Ultra Low Noise Crystal Oscillator with 1:4 or 1:8 fan out buffer


Main function blocks are seen on the block diagram below:

LO Module

XO is of a Driscoll type A design - there were only few documented ham radio experiments conducted so far - and it is a modified Uwe/DC8RI circuit (also check this design from Leif/SM5BSZ).
Followed by an isolation amplifier and power splitter that feeds two 1:4 distribution boards (second distribution board is optional).
TX/RX sequencer drives high power relais (all in parallel) and provides 12V power supply for RX and TX converter(s) via LO output connectors.
Power supply outputs are configurable (RX, TX or zero voltage - only two outputs can supply TX voltage).
Phase noise plot of the prototype unit shows excellent performance (isolation amplifier improves the PN by few more dBs - measurements of the final design will be taken shortly).

PN plot 

Any 5th overtone crystal in the range of about 100 MHz to 150 MHz can be used in this design with only few passive component changes.
Few exqmples:
Output power level: +8 ... +10 dBm. @ 50 ohm
Phase noise data:
@offset Phase noise 
1 kHz -145 dBc/Hz
10 kHz -165 dBc/Hz
100 kHz -168 dBc/Hz
1 MHz -170 dBc/Hz

ULN XO view

ULN XO side view

The LO module can be used to drive two (or more) Javornik-144/14 transverters - modification instructions will be published shortly. 

Date published: Aug. 2018