Hi If you are doing direct measurements on a 10 MHz signal *and* counting on the expanded frequency resolution of a 53131, that’s not going to work. There is an HP app note somewhere that explains why in great detail. The quick read version is that the sampling process falls apart.
Bob > On Jan 21, 2020, at 4:49 PM, Taka Kamiya via time-nuts > <[email protected]> wrote: > > I'm not the OP but I was just throwing some ideas about cheap way to > distribute. > But the responses were very timely. I am, indeed, using HP53132A, RG58, and > were doing ADEV measurement of a 10MHz signal. I have my answers already so > I won't go into details but I was seeing some explainable indications. It > might very likely be leak from or into the reference/input. I will use > double shielded and phase stable cables and see if I can eliminate the issue. > > Thanks a-bunch! > --------------------------------------- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > > > On Tuesday, January 21, 2020, 4:27:26 PM EST, Bob kb8tq <[email protected]> > wrote: > > Hi > > If all you are doing is driving a 5335 and running at 1 second gate times, > then there’s not > a lot to worry about. If indeed you are multiplying this or that up to X band > for various purposes > then ….. that’s different. Both are in the “hobbyist” range. > > Spurs matter for some things and don’t matter much for others. A spur at -120 > at 10 MHz > may be up around -60 db at 10 GHz. It might matter there … it might not. A > -60 db spur > at 10 MHz gets into the “yikes” range if directly multiplied. > > How big is your bench? How long are your feed cables? You are getting into a > significant > fraction of a wavelength at 10’ of cable. If unterminated (and / or poorly > shielded) it will spray > a bit of RF. > > Lots of details and no single answer without digging deeper into what you are > trying to do. > > Bob > >> On Jan 21, 2020, at 4:06 PM, Bryan _ <[email protected]> wrote: >> >> On the point of using a MDA-3V at the hobbyist bench level, any issues that >> one needs to be concerned about. A few modification projects online, but >> none really comment on any issues or performance. >> >> -=Bryan=- >> >> ________________________________ >> From: time-nuts <[email protected]> on behalf of Bob kb8tq >> <[email protected]> >> Sent: January 21, 2020 7:57 AM >> To: Taka Kamiya <[email protected]>; Discussion of precise time and >> frequency measurement <[email protected]> >> Subject: Re: [time-nuts] Simple GPSDO Multiple Outputs - buffered line >> driver options? >> >> Hi >> >> Cross talk between the reference in and the measured signal on the 53131 >> series can be an >> issue . The counter drops resolution in the vicinity of 10 MHz as a result. >> There is also an issue >> with the sampling process rather than direct feedthrough. >> >> If you are measuring things like phase noise, having a lot of 10 MHz running >> around the lab will put a >> spur in the phase noise plot. It may be close enough in that you don’t >> notice it every time. The same >> sort of spur will play nasties with things like ADEV measurements. Getting a >> 10V RMS signal down >> 120 db is tough … >> >> Finally if you happen to be playing with radios, WWV is at 10 MHz. It does >> not take a lot of reference >> signal to get back into the typical receiving antenna. >> >> ====== >> >> If you are daisy chaining counters, there are several ways to do it: >> >> 1) Drive the “ext ref in” and daisy chain off of “ext ref out”. This way the >> signal is buffered at each device. >> It may add a bit of noise, but you can go a long way doing this. >> >> 2) Put a coax Tee connector at each instrument. If the device is high Z in, >> this can do ok. If it is a 50 ohm >> termination all the time … not so much. Even with the high Z input it’s >> better for short runs than long ones. >> >> 3) Mix the two approaches. If you have a variety of gear, use the ones with >> ref in / ref out as buffers. String >> the other gear in-between those boxes. >> >> Bob >> >>> On Jan 21, 2020, at 10:27 AM, Taka Kamiya via time-nuts >>> <[email protected]> wrote: >>> >>> I've tried daisy chaining 4 HP5335A. By the time signal got to the 4th >>> box, it was too weak to reliably drive the 1 pps. I had a terminator at >>> the last tee with short length of RG58s between boxes. I guess some box >>> puts relatively heavy load on the signal? >>> >>> I'd like to know why 10V is a bad idea. (besides too close to the upper >>> limit) Cross talk between what/where? >>> >>> To OP:I have video amplifiers Extron MDA-3V successfully used for this. 1 >>> port in, 3 ports out ones by Extron are very inexpensive at 10 dollars+/-. >>> I never did formal testing but reading on all counters matched exactly. >>> They are 75 ohms but it didn't matter in my use case. You can >>> change/adjust internal resisters if you are concerned. >>> >>> --------------------------------------- >>> (Mr.) Taka Kamiya >>> KB4EMF / ex JF2DKG >>> >>> >>> On Tuesday, January 21, 2020, 7:45:22 AM EST, Bob kb8tq <[email protected]> >>> wrote: >>> >>> Hi >>> >>> What are you driving? >>> >>> Most “normal” gear is pretty happy with a fairly wide range of input >>> levels. Obviously things >>> like termination and long lengths of coax can get into the act. For 4 >>> outputs, a passive splitter >>> with 6 db of loss should do just fine. You have only taken the output >>> voltage down by 2:1 …. >>> >>> Just for reference: >>> >>> https://www.avionteq.com/Document/53131A-specification-sheet.pdf >>> <https://www.avionteq.com/Document/53131A-specification-sheet.pdf> >>> >>> Calls out a 200 mv to 10V RMS input level as acceptable For a variety of >>> reasons, 10V RMS >>> is a really bad idea (cross talk ….). Lower is better in this case. >>> >>> Bob >>> >>>> On Jan 21, 2020, at 4:19 AM, skipp isaham via time-nuts >>>> <[email protected]> wrote: >>>> >>>> Hello once again to the Group, >>>> >>>> May I ask what the current relatively simple options are for >>>> expanding a Thunderbolt or equivalent... output for distribution >>>> to multiple devices? >>>> >>>> Although I expect only two or three isolated / buffered outputs >>>> will be required in my example. I'm worried about signal level >>>> if a passive system (Mini Circuits divider or equivalent type) >>>> is used. >>>> >>>> Would appreciate a few quick opinions on what is practical and >>>> seems to work well. >>>> >>>> thank you in advance >>>> >>>> regards, >>>> >>>> skipp >>>> >>>> skipp025 at yahoo dot com >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
