The prototype - mounted in a Sucobox

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.

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.

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