HMC472 Digital RF Attenuator Module DC-3.8GHz Parallel 0.5dB Step 31.5dB Attenuation Value

FYI, This unit worked perfectly as is when I tested it at 100MHz. It follows the evaluation board parts list from the data sheet. To use this for HF I changed C5 and C6 to 1.0uF. Also C1 - C4 were changed to 0.01uF. I decided to also remove the header, put 0.01uF on each of the control lines V1 - V6, and attach a ribbon cable for external control. I also trimmed the top edge of the board about 1/8” to fit it into an RF tight enclosure (see picture) and removed the solder mask on the bottom of the board for good grounding to the enclosure. That last part isn’t absolutely necessary for use at HF but I chose to do so. Note that the control lines are active low. They work fine with 3.3V signals. The pins opposite V1 - V6 have 5V on them. Hope this info helps. K4SDR.