Re: [time-nuts] GPScon running on Raspberry Pi 3b
Mark, That is exactly the right processing order. However, it shouldn't actually try the USB port until after that processing is done. In other words, if the configuration file has -1u and the command line has -4u, it should never try USB0 because that was overridden on the command line. It should try USB3 and succeed or fail based on that. Did you get what you needed from the build this morning? Michael Lee Finney > Heather's configuration priority is to process: hard coded defaults, then > the config file, and finally the command line options. This lets you set > your preferred settings in the config file and then override your config file > options from the command line. > >> When I ran it with ./heather -4u, it first told me that it was unable to >> open /dev/ttyUSB0 and > then told me it was unable to open /dev/ttyUSB3. This is probably due to the > configuration file containing "-1u", but if that option is given on the > command line then the configuration file value should be ignored - or at the > least it should be tried after the command line option. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] GPScon running on Raspberry Pi 3b
Mark, I compiled and ran Lady Heather on my Tinker this morning. This is using the "stretch" distribution with GCC version 6.3.0 (and of course, the current version is 7.1.0 with more language changes). I received 8 warning messages, the first three are a language change and remainder are "misleading indentation" messages. To get a clean compile, I fixed the spaces and indentation, but looking at the code it is the type of thing that I would check to make sure that the control flow is correct - the indentation is indeed misleading which is always a potential sign of a bug. Here are the warning messages that I got: heather.cpp:13720:10: warning: invalid suffix on literal; C++11 requires a space between literal and string macro [-Wliteral-suffix] heather.cpp:13720:27: warning: invalid suffix on literal; C++11 requires a space between literal and string macro [-Wliteral-suffix] heather.cpp:13720:40: warning: invalid suffix on literal; C++11 requires a space between literal and string macro [-Wliteral-suffix] heather.cpp:10881:26: warning: this ‘else’ clause does not guard... [-Wmisleading-indentation] heather.cpp:10883:4: warning: this ‘else’ clause does not guard... [-Wmisleading-indentation] heathmsc.cpp:2124:28: warning: this ‘else’ clause does not guard... [-Wmisleading-indentation] heathmsc.cpp:6710:24: warning: this ‘else’ clause does not guard... [-Wmisleading-indentation] heathgps.cpp:20433:7: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation] Also, I am waiting for my USB to RS232 adapter, so I don't have anything plugged into the USB ports (other than keyboard and mouse). When I ran it with ./heather -4u, it first told me that it was unable to open /dev/ttyUSB0 and then told me it was unable to open /dev/ttyUSB3. This is probably due to the configuration file containing "-1u", but if that option is given on the command line then the configuration file value should be ignored - or at the least it should be tried after the command line option. Other than the above, it looks great given that nothing is plugged in! Thanks for the work you do maintaining this program. Michael ___ time-nuts mailing 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] GPScon running on Raspberry Pi 3b
Mark, Are there any special requirements for using a USB to RS-232 adapter on the Pi? Any specific features for the RS-232 adapter to get all of the features for Lady Heather? Looking at eBay, it is not clear which adapter would be best. Some don't say anything about supported pins, other list the pins that are supported (and may differ). Which pins do you require / support? Are any device drivers needed for the Pi or Linux for those adapters? New to Linux, Pi and Lady Heather. Thanks. Michael > Lady Heather can run under Linux, macOS, FreeBSD, and Windoze. It runs > well on the PI (2 or 3) and the soon to be released version 6 has support > for the touchscreen and several new devices. I can send anybody interested > in testing the new version the latest source code to build. Contact me off > list. > New devices include the RFTG-m, Truepostion GPSDO, Zyfer Nanosync 380, > Brandywine GPS4, Jackson Labs LTE-lite, Oscilloquartz Star-4, NEC GPSDO, > Trimble TAIP receivers, most SCPI GPSDOs (Z38xx, HP-5), HP-5071A, TAPR > TICC, HP-531xx counters, generic time/frequency counters, etc > -- >> I believe that having a native GPS monitoring software on a Raspberry Pi >> instead of PC would become a game changer. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] GPScon running on Raspberry Pi 3b
Neat! I just happen to be playing with a Pi this week as a class assignment (retirement is wonderful - finally going back to college). I downloaded Lady Heather, compiled it, and got it to come up and run. Nothing that I can plug in this week though, but it looks good. I also installed QEMU in user mode which is similar to ExaGear, but slower and free (long run I will probably get an ASUS Tinker as my lab computer, and it is a different ExaGear). However, I could not find the steps to download wine. I understand that some sort of patch is required, but all that I could find was complete linux images that were already patched. What were your steps to download and install wine? Michael > Hi, > This is my first post to the community I learned so much from. Just wanted > to share -- I managed to succesfully install today the GPScon windows > application on a micro computer Raspberry Pi 3 model B. CPU utilisation is 2% > - a perfect overall result. > I used an FTDI RS232 USB dongle to connect Z3805A/58503B to the Pi. First I > installed on the Pi a Russian commercial I686 emulation software called > ExaGear Desktop by Eltechs.com ($30). It provides a Debian-8 Intel > environment on the Arm CPU. Next move was to (sudo apt-get) install wine > Windows XP emulator and symlink therein com1 as /dev/ttyUSB0 - to enable the > usb dongle to be seen by Wine as com1. > Then I installed my copy of GPScon from 2013, which turned out to work pretty > well. > Hope this post was usefull. In case of interest I would exact steps to make > this working. > Best regards > Olgierd > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Lady Heather Version 5 is now available
Mark, While I have not (yet) used Lady Heather, I plan on doing so as soon as I can get my GPSDO. However, I do have a feature suggestion. You have an option that allows dates to be expressions in the European format DD-MM- vs. the US format of MM-DD-. What about an option to express dates in ISO standard format: -MM-DD. Personally, that is the only date format that I use and it has the advantage of being easily sorted. That may make processing collected data easier. Michael > Lady Heather version 5.0 is now available for download from: >http://www.ke5fx.com/heather/readme.htm > Many thanks to John Miles for hosting the distribution and his work on the > Windows installer, PDF documentation file, readme file, and bring an > all-around good guy. > Heather now has some proper user documentation. Check the heather.pdf file > and/or the comments in the first 3500+ lines of the heather.cpp file. > Heather can be compiled for Linux (including the Raspberry Pi) and macOS. > Download the heatherx11.zip file and check the readme.txt file for > compilation instructions. > There are MANY new features in Heather. One of the main ones is support > for many new receiver types. When Heather is started it defaults to > attempting to automatically determine the receiver type. You can bypass > this and force the receiver type using the new "/rx..." command line > options. Some receiver types cannot be auto-detected. Also many receivers > power up speaking NMEA and you can enable their native binary language using > the /rx commands. Native binary mode gives better information and allows > controlling the receiver configuration and settings. > Currently-supported receivers include: > Trimble Thunderbolt and Thunderbolt-E > Acron Zeit WWVB receiver > UCCM - Trimble / Symmetricom GPSDOs > DATUM STARLOC II GPSDO > NEC GPSDO (STAR-4 compatible) > GPSD interface > Jupiter-T (aka Zodiac) > Lucent KS24361 REF0/Z3811A (19200:8:N:1) > Motorola binary format > Generic NMEA receiver > Trimble Resolution T family with odd parity > Sirf binary > Generic Trimble TSIP binary > Ublox UBX binary > Venus mixed binary / NMEA > Nortel SCPI-compatible GPSDOs (NTWB, NTPX, etc.) > Z3801A and compatible SCPI GPSDOs > HP 5-style SCPI > Oscilloquartz STAR-4 (via the management interface) > NVS binary > PC system clock (no receiver) > After installing Heather, you should edit the heather.cfg file (or the > PROPERTIES setting for the desktop icon) for your desired configuration. > Everybody should change the "/tz" option for their time zone... it comes set > up for the US central time zone. International uses should add a "/b..." > command to set their daylight savings time information. On Windows, you > can press the "n" key and that will bring up NOTEPAD to edit the file. For > the changes to take effect you will need to re-start Heather (or do a "r > heather.cfg" keyboard command). > _______ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Time math libraries
