This is a security add-on for any Spectrum Analyzer. It is widely used in EMI-precompliance testing. And yes, as we don't want to re-invent the wheel, this is strongly inspired by the Hewlett-Packard hp 11947A.

The design was strongly inspired by the hp 11947A. We just ported the attenuators to an E24 value. The overall dielectric strength is slightly lower (we used 75V Gas Discharge Tubes), but still acceptable for homebrewing. We therefore squeezed all in a Sucobox which has a cute formfactor. The Frequency Response measured with a hp8753 looks like this :



Frequency Response, S21 of the Transient Limiter

Summed up, it has an insertion loss of 12 dB - which is different from the usual 10 dB. But that's not a drawback, as the matching is very good up to 1 GHz / 2 GHz.

The Power handling is somehow lower than the Hewlett Packard type, but the goal is to protect the Spectrum Analyzer. Goal achieved !

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