Improving portable radio performance

The performance of the average portable radio (not including the tiny plastic one and the huge ghetto blaster) is usually quite adequate for general domestic and portable listening. Unfortunately, for the more serious DX enthusiast, various limitations appear: however good the audio amplification may be, it can not improve an inadequate signal at the RF input, or a signal which is subject to heavy interference. All is not lost, and the 'RF pick-up' performance can be improved with some simple low-cost DIY construction. Simple as the suggestions given here may appear, the result can be quiet dramatic!