I like helical antennas, folks. Broadband, mechanically reasonably easy to make, rather compact and can be even made without large backplane (backfire helix). Catch both vertical and horizontal polarized signals which makes them good for scanners and resistant to polarization fading (important for satellites)
For terrestial work, circular polarization doesn’t seem to be extremely common. Would it be a bad form to use circular polarization at UHF for simplex, or to hit a repeater?
I can’t honestly say for sure. I don’t imagine many people would even notice unless it causes some warble in the transmission, which seems unlikely.
is it likely that two different things will be happening at the exact same frequency but with orthogonal polarizations? outside of satellite/EME uplink/downlink (circular)
Maybe there’s a way to make traveling wave antenna with linear polarization, but i’ll have to learn some NEC for this