On opening up the unit I was mystified by the values used for four of the PADS. The parallel and series values appeared to have been transposed in error. I reworked these values using standard nearest value resistors.
The switches are in excellent condition with no signs of wear. As can be seen from the linked spreadsheets below, I tested the attenuator over the HF frequency range only. A maximum of 0.1dB insertion loss was observed at 28MHz.
The worst case error observed was +0.4dB for the 16dB PAD.
With all PADS switched in to yield a maximum attenuation of 71dB the maximum error was 0.8dB at 10MHz.
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Pi Network Resistor Values, dB(calculated), Return Loss (calculated)