purchased from the bay asubj. in the LPRO configuration. After some problems encountered during the first power ups, he asked for help - I'm passing the questions further... After about 9 minutes of warm-up from room temperature (22°C) the lock signal goes low, but after a short time starts to switch low/high with decreasing low periods, until it remains high with short low pulses, spaced at about 2 seconds. After power-down, and sufficient cooling time, the cycle repeats. First step was to reapply the thermal interface to the integrated Al radiator, which helped a bit, the time during which the unit is locked growing slightly. Next step was forced cooling, which helped more, so the lock loss could be attributed with high probability to elevated operating temperatures. The temperature of the base plate (integrated Al radiator) at which lock gets lost is about 40°C, so for a reasonable operation it should not pass about 36°C, at which the power consumption raises to about 17W. That also means that for a 1°C/W heat sinking - obtainable with a larger passive HS or active cooling - operation above 30°C ambient gets practically impossible (except refrigeration, Peltier, etc.). Any further help or suggestions are welcome. Regards, bbg ___ time-nuts mailing 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] Temex LPFRS-01
After further testing, including a simple lost lock detector (2 555s: manually resettable bistable + multivibrator and a buzzer), with the serial port the whole picture looks even grimmer. Most parameters seem to be in nominal range, relatively stable after warmup, with the notable exception of a very low dip detector amplitude, which fluctuates, and also gets lower with increasing temperature. Even at lower temperatures, than first mentioned, lock losses do appear sporadically. Regarding the adjusting of the LPFRS's frequency, it seems it's possible just discreetly, even with the analog input, the smallest step being 1E-11, as the analog way is, with high probability, also going through an 8 bit ADC and the CPU. To have a more fine control, the access directly to the internal C-Field adjustment circuit seems necessary - maybe a future project with a fully working unit. Regards, bbg PS: Mark, is the busted one from the same source, mentioned earlier? On 3/17/2012 6:20 PM, Mark Spencer wrote: This is interesting. I have two temex units one which works and one which has similar issues to yours. The performance of my working one is quite good. (If you want any specifics let me know and I can provide more details in a few days, but I recall it is notably better than either of my 5680's. I found the performance was best with a fan blowing air over the heat sink.) I'm glad you were able to get a refund for yours. I gave up debating with the seller of my defective unit and wrote it off to experience (also I figured since it did put out a signal and locked up from time to time that it wasn't entirely dead.) I probably should have pushed harder with the seller. I'll leave my busted temex in the projects pile for now. With the benefit of hindsight the picture I saw on ebay of the non working unit was not very confidence inspiring and I wish I had bought a second unit from the original source. The first unit was very clean and came with an attached heat sink and worked fine from day one. I've been contemplating building a system to periodically adjust the frequency and I want a second working unit before I put any time and effort into sorting out a pic tic micro controller solution. Please excuse typos and top posting sending from pda. -- On Sat, 17 Mar, 2012 10:58 AM EDT Azelio Boriani wrote: Yes, correct. The problem is that I have no deionized water nor a suitable oven. The use of the tetrachloroethylene has simplified the procedure for me (after all I was refunded, should the Rb fail it is not a money loss). Anyway I'll try to locate a supply for high quality deionized water, the oven can be built... I have one item to process more carefully. On Sat, Mar 17, 2012 at 3:21 PM, Bob Campli...@rtty.us wrote: Hi If it is water immersion damage, wash it in soap and water. Then rinse it in hot deionized water (above 10 mega ohms if you can get it). After that bake it at 80C with good air flow for 24 hours. It still may rust, but most of the guck from the water will be gone. I once spent a lot of quality time with many truck loads of flood damaged gear Bob On Mar 17, 2012, at 10:10 AM, Azelio Borianiazelio.bori...@screen.it wrote: LPFRS from fluke.l? OK, then open it up and clean it, the LPFRS from fluke.l suffers from high humidity/water immersion and usually are very rusty inside. I have received one that was very bad but after cleaning with tetrachloroethylene (translated with google) it is working properly, maybe it will fail soon but now works. I complained with fluke.l and he refunded me without asking to ship back the LPFRS. TIP: handle with extreme care an opened LPFRS, there is a flexible PCB that holds the DB9 connector that can tear in the corners. On Sat, Mar 17, 2012 at 10:59 AM, MailListsli...@medesign.ro wrote: Hello all, a friend purchased from the bay asubj. in the LPRO configuration. After some problems encountered during the first power ups, he asked for help - I'm passing the questions further... After about 9 minutes of warm-up from room temperature (22°C) the lock signal goes low, but after a short time starts to switch low/high with decreasing low periods, until it remains high with short low pulses, spaced at about 2 seconds. After power-down, and sufficient cooling time, the cycle repeats. First step was to reapply the thermal interface to the integrated Al radiator, which helped a bit, the time during which the unit is locked growing slightly. Next step was forced cooling, which helped more, so the lock loss could be attributed with high probability to elevated operating temperatures. The temperature of the base plate (integrated Al radiator) at which lock gets lost is about 40°C, so for a reasonable operation it should not pass about 36°C, at which the power consumption raises to about 17W. That also means that for a 1°C/W heat sinking - obtainable with a larger passive HS or
[time-nuts] Temex LPFRS-01
Hello all, a friend purchased from the bay a subj. in the LPRO configuration. After some problems encountered during the first power ups, he asked for help - I'm passing the questions further... After about 9 minutes of warm-up from room temperature (22°C) the lock signal goes low, but after a short time starts to switch low/high with decreasing low periods, until it remains high with short low pulses, spaced at about 2 seconds. After power-down, and sufficient cooling time, the cycle repeats. First step was to reapply the thermal interface to the integrated Al radiator, which helped a bit, the time during which the unit is locked growing slightly. Next step was forced cooling, which helped more, so the lock loss could be attributed with high probability to elevated operating temperatures. The temperature of the base plate (integrated Al radiator) at which lock gets lost is about 40°C, so for a reasonable operation it should not pass about 36°C, at which the power consumption raises to about 17W. That also means that for a 1°C/W heat sinking - obtainable with a larger passive HS or active cooling - operation above 30°C ambient gets practically impossible (except refrigeration, Peltier, etc.). Any further help or suggestions are welcome. Regards, bbg ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