Eric, I speak as someone who has implemented many calendrical packages. I have always tried to achieve the maximum degree of generality, and have considered the issues with leap seconds on more than one occassion. The first problem with leap seconds is that you need a list of them, and that list needs constant updating. If date/times are maintained in a standard form such as seconds since the beginning of an epoch (e.g. 0 AD) then even the conversion into a conventional date/time is dependent upon the country you are in. That is just too much overkill for the usual purpose. In practice, a date/time is loaded from a file or obtained from an operating system (which MAY take leap seconds into account). At that point it is just a date/time to be manipulated. If you should be unlucky enough to get a date/time exactly in a leap second - it really doesn't matter because date/times are just not synchronized well enough for it to matter. Where it does matter, there is some local clock which is used and the date/times are relative to it. This is almost always for timestamps, and the time since the system boot will generally do well unless you need it across a network. Then even cable delays become a problem. So taking leap seconds into account requires a substantial amount of additional coding, constant updates of possibly distributed code to keep the list of leap seconds maintained and adversely affects both storage and performance. For practical matters, even if it could be done at zero cost, there is no real benefit. Just allowing a day to have 86,401 seconds causes all sorts of problems with data storage, consistency verification, editing and ensuring that data entry is correct. It is the rare application that needs leap seconds - even though it may be "correct", and certainly an option I have considered many times - but it has never been justified for anything that I have ever written (which actually includes operating systems). Consider that the system clock for any processor will "slip" on a regular basis and need to be reset. The accuracy that most operating systems can maintain in practice is, at best, only on the order of a second or two - and that is with regular updates from a timing source. Now, if you have a processor with a built-in GPSDO, perhaps that could be used to regulate the system clock (which is just a cheap quartz crystal) and keep time synchronized to perhaps a millisecond or so. Maybe. But, probably not. All that is left would be specialized applications that actually require leap seconds. I don't know of any, but there may be some available. Certainly an operating system could maintain the necessary lists (assuming that it is regularly updated). It could use that data for conversions. I don't know of an operating system that does that though because of the data format problems. They would report a time such as 24:00:00 which would otherwise be invalid. That specific time is usually taken as 00:00:00 of the next day. Very few, if any applications would understand 24:00:00 as a valid time. So, operating systems can't really afford to take leap seconds into account either. Michael >(Apologies if this question has been addressed before. Archive search is > rather cumbersome on a month-by-month basis.) >Few people will be surprised to learn that MS Excel does not account for > leap seconds when doing time math. See below for an example. This is just an > example of many instances of programming failures. >Are there good time math software libraries (e.g., Java, C++/C#, etc) > that will do time math correctly for the chosen time scale? >Thanks. > — Eric > 2016 Dec 31 Sat 23:59:57 > 2016 Dec 31 Sat 23:59:58 > 2016 Dec 31 Sat 23:59:59 > 2017 Jan 01 Sun 00:00:00 > 2017 Jan 01 Sun 00:00:01 > 2017 Jan 01 Sun 00:00:02 > My machine is on EST right now. Is it a time zone question? > 2016 Dec 31 Sat 18:59:57 > 2016 Dec 31 Sat 18:59:58 > 2016 Dec 31 Sat 18:59:59 > 2016 Dec 31 Sat 19:00:00 > 2016 Dec 31 Sat 19:00:01 > 2016 Dec 31 Sat 19:00:02 > Nope! > What about past leap seconds? > 2015 Jun 30 Tue 23:59:57 > 2015 Jun 30 Tue 23:59:58 > 2015 Jun 30 Tue 23:59:59 > 2015 Jul 01 Wed 00:00:00 > 2015 Jul 01 Wed 00:00:01 > 2015 Jul 01 Wed 00:00:02 > Also fail! > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] patents and hobbyist projects (was: Temperature controlled TCVCXO)
If I understand it correctly, you only violate a patent if you manufacture and SELL a product covered by the patent. If you build it for yourself, then there is no violation. Even if you are a company, and you build one for testing and evaluation, as long as you don't sell it there is no violation. That is because there is no "harm" to the patent holder. They have to show that your production affected their potential sales and rights to profit from the patent. If you build a bunch and GIVE them away, that counts as a violation as well. Of course, giving is just selling with a zero price. Michael > In addition to what others write about nobody will come after you for > hobbyist/testing purposes... > It is surprisingly easy for a patent non-professional to be confused, about > what a patent actually covers (claims) vs does not cover (claim). > There is a section called "description" that is useful and interesting for > techie guys. Especially when the patent was the result of a actual real > device, anyone skilled in the field will be able to read the "description" > section of a patent and figure out the device and learn something from the > patent. The "citations" and "referred to by" are usually interesting > reading too. > Beyond that, there is a section called "claims" that actually sets out the > legal language about what the inventors, and their patent lawyers, and the > patent examiner, eventually decided (probably over a period of months to > years) could be patented. Reading the claim section is surprisingly tricky. > Lots of interesting things (to you and me) in the description are probably > not actually claimed because they were claimed by previous patents (See the > patent citations at the bottom). When I'm in a room with the patent lawyers > and they are telling me how to read it, I can manage to follow them and > even learn a little bit of the patent phrase-ology in a way that makes > sense to me. These lessons in patent phrase-ology stick with me for only a > matter of days after we leave the room. The language of the claims is very > highly specialized, and even further the patent lawyers have "optimized" > the claims, so that base claims are elaborated on in a very complicated and > ornate way in later claims such that a challenge to any one claim of the > patent will have minimized the effect on negating the whole patent. > Tim N3QE > On Sat, May 14, 2016 at 5:56 AM, Attila Kinali <att...@kinali.ch> wrote: >> On Fri, 13 May 2016 19:32:58 -0500 >> David <davidwh...@gmail.com> wrote: >> >> > Thanks for those. I went over them pretty carefully and what I am >> > proposing is not covered by either although that would not protect me >> > from a debilitating patent lawsuit. >> >> I wouldn't worry about patent lawsuits at all unless you intend to >> start a multi-million business. >> > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] [Announce] Simulation software for powerlaw noise and PTP clock synchronization
Wolfgang, Thank you for sharing. I would like a copy of your Thesis when it published (I don't need a physical copy, .pdf is ok). I'm sure others out here would like to see it as well. Mike > Dear Timenuts community, > I would like to announce the public availabilty of two software projects > which I have been working on for my master thesis: > * LibPLN: a portable C++ library for the efficient simulation of > Powerlaw Noise (PLN) > * LibPTP: a simulation framework based on the OMNeT++ network simulation > environment, for the simulation of the Precision Time Protocol (PTP) as > it is specified in IEEE 1588-2008 > Getting started: > -- > Both software project are available as open source from my Github > account: https://github.com/w-wallner > The readme files present on the Github page should give you an idea on > how to get started using the individual components. > License: > -- > All code is licensed using open source licenses. > Most parts of the software are licensed as GPLv3, some parts use the > GPLv2 and BSD licenses. > See the respective COPYING files for details. > Detailed documentation: > -- > A detailed description of all design design decisions and how the > fundamental concepts of the libraries work is contained in my master thesis: > Simulation of Time-synchronized Networks using IEEE 1588-2008, > 2016, Vienna University of Technology > As of this writing (April 2016), it is not yet published, the expected > publication date will be May or June 2016. > I hope these projects can be useful for some of you :) > In case you have any questions, feel free to ask. > Kind regards, > Wolfgang Wallner > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] Advise on building a DIY GPSDO?
