Hi Corby,
I would first like to thank you for sharing your precious studies with us. I love the HP5065A because it's an extremely interesting project and I'm convinced like you we have a lot of room for improving its performance. ********************************* In addition to the power supply mods: -removed AC components -power now supplied with an external DC lab grade low noise highly regulated supply. -temperature coefficient of +20 Volt supply adjusted to be below 1PPM/deg C See: https://www.febo.com/pipermail/time-nuts/2017-August/106634.html ********************************** My approach to modifying some equipment is to try to keep it as good as possible under original conditions unless the modification leads to a substantial increase in specifications. For this reason I do not understand why you have removed the power transformer and its filter inductance. You could power it from the DC input and leave disconnected the AC power supply or have I missed a reason to do this? ********************************** I've now installed the improved C-field circuit that has less than +- 1PPM variation per degree C. ********************************** It would be very interesting to see the schematic of your solution. I have tested a simple ssolution replacing the R12 (333Ohms) with parallel of a 470 Ohms and a 5k Ohms NTC, this mounted in the middle of the chassis. I must admit, however, that I do not have a suitable instrumentation and a Maser reference to make appropriate measures. ********************************** The optical unit has been installed into a sealed enclosure that has been purged with dry Nitrogen. This eliminates any Barometric pressure effects and also eliminates drift caused by Helium permeation. Tests at this point show a very nice long term stability. Last mod will use a small PC closed loop liquid cooler to keep the outside of the sealed enclosure at a constant temperature essentially making it a double oven. *********************************** Do you have any more detailed photographs? *********************************** I'm also working on: An active temp compensation scheme to add to the active barometric compensation I outlined earlier. See: https://www.febo.com/pipermail/time-nuts/2016-May/097829.html And a passive optical unit temperature compensation using a thermistor/resistor arrangement. ************************************* [C:\Users\PRINCI~1\AppData\Local\Temp\msohtml1\01\clip_image001.gif] As you have previously written , boxing the 5065A physical module solve the problem of barometric pressure variation, making an active compensation is an alternative are you studying? Hope to read you soon, Luciano Timeok Da "time-nuts" [email protected] A [email protected] Cc Data Thu, 16 Nov 2017 12:58:13 -0800 Oggetto [time-nuts] HP5065A C-field mods and optical unit mods HP5065A C-field mods and optical unit mods In addition to the power supply mods: -removed AC components -power now supplied with an external DC lab grade low noise highly regulated supply. -temperature coefficient of +20 Volt supply adjusted to be below 1PPM/deg C See: https://www.febo.com/pipermail/time-nuts/2017-August/106634.html I've now installed the improved C-field circuit that has less than +- 1PPM variation per degree C. The optical unit has been installed into a sealed enclosure that has been purged with dry Nitrogen. This eliminates any Barometric pressure effects and also eliminates drift caused by Helium permeation. Tests at this point show a very nice long term stability. Last mod will use a small PC closed loop liquid cooler to keep the outside of the sealed enclosure at a constant temperature essentially making it a double oven. I'm also working on: An active temp compensation scheme to add to the active barometric compensation I outlined earlier. See: https://www.febo.com/pipermail/time-nuts/2016-May/097829.html And a passive optical unit temperature compensation using a thermistor/resistor arrangement. PIX shows the sealed optical unit installed into a slightly taller chassis. (The 5065C ?) Cheers! Corby _______________________________________________ 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.
