10MHz OCXO for Philips/Fluke PM6666 counter

Alternative 10MHz oscillator for Philips/Fluke PM6665 and PM6666 frequency counters.

Schematic

Created with KiCAD ver. 7.0.11

Design ideas

• fuse/PTCC
• Vref with trim-pot for fine tune (Vc xtal: 0-4V)
• DC-DC conv (12V-to-5V)
• LCD-backlight power & trim-pot
• jumper to choose always-on or power-switch
• SMA and Vref test-point
• 4 mount holes for alternative use
• status LED after fuse/DC-DC conv.

• temp.sensor under/near OCXO (LM35/DS18b20)
• Window-comparator with warm/cold LED indicator
• filter/circuit to convert square to sine-wave
• freq. divider

• currently usable OCXO: CTI OSC5A2B02 / NDK ENE3311B

• allow multiple footprints to fit other OCXO (ISOtemp/Vectron)

Issues/todo

• Pk-Pk voltage from OCXO to high, need 470 load resistor
• change diameter hole for OCXO (0.8mm is to narrow)
• update/correct footprint thp Elco's (47uF & 100uF)
• improv. Vref tuning (20-turn trim-pot?)
• add solder-jumper to seperate 10MHz signal (antenne!)
• power-on LED at better location
• update part marking (pin.1, +, etc)

MHz.kHz.Hz 010.000.000 123.456.789

Possible voltage references

• ADR4540 4.096V 2ppm Vin: 4.2 - 15V

• LM4140 4.096V 3ppm Vin: 5V

• LT1019-5 5.000V 5ppm
• LT1021 5.000V 5ppm Vin: >10V
• MAX874 4.096V 20ppm Vin: 4.3 - 20V
• MAX6070AAUT 4.096V 6ppm Vin: 4.3 - 5.5V
• MAX6194A 4.500V 5ppm Vin: 5 - 12.6V

• MAX6198A 4.096V 2ppm Vin: 5 - 12.6V

• MAX6241 4.096V 5ppm Vin: 8 - 36V
• MAX6341 4.096V 2.5ppm Vin: 8 - 36V
• MAX6250BESA 5.000V 7ppm
• REF5040 4.096V 3ppm Vin: 4.3 - 18V