DaveC wrote in
al.net:

My brother is a serious SWL'er with a recent model of Drake SW
receiver. He listens exclusively to 30MHz.

He has asked me (the family electronics geek) what his options are for
an antenna on his balcony. (The management doesn't allow anything on
the roof of the building.) The balcony is a roofed 6 ft x 8 ft affair.

Is it possible to put a loop antenna, coiled inside the balcony roof,
each coil being supported, possibly, by a custom plexiglas support in
each corner?

Loops are not very effective above 5 MHz, and are inherently narrow band.
So called wide band loops (untuned) deliver low signal strength and need
amplification.

The best resort would be a very thin wire run where ever possible.