Jon Ogden wrote:
>
>At the present level of technology these sort of specs are either
>impossible or very costly to obtain let alone manufacture en masse.
>Sure, you could probably build one in the lab, but on the assembly line
>is a different story. So a compromise has to be reached.
>
It's a bit like the old automobile industry saying: "Cheaper, faster,
safer - pick any TWO."
Getting back to capacitors, remember that the 85C or 105C ratings are
external temperature, but what determines the lifetime is the
temperature of the inside. That is a combination of external temperature
and internal heating by ripple current.
By comparing 105C and 85C components that have similar size, capacitance
and voltage ratings, it seems that some of the difference is due to
down-rating the ripple current in the 105C components, to bring the
inside temperatures down. The rest of the difference must be due to
different construction and processing to withstand higher internal
temperatures.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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