文件列表:

Design/ (0, 2019-12-11)
Design/gps-bom.csv (637, 2019-12-11)
Design/gps-bottom.png (50730, 2019-12-11)
Design/gps-gerbers.zip (171753, 2019-12-11)
Design/gps-top.png (178597, 2019-12-11)
LICENSE (35149, 2019-12-11)
Schematics/ (0, 2019-12-11)
Schematics/gps.brd (102174, 2019-12-11)
Schematics/gps.sch (565604, 2019-12-11)
gps-schematics.pdf (19141, 2019-12-11)

# GPS-Referenced Programmable Precision Signal Generator **Current state:** Board built and operational! However, you will want to check [Issues](https://github.com/rfrht/gps-reference/issues) **Next steps:** Fix issues and release a [Revision B](https://github.com/rfrht/gps-reference/tree/Experimental) - Already WIP. ## Overview This is the do-it-yourself version of the u-Blox-based **GPS-Referenced Programmable Precision Signal Generator**. The board design is largely inspired by [ZL2PD design](https://www.zl2pd.com/GPS_Freq_Ref.html) and features a few other stuff, like break-out headers for I2C, Serial, USB, External Battery and antenna selector. There are two signal outputs; one [DC-coupled (0-3.3V)](https://rf3.org:8443/q/gps/gps-ref-1-mhz.png), suitable for logic level output and an [AC-coupled (-1.6V - 1.6V)](https://rf3.org:8443/q/gps/gps-ref-dc-1-hz.png) output. RA3APW [did some some extensive research (Russian content)](http://www.ra3apw.ru/proekty/ublox-neo-7m/) and found that there are a few frequencies where there is some very good precision for the general hobbyist, yielding precision between 0.1 PPM to 1 PPB. This is not a [GPS-Disciplined Oscillator](https://en.wikipedia.org/wiki/GPS_disciplined_oscillator) but a high precision [Numerically Controlled Oscillator](https://en.wikipedia.org/wiki/Numerically_controlled_oscillator) instead. Bear in mind that the RA3APW tested U-Blox M-7 hardware, while in this project we will be using the newer generation [NEO-M8Q-01A Automotive grade](https://www.u-blox.com/en/product/neo-m8q-01a-module), which sports a [TCXO](https://en.wikipedia.org/wiki/Crystal_oscillator#Temperature), (hopefully) increasing precision. ## Frequencies The tested high reliability frequencies are, namely: | Frequency | Frequency | | --- | --- | | [300 kHz](https://rf3.org:8443/q/gps/gps-ref-300-khz.png) | [500 kHz](https://rf3.org:8443/q/gps/gps-ref-500-khz.png) | | [1 MHz](https://rf3.org:8443/q/gps/gps-ref-1-mhz.png) | [1.2 MHz](https://rf3.org:8443/q/gps/gps-ref-1-2-mhz.png) | | [1.5 MHz](https://rf3.org:8443/q/gps/gps-ref-1-5-mhz.png) | [1.6 MHz](https://rf3.org:8443/q/gps/gps-ref-1-6-mhz.png) | | [2 MHz](https://rf3.org:8443/q/gps/gps-ref-2-mhz.png) | [2.4 MHz](https://rf3.org:8443/q/gps/gps-ref-2-4-mhz.png) | | [3 MHz](https://rf3.org:8443/q/gps/gps-ref-3-mhz.png) | [4 MHz](https://rf3.org:8443/q/gps/gps-ref-4-mhz.png) | | [4.8 MHz](https://rf3.org:8443/q/gps/gps-ref-4-8-mhz.png) | [6 MHz](https://rf3.org:8443/q/gps/gps-ref-6-mhz.png) | | [8 MHz](https://rf3.org:8443/q/gps/gps-ref-8-mhz.png) | [12 MHz](https://rf3.org:8443/q/gps/gps-ref-12-mhz.png) | | [24 MHz](https://rf3.org:8443/q/gps/gps-ref-24-mhz.png) | --- | There are certainly others. It seem to follow some mathematical order, but I failed to figure out the proper sequence. ### Good frequency waveform This is a 1 MHz waveform:  ### Non-optimal frequencies Check this 16 MHz signal, there are harmonics along the main waveform:  This is how the problem manifests in low frequencies. Check the falling edge of a 360 kHz:  ## Configuration Use the [U-Blox U-Center](https://www.u-blox.com/en/product/u-center) tool to configure your board. Open the Config page, in `TP5 (Timepulse 5)` menu and configure as per the below screenshot:  *U-Blox Configuration page - Click to enlarge* ## Artefacts The [schematics](/Schematics) are in Autodesk Eagle CAD format. There is a [Gerber](https://github.com/rfrht/gps-reference/raw/master/Design/gps-gerbers.zip) for ordering a PCB from your favourite PCB shop (Hint: $2 in jlcpcb.com for 5 units), as well a Digi-Key friendly [Bill of Materials](/Design/gps-bom.csv), which currently costs around $27 (including the GPS module). ## Board pictures: Board:  Cabled (with external wire antenna):  ## TODO: Check [Issues](https://github.com/rfrht/gps-reference/issues)

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