I too use a tap to reduce the output of the device under test to acceptable levels for the test instrument.? I found a reference with all of the parts listed to make the tap, including the metal case for it.
One point I would make on the tap, be sure to run a characterization test (I used a NanoVNA for that test) to ensure a flat response over the frequency range in question.? I found that I needed to increase the capacitor specified to get a flat response (within 1 dB).? Ultimately I used a combination of capacitors that I had on hand to get the best match.
Just my 2 cents?
73
Evan
AC9TU
