There are currently two fading model blocks that are usable in 3.7
both should show up in GRC - or from python you can use:
the flat fading model:
channels.fading_model( 8, 10.0/samp_rate, False, 4.0, 0 )
where args are {# sinusoids, fDTs, los_component, rician_factor, prng_seed }
and a simple frequency selective fading model combining N flat fading channels of a fixed PDP:
channels.selective_fading_model( 8, 10.0/samp_rate, False, 4.0, 0, (0.0,0.1,1.3), (1,0.99,0.97), 8 )
where args are {# sinusois, fDTs, los_component, rician_factor, prng_seed, power_delay_profile_delays_samples, power_delay_profile_amplitudes, max_channel_taps}
-Tim