  Weighted discrete Hilbert transforms $(a_n)_n \mapsto \sum_n a_n
v_n/(z-\gamma_n)$ from $\ell^2_v$ to a weighted $L^2$ space are studied, with
$\Gamma=(\gamma_n)$ a sequence of distinct points in the complex plane and
$v=(v_n)$ a corresponding sequence of positive numbers. In the special case
when $|\gamma_n|$ grows at least exponentially, bounded transforms of this kind
are described in terms of a simple relative to the Muckenhoupt $(A_2)$
condition. The special case when $z$ is restricted to another sequence
$\Lambda$ is studied in detail; it is shown that a bounded transform satisfying
a certain admissibility condition can be split into finitely many surjective
transforms, and precise geometric conditions are found for invertibility of
such two weight transforms. These results can be interpreted as statements
about systems of reproducing kernels in certain Hilbert spaces of which de
Branges spaces and model subspaces of $H^2$ are prime examples. In particular,
a connection to the Feichtinger conjecture is pointed out. Descriptions of
Carleson measures and Riesz bases of normalized reproducing kernels for certain
"small" de Branges spaces follow from the results of this paper.
