You do not give many details about your situation.
E.g. Which transmitter you believe you recieve your TV from.
E.g. Examples of channels you are missing.
One possibilty is that for the best reception you had a 'grouped' aerial to recieve analogue channels which also recieved most of the pre-DSO channels OK but post-DSO some of the channels were moved out of the frequency range of your aerial.
NS, September 2012
