[time-nuts] FE-405B Reprogramming

Logan Cummings logan.cummings at gmail.com
Wed Jun 8 15:08:20 EDT 2016

Hi All,

    Nick's request for a divide-by-three circuit to get his FE-405B to
output a 10MHz signal got me thinking - didn't want to threadjack.

    I had assumed that the FE-405B's DDS output and FE-5680 compatibility
made it a good candidate for output frequency reprogramming. Has anyone
determined that this is not possible? My biggest concern was that if the
internal crystal is also at 10MHz you'd get bad spurs trying to output the
DDS at the same frequency..

    Does anyone know if the FE-405B uses the original FE-5680 DDS circuit
or the more recent one that is only narrowly (EFC) tunable over the serial
interface? Would be great to have a stable reference at 1, 5, 10, etc. MHz.

     Any info/references on the FE-XXX internals would be appreciated!


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