[time-nuts] Jackson Labs Fury & Isotemp OCXO134-10

[SAIDJACK at aol.com]

Hello Matt,
 
let me try to answer some of your questions about the Fury with an  
Isotemp-134.
 
First I tried finding a datasheet for it, but Isotemp removed it from their  
website. All I could find was that it has about 5ppb -30 to +60C stability. So 
 it's performance is between our JLT standard single oven and double oven  
OCXO's. Not knowing the EFC sensitivity of the unit, I will give you some servo  
settings to try out and play with.
 
On the power up issues, you can try to run both the OCXO and the Fury from  
the same power supply. If the OCXO does not provide a stable 10MHz before the  
Fury comes out of reset then it won't boot up. So if you try power  cycling 
say 5 to 10 times and it always comes up (LED's turn on for several  seconds) 
then you are good to go. If it is marginal, then you may have to delay  the Fury 
power as some have suggested here. Or simply press the reset   button after 
power on (I presume you won't power cycle the unit very often when  in 
operation, so pressing reset after power on may work for you if the unit does  not 
boot).
 
On the EFC range, this depends on the aging and thermal sensitivity of the  
OCXO. 4.64V is still quite a ways below 5V, but it's getting to the edge of the 
 Fury range. There is no reason that it should not work, even if you go up to 
 4.8V or so due to aging etc.
 
If the unit ages downward (EFC voltage decreasing over time) then I would  
not worry. I would only add external circuitry to increase the EFC range if  
absolutely necessary, since any circuitry you will add will probably add  noise.
 
Now on the servo settings, try the following:
 
* Slope polarity: depends on the OCXO. If frequency goes up with increased  
EFC voltage, then set it to "positive". You can try changing the coarsedac up  
and down to see the slope of your OCXO (use the command serv:coarsedac  x   
where x is 0 to 255. Higher values result in higher efc  voltage.
 
* For this type of thermal stability, I would try a servo:efcs setting of  
about 2 to 4
 
* Try damping of 30. This value is not really that critical, any value will  
work that does not cause oscillation. Higher values result in "slower" 
sawtooth  filters and thus less noise
 
* Phaseco: try values of 15 to 25 and see how fast the unit pushes the  phase 
offset to 0ns. If its too slow for you, increase this value, but not to  the 
point where it oscillates.
 
* DAC gain: this depends on the OCXO EFC sensitivity. If it is a standard  
-20Hz to +20Hz over 0V to 5V then a value of 15 seems to work well.
 
If your unit locks up without overshoot/oscillation within 30 minutes with  
these settings then you are doing well, and can fine-tune the parameters from  
there.
 
Hope this helps,
bye,
Said
 
 
 
 
 




From: Matt Osborn <_kc0ukk at msosborn.com_ (mailto:kc0ukk at msosborn.com) >
Date:  November 1, 2008 23:28:34 PDT
To: time-nuts <_time-nuts at febo.com_ (mailto:time-nuts at febo.com) >
Subject:  [time-nuts] Jackson Labs Fury & Isotemp  OCXO134-10
Reply-To: Discussion of precise time and frequency  measurement 
<_time-nuts at febo.com_ (mailto:time-nuts at febo.com) >





I think that I've managed to keep a low profile here, trusting  that I
would learn more if I refrained from random  interjections of
ill-informed thoughts.  However, there  comes a point in every  man's
life...

A year or two  ago, I took advantage of Said's offer and purchased one
of  the Jackson Labs OEM external OCXO Fury units and am attempting  to
put it to work. I've decided to use an Isotemp OCXO134-10  oscillator
and have several decisions which I would like to  vet with those of you
that have been down this road  before.

The Isotemp unit has an EFC range  of 0 to 8 Volts; the Fury has an EFC
range of 0 to 5 volts.  Using my HP 53131A, I'm able to adjust the
Isotemp to  10 MHz +- 5 mHz with an EFC voltage of 4.64 volts. That  is
within the adjustment range of the Fury, but I'm not sure  of the
accuracy of the HP53131A.  Should I construct a  resistive network ala
Brooks Shera to 'boost' the EFC range  just in case or would I be
better off just using the Fury  'as is'?

Secondly, the Jackson Labs advises  that since the Fury uses the
external oscillator as its  clock, that the oscillator should be
powered up before the  Fury itself.  I was hoping that I would be able
to use  a single power switch to power both the oscillator and the  Fury
simultaneously, but now I'm not so  sure.

Finally, are there any of you that  have used the Isotemp OXCO134-10
with the Fury?  Have  any of you worked out the various SERVO settings
that the  Fury makes available?  I'm interested in the  DAC gain,  EFC
scale, EFC dampening and Phase  compensation.

Any and all advice will be  gratefully accepted.

-- kc0ukk at msosborn  dot  com

_______________________________________________
time-nuts  mailing list -- _time-nuts at febo.com_ (mailto:time-nuts at febo.com) 
To  unsubscribe, go to 
_https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts_ (https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts) 
and  follow the instructions  there.


=