  An arbitrary qubit can be transmitted through a spin chain by perturbatively
coupling both communicating parties to it. Those so-called weak-coupling models
rely on effective Rabi oscillations between them, yielding nearly maximum
fidelity while offering great resilience against disorder with the cost of
having long transfer times. Considering this framework, here we address a 1D
non-symmetric channel connecting two spins, one placed at each end of it. Given
any pattern of nearest-neighbor coupling strengths, we obtain an analytical
expression that accounts for the effective long-range interaction between them
and study the interplay between transfer time and fidelity. Furthermore, we
show that homogeneous channels provide the best speed-fidelity tradeoff.
