  In this note we give a new construction of the N=2 superconformal algebra
using currents of the affine superalgebra $\hat{sl}(2 | 1)$ and free bosonic
fields, and also the N=4 superconformal algebra without central charge in terms
of currents of $\hat{sl}(2 | 2)$ and free bosonic fields. Arguments on
commutants and invariant subspaces are added.
