I see someone has commented about the splitters and such.. Forget that. If you get ANY channels. then you have a good cable between tailgater and receiver, no splitters or the thing would not work at all.
Dish HD depends on where you are parked. Dish network for many years used two Satellites locatec over the equator at 110 and 119 degrees west.> As I recall w/o looking 110 is kind of close to the California coast.. 119 is farther west, and 127. Well that is even farther.. So if you are on the east coast that is kind of close to the horizon.. Putting it on the roof MIGHT help... or not.
There is an east coast alternative,,,,, However.... the Tailgater is not set up for it.
Finally, though you have a straight coax between ANTENNA and RECEIVER.. it is likely low end RG-59 Which is a high loss cable, Quality RG-6 is the specified cable.. or RG-9, and I would not recommend RG-9 (Big Thick Heavy Cable that will tear the connectors off the receiver and antenna if moved.. Which is why RG-6 is recommended).