Hello Bob, Friday, April 8, 2016, 6:13:07 PM, you wrote: > Hi > If you start from a 24 MHz TCXO (different modules use different TCXO’s): > On an 8 MHz output, most of the time you divide by three. > On a 10 MHz output, you need to divide by 2.4. The net result is that you > divide by 2 sometimes and 3 other times. > In the 10 MHz case, there is a *lot* of energy at 12 MHz and 8 MHz, along with > the 10 MHz output. > In the 8 MHz case, most of the RF energy is at 8 MHz. > > To correct the output by 1 ppm on the 8 MHz output, you need to either drop or > add one pulse out of every million pulses. Effectively you divide the 24 MHz > by > 2 or by 4 when you do that. You get a bit of 12 MHz or a bit of 6 MHz as a > result. If you know you are doing a 24Mhz and a 10Mhz, why not divide the first by 12 and the second by 5 and then phase lock the resulting 2Mhz? Or divide by 24 and 10, respectively and lock the 1Mhz? That way, everything is exact. Mike > That can be filtered out with a RF filter. The same is true with a (somewhat > more > complex) filter on the 10 MHz output. > In addition to the “big” RF spurs, you get a low frequency component to the > output > modulation. You are “phase hitting” the output eight times a second. That > gives you > an 8 Hz sideband along with the further removed stuff. Since it’s not simple > / clean > phase modulation, there are more sidebands than just the few mentioned above. > What messes things up even more is that you never are quite doing one ppm. > You are doing > corrections like 0.12356 ppm this second and 0.120201 ppm the next second. > The pattern of pulse drop and add is not as simple as you might hope. The low > frequency part of the jitter (and it will be there) is no different than the > noise on > a 1 pps output. You still need to do very long time constant (or very narrow > band) > filtering to take it out. > Bob >> On Apr 8, 2016, at 7:06 AM, Herbert Poetzl <herb...@13thfloor.at> wrote: >> >> On Mon, Apr 04, 2016 at 06:07:54PM -0700, Alexander Pummer wrote: >>> and it is relative easy to make 10MHz from 8MHz with analog >>> frequency manipulation, which generates less jitter >> >> Could you elaborate on this a little if time permits? >> I'm more a 'digital person' but it sounds interesting. >> >> Thanks in advance, >> Herbert >> >>> 73 >> >>> On 4/4/2016 4:27 PM, Attila Kinali wrote: >>>> On Mon, 4 Apr 2016 17:56:29 -0400 >>>> Bob Camp <kb...@n1k.org> wrote: >> >>>>> The variable frequency output on the uBlox (and other) GPS >>>>> receivers has come up many times in the past. >> >>>>> If you dig into the archives you can find quite a bit of >>>>> data on the (lack of) performance of the high(er) frequency >>>>> outputs from the various GPS modules. They all depend on >>>>> cycle add / drop at the frequency of their free running TCXO. >>>>> Regardless of the output frequency, that will put a *lot* of >>>>> jitter into the output. >>>> That's why you should put the output frequency of the ublox modules >>>> to an integer divisor of 24MHz. Ie 8MHz works but not 10MHz. >> >>>> 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. >> ___ >> time-nuts mailing 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] LEA-M8T
So... Back to Bob's original observation. He stated that he DID shut off all sats except GPS. So, is the LEA-8MT better or worse than the LEA-6T (or LEA-7T, if available) when only GPS is used? I wouldn't think that it would be worse, but it wouldn't be the first product that an "enhancement" messed it up. Sometimes generalizing something can make it worse. Does the LEA-8MT pick up fewer sats due to the wider bandwidth? Or perhaps, is more sensitive to noise or interference? Mike > I recently bought a number of LEA-M8T receivers and I have to say that I am > unimpressed, so far. They don't survey to the same reported accuracy as the > LEA-6T in the same amount of time. They certainly aren't better in the > jitter after sawtooth correction. So, have I managed to overlook some new > field, or are they just not the same receiver as the 6T? I did shut all sats > off except GPS sats. > 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] Spectrum Analyzer Specifications
Thanks everybody! You have all given me a bit to think about. Clearly, what I thought that I needed is not necessarily what I actually need. To summarize... 1. There are various options and approaches for a Spectrum Analyzer. BUT, I probably don't actually need one because they are inadequate to the task at hand. One that might be sufficient would probably cost as much as a small house (or new car). Not cost effective for me. 2. The next big test tool should probably be a time interval counter, with possibly a cheaper higher-precision frequency counter without time interval capabilities before that. 3. But first, a GPSDO for a frequency reference is a good idea (I was already planning on that, in any case). I also think that a higher precision DMM (one of the 6 or 7 digit meters) is probably also a good idea. Mike ___ time-nuts mailing 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] Spectrum Analyzer Specifications
Charles, >>When using a spectrum analyzer to examine the output of a frequency >>standard, what are the minimum specification needed? Bandwidth, >>resolution, sensitivity, etc? > It very much depends on what you hope to see with it. That said, > virtually no SA will do anything useful in this application without a > fair amount of preprocessing. > . . . > I am all for having one or several SAs around the lab, but I fear > that an SA may not be very useful for the particular tasks you are > hoping it will perform. Being new to this, I don't actually know what I need to see with it. However, I see charts that show the "spurs" on the output of an oscillator. I assume that I will want to do similar tasks. As I understand it, those are the main problem when multiplying the frequency by very much because they get multiplied as well. Thus, one of the differences between a "good" OCXO and a "bad" OCXO. > Pay attention to ergonomics -- suffering with an SA that doesn't > think like you do will drive you crazy. For example, I prefer > HP/Agilent SAs over Tek SAs because the HPs allow you to specify a > start and stop frequency *or* a center frequency and span, while the > Teks only allow you to specify a center frequency and span. As an example, I currently have a broken MTI 260 which I am repairing. I currently have it cleanly disassembled so that it can be reassembled with no damage. I know what needs to be done to fix it (at least the first pass) and am waiting on a tool that I need. But, if I succeed in repairing it, what test equipment do I need to determine the quality of output? I can measure frequency to a point (7 digits, uncalibrated - 8 once I have a frequency standard). That is not enough to determine very small deviations from 10Mhz, but it will tell me that I have a sine wave at approximately the correct frequency. The last one I (sort of) repaired, gave me a sine wave but with a duty cycle that wasn't exactly 50-50. So there must be some distortion present. Not surprising in that case because of the hacking that I did. However, I understand that the quality of the OCXOs can vary widely. What tools do I need to determine the quality of output? I assumed that a spectrum analyzer would be a first step - to look for large spurs, overtones and consistent noise (e.g. 120 kHz components) at unusual frequencies. Even jitter and phase noise should show up that way - at least with sufficient resolution, which might be unrealistic. Mike ___ time-nuts mailing 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] Spectrum Analyzer Specifications
Hi, I have another question about test equipment. When using a spectrum analyzer to examine the output of a frequency standard, what are the minimum specification needed? Bandwidth, resolution, sensitivity, etc? Looking at spectrum analyzers on eBay, I see quite a bit of difference between various models. Some have a resolution of 10Hz but others are 30Hz or even 100Hz. Some have a minimum frequency of 0.01Hz, 100Hz or even in the kHz range. Some are only sensitive to 60dBm, but others over 100dBm. Are any of the cheaper USB spectrum analyzers worth getting? Most of these are appallingly expensive, so knowing what is needed can certainly help guide a purchase or to minimize cost. And if a "deal" is found, knowing that it is or is not adequate can help. Clearly, better specifications are preferable, but I'm also sure that the intended application makes a large difference. What is needed for examining a 10Mhz frequency standard might be remarkably different from what is needed for high-frequency RF work. Mike ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best Rubidium Frequency Standard
