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NEO-6M GPS receiver - description and review.

grala1 9066 16
This content has been translated flag-pl » flag-en View the original version here.
  • Today I would like to introduce you to GPS signal receivers. I will try to do it on the basis of a ready-made module that uses a U-BLOX chip, namely a system called NEO-6 in the "M" version.
    NEO-6M GPS receiver - description and review.

    I will not describe here how the receiver position measurement works. The NEO6-M module is equipped with a UART TTL interface thanks to which we can communicate with it and receive data using the NMEA-0183 protocol.
    NMEA is the National Marine Electronics Association, it is a protocol specification that allows communication between various types of measuring devices and a simple connection of the GPS receiver with other devices.
    The NMEA standard sends out independent lines of data, where each line:
    - starts with $ sign;
    - has a header;
    - cannot exceed 80 characters;
    - each nada is separated from the next by a comma;
    - data in the number format may have fractional values expressed after the dot sign;
    - may be ended with a checksum in the form of a two-digit hexadecimal number preceded by an asterisk.
    Below I will describe a few lines of data, they will not be all possible in the NMEA protocol, but only those that our NEO-6M receiver sends to us via UART.
    GGA - Fix information
    Example:
    $ GPGGA, 151654.00,5145.11403, N, 01803.73294, E, 1.04,4.86,131.8, M, 38.3, M ,, * 50
    GGA - header identifier;
    151654.00 - time when the data was received. 15:16:54 UTC time;
    5145.11403, N - latitude, 51 45.11403'N;
    01803.73294, E - longitude, 18 03.73294'E;
    1 - measurement quality;
    04 - number of tracked satellites;
    4.86 - position accuracy - HDOP;
    131.8, M - height above sea level;
    38.3M - height of the geoid above the WGS84 ellipsoid;
    no data - time since the last DGPS update;
    no data - DGPS station ID number;
    * 50 - checksum.
    As you can see above, we are missing two data. DGPS stands for Differential GPS, it is data sent by ground stations and our receiver does not support it.
    The measurement quality can have the following values:
    0 - no item or item with a very large error;
    1 - position determined on the basis of GPS;
    2 - position determined with the participation of DGPS;
    3 - PPS position;
    4 - Real Time Cinematic;
    5 - Float RTK;
    6 - estimated;
    7 - manual impet mode;
    8 - simulation mode.
    The position accuracy, more precisely the horizontal position accuracy of the HDOP, determines the estimated position accuracy. It is generally assumed that a HDOP value lower than 6 is sufficient to make a decision, for example, to turn at an intersection.

    GSA - Overall Satellite data
    Example:
    $ GPGSA, A, 3,16,26,21,31 ,,,,,,,,, 5.98,4.86,3.49 * 00
    GSA - header;
    A - automatic position selection, another option here is M - manual;
    3 - 3D position, other possibilities 1 - no fixed position, 2 - 2D position, 3 - 3D position;
    16,26,21,31 ,,,,,,,, - numbers of satellites used to calculate the position, space for data from 12 satellites;
    5.98 - DOP - precision of the designated position;
    4.86 - HDOP - horizontal precision;
    3.49 - VDOP - vertical precision;
    * 00 - checksum.

    GSV - Detailed Satellite data
    Example:
    $ GPGSV, 3.1, 12.02, 11, 045, 05, 24, 069, 13, 09.02, 357, 12, 03, 126, * 7A
    GSV - header;
    3 - the number of lines the application should read in order to obtain complete data on all satellites. We are limited to 80 characters here, because of you this information is presented on three lines;
    1 - current line number - see above;
    12 - number of currently visible satellites;
    02 - satellite identifier - PRN;
    11 - the elevation of the satellite above the equator - expressed in degrees;
    045 - satellite azimuth - expressed in degrees;
    no data - SNR - received signal level;
    successive values define subsequent satellites - we can have a maximum of 4 satellites described in one line;
    * 7A - checksum

    GLL - Lattitudal / Longitunal data
    Example:
    $ GPGLL, 5145.11403, N, 01803.73294, E, 151 654.00, A, * 68
    GLL - header;
    5145.11403, N - latitude 51 45.11403'N;
    01803.73294, E - longitude 18 03.73294'E;
    151654.00 - position fix time, UTC time;
    A - active status, V - inactive;
    * 68 - checksum.

