The sensitivity of that EFC input is so low on my LPRO unit, that the PS and DAC noises are not a problem at all. Should add a 1K resistor in series with the Dac out before connecting it to anything outside of the TBolt. Attached is an expanded 4 day plot showing part of the same LPRO run where the Dac is not changing at all. Using just the Phase data, The freq offset calculates to 7e-14 and the ageing rate is under 1e-14
ws ******************* Azelio Boriani azelio.boriani at screen.it posted: The frequency accuracy is measured based on the EFC variation. I have recently received my TBolts, not yet fired up, actually preparing the power supply. Where is the DAC? I can't find... the LT1014 is not a DAC, the SO8 2105 is not an LT2105 nor an LTC2105. The DAC is 20bit as I can read in the manual and for a 10-volt range (-5..+5) the resolution is 9.54uV. I think I have to take great care in the power supply... ****************** On Tue, Nov 22, 2011 at 11:00 PM, WarrenS <warrensjmail-one at yahoo.com>wrote:
To TBolt nuts A Tbolt that has been modified to use an external 10 MHz osc is all that is needed to be able to measure freq and aging of an Rb osc to better than 1e-14 using a week long test run. Attached is a plot showing a recent 13 day long LPRO Rb test I did. This modified LPRO showed an unbelievable average ageing rate of only 2e-15/day over the first 12 days. Of course anytime you get much below 1e-13 for a non Cs osc, it has some luck evolved. But still interesting that using ONLY a Tbolt and LadyHeather one is able to measure freq that accurately. (Can do even better using Dual Tbolts. Used to cancel the shorter term GPS phase noise) ws
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