Bert, Bob, Charles, Corby, Eric, Luciano, Mark, Rob, . . . Thanks for the excellent advice. It has been very helpful. Let me see if I can summarize what different people are saying. 1. The absolute best rubidium standard is the HP 5065A. It has excellent short term stability. The only disadvantages are - a) the price, B) it is harder to use for disciplining via GPS, c) it is sufficiently old that life span could be an issue and d) has poor temperature control and suffers from pressure sensitivity. 2. The second best is the PRS-10. Provided it is working. Its phase noise is generally very good, and above 100Hz may even be better than the HP 5065A but is poor under 1Hz. It is difficult to repair, but that problem appears to be shared by everything except the HP 5065A which is still through-hole. Other than its performance, it has some advantages - a) it is still in production and so can be repaired by SRS, B) it has a built-in 1 pps locking circuit that can be used to lock to GPS and c) given (a) and the 22 year design, life span issues are not a significant problem. It also has several disadvantages - a) that same locking circuit may not always be present and B) that locking circuit does not perform as well as one would wish for GPS 1 pps signals (although pre-applying the sawtooth correction apparently helps a lot as does pre-filtering the GPS signal for an effectively larger time constant). 3. The Efratom M-100 and FRM rubidium standards are also highly recommended. Their main disadvantages are a) the same repair issues that most of these units have, B) the potential life span limitations and c) they are smaller units and not as good as either the PRS-10 or HP 5065A. They do have the service manual available. I don't know about schematics. 4. The LPRO-101 is far from the worst of the lot. As far as repair, there is a repair guide that people have put together but no official service manual with schematics. 5. The FE-5650A / FE-5680A may also be acceptable, with the same disadvantages of life span and difficultly repairing but have very high noise levels. So, as I interpret the above, if I can score a working HP 5065A for an affordable cost then it would be the way to go. While possible, that is not likely. Otherwise, a working PRS-10 with a functioning 1 pps input is very good, again assuming affordable cost which is much more likely. The ability to personally repair either may be limited. For the HP 5065A there are no parts available - especially lamps - and the only way to fix one is to use a parts unit. That gets very expensive and could take many months finding an appropriate parts unit. For the PRS-10, firmware issues and the heavy use of SMD would make repair more difficult. But, for it, at least factory repair is available for a reasonable cost. It may be possible to get some of the other rubidiums somewhat cheaper, but all have their disadvantages. Most share the repair issue and life span issues of the HP 5065A and the SMD construction of the PRS-10. Most of them would also need to have their output cleaned up when used in an application requiring low phase noise. Buying some of them in lots may enable repair via parts units for a reasonable cost. That might be thing to do just to have some as comparisons. I plan on more research, especially with respect to the PRS-10, but with respect to what is currently known, have I missed anything? Any additional feedback? Other units that are worthy of consideration (and actually available, of course)? I have asked SRS about some of the PRS-10 issues. I will everybody know what they say (assuming that they respond). Mike ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best Rubidium Frequency Standard
Joseph, There are a few data points that lead to this conclusion... 1. Look at the images on eBay for various PRS-10 and TSD-12 auctions. You will see that they all have the same customer part number 143-44101-xx where xx is 04, 08 or 10. Further, you will find a PRS-10 and a TSD-12 with the exact same customer part number of 143-44101-08. This indicates that the TSD-12 is a "drop-in" replacement for the PRS-10 for that customer. 2. In the timenut's archive, there is a user who has / had both. He reported that the TSD-12 self-reports as a PRS12, and additionally have the same firmware version number. 3. The PRS-10 and TSD-12 are physically and electrically identical based on the various eBay pictures. There are two variations that I see. The first is that on apparently newer devices the back side has four mounting holes not present on the older devices. The second is that on some devices the Cannon connector is on the bottom rather that on the back end. All of the TSD versions (-11 and -12) appear to have the mounting holes. Like the PRS-10, some have the Cannon connector on the back end and some have it on the side. 4. The same user reported that all of the PRS-10 devices he examined had the default locking mode of 1 and the TSD-12 devices had a default locking mode of 3. However, the LM command allows the locking mode to be set, and there is another command that will make that change to the power up state. 5. Since the package is physically identical, the firmware is physically identical, if you look at the service manual, there are not a lot of things that could be changed or omitted. Almost everything is in software, including the 1 pps locking (which hijacks the trim pot to do its dirty work). 6. The only option listed on the SRS site for new devices is an option that has a reduced aging rate (at an extra $495). There could be some other minor options like that, but effectively it appears as if the TSD-12 (or -11) is interchangable with the PRS-10 if the LM command is used to set the default locking mode. Mike >> Or, perhaps not. The two working TSD12s that I see on eBay (apparently >> the same as the PRS-10 except the lock flag is set to 3 instead of 1 >> and >> which can be reset) > Would you elaborate on this? I Googled for TSD12 and except for the > auction listings, found nothing. > Joe Gray > WW5JG -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] MTI 260-0624-D OCXO
> Hi > Anything electrical (duty cycle/ harmonics / output level / etc) > is designed in on a modern part done in high volume. > The only candidates for a pot on top of the oven are: > Inner oven temperature > Outer oven temperature > EFC > You have already ruled out EFC (it would be a coarse set so > visible on a normal counter). > That leaves inner oven and outer oven. > Why inner oven - to adjust for the data from your temperature run. The parts > are at best coarse set based on crystal temperature. > Why outer oven - same as above or to set for inner / outer separation > and clearance after the thermal stabilization in the sealed can. > If there is no apparent change in frequency (and from the location of > the pot) that suggests the outer oven. Regardless of which oven is being set, > the > adjustment is likely a “move it 1.25 turns" sort of thing. You then > re-run the temperature test to see if it is in spec yet. > Bob Bob, In a separate communication, Angus has stated... > On the two that I tested, it appeared to adjust the temperature of > both of the ovens. > One was a 5 MHz 260-0545-B. The outer oven was at 78.2 degC and at > least around that point the temp changed at about 1 degC per turn. The > EFC adjustment on this one was not quite enough to bring the frequency > to exactly 5 MHz, but the oven temp did look to be close to correct. > The other was a 16.384 MHz 260-0546-G which was unused old stock, but > had overall poor stability. It turned out that the oven temp on it was > 1-3/8 turns from the turnover point, but when or how that happened I > don't know. > It would be interesting to hear from somebody who knows how this type > of thing is actually adjusted in production. I finally got my 260 (sort of) repaired and have done some measurements. Generally, I can confirm what Angus was saying, to the limits of my ability to measure. One of the things that I can measure is the source voltage. I have a hacked together 12v supply. When hooked up to the 260, it initially reads just over 9v. As it warms up, it eventually tops out just under 10v. There appears to be roughly four different points, around 9.1v, 9.35v, 9.8v and 10v. The 260 starts at around 9.1v, quickly moves up to 9.35v and after a while to 9.8v. It will then sometimes move briefly up to 10v and back down to 9.8v. I interpret this as different heating stages - probably both ovens on, one oven on, some sort of maintenance heating point and no heaters on. What I find as I adjust the pot (after letting the 260 warm up) is that turning the pot counter clockwise the supply voltage will go up to 10v and turning it clockwise it will drop to 9.35v or 9.1v. So, from that it would appear that you are right in that the temperature set points are being adjusted by the pot. Whether only one is adjusted or both are changed as Angus says isn't clear. I also noticed that the 260 consistently has an adjustment range of +/-2e-7, regardless of where the frequency is set, with 0v applied to the adjustment pin giving a frequency 4Hz higher than when the 5.65v reference voltage is applied to the adjustment pin. It will adjust further if the reference pin is hooked up to the supply voltage. So, I decided to get as much information as I could. I turned the pot clockwise until it "ticked" once each turn. That dropped the temperature to the minimum. I then turned it counter clockwise 1/2 turn at a time and recorded each temperature / frequency reading. I did this until it "ticked" once each turn. That took nearly three days. To obtain the temperature, I used Kapton tape to tape a temperature sensor for my multimeter to the casing of the outer oven. This is not necessarily the hottest spot, nor does it actually measure the temperature in either the inner or outer oven. Further, the multimeter's precision is only around 1 degree C. The accuracy is unknown, but it should be repeatable and roughly linear. I used my (uncalibrated) 2465BCT to measure the frequency. This is limited to 7 digits without a calibrated frequency standard and is probably slightly off. Still, that gave me a good bit of data. Here is the raw data. 605.01 615.02 615.03 625.03 625.04 635.05 635.06 645.06 655.07 655.08 665.08 665.09 675.09 675.10 685.10 695.10 705.11 715.11 725.12 735.12 745.12 755.12 765.12 765.13 775.13 785.12 795.12 805.12 815.12 Here is a rough graph. It shows the expected SC temperature / frequency type of curve. However, what is interesting is the range over which adjusting the temperature affects the frequency. This is a total of 12Hz! Also, it should be noted that the outer case was not in place, so the outer oven is