    RMC - Recommended minimum of data
    Example:
    $ GPRMC, 151655.00, A, 5145.11396, N, 01803.73254, E, 0.055,, 300418 ,,, A * 79

    RMC - header;
    151655.00 - position fix time, UTC time;
    A - status, A - active, V - inactive:
    5145.11396, N - latitude 51 45.11396'N;
    01803.73254, E - longitude 18 03.73254'E;
    0.555 - object speed in knots;
    no data - the angle of the object moving;
    300418 - April 30, 2018;
    No data - there should be Earth's magnetic variation;
    * 79 - check sum.



    VTG - Vector track and speed over the Ground
    Example:
    $ GPVTG ,, T ,, M, 0.055, N, 0.102, K * 20
    VTG - header;
    lack of data - walking path in degrees - ,, T;
    no data - path based on magnetic coordinates in degrees - ,, M;
    0.55N - speed in knots;
    0.102K - speed in km / h;
    * 20 - checksum.

    Some data on our finished GPS receiver.
    The most important element here is the NEO-6M module which is powered from the RT9193-33 stabilizer, the maximum supply voltage of which is 6VDC, so it is best to use a 5V voltage source. According to the documentation for the NEO-6M, the current consumption is a maximum of 67mA but our receiver uses 60mA before catching the "FIX" and about 50mA after catching the "FIX". On the board we can also find 24C32 eeprom memory and a small battery thanks to which we can use the "warm start" function. According to the documentation, the cold start is 27 seconds and the warm start is 1 second. What does the concept of cold and warm start mean? Cold start means starting a long unused receiver and waiting for the receiver to fix the position, i.e. catching the FIX, while warm start means finding the FIX after a momentary loss of signal or after a momentary power outage. In the case of my receiver, you have to wait about 15 minutes from turning on the power to find the FIX - this time also depends on whether the receiver is inside or outside. The more the receiver sees the "cleaner" sky, the faster it will catch the signal. The rechargeable battery in my receiver is enough for about 60 minutes of power backup.
    The NEO-6M module is equipped with interfaces such as UART, SPI and USB. Unfortunately, in this receiver model, the board manufacturer only provides the UART interface, where its logic is at 3.3V, the data provided by this interface is refreshed with a frequency of 1Hz. On the board we also have a goldpin connector where the power supply should be given - VCC, GND, output for the already mentioned UART - TXD, RXD, and the PPS output - pulse per second, i.e. the output on which we receive a signal with a frequency of 1Hz - more precisely, we have the state here high with a duration of 100ms and low status with a duration of 900ms. To this output we have a LED diode connected, which after connecting the power supply shines continuously and after catching the FIX by the receiver it flashes at 1Hz.
    To communicate with this version of the receiver you will need a USB-UART adapter, eg FT232.
    The dimensions of the receiver are 36x24x12mm, the dimensions of the antenna are 21x6x7mm.
    The figure below shows a diagram for this GPS receiver.
    NEO-6M GPS receiver - description and review.

    The price of the receiver on Aliexpress starts at $ 3.33 with the antenna included and shipping. On Allegro, you have to spend from PLN 43.65 for an identical GPS receiver with shipping. As you can see, the prices on Aliexpress are quite low, but remember that these NEO modules are not new, they are recycled items.
    The module I got didn't work at the beginning. After connecting it to a laboratory power supply, the current limit was set to 100mA, the supply voltage dropped due to the activation of the current limit. Increasing the current did not help - it turned out that it is not the receiver that gets that much, but rather a short circuit. I desoldered the NEO module and after connecting the power supply, the current limitation of the power supply was still working. It gave some hope that the module could be functional, and after carefully examining the board, I found two places where there were short circuits. They were on the eeprom memory.
    You can see it in the pictures below.
    NEO-6M GPS receiver - description and review. NEO-6M GPS receiver - description and review.

