); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY From: "CHazlitt" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] time-nuts, frequency counters Date: Wed, 26 Sep 2007 13:41:30 -0800 Message-ID: <[EMAIL PROTECTED]>
Hi! > I just joined the group a couple of weeks ago and have one remark about an > HP counter that I bought on ebay and also one question. The HP 5386A I own > incorporates a 12-character display which works out wonderfully when using > the 10 MHz output of a Rubidium source to clock the counter. The one I > bought goes up to 3 GHz but there is a less expensive version of the same > thing which although doesn't go to 3 Gig, has the same resolution. I found > this unit to be a great way to compare the Rubidium's frequency with an HP > GPS clock source. The cheaper ones is the HP 5384A (50 Hz - 225 MHz) and HP 5385A (50 Hz - 1 GHz). > I bought a Frequency Electronics FE 5680A Rubidium card on ebay too and > found that when comparing it's output at 10 MHz to the output of the HP GPS > standard that they did not agree when comparing the two using the above > mentioned HP counter (using the HP GPS as the clock for the counter). The > Rubidium I purchased is a few years old but locks up every time in just > three minutes so I know it is in good shape but yet it didn't agree to > the -9 on the frequency counter. > > So, here is my question, do Rubidium standards drift that much over a period > of years to where they have to be brought back on frequency? Yes. > If so, what is tuned on the Rubidium to do so, C-field? You can either tune the C-field or you can tune the synthesis-chain. For my old R&S Rubidium the synthesis-chain is fixed and the C-field is adjusted instead. Big vernier knob on the front and a CV-input on the back. > I didn't touch anything on the physics package of the FE 5680A but the unit > has a DDS divider built into it so I was able to adjust the Rubidium to agree > with the HP GPS standard through an RS 232 serial connection and hexidecimal > inputs to change the frequency of the dividers output. The divider they use > can adjust the frequency far finer than the best resolution of any Rubidium > standard so I thought that would be a good way to match the output of the GPS > standard. I think it is a good strategy. > I'm new to time standards, GPS or Rubidium units and purchased it for some > telecom work so I'd appreciate any suggestions or comments anyone here might > have. We tend to use time interval counters and the HP 5370A or HP 5370B is popular. Get once of those. > One last question in regard to counters. Is it possible, or does anyone make > a frequency counter which has 12 digits but only displays 1 Hz and below > regardless of the frequency which is fed into it? i.e. 1 Ghz reads out as > 1.000 000 000 00 (if on frequency) only displaying the last cycle of the > count down to -11 ? I have counters which display more digits than 12 if needed. Also, for stable sources we use spaced time-interval measures and plot those over time. We time-nuts seems eager to calculate our Allan Deviation charts, mumble obscuria about not optimal here and there... and for tau this and that you would have to consider... :) Welcome to the group! > Thanks for the bandwidth You didn't waste any bandwidth, but you did use up some bits. Not the same! :) (time-nuts are notorious nitpickers too!) Cheers, Magnus _______________________________________________ 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.
