  We study Whittaker vectors (and Jacquet integrals) in the generalized
principal series for a real reductive group. A functional equation for them is
obtained. This allows to establish uniform estimates for their holomorphic
extensions with respect to the continuous induction parameter. Finally, we link
the Whittaker vectors to Harish-Chandra's Whittaker integrals for which we then
prove uniform tempered estimates. This allows us to establish rapid decay for a
class of Fourier transforms on the space of Whittaker Schwartz functions.