Re: [time-nuts] Best Rubidium Frequency Standard
>> >> ___ >> time-nuts mailing 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] Rubidium Frequency Standard
Pete, I will be using it for a general lab standard, to feed into other test equipment. But, I can't predict my future usage, so I want the best that I can get. I also plan on eventually locking it to a GPS (probably a U-Blox board). I am retired, so my budget is nearly non-existent. :-) I have to spread the cost around, so cheaper is better even if I then have to spend extra later. The HP 5065A that Paul found at 1800 EUR is very much out of range. A new PRS10 is only 1495! I am considering a PRS10 or LSD12 that needs repair. Schematics are available, the ones available are within the 20 year life span of the rubidium bulb and are much more affordable than a working unit. It is, of course, a gamble. Right now, I am researching. Actual purchase will be later once I decide which way to go and budget the money. I may need other things first (a power supply springs to mind). I researched the scope that I wanted to buy for a couple of months before I pulled the trigger. It blew within 5 minutes, but fortunately only needed recapping. I also made a few other modifications while I was at it. It still needs calibration. All that took another three months after purchasing. Mike > Corby mentioned one very important thing .. what are you going to be using > it for ? > and I'll ask what is your budget ? > That will determine quite a bit. > -pete > On Fri, Mar 11, 2016 at 11:02 AM, <cdel...@juno.com> wrote: >> Mike, >> >> Luciano is correct. The HP 5065A beats all the others easily. >> >> It is not configured however to be disciplined although it can be >> modified. >> >> It's main claim to fame is the excellent short term stability. >> >> If all you are after is a long term accuracy standard then any of the >> others would work. >> >> There has been a lot of work done with disciplining the FE-5680 and also >> temperature controlling its baseplate. >> >> Results are very good! >> >> Cheers, >> >> Corby Dawson >> >> ___ >> time-nuts mailing 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best Rubidium Frequency Standard
Luciano, Why? Why the Efratom FRK or M100 over the Efratom LPRO-101? The M100 appears to be manufactured in '91. Given the limited lifespan, why such an older choice? I didn't list the HP5065A because I didn't see it on eBay. What makes it better than the others? Why not one of the Symnmetricom versions (which also appear to be Datum / Efratom)? Can the M100 be disciplined electronically? That wasn't clear from the eBay pictures that I saw. I also saw a 5Mhz and a 1Mhz version. Is one better than the other? Thanks. Mike. P.S. I have jury duty today and the Charlotte hamfest tomorrow, so I may not be online as often as usual for the next couple of days. > Hi Mike, > You have not mentioned the best Rubidium available, the HP5065A. Last week > two of them are sold on ebay. > Second chose can be the Efratom FRK or M100, than all the others. > Luciano > On Fri 11/03/16 12:02 , time...@metachaos.net wrote: >> Hi, >> >> In looking at eBay, I current see quite a few different types of rubidium >> frequency standards. I have seen some of these mentioned here, but no real >> comparisions. The question, is what are the pros and cons of these >> specific >> models? Which ones are best or most reliable? Which ones cannot be >> disciplined >> by a GPS? Is there some specific ones I should never buy or others that I >> should stalk, waiting for one to show up? I know that some of these may be >> from the same company, but are typically listed differently. Here are some >> of >> the ones that I currently see on eBay. Also, is it worth it to buy "lot of >> 5" >> of "for parts or not working"? What is the likelyhood that at least one >> can be >> made to work? Thanks. >> >> AT KS-23823 L2 Disciplined Rubidium Oscillator >> Datum Efatom LPRO-101 >> EDIC Systems YP-1079B portable Rubidium Standard Oscillator >> Efatom FRS-A >> Efatom FRS-C >> Efatom M-100 >> Efratom 2100-003 Rubidium Oscillator >> FE-1995A >> FE-5650A >> FE-5680A >> SRS TSD12 >> SpectraTime SRO-100 GPS Synchronized Rubidium Frequency Standard >> Symmetricom 23478272-004-0-Stratum-2-Rubidium Clock >> Symmetricom Efatom SLCR=101 >> Symmetricom SA.22c >> Symmetricom X72 >> >> Mike >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [1] >> and follow the instructions there. >> >> >> >> Links: >> -- >> [1] >> http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-bin/ma >> ilman/listinfo/time-nuts >> > Message sent via Atmail Open - http://atmail.org/ -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] Best Rubidium Frequency Standard
Hi, In looking at eBay, I current see quite a few different types of rubidium frequency standards. I have seen some of these mentioned here, but no real comparisions. The question, is what are the pros and cons of these specific models? Which ones are best or most reliable? Which ones cannot be disciplined by a GPS? Is there some specific ones I should never buy or others that I should stalk, waiting for one to show up? I know that some of these may be from the same company, but are typically listed differently. Here are some of the ones that I currently see on eBay. Also, is it worth it to buy "lot of 5" of "for parts or not working"? What is the likelyhood that at least one can be made to work? Thanks. AT KS-23823 L2 Disciplined Rubidium Oscillator Datum Efatom LPRO-101 EDIC Systems YP-1079B portable Rubidium Standard Oscillator Efatom FRS-A Efatom FRS-C Efatom M-100 Efratom 2100-003 Rubidium Oscillator FE-1995A FE-5650A FE-5680A SRS TSD12 SpectraTime SRO-100 GPS Synchronized Rubidium Frequency Standard Symmetricom 23478272-004-0-Stratum-2-Rubidium Clock Symmetricom Efatom SLCR=101 Symmetricom SA.22c Symmetricom X72 Mike ___ time-nuts mailing 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] MTI 260-0624-D OCXO
Magnus, In this case, the rattle is not of light weight pieces, but of a heavy object. So, I am guessing that the outer oven broke off somehow. Won't really know until and unless I open it up. The vendor probably won't want it back, but they might, so I won't touch it until I hear from them. Mike > Hi, > On 03/05/2016 10:45 PM, time...@metachaos.net wrote: >> I got the replacement MTI 260-0624-D OCXO today. >> >> It rattles! > I've seen that on one oscillator. I did a RMA and complained about the > maracas mode, which I had demonstrated to the rep. When it arrived they > wondered what that mean and the rep just smiled and ask them to pick it > up... and it rattle. Turns out that the way they soldered their ovens, > drops of solder could form and get loose, so they changed the process. > Unfortunatly, it is also the failure mode of rough shipping/handling for > some oscillators. > Cheers, > Magnus >> I didn't even bother trying to power it up. Not much point. I have not taken >> it apart, but have notified the seller. I may disassemble this one as well, >> depending on what the seller says. >> >> Mike >> >> >>> I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After testing >>> it, >>> it is clear that it is defective. >> >>> 1. It never heats up. >> >>> 2. The reference voltage is zero. >> >>> 3. Only noise is seen on the output pin. >> >>> I tested with a 12.54V, 2A supply voltage with around 30mV noise. That >>> should >>> be sufficient to test. >> >>> All I was looking for was a 5Mhz signal whose frequency changed when the >>> adjustment pin was either tied to ground or the reference voltage. Never got >>> that far because I never go a signal at all. >> >>> The seller packed it well and shipped it promptly. I will see how he handles >>> it. >> >> >>> Mike >> >>> ___ >>> time-nuts mailing 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] MTI 260-0624-D OCXO
I got the replacement MTI 260-0624-D OCXO today. It rattles! I didn't even bother trying to power it up. Not much point. I have not taken it apart, but have notified the seller. I may disassemble this one as well, depending on what the seller says. Mike > I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After testing it, > it is clear that it is defective. >1. It never heats up. >2. The reference voltage is zero. >3. Only noise is seen on the output pin. > I tested with a 12.54V, 2A supply voltage with around 30mV noise. That should > be sufficient to test. > All I was looking for was a 5Mhz signal whose frequency changed when the > adjustment pin was either tied to ground or the reference voltage. Never got > that far because I never go a signal at all. > The seller packed it well and shipped it promptly. I will see how he handles > it. > Mike > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] MTI 260-0624-D OCXO
