What is it?

This is the revised version of my previous item. This GPS trained frequency standard (signal generator), can provide arbitral frequency from 1 MHz to 200 MHz with 4-outputs. This is the most practical item I've ever made. Any 70's 80's 90's and up-to-date time domain related instrument (VNA, SPA, oscilloscope, SG) with 10 MHz input will get the atomic clock precision from GPS by ultra low cost!

Why did you make it?

My previous version was "naked" and I believe we needed some kind of enclosure for continuous usage. For enclosing inside metal case, PCB was completely re-designed. The circuit is almost the same as before but now it is with Neo 7M, which is one generation advanced to Neo 6M. In addition, the main SW now has a green LED indicator which apparently can indicate "now it's operating". Moreover RED/GREEN LED will indicate Lipo state (full or charging).

What makes it special?

The feature is same as previous version,

• Four output signals are independently programmable. The frequency is generated by PLL IC (Silicon Labs Si5356 with GPS trained 8 MHz clock), and its output is programmable from 1 MHz to 200 MHz. Programming details is available from Application note of Si5356 Silicon labs's software Clock Builder Pro will automatically generate register values for your frequency configuration and copying them to Arduino source will provide the signal of your demand!

• Default firmware supports 10, 20, 30, 40 MHz high precision signal output. The firmware is written in onboard ATmega88PA with Arduino sketch released in my GitHub account

• Onboard Lipo battery charger enables portable application. USB-bus power operation is also supported.

• Output waveform is 3.3 V square wave (mainly good for digital clock). If sine-wave preferred for analogue application, harmonics suppression required.

Phase noise is around -75dBc/Hz at 10MHz. More details are available at my Hackaday log.

What is included in this item

• Fully tested and initial firmware (10, 20, 100, 200 MHz output) loaded GPS trained signal generator board inside metal enclosure.

• Two stage LNA embedded active GPS antenna (3m cable, IP67, embedded amplifier: MAX2659 two stage, Gain 28dB / NF <1.5dB)

What is NOT included in this item

• Lipo battery. It is not essential for operation for USB bus power mode but you may need it for portable application. For Lipo operation, please don't forget to change onboard jumper setting.

The following video is taken by the prototype version (main SW is toggle sw). The final item is as in the picture.