There is a critical typo below: The author's name is "Levinzon", not "Levinson", the s becoming a z. The rest of the cite is correct.
[email protected] wrote on 08/21/2010 08:03:46 AM: > From: > > [email protected] > > To: > > [email protected] > > Date: > > 08/21/2010 08:04 AM > > Subject: > > Re: [time-nuts] Phase noise measurement (Levinson cite) > > Sent by: > > [email protected] > > > On all phase noise measurements I use AGM batteries. specially for the > signal source to be measured. Keep six 12 V batteries for that > around, every > thing from 7 to 20 Amps. > Bert > > > In a message dated 8/21/2010 7:33:57 A.M. Eastern Daylight Time, > [email protected] writes: > > The Wenzel Audio amp is a little noisier than it need be and it has a > poor PSRR, so that a very low noise power supply with low ripple is > essential. > Its not too hard to improve the PSRR and the input noise of such a > current feedback amplifier. > > There are JFETS (IF9030) with similar noise floors and significantly > lower flicker noise. > However the minimum order from Interfet is about $250. > For noise measurements on several JFETS (including the IF9030 and the > 2SK369) see: > "/Ultra-Low-Noise High Input Impedance Amplifier for Low-Frequency > Measurement Applications/" > Felix A Levinson, IEEE Transactions on Circuits and Systems > Vol 55 No 7, > August 2008 pp1815-1821. > > Bruce > > [email protected] wrote: > > Hi > > I have the Hp phase noise system with the 35601A but use > most the time > the > > Wenzel Audio Amp referred to in this email. Perfect! I drive with it a > > 3561A and a 7L5! Works for me. The only problem is > getting any more > 2SK369. > > Any recommendations? > > Thanks Bert Kehren > > > > > > In a message dated 8/20/2010 6:54:05 P.M. Eastern Daylight Time, > > [email protected] writes: > > > > > > > >> Would anyone else like to suggest a known good low phase noise > >> buffer amplifier? Maybe something from a Fred Walls paper? > >> > > You can always build HF isolation amps by rigging MMICs and > attenuators > > together, but this will not reliably get you below -160 > dBc/Hz. Bruce > G. > > has given some good advice in this regard, with some > circuit designs > at > > http://www.ko4bb.com/~bruce/IsolationAmplifiers.html and elsewhere. > I'm a > > fan of this version (also from Bruce): > > http://www.ke5fx.com/norton.htm > > > > This one has the advantage of simplicity. No weird parts, > nothing that > is > > likely to be out of production or hard to find, and dirt cheap. I've > > measured the broadband floor at near -170 dBc/Hz at 10 MHz, and its > noise > > contribution at 100 Hz is below what the 3048A can see. > These figures > are > > adequate to measure any 10811-class OCXOs. > > > > A practical PN measurement system for 10811-class oscillators can be > made > > by > > building two of those amplifiers and using them to drive > pretty much > any > > random double-balanced mixer found on eBay with +10 dBm LO specs or > more. > > Both ports should be driven strongly to reject AM artifactsand avoid > > degrading the excellent noise floor offered by the amps. > I'd hit the LO > > port with +10 to +12 dBm and the RF port with at least 0 dBm. > > > > Then, see the Wenzel app note here ( > > http://www.wenzel.com/documents/measuringphasenoise.htm ) tolock the > two > > oscillators in quadrature and amplify the resulting basebandoutput. > Any > > of > > several sound-card FFT programs can be used to generate an > output graph, > > although if you want absolute calibration in dBc/Hz you need to be > prepared > > to sweep the actual test setup from mixer output to FFT > input to watch > for > > various sources of flatness error. > > > > A combination of an AD7760-EVAL board and a Digilent Nexys2 > can be used > to > > construct an excellent baseband digitizer for the DC-1 MHz > spectrum, but > > most of the time a good-quality 192-kHz sound card is fine for this > sort of > > work. Most good crystal oscillators reach their broadband > floor by 10 > kHz, > > so there's no real need to go out to 1 MHz or more. > > > > -- john, KE5FX > > > > > > _______________________________________________ > > 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.
