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, bruce.griffi...@xtra.co.nz 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 ewkeh...@aol.com 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, > jmi...@pop.net 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 artifacts and 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 ) to lock the two > oscillators in quadrature and amplify the resulting baseband output. 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 -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.