OTA channelsthrough an AM21

I take my home receiver with me in my RV and also have an AM21 to receive OTA channels. What I would like to do in some cases is connect the cable tv that the campground has and record it on my directv receiver. This should work except when you enter the zipcode for the location it only list the channels that you would get over an antenna. I would like for it to see channels 1-69. I am not so concerned about the scheduler. Has anyone ever done this? I would think that directv probably has a test zipcode that would see all these, but I am not sure if I would ever get the information by a phone call to them. I am pretty sure that the format for the campground cable and OTA antenna channels are the same.

Does the campground have actual cable tv. Or is it distributed OTA TV (perhaps with a few extra cable channels inserted).