Bob, I still have a problem with the various theories. Again, how is it measured? If you have a production line, you don't want a "tweak" that requires hours or days to determine. As far as setting the crystal set point (presumably the inner over set point), that makes even less sense. Consider that they clearly knew the turn over point of the crystal BEFORE it was packaged. They wrote it on the sticker inside. So, they would have no need to adjust the inner oven. That could easily have been done on the bench during assembly. It could also be done via a selection from a standardized set of components. That temperature is "sort of" critical. The curve is very flat, to it could be a little off. Since they knew the crystal turn over point in advance, there wouldn't be any need to "hunt" for it by an elaborate procedure after assembly. However, the temperature of the outer oven is much less critical and I would suspect is simply set by the choice of components. And, if it needed tweaking then it could also have been done on the bench. Since they would know the thermal transfer characteristics, I suppose that they could measure the outer case's temperature to deduce the correct temperature of the outer oven. But, again, that doesn't make sense from a production standpoint. It would simply take too long. Perhaps, they would be willing to eat the time needed for that type of adjustment, but it doesn't seem likely. All they would need to do would be to add some monitoring circuits that they could access. I've seen that type of thing a lot. It would be cheaper to add a few circuits for a quick adjustment than it would be to spend the time on the adjustment. People's time is worth a lot more than a few components. On the other hand, tweaking the output voltage is something that is quickly measured as part of testing. Put it in a jig, make a quick check for functionality, tweak the output voltage and you are done. Or, perhaps it adjusts the duty cycle, the bias point or some other characteristic of the output signal. Perhaps it adjusts the reference voltage. I think I showed that it doesn't make a large change in the frequency. But, it doesn't make sense for it to make a small change (although I would be unable to measure a small change). I think that there are a lot of unexplored possibilities, but I definitely am not convinced that it sets either the inner or outer oven temperature. There are simply better ways to do that in production. I really, really want to know, though! I am going to try to repair mine one more time and see what I can measure. I didn't try very hard the first time, but I think its worth doing. If I can get it repaired again (I have to fix some traces, especially for the ground pin) it will probably take a couple of days. I have the parts to fix my fan circuit in my oscilloscope and I will do that first. And possibly tweak the power supply capacitors to reduce noise. Mike > If this is a double oven, there are two oven circuits and two oven > controllers. > Both would have a set point and both would be adjusted somehow. The pot > may be the adjustment on the outer oven. Get things all set up and packaged, > then adjust the outer oven to make things do what the should do. ___ time-nuts mailing 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] MTI 260-0624-D OCXO
I have just about finished trashing this OCXO. I was able to run it outside of its case, and I have repaired the case, but I was unable to reinstall it into the case because I have to patch it on both the top and bottom. I could, perhaps, put it into a larger case and might do that later. For now, I will keep it as a potential future resource. The SC crystal is worth that much - they aren't cheap and nothing wrong with that. Also, just the bottom circuit board has problems, possibly another bad unit could be used for parts. That leaves one final question. The suggestion that the POT adjusts the temperature set point for the crystal sounds very reasonable. It clearly does not significantly affect the frequency. At least, not in the range that would allow for tuning the output frequency. However, the POT is clearly designed to be adjusted AFTER everything is assembled because it is intended to be adjusted through the hole in the case. That assumes some sort of feedback. What feedback? What can it affect on the available five pins that would let you know when the temperature is set correctly? If it is not for setting the temperature, and not for setting the frequency, what is it for? Perhaps output voltage level? I would have to get it working again, but I could test that. Any ideas? Mike ___ time-nuts mailing 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] MTI 260-0624-D OCXO
>>>>>> >>>>>> Bob, >>>>>> >>>>>> In this case, I know how it was taken off the board - it wasn't. They >>>>> just cut >>>>>> the board around it. I had to remove it myself. Nice thing about that, >>>>> is that >>>>>> I got a nice plastic, pre-formed part that fits between the board and the >>>>>> OCXO, probably as an insulator. >>>>>> >>>>>> You are also right about the number of things that you need to test to >>>>> make >>>>>> sure that one of these is fully functional. However, this is a "starter" >>>>> OCXO >>>>>> for me and I don't yet have the equipment to perform the tests. The best >>>>> that >>>>>> I can do is to make sure that, when powered up >>>>>> >>>>>> 1. I see something that sort of looks like a sine wave at a reasonable >>>>>> magnitude. >>>>>> >>>>>> 2. My 2465B CT frequency counter thinks that it is somewhere near 5Mhz. >>>>>> >>>>>> 3. If I apply gnd, or VRef to the adjustment pin I see the frequency >>>>> change >>>>>> at least a small amount. >>>>>> >>>>>> Without more equipment, there isn't much more that I can do to test. >>>>> Unless >>>>>> you have some suggestions? >>>>>> >>>>>> >>>>>> Mike >>>>>> >>>>>> >>>>>>> Hi >>>>>>> Best guess is these things get taken off the board with either a big >>>>> torch or a charcoal fire. >>>>>>> You can ask Mr Google to dig up pictures of the process. Depending on >>>>> just how quick >>>>>>> they are, the insides of the OCXO can easily be reflowed. The >>>>> likelihood of it reflowing and >>>>>>> cooling back to a reliable joint … not real good. >>>>>>> Bob >>>>>>>> On Feb 17, 2016, at 5:16 AM, Andrea Baldoni <erm1ea...@ermione.com> >>>>> wrote: >>>>>>>> On Tue, Feb 16, 2016 at 07:58:21PM -0500, time...@metachaos.net wrote: >>>>>>>> >>>>>>>>> I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After >>>>> testing it, >>>>>>>>> it is clear that it is defective. >>>>>>>>> >>>>>>>>> 1. It never heats up. >>>>>>>>> 2. The reference voltage is zero. >>>>>>>>> 3. Only noise is seen on the output pin. >>>>>>>> I had the same issue with some of them. It's very likely that the >>>>> internal >>>>>>>> solder connections from pins to PCB are broken, at least, the one for >>>>> power. >>>>>>>> It happens because the inner oven is heavy and there isn't any thermal >>>>>>>> insulator (besides air) to keep it from moving. >>>>>>>> >>>>>>>> Wheter the crystal has been damaged or not, it's unknown. I had one >>>>> where the >>>>>>>> crystal actually fell off from its supports too. >>>>>>>> >>>>>>>> I posted a link to photos of the internals, time ago. The link is dead >>>>> now >>>>>>>> and I don't think to have the photos anymore but perhaps someone >>>>> downloaded >>>>>>>> them. >>>>>>>> >>>>>>>> Best regards, >>>>>>>> Andrea Baldoni >>>>>>>> ___ >>>>>>>> time-nuts mailing 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. >>>>>> >>>>>> >>>>>> -- >>>>>> Best regards, >>>>>> Timenutmailto:time...@metachaos.net >>>>>> >>>>>> ___ >>>>>> time-nuts mailing 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. >> >> -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] MTI 260-0624-D OCXO
sts rather than china (and mostly pre-ebay). >> >> What sort of testing regime would you put them through ? I don't have >> anything as exotic as a timepod but I do have an HP53131A, the Tait Rb >> source, and a KS-24361 set up. And always keen to get hints on the >> acquisition of new toys ! >> >> >> >> On Thu, Feb 18, 2016 at 12:09 PM, Bob Camp <kb...@n1k.org> wrote: >> >>> Hi >>> >>> It is *much* better to have an OCXO that you do not need to test to death. >>> There is simply to much testing to do. A modern factory does not test the >>> quality into the product (of any sort) they design in and build it in. The >>> same >>> is true of the normal customer for virtually any component. They make sure >>> the parts come from somebody they can trust and save a lot of testing time. >>> >>> That said, yes, I have a pile of scrap parts sitting in front of me as I >>> type this. >>> It’s a hobby. Time does not count. It lets me play with all sorts of toys >>> doing >>> the testing. I occasionally learn things in the process. Mostly I learn >>> that >>> my hope of a 100% perfect batch is still a dream …. >>> >>> Bob >>> >>> >>> >>>> On Feb 17, 2016, at 9:56 PM, time...@metachaos.net wrote: >>>> >>>> Bob, >>>> >>>> In this case, I know how it was taken off the board - it wasn't. They >>> just cut >>>> the board around it. I had to remove it myself. Nice thing about that, >>> is that >>>> I got a nice plastic, pre-formed part that fits between the board and the >>>> OCXO, probably as an insulator. >>>> >>>> You are also right about the number of things that you need to test to >>> make >>>> sure that one of these is fully functional. However, this is a "starter" >>> OCXO >>>> for me and I don't yet have the equipment to perform the tests. The best >>> that >>>> I can do is to make sure that, when powered up >>>> >>>> 1. I see something that sort of looks like a sine wave at a reasonable >>>> magnitude. >>>> >>>> 2. My 2465B CT frequency counter thinks that it is somewhere near 5Mhz. >>>> >>>> 3. If I apply gnd, or VRef to the adjustment pin I see the frequency >>> change >>>> at least a small amount. >>>> >>>> Without more equipment, there isn't much more that I can do to test. >>> Unless >>>> you have some suggestions? >>>> >>>> >>>> Mike >>>> >>>> >>>>> Hi >>>> >>>>> Best guess is these things get taken off the board with either a big >>> torch or a charcoal fire. >>>>> You can ask Mr Google to dig up pictures of the process. Depending on >>> just how quick >>>>> they are, the insides of the OCXO can easily be reflowed. The >>> likelihood of it reflowing and >>>>> cooling back to a reliable joint … not real good. >>>> >>>>> Bob >>>> >>>>>> On Feb 17, 2016, at 5:16 AM, Andrea Baldoni <erm1ea...@ermione.com> >>> wrote: >>>>>> >>>>>> On Tue, Feb 16, 2016 at 07:58:21PM -0500, time...@metachaos.net wrote: >>>>>> >>>>>>> I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After >>> testing it, >>>>>>> it is clear that it is defective. >>>>>>> >>>>>>> 1. It never heats up. >>>>>>> 2. The reference voltage is zero. >>>>>>> 3. Only noise is seen on the output pin. >>>>>> >>>>>> I had the same issue with some of them. It's very likely that the >>> internal >>>>>> solder connections from pins to PCB are broken, at least, the one for >>> power. >>>>>> It happens because the inner oven is heavy and there isn't any thermal >>>>>> insulator (besides air) to keep it from moving. >>>>>> >>>>>> Wheter the crystal has been damaged or not, it's unknown. I had one >>> where the >>>>>> crystal actually fell off from its supports too. >>>>>> >>>>>> I posted a link to photos of the internals, time ago. The link is dead >>> now >>>>
