Hi On a normal 10811, you should see at least +/- 1 Hz change. It should go from 10,000,001.xx to 9,999,999.xx. That of course assumes the counter reference is right on frequency. Since it may not be, it's the 2 Hz delta between +5V and -5V you need to spot first.
Right now you data shows < 0.1 Hz. Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Howard Sent: Thursday, November 15, 2012 9:57 PM To: WarrenS Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] getting a grip on 10811 drift (trying to read my instruments) You all were right, my targeting of the 50 ohm resistor across the oscillator output does not seem to have solved the problem. A good thing to do, probably, but not the answer. While I was all excited about the resistor change I also mapped out the control voltage (EFC) vs frequency change. I wrote it out but didn't pay much attention. Now I've been pondering over that a bit. My next theory is that my EFC maybe isn't really doing very much. First I need to know if I am reading this right. My frequency counter is a Racal 1992 It reads 9.99999997^6 as I write. A total of 9 digits with a smaller "6" to the right. If I read this correctly, I'm looking at 9,999,999.97 Hz ? If so, then I've got an EFC problem. My EFC mapping looks like this (this was done before I adjusted the coarse control) -4.94 VDC 9,999,999.95 -3.70 9,999,999.95 -1.24 9.999.999.93 0 VDC 9,999,999.93 +1.21 9,999,999.92 +2.44 9,999,999.92 +3.67 9,999,999.91 +4.90 VDC 9,999,999.90 It doesn't look to me like I am getting anything like 1/2 hertz range using the EFC. If that's the case than my controller card is frantically steering but not getting the desired result. Or, if I'm reading it wrong, maybe that last digit is 0-5 meaning 1/2 a hertz and I am all wet (again). This particular oscillator came out of an old HP counter and I believe the EFC was wired to ground. So maybe the thing has never been exercised. Are there versions of the 10811 that don't have EFC guts inside? Hope I'm not boring you all to death. Chris w0ep On 11/9/2012 11:26 PM, WarrenS wrote: > Chris > > HP 10811 can't drift that much that fast unless something is near broken, or being connected wrong like gnds or PS voltage. > Check the operation of the oven. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.