    One of them did not matter because 1-2-3-4 legs were tightened, but here 1-2-3-4 legs are tight on the board. The legs 7-8, i.e. on the memory power supply, were also tight. After removing these short circuits, surprisingly, the stabilizer worked - a tough beast. After soldering the NEO module and powering the receiver, the LED finally turned on and it was possible to establish a connection with the receiver.
    I used FT232 and the HyperTerminal program to communicate with the receiver. Settings for communication in the program below in the photo.
    NEO-6M GPS receiver - description and review.

    After communicating with the receiver, we get a "frame" of data, which before catching the FIX looks like this:
    $ GPGGA, 173745.00 ,,,,, 0.05.99.99 ,,,,,, * 60
    $ GPGSA, A, 1,10,29,27,26,16 ,,,,,,,, 99.99.99.99,1.00 * 0D
    $ GPGSV, 3,1,12,04,41,180,24,07,08,337,21,08,04,289,18,10,24,173.24 * 7F
    $ GPGSV, 3.2,12,13.07.049, 15.10.081.06.16.64.256.10.20.53.103, * 7A
    $ GPGSV, 3,3,12,21.71,072.09.26.51,200,19,27,41,291,24,29,15,104.16 * 78
    $ GPGLL ,,,,, 173745.00, V, N * 49
    $ GPRMC, 173746.00, V ,,,,,,, 300418 ,,, N * 73
    $ GPVTG ,,,,,,,,, N * 30

    After catching FIX the "frame" looks like this:
    $ GPGGA, 173747.00,5145.08762, N, 01803.70069, E, 1.04,12.82,184.1, M, 38.3, M ,, * 68
    $ GPGSA, A, 2,10,29,27,26 ,,,,,,,,,, 12.86,12.82,1.00 * 0D
    $ GPGSV, 3,1,12,04,41,180,24,07,08,337,22,08,04,289,17,10,24,173.25 * 72
    $ GPGSV, 3.2,12,13.07.049, 15.10.081, 16.64.256, 20.53.103, * 7D
    $ GPGSV, 3,3,12,21.71,072.08.26.51,200,19,27,41,291,25,29,15,104.17 * 79
    $ GPGLL, 5145.08762, N, 01803.70069, E, 173747.00, A, A * 64
    $ GPRMC, 173748.00, A, 5145.08837, N, 01803.70165, E, 0.382,, 300418 ,,, A * 77
    $ GPVTG ,, T ,, M, 0.382, N, 0.708, K, A * 25

    After getting acquainted with the NMEA protocol, we are able to determine the position of our receiver, time and altitude above sea level on the basis of such a frame.
    We can enter this data, for example, in Google Maps to find the receiver's position on the map.
    At the beginning, I entered the data 51.4508762 18.0370069 which gave a difference in the measurement by about 20 km. At first I thought that maybe it was a damage caused by an earlier short circuit on the PCB or maybe the quality of the system, what to expect for a dozen or so zlotys. The receiver went into the corner and I was waiting for the washerwoman with a new GPS receiver. After a few days, I sat back to this receiver, looked for data on the NMEA protocol and finally noticed where the error was in reading the coordinates from the "frame". At the beginning you have a description of the protocol and the conversion of data to coordinates. Below are some other options for converting coordinates from the "frame".
    In the box above, the position is 51 45.08762'N, 18 03.70069'E, UTC time 17:37:47 (19:37:47 CEST), 184.1m above sea level.
    51 45.08762N 18 03.70069E
    As you can see here, the seconds are written in "decimal" form. You can also enter 51 45'05.3 "N 18 03'42.0" E where the record is already in the form of minutes and seconds. This notation is obtained by multiplying the value of the decimal minutes by the value 60.
    0.8762x60 = 5.2572sec?5.3sec
    0.70069x60 = 42.0414sec?42.0sec
    This data can also be entered in other ways. We can divide the value of minutes by 60.
    45.08762: 60 = 0.751460
    3.70069: 60 = 0.061678
    Then enter: 51.751460N, 18.061678E

    Below is a picture from the HyperTerminal program while using the receiver while driving the car.
    NEO-6M GPS receiver - description and review.

