  We study dynamics of electrons in a magnetic field using a network model with
two channels per link with random mixing in a random intrachannel potential;
the channels represent either two Landau levels or two spin states. We consider
channel mixing as function of the energy separation of the two extended states
and show that its effect changes from repulsion to attraction as the energy
separation increases. For two Landau levels this leads to level floating at low
magnetic fields while for Zeeman split spin states we predict level attraction
at high magnetic fields, accounting for ESR data. We also study random mixing
of two degenerate channels, while the intrachannel potential is periodic
(non-random). We find a single extended state with a localization exponent
$\nu\approx 1.1$ for real scattering at nodes; the general case has also a
single extended state, though the localized nature of nearby states sets in at
unusually large scales.
