[time-nuts] Thunderbolt - any negatives ?

Paul Christensen w9ac at arrl.net
Fri Jun 19 12:38:17 EDT 2009


> "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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