I have had various antennas over the decades 300Ohm ribbons, full dipoles, bit of wire in specific places.. added on bits of wire.
The minimum for FM is of course 75cms long, no whip antenna on any FM receiver should be less than that for decent reception.
SW as long as you like, used to throw 10m up a tree for 6200-6400 Sunday morning listening.
I used a 40m band dipole (20m) long 2m above ground for some Dutch pirate listening worked great.
I have a Tecsun with a 0.75cms whip and 0.75cms piece of thin copper wire glued onto the plastic just below the whip as it terminates onto
the radio (screwed in) hanging down it seems to add 2-3dB gain on reception.
Also try 1.875m which is 5/8 of a wavelength on the FM broadcast band, that is sometimes better than 1/2 wavelength or 1/4 wave length.
And sometimes loop the top wire into a 7-10cms loop if it is stiff enough and tape it, at the top, that can also seem to help like a capacitor hat.
If you like signals you mess around with wires, it is part and parcel of the radio game.
All about the bits of wire.

I like coming over here as I am not finding that RN is a reliable site. Common sense suggests spreading things out a bit and not putting all eggs in one basket.