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.

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.

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

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