TV is another kettle of fish entirely ......
number 1 biggest cause of poor signal is the booster. easy check if you can swing a multi meter, turn on booster, get up on the roof with your multimeter, remove the coax terminal from antenna measure across the centre pin of the van side to the outside nut of the cable with DC volts on the multimeter, you should get around 12v or more (centre wire positive), no volts booster is probably cactus ..... or..... some twit at a factory has connected it wrong, test the external feed socket for caravan parks, if you get volts there then it's connected wrong, also check any other outlets. a Splitter upstream from the booster can be a culprit as well. I don't think i've ever seen 2 vans wired the same ........
broken connectors on the back of the booster are another fault, and the one under the wineguard (yes there's one there as well) are a deadset bugger to fix (wineguard base has to come off ..... if your lucky ..)
if your still hunting gremlins with no volts to the antenna, disconnect coax wires on back of booster ( so we don't blow it up!) short the connections together at the antenna (connect centre pin to outside with a piece of wire, go back to booster and test continuity of outside to inside of cable, should be a full tone on the meter or very low resistance
no tone = broken connection somewhere ( hint it's always the last place you look)
I could go on and on .... but it usually comes down to a lot of fault finding and knowing where to look
One other thing .... maybe i should make a post for this seperate, but a handy little app if you have a apple device is "antenna mate" (costs a small fee) but it will show you which way to point the antenna to get a signal ..... worth the purchase ..