ML 320 Radio

My '99 ML320 has a standard radio (Panasonic) and the reception on the AM band is poor.
On a very strong station it is fine but on a moderate or week station the sound is very full of static and hissing.
Is there any objective way of measuring the reception and noise elimination ability of the radio and is there some kind of standard.
The dealer simply tunes in a local station and says the reception is fine.
This seems to me to be a rather subjective approach.
One other indicator of the poor performance is that in comparison to my 1990 Jeep's really cheap radio, the AM reception is better.
Any advice would be appreciated.