    You can find the movement speed here. The speed indicated by the car's counter was 110 km / h. while the GPS receiver showed 107 km / h. From my experience, I can write that the speed shown by the GPS is always lower than the car's odometer - usually it is approx. 5 km / h, of course it depends on the speed of the car.
    Honestly, I thought that reading data from this receiver would be much more difficult and as you can see it is quite simple.
    This module can lose the signal if, for example, we have it placed at home. When viewing the data received via UART, you can see that it can lose the signal for several seconds or longer (it depends of course how well it sees the sky) and then find the signal again. I have not noticed similar symptoms when the module works "in the open air". When using it in the car, I also did not notice the loss of the signal when the receiver was placed on the dashboard. I think that with a larger antenna this problem will occur less frequently and the time of catching FIX after the first turn on should decrease.
    This module can be used to build e.g. a position recorder by combining such a module with a microcontroller or by adding a SIM module to this set, you can build a GPS tracker. In Google you can find examples of building a GPS tracker using this receiver, SIM module and Arduino.
    In the attachment documentation for the NEO-6 module.

    Cool? Ranking DIY
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    About Author
    grala1
    VAG group specialist
    Offline 
    grala1 wrote 9499 posts with rating 3981, helped 1363 times. Live in city Kalisz. Been with us since 2006 year.
  • #2
    TechEkspert
    Editor
    Interesting description, is it "real" u-blox or "compatible" with u-blox?

    The 1Hz PPS output allows you to obtain a reference frequency cheaply.
    I used the Waveshare NEO-7M module with an external antenna for testing frequency variation of 50Hz mains voltage .

    My module was "compatible" with u-blox.
    Some modules allow you to change the frequency of the PPS signal up to 10MHz, which makes it possible to obtain a cheap frequency standard.
  • #3
    mkpl
    Level 37  
    TechEkspert, this 1pps can also be of different quality and is not always suitable for reference. Although the price of the module encourages you to experiment anyway.
  • #4
    TechEkspert
    Editor
    @mkpl rightly, the reverse experiment and checking the stability of the 1PPS GPS signal would be interesting, e.g. with a thermostated quartz generator or, for example, if someone has access to the rubidium standard.

    Perhaps simpler solutions, you can check the quality of the 1PPS signal with another generator of similar accuracy. In the specification of one of the GPS modules, I found information about the stability of 1PPS at the level of +/- 10ns, the question is what is the stability of the mentioned NEO series modules.
  • #5
    atek000
    Level 17  
    Such a little information from me. Maybe you already know, but you haven't written, and if you don't know, you'll find out. After entering the coordinates into Google Maps, you won't get the result you want. NMEA-compatible GPS receivers provide degrees, minutes, and seconds coordinates, and Google maps use degrees and fractions of a degree. To illustrate this, let's present it in the form of time, e.g. we have 2:30, which is 2h and 30min, the same can be represented as 2.5 as 2h and 0.5h. Another example is Mon. 1:15 is the same as 1.25, then 3:45 is going to be 3.75.
    I hope I explained it straight away somehow. I also used to build a GPS receiver and struggled with it for 2 days before noticing this difference.
  • #6
    Owiec_
    Level 8  
    It is enough to multiply the seconds by 0.6, as the author wrote (or added later)
    More info here:
    https://support.google.com/maps/answer/18539?hl=pl&co=GENIE.Platform%3DDesktop
    The link "www.google.pl/maps/place/%s+%s" also works.
    The introduction of a third standard that would take into account both standards that are preferred by both teams (Google engineers and GPS designers) would cause even more chaos IMO ;)

