• Ultralow Noise Tester: 9V Battery vs 7805 vs LTZ1000

    From Mike Monett@21:1/5 to All on Wed Apr 13 17:02:07 2022
    Marco Reps has an interesting article on low noise amplifiers:

    Ultralow Noise Tester: 9V Battery vs. 7805 vs. LTZ1000 https://www.youtube.com/watch?v=XpbDMo8an5w

    - uses ADA4523: $3.030 Mouser, Digikey, 4.2 nV/sqrt(Hz), RRIO, 100pA Ib
    - Datasheet https://octopart.com/search?q=ada4523

    Cross-correlation would improve noise floor. Hard to get down to
    Gerhard's level, but maybe doable.

    1. Here is a brief explanation of how cross-correlation works:
    "Understanding Phase Noise - the Cross Correlation Method"

    https://www.youtube.com/watch?v=Sf7qiysPFbQ

    2. The benefit of cross-correlation depends on how long you are
    willing to wait. From

    "TSP #162 Tutorial on Theory, Characterization & Measurement Techniques of Phase Noise"

    https://www.youtube.com/watch?v=SOHjFtw0sgo

    each 5db of improvement requires an order of magnitude increase in
    the number of correlations.

    dB 5 10 15 20 25 30 35 40
    N 10 100 1000 1E4 1E5 1E6 1e7 1e8

    So going from -180dBc/Hz to 220dBc/Hz would require 1e8 correlations.

    3. Nobody would wait that long. But how many correlations do you need?

    A commonly accepted figure is your measurement noise floor has to be
    at least 10 dB below the noise you are trying to measure. We could
    pad that by 5 db, which would require

    15 / 5 = 3
    1e3 = 1000 correlations. That is not too bad.

    4. It is interesting to note the Holsworth HA7062C Phase Noise
    Analyzer goes to a maximum of 1024 cross-correlations. 100 correlations (-10dB) takes 7 min, 9s at 10 MHz.

    https://holzworth.com/Portals/0/HA7062C_Web_Datasheet.pdf

    5. Finally, "Frequency Signal Source's PN (Phase Noise) Measurements
    Challenges and Uncertainty", by Ulrich L. Rohde, has some very
    important information on cross-correlation errors. This file is at

    https://www.mrmonett.com/pdfs/2015-IFCS-Rohde-Oscillator-noise.pdf




    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Anthony William Sloman@21:1/5 to All on Wed Apr 13 20:31:21 2022
    On Thursday, April 14, 2022 at 3:02:14 AM UTC+10, Mike Monett wrote:

    <snip>

    https://www.analog.com/en/parametricsearch/11010#/p4007=300n|2u

    https://www.analog.com/media/en/technical-documentation/data-sheets/ltc6655-6655ln.pdf

    It's quieter than even the LTZ1000. And quite a lot cheaper. I suspect that the LTZ1000 parts are only being made for the legacy market, where it's cheaper to pay through the nose for a drop-in replacement than it would be to change the board to
    accommodate something newer and marginally better.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)