[time-nuts] Z3801A OCXO manual trimming

Joe Hobart nova at npgcable.com
Tue Mar 6 12:51:05 EST 2018


Success!

I disassembled the oven and adjusted the OCXO frequency up about 5 Hz.  Lady
Heather reported the DAC changed from +99.99% with no lock to -90% with lock to
GPS.  Hopefully I did not increase the frequency too much.  The long term
aging/drift direction has been down - which caused the loss of lock.  At this
time the DAC has increased slightly to -90.5 as the system settles.

Paul, I also thought about adding an offset voltage to the DAC, but I was
concerned about stability.

Adrian, I thought about an access hole, but when I disassembled the oven, a
piece of the outer heater was partially covering the adjustment access cover and
adjustment.  That required careful moving to access the oscillator adjustment.

Disassembling (ripping is more descriptive) the oven was not difficult.  Putting
everything back together was more tedious.

A huge thanks for all the replies, links to pictures, encouragement, etc.

Joe, W7LUX



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