In a message dated 23/07/2008 00:15:51 GMT Daylight Time, [EMAIL PROTECTED] writes:
The 10MHz output seems, as far as my old Multifunction Counter is concerned, to be to 10.00000MHz within +/-0.00001 MHz. The display showing 10.00003 to 10.00004 MHz all evening. So, my guess is that my poor old counter is +/- 10Hz out, but that may be due to the age and non-calibration of my frequency counter over the years. Or... The Thunderbolt 10MHz output is moving up and down by 0.00001 MHz within a 10MHz band. This is where I start to get to grips with the spectrum analyser that a friend of mine lent to me. I hope... ------------- Hi Dave One of the problems with becoming a time-nut is that the first step, whatever that might be, is fatal. And after that it just gets worse:-) Unless your Thunderbolt is very unwell, which I doubt, it won't be moving anywhere near that much. Not only is the reference in your counter likley to be off frequency but it's also likely that the stability of the reference is much worse than what you're trying to measure, and this is where the downward spiral really begins. Earlier this year I bought an HP 53132A counter to give me the resolution I'd decided I needed and promptly used it to measure the 10MHz output of a Thunderbolt. The result was similar to what you're seeing and a great disappointment, especially as I didn't know at first whether to trust the counter or the Thunderbolt. However, using another Thunderbolt to drive the external reference input on the counter gave a very different result, and immediately any variation became just a few figures in the 10th decimal place. It turned out that the basic reference as fitted to the 3132A was fine to demonstrate that the counter was working, but that was it. If your counter will accept an external reference I'd suggest using the Thunderbolt for that and just trusting the results. However, if the figures you've shown represent the resolution limit of your counter then you may want to consider a counter with better resolution, still using the Thunderbolt as a reference of course, but just watch your balance as the downward slide continues:-) 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.
