From: Dr Bruce Griffiths <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Fury Realhamradio listing Date: Sun, 29 Apr 2007 17:20:03 +1200 Message-ID: <[EMAIL PROTECTED]>
> [EMAIL PROTECTED] wrote: > > They can get 0.1ns resolution on the printout because of averaging. I > > don't > > know what their native granularity is. > > > > Single shot resolution may not have such a significant impact since the > > GPS > > used in the Z3801A is so much worse than the M12+. > > > > Our resolution is more coarse than 100ps, but our inherent GPS noise is > > very > > significantly lower than the Z3801. Resolution of 100ps with a peak to peak > > > > noise of 100ns or more is not as good as peak to peak noise of 31ns with > > RMS > > noise of <10ns. > > > > So even if they have true 100ps hardware resolution (I somehow doubt it > > since an expensive 54132A only has 150ps resolution) then that's more than > > two > > orders of magnitude less than their sawtooth noise - does it really matter > > at > > that point? > > > Said > > Obtaining 100ps resolution, particularly when one is only making 1 > measurement per second, is relatively easy and inexpensive to do with a > few discrete components. Indeed. Three-four transistors and a handfull of caps and resistors. The Z3801A uses the 10 MHz clock and thus require a x1000 interpolation, which is easy enought to acheive. Look at the HP5335A service manual for further details. What you do is that you stretch the error-pulse (1-2 cycles) by charging a cap with one current and discharging it with another, the output is then run into a comparator for the sake of gain. This stretched pulse is then measured with the coarse clock and voila! Cheers, Magnus _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts