Hello Sebastian,
There are a couple of good routes to go for better AM Broadcast reception.
1. You could buy a quality AM portable such as the GE Superadio II on Ebay
for $50 > $80. Use a 12V DC adapter so you can run off the trailer
battery.
http://mysite.verizon.net/vze20h45/radio/s...r_tech.html#N5A
There is a current Superadio III but its performance is slightly inferior to the
previous model.
Almost forgot about the C.Crane CC Radio Plus. It is a good radio with pretty good sensitivity on AM.
I have one, but the tuning mechanism went out after about a year and will only tune down now.
That is why I am not too anxious to recommend it.
2. Get a good car radio and put up a good antenna. I have found that the
older (early 80s) car radios with analog tuning make a better radio for tuning around
finding weak stations because you can tune slightly off the station. I like the old analog radios from Toyota which are
quite sensitive, AM/FM Stereo and cost $10-20 when they come up occasionally on Ebay. For
an antenna you might consider a bumper mount 8' CB whip with a quick coupling
to remove it for travel.
Hope this helps you. Larry H
Larry .