Re: [time-nuts] MTI 260-0624-D OCXO
Bob, In this case, I know how it was taken off the board - it wasn't. They just cut the board around it. I had to remove it myself. Nice thing about that, is that I got a nice plastic, pre-formed part that fits between the board and the OCXO, probably as an insulator. You are also right about the number of things that you need to test to make sure that one of these is fully functional. However, this is a "starter" OCXO for me and I don't yet have the equipment to perform the tests. The best that I can do is to make sure that, when powered up 1. I see something that sort of looks like a sine wave at a reasonable magnitude. 2. My 2465B CT frequency counter thinks that it is somewhere near 5Mhz. 3. If I apply gnd, or VRef to the adjustment pin I see the frequency change at least a small amount. Without more equipment, there isn't much more that I can do to test. Unless you have some suggestions? Mike > Hi > Best guess is these things get taken off the board with either a big torch or > a charcoal fire. > You can ask Mr Google to dig up pictures of the process. Depending on just > how quick > they are, the insides of the OCXO can easily be reflowed. The likelihood of > it reflowing and > cooling back to a reliable joint … not real good. > Bob >> On Feb 17, 2016, at 5:16 AM, Andrea Baldoni <erm1ea...@ermione.com> wrote: >> >> On Tue, Feb 16, 2016 at 07:58:21PM -0500, time...@metachaos.net wrote: >> >>> I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After testing >>> it, >>> it is clear that it is defective. >>> >>> 1. It never heats up. >>> 2. The reference voltage is zero. >>> 3. Only noise is seen on the output pin. >> >> I had the same issue with some of them. It's very likely that the internal >> solder connections from pins to PCB are broken, at least, the one for power. >> It happens because the inner oven is heavy and there isn't any thermal >> insulator (besides air) to keep it from moving. >> >> Wheter the crystal has been damaged or not, it's unknown. I had one where the >> crystal actually fell off from its supports too. >> >> I posted a link to photos of the internals, time ago. The link is dead now >> and I don't think to have the photos anymore but perhaps someone downloaded >> them. >> >> Best regards, >> Andrea Baldoni >> ___ >> time-nuts mailing 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] MTI 260-0624-D OCXO
The vendor is resending it. He has not said what he wants done with the dead one. Probably nothing, in which case I will tear it apart. Probably won't fix anything, but at least I'll get a good look inside. And the SC crystal could always be used in a custom DOCXO. Mike > I've had essentially the same experience with a batch of 34310-Ts that I > got from China. Some are very good, most are good enough, some work but are > useless for anything serious. I haven't gone through enough of them to get > any feel for the waste rate. Hopefully it won't be more than 2 out of 10. > Bob > > On Tue, 2/16/16, Bob Camp <kb...@n1k.org> wrote: > Subject: Re: [time-nuts] MTI 260-0624-D OCXO > To: time...@metachaos.net, "Discussion of precise time and frequency > measurement" <time-nuts@febo.com> > Date: Tuesday, February 16, 2016, 8:27 PM > > Hi > > The 260’s that I have seen from inside the > USA have been pretty good (not perfect, but > certainly not dead). Most of the issues have > been quibbles. Phase noise not quite in spec. > ADEV not quite as good as it might have been. > > > Everything I have seen so > far from China (260 or not) has been very hit or > miss. Stuff that is called “scrap for parts > only” (like a pile of 10 Rb’s I have here) may turn > up more working parts than something labeled > “great / tested / buy now / first best great > product (a direct quote)“. I have tried the > “buy a few and then go back” approach. There > has been little correlation between what I got > the second time and what came in first. My > conclusion (often stated) is that the salvage > process over there is pretty brutal. > > Bob > >> On > Feb 16, 2016, at 7:58 PM, time...@metachaos.net > wrote: >> >> I just > received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After > testing it, >> it is clear that it is > defective. >> >> 1. It never heats up. >> >> 2. The > reference voltage is zero. >> >> 3. Only noise is seen on the > output pin. >> >> I > tested with a 12.54V, 2A supply voltage with around 30mV > noise. That should >> be sufficient to > test. >> >> All I was > looking for was a 5Mhz signal whose frequency changed when > the >> adjustment pin was either tied to > ground or the reference voltage. Never got >> that far because I never go a signal at > all. >> >> The seller > packed it well and shipped it promptly. I will see how he > handles >> it. >> >> >> Mike >> >> > ___ >> time-nuts mailing 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] MTI 260-0624-D OCXO
I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After testing it, it is clear that it is defective. 1. It never heats up. 2. The reference voltage is zero. 3. Only noise is seen on the output pin. I tested with a 12.54V, 2A supply voltage with around 30mV noise. That should be sufficient to test. All I was looking for was a 5Mhz signal whose frequency changed when the adjustment pin was either tied to ground or the reference voltage. Never got that far because I never go a signal at all. The seller packed it well and shipped it promptly. I will see how he handles it. Mike ___ time-nuts mailing 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] Newbie questions
fference >> between >> an active GPS antenna and an active GPS Timing Reference Antenna. >> >> 1. What is the difference between a "normal" GPS antenna and a GPS >> Timing >> Reference antenna? What features are of interest? >> >> 2. Is there anything extra needed besides a GPS antenna to enable the >> use >> of WAAS or other services? Apparently the ubolt receivers can make >> use >> of some of that, but it is not clear what is needed to provide that >> information to them, or if they just pick it up automatically using >> a >> standard GPS antenna. >> >> Also, from what I have read, using carrier phase for timing is >> potentially >> more accurate by a couple orders of magnitude. Are there any GPS timing >> receivers available that use carrier phase? Or use both L1 and L2 for >> increased accuracy? I see that the ubolt receivers can report some >> carrier >> phase information, but that doesn't appear to translate to increased >> accuracy. >> And the LEA M8T use dual channels, but don't appear to mix GPS and >> GLASNOS to >> improve accuracy. Do any receivers do that? I suspect that building a GPS >> receiver is probably more complex than can be easily handled by an >> amateur so >> I am most likely restricted by available receivers. >> >> I have also read, more than once, statements in this forum that something >> or >> another could be had for some low, low price so why build it yourself? I >> think >> that there are several reasons, including but not limited to the >> following. >> >> 1. It is an interesting project. >> >> 2. It is an educational project. >> >> 3. You may have some ideas about how things could be done differently >> or >> better. >> >> 4. You may want some combination of features that is not commercially >> available or perhaps is not affordable even with a generous budget. >> >> 5. Many people on limited budgets are not limited by total cost, but >> rather >> by incremental cost. So, someone may not be able to afford several >> hundred >> dollars for a pre-built system. But, they may be able to afford $50 >> here >> and there. So, building it themselves is the only practical option. >> >> >> Mike >> >> >> >> >> >> >> _ >> time-nuts mailing 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. -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] Newbie questions
