[time-nuts] FE-5680A results

EWKehren at aol.com EWKehren at aol.com
Tue Nov 29 18:55:31 UTC 2011


Murray
Thank you for the info. It would how ever tie up equipment which I  want to 
use for other projects. I am only looking at the FE5680A once a week and  
since we have right now what we call Chamber of Commerce weather the AC is 
most  the time off. Temperature control will be a must any way, so now is as 
good a  time as any to integrate it. 
I am  working with two other individuals on integrating the Austron  
circuit with its own 100 MHz counter with LCD display, temperature monitoring  and 
the ability to store it on an USB memory stick or via Bluetooth to a PC. 
The  counter has gate times of .1, 1 10 and 100 sec. and in 100 sec. the 
resolution  will be E-14.
Right now the FE 5680A is just a curiosity, as to what you can get for $  
40.
Bert Kehren
 
 
In a message dated 11/29/2011 12:44:15 P.M. Eastern Standard Time,  
denwood at orcon.net.nz writes:

Bert,
There's a very nice way to separate diurnal thermal  sensitivity from long 
term ageing. It applies equally well to Rb sources  as to OCXOs, which is 
where I've used it.

What you do is set up to  make frequency observations against a more stable 
reference (of course in  this case a GPSDO or a similar), and then make 
several observations per  day for a week or so, preferably at or about the 
same time of day each  day. Then you plot the results using a spreadsheet, 
as 
ppb offset on the  vertical axis and time of day (NOT total elapsed time) 
on 
the horizontal  axis.

What will result after several days of observations is either a  zig-zag or 
a 
spiral, depending on the relative sizes of the thermal and  ageing effects. 
You can extract the ageing rate out quite nicely by adding  a column with 
an 
estimated ageing rate which you add to the measured  offset. If you then 
plot 
this against time of day you should end up with a  static rough retraced 
circle or line when the estimated offset is correct.  The width and height 
of 
the result gives you an estimate of the thermal  sensitivity with time of 
day.

If you are able also to plot against  ambient temperature instead of time 
of 
day, the same process applies, and  you can extract the thermal sensitivity.

73,
Murray  ZL1BPU


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