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DIY-NoiseSourceBFR92.php    5678 Bytes    28-07-2022 19:25:20


A DIY Noise Source with a BFR92A


#1 - The construction details




DIY Noise Source BFR92A


The prototype - mounted in a Sucobox




✈ Circuit Description




This circuit uses a BFR92A (NPN 5 GHz wideband transistor) in a reverse biased configuration. From the 28 V at the BNC input, an LM317EMP generates a stable 9 V.

This is supplied via a lowpass (3.3kΩ, 1µF) to the emitter of the rf-transistor. The noise is taken from the base, beeing connected to gnd via two resistors. The collector is floating.

The coupling capacitor is a 100 nF (560L104YTRN, ATC 560L Series, Ultra-Broadband Capacitor from ATC / Kyocera AVX). It is used as a dc-block. At the output, a 10 dB attenuator (50 Ω, 1.7 W, DC to 18 GHz from Mini Circuits) shall guarantee a good matching, independant of the operation.




✈ Downloads








✈ Assembly completed - How does it work ?




Apply 28 Vdc via the BNC connector and verify, that the current consumption is around 14 mA. The Output of the Voltage regulator should be 9 Vdc. If your measurements are similiar, at least the bias seems working properly.

Further noise characterization can be found in the tab What's all this ENR stuff, anyhow ?

Yet easy to measure is the Impedance. Below, you see the S11 in off and on state, measured with a hp 8753 ES.


S11, off
S11, on




✈ Share your thoughts



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t1 = 6584 d

t2 = 310 ms

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