[time-nuts] Phase noise measurement (Levinzon cite)

[Joseph M Gwinn]

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.


time-nuts-bounces at febo.com wrote on 08/21/2010 08:03:46 AM:

> From:
> 
> EWKehren at aol.com
> 
> To:
> 
> time-nuts at febo.com
> 
> Date:
> 
> 08/21/2010 08:04 AM
> 
> Subject:
> 
> Re: [time-nuts] Phase noise measurement (Levinson cite)
> 
> Sent by:
> 
> time-nuts-bounces at febo.com
> 
> 

> 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.griffiths at 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
> 
> EWKehren at 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,
> > jmiles at 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  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
> >
> >
> >  _______________________________________________
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> 
> 
> 
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