How do you have your antennas positioned?
MANY people get it wrong.
They should be at 90* to each other. So either one pointing up and the other to the side.
Or each one at a 45 OPPOSITE angle.
I know it looks weird, but you will get the most benefit from the diversity that way.
^^^ This.
If I had a nickel for every diversity RF kit I've seen with the antennas pointing the same direction, I'd probably have a dollar. Or two. If I had a dollar for every time I fixed the same kit over and over again....
Think of a TV with a single "rabbit ear." Or an FM radio with the telescoping antenna. You move it around to different
angles to find the optimum reception.
With a "diversity" microphone receiver (whether VHF or UHF), there are actually two radio receivers, and the system automatically switches to whichever one has the strongest RF signal. There's one antenna for each radio. So think about it: if both antennas are at the same angle (parallel to each other), both radios are going to get approximately the same signal strength. So when one loses signal, the other does too. You start to hear interference as the RF signal-to-noise ratio falls because the receiver's automatic gain control increases the RF gain, lifting the desired signal to maintain a steady output but also lifting the noise to an audible level.
So by putting the antennas at different angles, you increase the chances that as one receiver's signal drops out, the other receiver's signal will be stronger, so you have less chance for the signal-to-noise ratio to fall to levels where the noise becomes audible, and less chance of losing the signal altogether.
This works because the transmitter's antenna is not omnidirectional (it's more like a doughnut), and the receiver's antenna is also not omnidirectional in sensitivity. As you move the transmitter around, its "cloud" of signal strength moves around too, so by having your receiver antennas splayed one or the other will always be more optimally positioned.
That's a gross oversimplification, and there may be many technical errors, but the basic concept still applies.
* * * *
If the receiver can be moved closer to the stage, that can also improve the RF signal-to-noise ratio and reduce fading and dropouts. Human bodies are very effective RF shields.
If you're not getting interference (just dropping signal-to-noise ratio), and changing the antenna position and/or receiver placement fixes the issue, and you don't
lose signal, there probably is no real good reason to replace your existing wireless microphone kit.
