Jackson Labs Fury & Isotemp OCXO134-10
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
Matt Osborn wrote:
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'?
If you use a non inverting buffer amplifier with a gain of 1.6 you will
increase the allowance for OCXO aging, otherwise you are a little close
to the Fury EFC output limit of 5V.
Have you tried connecting the OCXO to the Fury and seen how close to the
limit the OCXO EFC is when lock is achieved?
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.
You still can if you use a suitable delay circuit.
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
Bruce
Regarding your second question concerning power supply sequencing. How
about using one of the "Power Supply Sequencer" chips (e.g. MAX6819)). The
output of your power supply would go directly to the external OCXO, the
Power Supply Sequencer chip and the input to a MOSFET switch. Output of the
MOSFET switch goes to the Fury.
When the power supply is switched on the following sequence occurs (assuming
a MAX6819):
- Power is applied to the OCXO, MAX6819 and MOSFET switch input
- The MAX6819 starts a 200 millisecond delay
- After 200 milliseconds the MAX6819 turns the MOSFET switch On, powering
the Fury On
MOSFET switches can be used that have only a few tenths (or less) of an ohm
of "ON" resistance. This minimizes degradation in voltage regulation of the
power applied to the Fury.
The MAX6819 data sheet gives useful examples applicable to the above
application.
73,
Jim Hall W4TVI
From: "Matt Osborn" kc0ukk@msosborn.com
Sent: Saturday, November 01, 2008 11:28 PM
To: "time-nuts" time-nuts@febo.com
Subject: [time-nuts] Jackson Labs Fury & Isotemp OCXO134-10
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
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On Sun, 02 Nov 2008 01:28:34 -0500, Matt Osborn kc0ukk@msosborn.com
wrote:
Hi all,
Thanks for all the help and ideas with the IsoTemp/Fury combination. I
followed Hal Murray's advice fired up the combination yesterday (its
been running for about 24 hours now) and everything is working as
advertised. The IsoTemp locked in with an EFC of 4.523xxxx and today
is down to 4.498xxxx volts and falling slowly, so it would appear that
boosting the Fury EFC range won't be necessary.
Bruce Griffiths suggested a 1.6 gain buffer amplifier and Jim Miller
had designed that exact amplifier to boost an EFC range of 0 - 5v to 0
- 8v specifically for the IsoTemp OCXO134. Jim had a PCB available,
so I ordered it and will build that up if the IsoTemp starts aging in
the wrong direction. I believe that problem has been addressed.
I've not yet solved the power sequence problem (if it exists); I'll
follow Said's advice and just try powering both from the same supply
and see if the Fury reset hold time is sufficient. If not, I'll
pursue Jim Hall's MAX6819 approach. That would seem to be a simple and
inexpensive solution.
Now I'm trying to understand Bill Jones' GPSCon program and what it is
telling me about the Fury GPSDO. With some history provided by GPSCon
and a better understanding of just what, exactly, I should expect to
see and to strive for, I will apply Said's suggestions and see what
develops.
BTW, it would appear as though my HP 53131A counter reads 220 mHz low
with a 2 second gate time. There appears to be no appreciable drift;
it always reads 220 mHz low. I'm sure there is a name for that
measurement, I hope to learn it soon.
Thanks to all for your help. I'm amazed at the high signal to noise
ratio on this list.
-- kc0ukk at msosborn dot com