i have experience with converters. i even built one with eight crystal
sockets to cover several bands! just calculate the crystal needed to
cover whatever you want to hear. my advise is to keep your portable and
put your time into rigging an outside antenna for your car, perhaps a
modified cb antenna. the converters work but are a pain to calculate
what frequency you are on. the portable radio will beat it on
convenience and performance, no matter how cheap it is.