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I also added a -5 V, 3 W switching supply for use with wideband opamps that I generally use for buffers. That supply (TDK CC3-1205SF-E) has a high switching frequency (700 kHz), is well-filtered, and resides in a soldered-up box with feedthru capacitors. Residual noise could not be detected on my spectrum analyzer without a low-noise preamp, with the only detectible peaks being less than 1 µV at 7 MHz. Now that’s quiet!

The Elrasoft USB interface board plugs directly into a wirewrapped fanout board that I made on perfboard for distribution of digital signals. I prefer double-row 0.1 inch headers since those are usable with mass-terminated cables. This board also has the driver transistors for the RF relays and attenuators that are part of a full S-parameter test set.

Below is an overview of the completed chassis, without the test set modules which are still in development. Interconnects are SMA jumpers that I got on Ebay--a really good deal--but watch out because a few of them had not been crimped!

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