10MHz Rubidium reference oscillator

OH2NLT 07.04.2011


Used Rubidium oscillators are already reasonable priced and in the reach of hobbyists. I purchased EFRATOM LPRO-101 module from the Ebay. When calibrated frequency accuracy can be as high as 5x10exp-11. To build complete lab reference power supply and 10MHz distribution amplifier is also neded. LPRO-101 operating voltage is 24VDC and power requirement about 13W. This time ready made Phoenix Contact 230/24V PSU module was selected. 10MHz 4+1 ch distribution amplifier was designed using Linear LT1364 op amps.


Distribution amplifier schematic diagram

Distribution amplifier board lay out

Picture of the distribution amplifier board

During the tests it was found that the LT1364 chips required some sort of heat sink. Aluminum plates were attached with heat conducting foam over the chips.

Whole thing was boxed in to old (large) RS232/RS485 converter box.

Face plate holds power and not locked indicator LEDs

Back plate had ready holes for the 10MHz connectors. There are four transformer-isolated outputs, one non isolated output and input connector if the amplifier board is neded for some other use. There are also measurement posts for the LPRO-101 lamp voltage and XTAL C-field voltage.

EFRATOM module needs some sort of heat sink. This time aluminum enclosure was enough. Heat transfer foam was placed between the oscillator and the enclocure.

Ready frequency standsrd

SDR Cube transceiver was test calibrated with the new frequency standsrd.

Trimble GPSDO was used for hp5385 counter reference clock and rubidium oscillator was measured with this setup. Unfortunatelly no more digits available in the hp5385A.