Tuner am reception problem

[philv]

I have a couple of tuners here.
Both pick up half a dozen fm stations.

Neither pick up a single am station.
They just scan endlessly.

I am using a small plastic loop antenna normally supplied with tuners.

What am i doing wrong?

I am sure my marantz receiver picked up am stations.

One of the tuners is a 20 year old sony rds.
The other is a 30 year old digital yamaha.

Thanks