[time-nuts] FE5680 GPS Disciplined Controller

Chris Albertson albertson.chris at gmail.com
Fri Jun 20 23:49:57 EDT 2014


I think the user FE5680  manual says you can change the tuning word as much
as you like.   But changing the EEPROM is different, that is used on power
up.  In a GPSDO you would likely want to send a command over the serial
interface when you need to make a change but you would only write to the
EEPROM as a special case, maybe if you wanted to place the Rb in a none GPS
mode so it could be portable.  I think you would store the power-on
defaults inside the GPSDO controller's uP.  Anyways changing the running
word and writing it to memory are different.

BTW I made a temperature controller for mine.   The unit is bolted to a
large heat sink and placed in a box with a fan.  The fan speed is
controlled by the heat sink temperature.  So it is an ovenized box that is
powered by waste heat.   My problem is finding a decent temperer sensor.
 I've tried several and they are noisy.

This version is simple.  The parts list is just three tab voltage
regulators, a power darlinton (for the fan motor) and an 8-pin AVR chip.
 The AVR uses one analog input to sense temperer and one analog output to
control the fan speed.    The software is very simple.

Once I find a good temperature sensors I want to also measure the ambient
air temperature and control the fan based on the delta between the heat
sink and ambient.




On Fri, Jun 20, 2014 at 5:11 PM, Mark Sims <holrum at hotmail.com> wrote:

> Maybe...  maybe not.  Some of the Rb's store the tuning word in the
> processor EEPROM and those have a rather limited number of write cycles.
>
> ----------------
> You can change the DDS tuning words almost as many times per minute or per
> second as you wish to achieve the desired average accuracy.
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-- 

Chris Albertson
Redondo Beach, California


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