Current state: Board built and operational! However, you will want to check Issues

Next steps: Fix issues and release a Revision B - Already WIP.

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 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), suitable for logic level output and an AC-coupled (-1.6V - 1.6V) output.

RA3APW did some some extensive research (Russian content) 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 but a high precision 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, which sports a TCXO, (hopefully) increasing precision.

The tested high reliability frequencies are, namely:

There are certainly others. It seem to follow some mathematical order, but I failed to figure out the proper sequence.

This is a 1 MHz waveform:

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:

Use the U-Blox 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

The schematics are in Autodesk Eagle CAD format.

There is a Gerber 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, which currently costs around $27 (including the GPS module).

Board:

Cabled (with external wire antenna):

Check Issues