    Author:
    0.8762x60 is 5.25 5 72, in this case the rounded result does not make any difference.
  • #8
    grala1
    VAG group specialist
    @ atek000 apparently you didn't read the text thoroughly.
    It explains how to convert.
    In Google Maps, you can enter coordinates in 3 ways:
    51 45.08762'N, 18 03.70069'E
    51 45'05.3 "N 18 03'42.0" E
    51.751472, 18.061667

    @Sheep I did not change anything in the text. If something changes, under the text there will be a note added automatically by the forum where it will tell you when it was and how many times the text was changed.
    0.8762x60 = 52.575
    I don't know where you got that extra "5" from. Thank you for paying attention because now I found a bug, but in a different place.
    Not 0.8762 but 0.08762 which will give 5.3 seconds.
    $ GPGGA, 173747.00.5145 .08762 , N, 01803.70069, E, 1.04, 12.82, 184.1, M, 38.3, M ,, * 68
    It should be written like this:
    0.08762x60 = 5.2572sec?5.3sec
    Incorrectly calculated but coordinates entered correctly. This mistake in moving the decimal point is about 1.5 km of difference in a straight line between these points.

    @MODI , I don't know if this is a question for me but I haven't tried it - so far I didn't have such a need.

    @TechEkspert , I do not know how to recognize if it is a real U-BLOX or only compatible. If you know, write how to check.
    I found information that these systems are recycled, but you can always come up with a fairy tale that would sell better.
    I have two modules and each has a sticker with a logo, although one looks better and the other worse. There is also a production date, where one is for week 10 of 2017 and the other is for week 22 of 2015. There is also a serial number and each has a different number.

    As for the quality of the PPS signal, unfortunately it does not have such precise equipment to check it.
    Below are two screenshots - one from Hantek6022BE and the other from Saleae clone.
    NEO-6M GPS receiver - description and review.
    NEO-6M GPS receiver - description and review.
  • #9
    TechEkspert
    Editor
    @ grala1 I know mine is not u-blox because in the description it had "compatible with u-blox" and there is no manufacturer's logo on the module.

    What is 1PPS? Perhaps it would be possible to examine the signal from two different GPS modules, although there will be no information as to which is OK, but if both signals have a similar shift, it means that both are relatively stable?

    In general, long-term tests, even with a thermostated quartz generator, could show something, although it will not be known what floats, but you may be able to observe some drift or no drift.
  • #10
    Galareta
    Level 22  
    Once I bought the cheapest of the cheapest modules from a Chinese, 99% had already been soldered before. In addition, they had traces of corrosion from the flux used for the discharge.

    I recommend sigrok for the Salae clone
  • #11
    tplewa
    Level 39  
    TechEkspert wrote:
    Interesting description, is it "real" u-blox or "compatible" with u-blox?


    I haven't met the original ones on Ali yet, and I have bought some from various sellers for testing.

    Therefore, at auctions in their titles there is no word uBlox but NEO something there (ot Aliexpress prohibits fakes) in case of a dispute, the seller is also covered because he has not written anywhere that it is uBlox ...
  • #12
    Sas_AS
    Level 16  
    TechEkspert wrote:

    What is 1PPS? Perhaps it would be possible to examine the signal from two different GPS modules, although there will be no information as to which is OK, but if both signals have a similar shift, it means that both are relatively stable?

    In general, long-term tests, even with a thermostated quartz generator, could show something, although it will not be known what floats, but you may be able to observe some drift or no drift.


    But for what and for what?

