If your receiver has binding post terminals, AM & GND, try connecting the GND to a cold water pipe and running a single wire to the AM terminal.
At 1000 KHz, a 1/4 wave will be 75 meters (multiplied by a velocity factor of .75 to .95), so you will be hard pessed to make the wire too long... experiment with placement and length to see if you pickup more signal or more noise...
A bit more sophisticated... make your own loop from about a 1/2 wave length of insulated wire. (about 150 meters * 0.75). Plastic plumbing parts can be used to make a frame... Google "crystal radio" to start a search for dimensioned plans. Here is a
Example Link