[time-nuts] E-5680A C-field trimer ??

Brian Kirby kirbybq at bellsouth.net
Mon Aug 25 21:22:02 EDT 2008

Mark, which pot is it ?

Rex and myself bought units that were not programmable.  Both of us have 
tweaked the pots and have not seen any change in drift.  I turned pots 1 
turn per day and did phase observations, over the course of a week.

They guy that sold these units on ebay claimed they were programmable 
but could not produce the information.  Its been noted he has changed 
his ebay user name about every 6 months (that might give you an idea 
about his operation - he also complained about whiny time-nuts postings 
about his operation).

Mark Sims wrote:
> Actually the 5680A and 5650A units that have the DDS do have a C-field pot.  The DDS is only accurate to 0.01 Hz.  They set the C-field to minimum,  program the DDS constant that gets the closest to the desired freq into the CPU chip (this is what gets reported by the "S" command),  then they tweak the C-field to get the unit exactly on freq.  The reference freq reported by the "S" command is NOT the reference freq that the unit is shipped adjusted to.
> ----------------------------------------
>> There are several models of the 5680A.  A lot use the DDS circuits to
>> set the output frequencies and  they do not have C field adjustments.
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