[time-nuts] Looking for some Frequency Electronics info....

walter shawlee 2 walter2 at sphere.bc.ca
Mon Feb 19 18:57:49 EST 2018

I recently got a strange little 1U FEI rack mounted unit called an FE-7923F-100-1,
which appears to have rear 10MHz and dual 100Mhz outputs. it is called a 
Frequency Reference Unit.

sadly, my unit has a fault light, and no outputs. All the internal supplies look 
good, and there is an FE-83AA (10.0Mhz) and FE-1020-100 (100Mhz) OCXO inside.  
both of these work (when measured at the oscillators), and seem to have 
meaningful control including EFC, and I tracked down the adjustments in a sea of 
what seem to be prototype boards next to the oscillators. so, I have two good 
sources, adjustable, but still no outputs.
the OCXO signals disappear into a set of boards with no useful markings as to 
function, and look mainly digital.

the 100Mhz unit has only about 200mV p-p output, which seems low to me, the 
other has lots of signal. I cannot find any data on either unit on line or at 
the FEI website, so any data that is out there would be very welcome, so I can 
be sure they at least are running correctly.

I am hoping to use this rack as a source of RF reference signals in other gear, 
but clearly I will have to either gut the rest of the circuitry and add some new 
buffers, or figure out the rats nest of hand wiring to determine why it's not 
working.  any help in that area hugely appreciated, and I can send pics to 
anybody interested to know more about the internals.

the rear apron has AC power in, a 10MHz output SMA, a switch next to it that 
says INT/EXT REF. (set to INT), but no way to attach an external ref.  then 
there's a D-Sub filtered connector, that runs to the stacked digital boards, but 
its purpose is unknown as I cannot see where the connections go.  there are also 
two 100Mhz SMA outputs, but all outputs are dead, with no signal, and the front 
ONLINE green LED is dark, and the red FAULT LED is lit. the oscillators do not 
run to the rear jacks but disappear into three pcbs.

hoping for some FEI data if anybody has some to share.
all the best,

Walter Shawlee 2, President
Sphere Research Corporation
3394 Sunnyside Rd.,  West Kelowna,  BC
V1Z 2V4  CANADA  Phone: (250) 769-1834
walter2 at sphere.bc.ca
WS2: We're all in one boat, no matter how it looks to you.
Love is all you need. (John Lennon)
But, that doesn't mean other things don't come in handy. (WS2)

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