2. Why use it for specifying voltage or power in a limited range? Why >> >> not >> >> just say that the output is 1.0v rms or 0.7v, or that it uses 50mW? >> >> There >> >> does not appear to be any actual advantage to using a logarithmic >> >> scale >> >> for a small range of values - and 1mV to 1kV IS a small range. >> >> Especially when you have to convert the logarithmic value to a >> "real" >> >> value to actually do anything with it. >> >> >> >> I have also been researching GPS antennas. From what I can see there are >> >> two >> >> basic types - the flat puck and the helical. I have not seen anything to >> >> distinguish the two types based on performance or usage or to indicate >> >> that >> >> one or the other might be better for GPS timing. However, I have seen >> "GPS >> >> Timing Reference Antennas" advertised. Most or all of those appear to be >> >> helical. But, I have not seen anything that specifies the difference >> >> between an active GPS antenna and an active GPS Timing Reference >> Antenna. >> >> >> >> 1. What is the difference between a "normal" GPS antenna and a GPS >> >> Timing >> >> Reference antenna? What features are of interest? >> >> >> >> 2. Is there anything extra needed besides a GPS antenna to enable the >> >> use >> >> of WAAS or other services? Apparently the ubolt receivers can make >> >> use >> >> of some of that, but it is not clear what is needed to provide that >> >> information to them, or if they just pick it up automatically >> using a >> >> standard GPS antenna. >> >> >> >> Also, from what I have read, using carrier phase for timing is >> potentially >> >> more accurate by a couple orders of magnitude. Are there any GPS timing >> >> receivers available that use carrier phase? Or use both L1 and L2 for >> >> increased accuracy? I see that the ubolt receivers can report some >> carrier >> >> phase information, but that doesn't appear to translate to increased >> >> accuracy. >> >> And the LEA M8T use dual channels, but don't appear to mix GPS and >> >> GLASNOS to >> >> improve accuracy. Do any receivers do that? I suspect that building a >> GPS >> >> receiver is probably more complex than can be easily handled by an >> >> amateur so >> >> I am most likely restricted by available receivers. >> >> >> >> I have also read, more than once, statements in this forum that >> something >> >> or >> >> another could be had for some low, low price so why build it yourself? I >> >> think >> >> that there are several reasons, including but not limited to the >> >> following. >> >> >> >> 1. It is an interesting project. >> >> >> >> 2. It is an educational project. >> >> >> >> 3. You may have some ideas about how things could be done differently >> or >> >> better. >> >> >> >> 4. You may want some combination of features that is not commercially >> >> available or perhaps is not affordable even with a generous budget. >> >> >> >> 5. Many people on limited budgets are not limited by total cost, but >> >> rather >> >> by incremental cost. So, someone may not be able to afford several >> >> hundred >> >> dollars for a pre-built system. But, they may be able to afford $50 >> >> here >> >> and there. So, building it themselves is the only practical option. >> >> >> >> >> >> Mike >> >> >> >> >> >> >> >> >> >> >> >> >> >> ___ >> >> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >> >> 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 <javascript:;> >> > To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > and follow the instructions there. >> > >> >> >> >> -- >> >> --Jim Harman >> ___ >> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> -- Best regards, Timenutmailto:time...@metachaos.net ___ time-nuts mailing 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] Newbie questions
Bob, et. al., Thanks for the advice and information. That has helped a lot in closing some holes and gives me a lot to consider. I am continuing to research and learn, this is not a short term project as in building it this week or month. I need to learn and work up to the full project. I will probably start small with pieces and gather what equipment I can. Like many of my projects, this one will probably have multiple sub-projects. Especially if I manage to snag test equipment that needs repair. Regrettably, the 260 was ordered from China, there were none from the US when I ordered. I did know that it would be a crap shoot, but for $26 it was something I could get now. I might even be lucky! I am planning on including sawtooth correction in hardware. But, I have a good bit to learn for that. It appears to be fairly simple given your processor reads the sawtooth correction from the GPS receiver and sets up a programmable delay for each cycle. I have a dozen pieces floating in my head, I am certain I will be back for more advice. Thanks again. Mike ___ time-nuts mailing 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] Newbie questions
Ha! I finally answered one of my questions that has been bugging me! I was taking dBm as the definition of voltage - which it is, but only round-about. The hidden variable is the assumed impedance of 50 ohms where 1mW is the zero point for power. That is also why I wasn't getting consistent answers - different application areas I am interest in assumed different values for the impedance and so my calculations were all over the place. I found a reference in the PRS10 reference that tied it all together for me. Mike ___ time-nuts mailing 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] Newbie questions
Hi, I am a newbie to this list. I have downloaded the archives and read about 5,000 of the past messages. I plan on building my own GPSDO, probably using a LEA-6T (but LEA-7T or LEA-M8T would be good if I can find one affordably). I have a MTI 260 on order (although it could wind up being a 261 since they all appear to ship one or the other randomly). Currently, my resources include a DMM (well, a couple) and soldering / desoldering stations and quite a few tools. I also have an oscilloscope that I am currently repairing - a 400Mhz Tektronix 2465BCT analog scope. I am waiting on the final parts from Mouser. Once that is done I need to get it calibrated. All of that will probably take me another month. I also need to finish fixing my cassette deck - and then to finish writing a special recording program to use raw device drivers to get around the fact that Windows is not real time. I interrupted that project to work on the scope. In the meantime, I am reading the time-nuts messages (and lots of other things) to gather information and ideas about how I am going to do this and generally to learn more. So, I have some questions. Let me tell you a bit about me, so that you know the context and my limitations. I am a retired programmer. I wrote just about everything including device drivers, operating systems, utilities, various AI programs, telephone systems, compilers, encryption, web applications and much more. If I need to throw 50,000 LOC at a project, no problem. I have used many languages including quite a few different assembly languages (I have also written an assembler). I consider myself a mathematician / programmer, although I haven't really needed Calculus or Differential Equations for decades, so I am pretty rusty in that area. I do more work in formal logic than higher mathematics. But, I THINK like a mathematician. Formalism and abstraction come naturally to me. During my career I also helped to debug hardware during S-100 days. I have sporadically messed with electronics off and on, informally, with no education in the area. Now that I am retired (and have more time, but less money - it IS a zero sum game!), I am trying to learn more about electronics and start doing hardware projects. I have never been into model building or anything similar, so my construction skills are lacking. I understand a lot of things in theory, but practice still eludes me. For example, knowing a part exists or determining which of 10,000 apparently identical parts is the "right" choice. It can hours or even days to find the "right" connector. In many cases, the names or descriptions are completely meaningless. That all appears to be an experience related issue, so I will (hopefully) overcome that in time. I have no problem with soldering / desoldering, but I haven't designed or built my own PCB yet. I have designed / redesigned some minor circuits, especially on the power supply side. I can follow schematics reasonably well, but I am not comfortable with Eagle or other PCB layout programs. Every time I have tried one of those programs, half of the parts I needed were not available. I have started using TinyCAD which is much easier to use. So, I have a lot to learn. But, that is basically what I do, all day, every day. I'm the type of person that gets bored easily and quickly. As #5 said "more input, more input"! 6.02059991327962 Paradoxically, I have no interest in time. As in time of day, day of week, etc.. I have never had a job where I got to work on time. My philosophy has always been "go to bed when sleepy, get up when not". I was notorious in high school for only showing up on test day. But, I am interested in being able to timestamp events accurately and in measuring time (and other things). I am also interested in how a very accurate frequency source can be used in other applications and test instruments. That brings me to my desire to build a GPSDO and my questions. I understand the logarithmic scaling used for voltage and power. I even understand why voltage uses a multiplier of 20 and power a multiplier of 10. It makes sense when working with a wide range of values. However, my DMM, my scope and generally schematics work directly with current, voltage and watts. So, I am constantly seeing statements like an output is 7 dBm or 13 dBm. If I knew the actual value for 0 dBm then the basic equations would resolve the values. However, I have not found a consistent answer for that. When I have attempted to work values backwards from various statements, again I don't get a consistent value (probably because those statements were approximations and not exact values). I always see statements that an increase of 6dBm doubles the value. It is used so often that most people forget it is an approximation. It is 6.02059991... and sometimes, it may make a difference. Worse, the zero value appears to be different for different applications. In some it appears to be
