This project is intend to be used for a SDRPlay , RSPdx-R2 24Mhz reference.

It’s should be low cost and can be easly reproductible.

That’s the reason it used, Arduino Nano , GPS NEO6 or 8M, and Si5351 board.

Design is from F6IDT, but code is refactored to give only 24 or 10Mhz.

The GPS module delivers NMEA data on PPS pin, after MCU calculation, based on this, the Si5351A clock is corrected, the trick is using this signal as a frequency meter gate to count the number of pulses delivered on the CLK0 output programmed at 2.5 MHz.

You can see the Arduino Nano, the GPS NEO8M, the SI5351, with at right the TCXO 25Mhz reference for it.

A little switch can isolate RX pin from GPS, if you need to reflash the MCU.

2.5Mhz clock is feed through the little coax to MCU.

Power output is around 8dbm.

A little push button can select 10 or 24Mhz out.

PPS blue LED blink at 1hz when GPS is locked, the green LED indicate 10 or 24Mhz selectable by the push black button (at left in back of box), default start is set on 24Mhz.

MCU, Arduino NANO ~2.5€from Aliexpress

SI5351 Board, ~1.8€ from Aliexpress

GPS NEO 6,7, or 8 ~12€ from Aliexpress

TCXO 25Mhz ~15€ from Ebay

Two LED 3mm, Cap, Resistor in 1206, header, push button, switch

Quality PCB from PCBway ~10€ , main board, and front panel (shipping cost included)

BOX, 10€ from Aliexpress

For the front panel, I draw a PCB with Proteus 8, then I used, the PCBWAY service, I now used this method for all new panel I want to build, beyond quality, PCBWay is known for its remarkable production speed, manufacturing in just a few days, with rapid international shipping aroung 3/5 days.

You can enjoy flawless solder masks, precise silkscreen printing, reliable copper finishes.

You can see the strange difference btw this project and Leobodnar

After 20min on preheat