Hi I have a 53230, but have not gotten around to looking at it’s PLL cleanup process.
Bob On Feb 17, 2014, at 2:38 PM, Tom Van Baak (lab) <[email protected]> wrote: > Bob, > > I'm wondering if you (or any else) has measured the PLL performance of the > 53230-series? > > I agree it will "clean up the crud" but this assumes the ext ref is dirtier > than the internal osc. > > What I found instead was that if you use a good external ref the PLL actually > makes it worse. This was very disappointing. The XO version of the counter > performed worse than the OCXO version even with a maser as the ext reference. > Did your reading of the schematic show a way to directly use the ext ref, > bypassing the noisy PLL? > > The other thing I found was that the ref out signal was a very polluted copy > of the ref in. > > /tvb (i5s) > >> On Feb 17, 2014, at 7:04 AM, Bob Camp <[email protected]> wrote: >> >> Hi >> >> If you dig into the schematics (when they supplied them … ): >> >> The external reference goes into a phase detector. It’s one of those digital >> ones that can lock up to many inputs. You could feed 3.33333333 MHz in as a >> standard input as well as 0.5, 1, 2.5, 5, and 10 MHz. The internal >> oscillator (or an internal oscillator) is phase locked to the external input >> through a fairly narrow analog loop. The idea is to clean up the crud on the >> standard line. >> >> With no external reference, the PLL drops out and you go back to what ever >> the local reference is. >> >> Yes there’s a little more to it than that and no the circuit is not exactly >> the same on every counter HP ever made. >> >> Bob >> >>> On Feb 17, 2014, at 7:55 AM, wb6bnq <[email protected]> wrote: >>> >>> Hi Mike, >>> >>> The most likely answer is when you select external time base for an input, >>> it disables the connection for the internal oscillator. The external input >>> signal is probably also routed straight to the reference output jack. >>> >>> However, it would be good to read the manual, as they usually cover how >>> those connections work. Otherwise, perhaps someone that owns one could >>> provide further insight. >>> >>> Bill....WB6BNQ >>> >>> mike cook wrote: >>> >>>> Something that must be simple to explain, but that I can't get my head >>>> round. >>>> >>>> I got a new 53230A. >>>> When first using it, I measured my T-Bolt 10MHz using the internal 10MHz >>>> timebase and it came up short of 10MHz, 9.999 998 5xx. I wasn't worried >>>> about it as the counter only has a TCXO internal oscillator. So I fired up >>>> my PRS10 and after leaving that on for some time, connected it to Ext >>>> Ref. , changed to the ext time base and measured again. This time >>>> 10.000.000.00x. Then I switched the two references, measuring the PRS10 >>>> against the T-Bolt. Again I got 10MHz down to the 11th digit. >>>> All that looked good so I have been using it with either the PRS10 locked >>>> to GPS, or the T-Bolt as the external time base. >>>> >>>> After leaving it on (but not inactive) for a month, I did an Autocal. No >>>> problem. >>>> I was wondering if that would have changed the internal time base >>>> frequency, but no, using that still gave similar figures to the above. >>>> >>>> So at that point I decided to measure the Internal TB against my >>>> reference. So I connected the Int. Ref. Out to channel 1, connected my >>>> PRS10 ref to Ext. Ref In, selected the EXT time base and found that the >>>> count was 10MHz dead on????? I don't get that at all. >>>> >>>> in summary: >>>> DUT against internal TB counts < 10MHz. To me that means that the >>>> internal timebase is a bit fast. Is that assumption correct? >>>> DUT against Ext.Ref counts 10MHz >>>> Internal TB against Ext.Ref counts 10MHz. If my assumption above is >>>> correct, the count should be greater than 10MHz, no? >>>> >>>> Can anyone shed any light on that? >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> 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. >>> >>> _______________________________________________ >>> 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. >> >> _______________________________________________ >> 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. > _______________________________________________ > 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. _______________________________________________ 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.
