[time-nuts] Sneaky Errors

David VanHorn D.VanHorn at elec-solutions.com
Fri Oct 21 16:43:28 UTC 2011

Playing with my A unit "Timex" (It takes a licking and keeps on ticking) I'm not getting a reliable unlock even at + or - 5V
Once unlocked, it seems to need to be inside 1.2V before locking.
That results in about 4 hz error, which would be ok for me.

Is there a way to automatically turn off the output if the GPS is unlocked?

From: time-nuts-bounces at febo.com [time-nuts-bounces at febo.com] On Behalf Of Mark Sims [holrum at hotmail.com]
Sent: Thursday, October 20, 2011 9:39 PM
To: time-nuts at febo.com
Subject: [time-nuts] Sneaky Errors

1 ppm at 10 MHz is 10 Hz.   It's been quite a while since I tested it,  but if I remember correctly,  if the Tbolt OCXO is off that far the GPS won't lock and the failure will be rather obvious.
The typical Tbolt oscillator has a DAC gain of 3.5 Hz/V.  10 Hz would be 3V of DAC offset.   Lady Heather can determine your actual oscillator gain constant using the oscillator autotune function (& A from the keyboard).   From that you can calculate the DAC offset required to get you 10 Hz of shift.  Put the unit into manual DAC control mode and set the DAC voltage to what is needed to shift the freq that much.  See if it locks...
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