[time-nuts] James Miller/Brooks Shera GPSDO 10 MHz

[Mervyn Thomas]

Hi All,

An update on the resolution of my problems with my unit.

I had a component value in the R5, R6 divider on the DAC output wrong - 
4.7K instead of 470R and while this had not caused any noticeable 
difference over the many years it had run properly it obviously became a 
problem in that it would no longer allow an EFC control voltage to the 
oscillator sufficient to keep it disciplined.  I inserted a 470R and 
also changed the DAC from the AD1861 that had been in for years and 
replaced it with a PCM61P which may or may not have been part of the 
solution.

I also, with the help of my Son-in-law, copied the PIC16F867A 
microprocessor using Matlab and a Pickit 3 on to another spare PIC so 
now have 2 PIC's with the Auto-N function.

My SIL also wrote a Terminal program that utilizes the three 5 digit 
numbers available from the DB9 ASCII I/O to a Terminal program.  I have 
attached a pic taken on my phone (not a very good one) showing just the 
"plot" tab results of the DACvalues and Phase detector values for each 
30 second.   It shows the fairly wild gyrations at turn on of the unit 
and how it eventually settles down to lock.  He still has a few further 
enhancements to make but I found it was a very useful program.

Merv  VK6BMT
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