Since time is money and my PCB home making skills are not the sharpest, I would rather fit my PCB design with two unbalanced antennas (no balun, just impedance matching parts, for 315 / 433 MHz) for the one and only transmitter on the board and later chose between them by means of a 0 ohm resistor / jumper. Does this sound practical ? Any particular aspects I ought to take care with ?
EDIT: both antennas are supposed to work for both frequencies (properly tuned, of course). But I don't know... I currently have a design with differential loop antenna (unrelated to this question) - it works noticeably better at 315 than at 433 MHz.
These two in question, one will be an unbalanced loop antenna the other an unbalanced printed helical antenna. Only one of them will be used and on only one of the two frequencies at a time.