In a message dated 11/10/2008 05:12:11 GMT Daylight Time, [EMAIL PROTECTED] writes:
Has anyone "upgraded" the oscillator on an older Datum BC637PCI card to the MTI crystal? Is it as simple as changing the crystal and adjusting the osc gain? --------- Hi Scott I've not changed the oscillator, but I did look into the possibility and also ran a BC637PCI for a while with an external Vectron ovened 10MHz oscillator. I assume you have the BC637PCI manual? Appendix A refers to field upgrades, both converting a 635 to 637 by adding the GPS module and upgrading to the ovened oscillator. In both instances a firmware "upgrade" was activated by entering a device specific password provided by Datum/Symmetricom. I doubt that option is still longer available even though the necessary firmware changes are obviously already there waiting to be activated. I suspect, in the case of the oscillator upgrade anyway, some default settings including oscillator gain will be all that's changed. When running with an external oscillator I found that loss of power would default any settings I had changed so no doubt that's what would happen if you upgraded the oscillator without the firmware change. Page 6-15, in the rev K manual anyway, gives details of the oscillator gain adjustment, I found approx 70 seemed reasonable with my Vectron oscillator but my BC637PCI, and perhaps others, has some conditioning issues anyway. The basic onboard oscillator was not very good, apologies for such an imprecise statement but I can't find the fairly extensive notes made several months ago, both accuracy and stability were relatively poor measured on an HP53132A using a known good Thunderbolt as a reference. In particular I noticed quite frequent, but seemingly random, jumps in output frequency that would then take a little while to recover, a bit like a fast acting automatic gain control with slow recovery time. These jumps were significantly greater than the "normal" variations I observed and fell outside of the unit specification. Using the Vectron oscillator greatly improved things, it was a much better oscillator anyway and I was able to observe the significant improvement in the Vectron performance when being conditioned by the BC637PCI. However, the frequency jumps still occured albeit with overall performance much improved and frequency stability much better and the jumps less than before, ie frequency jumps were seemingly reduced in proportion to the better accuracy. Without the jumps I would have been happy with the Vectron performance but didn't feel able to trust the combination without permanent computer monitoring, and still don't know if this was a function of my BC637PCI or something common to all of them. It was interesting to play with, and I'll probably go back to it at some time, but I was more concerned then to set up something I could rely on and eventually put it to one side. Whilst working with the BC637PCI I did find that I needed both the BC635PCI and BC637PCI software, both offer options the other lacks, and I have late copies of both if you need them. I also have two manuals, version H from Datum that includes schematics, and the fairly similar version K from Symmetricom but without schematics. regards Nigel GM8PZR ************** _______________________________________________ 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.
