We just use an antenna from a car stereo place, and for the tracks with FM, it's all good almost anywhere. You just have to put it on the
outside of the aluminum metal Faraday cage (your trailer).
I found that the brand of radio makes a huge difference. I had a Sony in our trailer and couldn't pick up squat. Talked to a car stereo guy and he said Pioneer has the best tuners, by far. Switched to a cheap one of those, and it picks up anything.
There are a couple of local tracks that still use AM, and holy cow, you can't pick that up unless you're standing under the speaker for the PA
Turn your generator on (or your neighbor does), and you're screwed too. Haven't found anything that works for those.
And Rick's right about the directional antennas. I think they're outbound, not inbound.