While not really a repair,but more of a question.

Why is it that I have one of the portable receivers with a whip antenna
that is about 2 feet long and can receive very well the short wave
stations, but my ham receiver with a couple of feet of wire on the back
receives almost nothing. When I hook the normal antenna to it, it
receives vey well. The signal generator shows the sensitivity is very
good. It is not just one ham receiver,but several.

My theory is that the portable receiver is matched for a high impedance
short antenna, where the ham receiver is matched for a 50 ohm antenna.