Hi Nice data !!!
Thanks for posting it. Bob > On Oct 3, 2016, at 1:29 PM, Adrian Rus <[email protected]> wrote: > > Hello, > The setup is the following: > make name type > level/attenuation > Tesla [?] T284 SWR > bridge > Rohde & Schwarz SMIQ 03 Generator > +10dBm > Rohde & Schwarz FSP 13 Spectrum > Analyzer > Agilent N9355B Power limiter > -0.98dBm@10MHz > > The notch filter attenuation @10MHz and @10dBm input is the following: > Att [dB] delta f [Hz] > 90 0.0 > 80 0.1 > 70 0.6 > 60 1.6 > 50 4.3 > 40 12.7 > 30 40.6 > 20 131.5 > 12.76 569.2 > 12.22 904.1 [this is the far out attenuation of the > setup] > > Disclaimer: I am not an advocate of this [notch filter] PN or PN+AN > measurement method. I just have the idea of compensating a SWR bridge having > on its DUT port an XC by a resistor at its reference port and I was amazed by > its simplicity [compared with other notch filter setups]. For the particular > XC I have used, the VSWR is not top notch as the XC proved to have some 15ohm > series resonance. So, losses given impedance mismatches shall be considered > [@ the 12dB far out attenuation of the setup]. > I have no deep knowledge about XCs at all and very little about their close > in noise [I can extend why, in private emails]. If this setup is useful for > somebody, it is fine. If not, it is also, fine. Do not shoot [on] me for > posting these findings. > Best regards, > Adrian > > > ________________________________________ > From: time-nuts [[email protected]] on behalf of Bob Camp > [[email protected]] > Sent: Monday, October 03, 2016 12:17 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] notch filter for close in phase noise measurement > > Hi > > If you do a power sweep on a crystal resonance, it’s a very predictable sort > of thing. > Essentially you “chase” the resonance up (or down) in frequency with the > sweep. At some > point, it “snaps” and drops back to the low power line. I suspect that what > is being observed > is the “snap” as the crystal stops accepting power. > > In some crystals, you can get a very observable effect at a few hundred > microwatts. With > other designs it’s 10’s of microwaves or maybe even up around a milliwatt. > > Liquid nitrogen cooled crystals anyone? :) > > Bob > >> On Oct 2, 2016, at 4:49 PM, Chuck Harris <[email protected]> wrote: >> >> That is a most interesting suggestion. >> >> Suppose the filter crystal was pulled to the DUT frequency, and due >> to the inertia of its very high Q, was able to show you the phase noise >> variations of the DUT better than one might expect? >> >> -Chuck Harris >> >> >> Bob Camp wrote: >>> .....One thing you may be seeing is the crystal shift frequency as it is >>> tuned to “accept” power from the source. >>> With milliwatts of power flying around, that would not be unusual. >> >> _______________________________________________ >> 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.
