The NBC Mux is not intended for South America. It an "internal" mux feed for SNG News operations, i.e. net return, prompter, channels of specific interest to field correspondents, etc. Weather Channel is owned by NBC Universal, hence its inclusion in the mux.You can pick it up on 72W. It is one of the NBC MUX feeds on ku band, but it does not come in all the time. I only get it sporadically. As I understand, these feeds are intended for South America. I'm getting them in SC. There are four NBC MUX feeds. I usually get the Weather Channel on the channel 3 feed.
Happy satellite hunting!!!