The HamStick dipole has already been mentioned.

Another HamStick or mobile antenna option is to use a single antenna with as 
many ground radials running along the railing and the balcony floor as 
possible. Some of these won't be resonant anywhere in particular, but that's 
okay.

I did this briefly with an old hustler mobile antenna at the same apartment 
where I ran the wire I described previously.

On 40 and 20 meters, the wire worked much better.



Mike Duke, K5XU
American Council of Blind Radio Amateurs