FE-405B Reprogramming
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!
Thanks,
-Logan
Hi
The 405 appears to have some “bandpass” elements in it. You can not tune it over a wide range.
Bob
On Jun 8, 2016, at 3:08 PM, Logan Cummings logan.cummings@gmail.com wrote:
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!
Thanks,
-Logan
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Thanks Bob,
I figured if it was that easy someone else would have already done
it. Went looking for a schematic and found Tom's page describing the
architecture at a high level and with ADEV plots providing evidence of said
architecture. Good block diagram from an FEI presentation at the bottom of
the page http://www.leapsecond.com/pages/fe405/
Takeaway: no, can't be done - 5MHz DOCXO clocks a DDS which outputs
at 15MHz feeds into a PLL steering a standard 15MHz VCXO which then
provides the output directly.
Very interesting architecture and gives me some food for thought, but
does not solve the 15 != 10 problem Nick was facing.
Cheers and thanks again!
-Logan
On Wed, Jun 8, 2016 at 3:06 PM, Bob Camp kb8tq@n1k.org wrote:
Hi
The 405 appears to have some “bandpass” elements in it. You can not tune
it over a wide range.
Bob
On Jun 8, 2016, at 3:08 PM, Logan Cummings logan.cummings@gmail.com
wrote:
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!
Thanks,
-Logan
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.