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 <kb...@n1k.org> 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 _ <bpl...@outlook.com> 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 <time-nuts-boun...@lists.febo.com> on behalf of Bob kb8tq > <kb...@n1k.org> > Sent: January 21, 2020 7:57 AM > To: Taka Kamiya <tkami...@yahoo.com>; Discussion of precise time and > frequency measurement <time-nuts@lists.febo.com> > 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 >> <time-nuts@lists.febo.com> 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 <kb...@n1k.org> >>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 >>> <time-nuts@lists.febo.com> 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 -- time-nuts@lists.febo.com >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.