We classify graded simple Jordan superalgebras of growth one which correspo
nd to the so called "superconformal algebras" via the Tits-Kantor-Koecher c
onstruction.
The superconformal algebras with a "hidden" Jordan structure are those of t
ype K and the recently discovered Cheng-Kac superalgebras CK(6), We show th
at Jordan superalgebras related to the type K are Kantor Doubles of some Jo
rdan brackets on associative commutative superalgebras and list these brack
ets.