    The 1PPS signal is not created as a direct reference signal, but only as information about the passage of another second. The signal typically for a commercial receiver has a phase shift of +/- 10nS, i.e. in theory, in the first measured period between the 1st and 2nd receiver, there may be a shift of + 20nS, in the second period e.g. -15nS and in the next period + 15nS, and it will be quite normal. I even think that the additional deviation by a few nS beyond the manufacturer's declaration is also not anything special, many factors must be taken into account, such as the stability and accuracy of the microcontroller reference generator, software, variable number of clock cycles, number of satellites taken, interference, signal quality, etc. If the receivers would catch fix you will not see a drift, i.e. the average phase shift between individual receivers, which will increase until it reaches a peak of 500 mS. 1PPS is the information about the passage of another second and the generation of the 1PPS signal by the receiver with an accuracy of +/- 10nS is of little importance from the point of time elapsed. Under these assumptions, both will be OK as long as they catch the fix and send a 1PPS signal. Relating this signal to the ocxo or rubidium standard will sooner or later show a phase shift. Even if the receiver temporarily loses the fix, it will still mean a detuning of the existing reference generator from international broadcasting stations with synchronized cesium generators (using the 1PPS signal :) ). Reproducing the 10MHz signal through the internal DAC as a cheap reference generator does not make much sense, possibly due to the internal tcxo used, or worse, the lack of it. The signal will show either a step correction of the phase shift with respect to the 1PPS signal, or a constantly changing frequency drift. During 20nS for 10Mhz quite a lot is happening, because if I count correctly 72 degrees of the period will pass and from time to time any shift must be corrected.
    Interestingly enough, the reproduction of the frequency and time standard of the datum cesium plus with a 20nS (+/- 10nS) gps receiver with an accuracy of 1E-11 takes 48 hours under favorable conditions. After 24 hours, the results are no better than with the gpsdo trimble thunderbolt. The clock synchronizes to the network of cesium clocks at the level of ~ 2E-14 for about a month (or at least it reaches the level of work which confirms this, 16-bit swimming gives 1 bit, provided that the ambient temperature does not change significantly ;) ).
  • #13
    TechEkspert
    Editor
    @Sas_AS Well, with regard to what is a good question, if we do not have the right model, it is difficult to investigate something,
    comparing two or three GPS receivers, perhaps, would give information about mutual differences (just like having several multimeters, you can check if one of them differs too much from the indications of the others). But anyway, I can see that as the accuracy requirements increase, the complexity of the system grows exponentially.

    As you write, 1PPS has other uses, although on the occasion of testing NavSpark-mini I came across a GPS receiver that is optimized to generate accurate time and has the ability to set the generated frequency in the range: 1Hz ~ 19.2MHz: http://navspark.mybigcommerce.com/ns-t-precision-timing-frequency-generation-gps- receiver /
  • #14
    tplewa
    Level 39  
    TechEkspert wrote:

    As you write, 1PPS has other uses, although on the occasion of testing NavSpark-mini I came across a GPS receiver that is optimized to generate accurate time and has the ability to set the generated frequency in the range: 1Hz ~ 19.2MHz: http://navspark.mybigcommerce.com/ns-t-precision-timing-frequency-generation-gps- receiver /


    Generally, you do not have to go far as uBlox has such modules on offer, for example LEA-M8T / NEO-M8T

    https://www.u-blox.com/sites/default/files/NEO-LEA-M8T-FW3_DataSheet_%28UBX-15025193%29.pdf

    Anyway, as they say, there is something good for everyone (here is also the question of how much we want to spend on it) ;)

    Regarding 1PPS, this can for example be used in conjunction with the GPSD Time Service http://www.catb.org/gpsd/gpsd-time-service-howto.html where in many cases this is sufficient ...

    Unfortunately, there is no need to hide that in many amateur applications (generating 10MHz) most often people are limited to trimble thunderbolt or possibly used rubidium generators (available on e-bay), and for many they are too expensive solutions to do something like this in a home laboratory .
  • #15
    Sas_AS
    Level 16  
    @TechEkspert as for the test of differences between receivers, I agree in terms of the reference standard.
    @tplewa for frequency standards for the amateur laboratory.

