Ultra Low Noise Crystal Oscillator with 1:4 or 1:8 fan out buffer
Main function blocks are seen on the block diagram below:
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
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
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).
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.
Output power level: +8 ... +10 dBm. @ 50 ohm
- 116 MHz crystal for driving 28 MHz IF 2m RX and/or TX convertres
- 137 MHz crystal for driving 21 MHz IF 70cm RX and/or TX convertres
- 125 MHz crystal for driving several SDR receivers (beamforming, MIMO, etc)
- 125 MHz crystal for high frequency (1 GHz+) DDS reference clock
Phase noise data:
The LO module can be used to drive two (or more) Javornik-144/14
transverters - modification instructions will be published
Date published: Aug. 2018