[time-nuts] FE-5680A Mechanical Question

EWKehren at aol.com EWKehren at aol.com
Thu Jan 12 15:04:42 EST 2012


I hear all these ideas from paper tigers. How about building something and  
report on it. I can do a Shera for $ 40 and add a $ 20 GPS.  And it works. 
I did fail to mention that I also have retrace data. Over the test period I 
 had at least 10 power outages from seconds to a couple of hours. The Rb 
goes  right back to 1 E-12. It would be nice if some one independent does a 
test on  aging, maybe I was lucky and got a particularly good unit.
Bert Kehren
 
 
In a message dated 1/12/2012 12:04:03 P.M. Eastern Standard Time,  
albertson.chris at gmail.com writes:

I plan  to lock my FE5380 to a GPS also.  But I want to mine to  "unplug
able".   The idea is to connect the GPS and let it sync  for some
period of time.  Perhaps hours or maybe weeks, the longer the  better
and then you can disconnect the GPS and the FE5680 free runs at  that
frequency.   Plug it back in to sync it.

I think it's  clear that a small micro processor is required or a
desktop computer could  be used.  The FE5680 uses the RS232 port for
frequency adjustment you  are going to need a computer.  I think a Tiny
AVR would do fine.   It is a $2, 8-pin chip.   It has a 10-bit A/D
converter to read  the phase offset and you can use another pin for
serial output to the  FE5680.  If you used a digital phase detector
you'd not need the  A/D.

The controller would work like the typical GPSDO controller  except
the DAC is physically inside the FE5680.  This make it  easier.

Physically,  It will be mounted inside a steel box about  the size of a
shoebox (The box once held a pair of large sized disk drives,  from
back in the days when drives where about 3" thick)  There is a  thick
aluminum plate the divides the box vertically. the FE5680 sits on  top
of the plate, a heat sink is bonded to the underside of the  plate.   A
low speed fan moves air through the box slowly.   The fan is
controlled by a temperature sensor bonded to the  plate the FE5680 is
mounted on.   This is a crude type of "oven"  using the FE5680 is a
heating element.   I hope to   stabilize temperature to about 2C.
I'll start with a simple comparator chip  as a on/off fan controller
and eventually use another 8-pin uP to do a full  PID controller with a
three wire fan

Chris Albertson
Redondo  Beach,  California

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