Adding a GPSDO will greatly improve the frequency stability in the receive chain. The block diagram below shows how the GPSDO injects a clock signal into the LNB. The clock signal from the GPSDO has superior stability compared to the LNB oscillator.
GPSDO generates a 25 MHz clock signal for the LNB.
I decided to buy a GPSDO developed by 4 danish radio amateurs. The project is named RFzero. The price of the RFzero board was less than 50% of the Leo Bodnar mini-GPSDO. Another advantage of the RFzero is the possibility of writing your own software using the Arduino IDE. The RFzero board is assembled, and only a few optional pins are soldered by the end-user.
The RFzero board.
I've mounted the RFzero board in an aluminium box. Power (5 V DC) is supplied via the USB interface. An external PSU can also power the board.
GPSDO front view.
GPSDO rear view.
GPSDO with lid removed.
Conclusion: Adding a GPSDO has greatly improved my receive chain. The Narrow-Band beacons are now rock-stable regardless of the LNB temperature.
Vy 73 OZ1BXM Lars
My webpage: http://oz1bxm.dk/
