That is actually a good question because signal drop outs have always been severe on AM HD radio stations. During the daytime CHLO is 10 watts digital. The closer to Ashgrove (near Georgetown) you get, the more solid the digital side of the broadcast becomes. Their daytime power is higher than their night power in both standard AM and HD. It always takes a few seconds for the digital to decode.
A very limited number of former AM only stations in the United States now use the 100% digital mode without the analog. These are supposed to be technically superior to the hybrid broadcasts.