You can tilt the antennas so that they are at 90 degree angles to one another. That is to say, bend one 45 degrees to the left and the other 45 degrees to the right. The tilted antennas are a reasonable way to operate and the best way if the antennas are fairly close together since they couple together much less than if they are both pointed in the same direction (parallel).
The antenna diversity used in our receivers does not select one antenna or the other; it sums the two antennas together and corrects the phase of one antenna so that the antenna signals do not cancel each other out as they might do if they were 180 degrees out of phase. So it does not make too much difference which way the antennas point since the receiver will correct the phase.
Additionally, in any usual environment, the signals coming to the receiver from the transmitter are not in any well defined phase relationship or direction. The signals are reflected from cars, the ground, metal studs, wire in walls, camera equipment and even people, so that the signal that gets to the receiver is pretty well scrambled and impossible to predict. The problem with reception occurs when all the signals from all the reflectors get to the antenna and cancel out. If you use two antennas, then the signals probably will not cancel out at both antennas simultaneously. There is a new problem, though, if you simply add the two signals together. When the signals at each antenna are equal and exactly out of phase they cancel out at the receiver. The phase diversity system that we use on our small receivers detects this condition and simply inverts the phase of one of the antennas. Now the antennas add the signals together for a 3 dB pickup in power. For a good explanation of this, that is more comprehensive than what I can do here, go to this link to our web site.
It is part of our wireless guide. In fact you might want to down load the entire wireless guide because it is pretty good and pretty neutral in its treatment of wireless microphones.