"The other issue is noise from a switcher."
And be mindful that some frequency-standard devices contain integrated DC-DC switching converters -- like my HP 58540A GPS-DO. The noise from the HP DC converters was spraying RFI every 100 kHz or so on the HF bands. After trying various RFI abatement measures, including additional bypass C and toroid-wound #31 ferrite material, my solution was scrap the entire PS board and bring in clean power from a triple-output linear supply made by Power-One. There's no switch-mode component anywhere in the path of my GPS-DO.
I love switch-mode devices for their light weight and package density; I hate them for their propensity to generate RFI and at least historically, their abysmal long-term reliability. That said, I do believe that recent SMPS product is significantly more reliable than those manufactured 10+ years ago.
Paul, W9AC
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