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 <[EMAIL PROTECTED] (mailto:[EMAIL PROTECTED]) > Date: November 1, 2008 23:28:34 PDT To: time-nuts <[EMAIL PROTECTED] (mailto:[email protected]) > Subject: [time-nuts] Jackson Labs Fury & Isotemp OCXO134-10 Reply-To: Discussion of precise time and frequency measurement <[EMAIL PROTECTED] (mailto:[email protected]) > 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 -- [EMAIL PROTECTED] (mailto:[email protected]) 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. = _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
