Frequency Reference Using the Efracom LPRO-101 Rubidium

I have installed the Efracom LPRO-101 into a used rack cabinet after removing the card cage. The cabinet had a power supply module outputting 32 vdc which will be reduced to 24 volts by a LM317 regulator to run the Rubidium. I decided to acquire a OCXO for providing the station 10-MHz Reference instead of using the Rubidium. I did this for two reasons: The Rubidium has a finite life and does not exhibit low phase noise. The OCXO was purchased from e-bay for $39.95. It feeds a Downeast Microwave 10-4 10-MHz 4-way distribution amplifier to feed equipment in the shack requiring an accurate reference frequency. A 12-volt sealed-acid battery is float charged to 14 volts to ensure the OCXO will run continuously even in event of a ac power outage. The OCXO can be periodically adjusted to match the Rubidium standard. The rubidium is mounted to a 1/4-inch aluminum plate with six counter-sunk 4-40 screws and the plate is attached to a 6-inch square heat sink with 2-inch deep fins (click image for larger view): Photo of a simple BITE lock indicator board made by Chuck, WA3IAC; Schematic diagram of the Rb and OCXO unit.

  • Rubidium power supply
  • DEMI 10-4 board and BNC outputs
  • Interior view showing OCXO, 10-4 board, rubidium and, power supply
  • View of unit installed in cabinet
  • Rubidium measurements: 1-volt peak (10mw); 10,000,000 Hz
Specifications: Rubidium: Efracom LPRO Freq. accuracy = E-11 Freq. = 6.834687500 GHz Phase noise = -86 dBc/Hz, -118 dBc/Hz (100-Hz), -119 dBc/Hz (1KHz) Lock time = 3-4 min. Load = 1.7 A (start), 500 mA (steady-state), 24v Output = 10-MHz, 7.8 dBm OCXO: Morion MV62 Freq. Stability = 5 x E-12 short-term, 5 x E-5 annual Warm up = 5 x E-8 >5min. Freq. Adj. = +/-3 E-7 (6-Hz) Var. Freq. bias = 0 to +5v (thru 20K) Phase noise = -97 dBc/Hz, -145 dBc/Hz (100-Hz), -150 dBc/Hz (1KHz) Load = 500 mA (start), 180 mA (steady-state), 12v output = 10-MHz, 10 dBm Return to the Home page.