    Rather, I wanted to instill that such a study does not make sense. The time of generating 1PPS is influenced by a lot of factors, the hardware of a particular piece has little influence, i.e. whether it is better or worse. Any changes in the phase shift depend mainly on the signal strength, interference, satellite availability, so ultimately how the software algorithm works. When selecting the reference source to generate 1PPS, i.e. taking into account specific satellites (transmitted signals from cesium clocks, their synchronization date), a typical receiver tracks up to 12 satellites, of which currently only the strongest or with the lowest delay time takes into account. There are better GPS receivers, they probably do more calculations to improve the stability of the 1PPS signal. Still, this is only a side effect, because their main goal is not to lose your fix in different weather conditions for as long as possible. The manufacturer's information that the 1PPS time is generated with a shorter shift time, e.g. +/- 7nS, is rather for the user, designer, programmer at what time can another 1PPS impulse be expected. It does not change the fact that when designing any classic gpsdo based on ocxo, duble ocxo, rubidium generator, we do not take into account individual 1PPS signals and their phase shift. The number of correctly received signals for the above-mentioned receiver is important. To put it simply, after 10 seconds we can count on the accuracy of ~ 2nS and after 100 seconds ~ 0.2nS, i.e. 2E-10. Signals with an error of +/- 10nS will be obtained only for the first and last seconds, and for the remaining 98 seconds, the phase shift of individual signals does not matter. If we were to build a 1PPS generator and would be able to achieve such stability after 100 seconds, then every next second would be generated with an accuracy better than ~ 0.2nS. For time servers this is perfectly accurate. For the 1MHz, 5MHz, 10MHz frequency standards, a longer time is needed, depending on the generator used, which we synchronize with the 1PPS signal. For cesium generators, time is counted in days or even months :) .
    Here we come to the hundredth, because for an amateur looking for a frequency standard, the use of gpsdo based on ocxo is better, e.g. trimble, datum, symmetricom and similar (just not a Chinese handmade, trivial way to repair the phase shift, the reference frequency generated from the dac and the phase shift jump from time to time) ) than a rubidium generator of unknown frequency. Even better is a self-made with a good ocxo or duble ocxo synchronized by 1PPS from the gps receiver (in the oldest solutions it is a few ttl crosswise), depending on the need, you can also use the ocxo in the LF version. After turning on gpsdo, after a few hours we have a reliable source of frequency and time standard at a decent level, additionally synchronized with cesium generators. You just have to remember not to change it due to the influence of the earth's magnetic field. I had a rubidium generatorFE-5680A in the version that could not be calibrated by software (probably possible, but no one figured it out for the version called blocked), and after the service life it had little to do with the manufacturer's declaration (alledrogo and the problem is solved). Another was the EFRATOM LPRO, which cannot be adjusted with a potentiometer (alle ...). I will come back to the FEI in some time and look for a programmable version, sets with gpsdo or cesium standard as if they turned off gps ;)
  • #16
    tplewa
    Level 39  
    @Sas_AS

    Oh, my friend probably didn't understand me. I am glad that my friend raised a lot of interesting matters here and it has a huge educational advantage, etc. My entry was supposed to be more honest, let's bring it down to earth, let's say to the level of such "poor" beetles like us amateurs / hobbyists, where sometimes we turn a blind eye to some imperfections (and as I mentioned, even for many it is financially painful - although I tried to put it quite delicately ;) ) Which does not change the fact that a colleague showed how it should look like we expect something more (here maybe I wrote something good for everyone - the question of how much we have to release ;) )
  • #17
    Sas_AS
    Level 16  
    @tplewa
    We understood each other ;) Just wanted to clarify so that somebody doesn't choke on a rubidium generator without checking with another generator which has 1PPS synchronized signal with gps. There is not and will not be any one cesium clock by which we set all the rest, there is their entire network linked by 1PPS which we poor beetles can use.

    I recommend watching: Keysight Standards Laboratory