Upgrade & Experiments with an Agilent 8445B Auto Preselector – Giveaway! (April 2020)

In this episode Shahriar retrofits a vintage HP 8445B Auto Preselector for testing and characterization of high-performance data converters and oscilloscopes. The Preselector is in essence an electronically tunable band-pass filter with exceptional tuning range and quality factor.

After examining the schematic and block diagram of the instrument the unit is equipped with additional potentiometer, low-band, high-band switch and a voltmeter LCD screen which displays the center frequency. The modifications are applied to the front panel as well as internal circuitry to enable manual control of the preselector without the need for any external devices.

The modified instrument is used to measure the harmonic improvement of a 20GHz synthesizer. Several oscilloscopes are then characterized using the new preselector to determine the absolute performance of their internal data converter.

Finally, it is also time for a new giveaway! A brand new Keysight DSOX1102G scope! Patreon supporters are automatically enrolled.


  1. Hey I’d like to enter the draw!

  2. Nice work there.

    I’ll go for the draw too.
    Certainly would be in a good home and used.

    Where you at U of Toronto by any chance?


  3. rick says:

    Very useful modification of the 8445b, essentially creating a new measurement tool !
    Are there modern instances where the “Knob” function would be varied automatically and
    remotely to automate the measurements of the scopes that you have discussed ?
    Say, with some “tracking” signal, from a swept Sweeper,
    while swept ? Thank you for this instrument suggestion !
    — What is the value of the blue Burns Pot control ?
    Please enter me in the draw.

  4. jeff says:

    Thanks for the great videos.
    Please enter me in the draw.

  5. Gavin Jacobs says:

    Nice adaptation of an otherwise limited instrument.
    Please enter me in the draw.

  6. kurt says:

    Very interesting video for an instrument I wasn’t familiar with. Thanks! Please enter me in the ‘scope draw.

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