GPSDO (GPS disciplined oscillator) precision

[Jim KD4YLQ]

Has anyone been using an external GPSDO precision reference clock with their HL2? If so, please reply with some details of your experience, what you chose and what it cost. Thanks!

73  de Jim KD4YQ

[Mike Lewis]

I use my shack 10Mhz distribution box (using either OCXO or GPSDO, selectable) or direct connect to a 10Mhz OCXO and GPSDO.  Works good.  Pay attention to the max input voltage spec of the HL2.  I have used both square and sine wave sources.  One of my sources did not work well until I buffered it with a distribution box (filtering/isolation).  

 

The dual Leo Bodnar GPSDO I am using has adjustable output.  The OCXOs are fixed output but have reasonable standardized output levels.  You need to run the hermeslite.py script modified to enable the clock in code for the reference frequency you are using, or in Thetis for HL2, it has a UI for it in setup.

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[Jan PA3JRK]

For my EME station I use a GPSDO from Leo Bodnar, which feeds a distribution amplifier (homemade TAPR/TADD-1 by N8UR) with isolated outputs. Output of the distribution amplifier is a sinewave of apx. 2.8Vpp or 1Vrms, which results,  via voltagedivider R39/R40, in apx. 1 Vpp on the internal clock generator U6 (5P49V5923). The level of the 10 MHz signal is rather critical, because the max. allowable level on the 5P49V5923 is 1.2 Vpp! So always check the outputlevel first! You could also feed the lowest output (8 mA, 6.4 dBm) of the Loe Bodnar to the HL2, but beware the signallevel on CL1 never exceeds 3.2Vpp! otherwise you may damage the 5P49V5923. In my experience, using a distribution amplifier works best, because the output is better controlable, much cleaner and isolated from the rest.

BTW: The internal oscillator of the HL2 is quite good. In my case it differs only 7-8 Hz from the GPSDO! Drift is also minimal.

73,

Jan

Op dinsdag 26 december 2023 om 19:34:26 UTC+1 schreef Jim KD4YLQ: