Can I default to SD channels?

When I record shows I usually prefer to use SD instead of HD since it takes up less space on the DVR. But even if I punch in an SD channel number (e.g. 124 for Smithsonian) I'm taken to the HD channel if one exists (915 for Smithsonian). I can set up the recording there but I have to remember to change the options to "SD preferred" or it will be recorded in HD. Is there some setting where I can stop going to the HD channel when I ask for the SD channel?