What is antenna polarization, must the remote and receiver antennas point the same way?
Polarization is the direction of the electric field produced by the antenna. If there is an angle theta between two linear antennas the loss is 20*log10(cos theta): 3 dB at 45 degrees, theoretically infinite at 90 degrees, 20-30 dB in practice. A 20 dB loss cuts range to roughly one tenth; this is why the remote and receiver antennas should be kept on the same axis as far as possible, typically vertical.
The loss formula follows directly from the angle: 0 dB at 0 degrees, 1.25 dB at 30 degrees, 3 dB at 45 degrees, 6 dB at 60 degrees. A 60 degree deviation alone halves the range, because 6 dB means exactly a factor of two in distance.
Practical rules for field application:
- Mount the receiver antenna vertically; the antenna of a handheld remote also stays largely vertical during use.
- Do not fix the receiver antenna horizontally on the side face of an enclosure; this is a classic installation mistake.
- If the operator carries the remote horizontally on their belt and presses buttons, a drop in range is normal, not a fault.
- In metallic environments such as a crane cabin, reflections partly scramble polarization; this is sometimes a loss, sometimes a rescue, but it is not reliable.
Polarization mismatch can, on its own, be a sufficient explanation for range even when every other item in the link budget is correct. When a range complaint comes in, checking the axis of both antennas before taking any measurement is the cheapest diagnosis.
Full article: 433 MHz or 2.4 GHz?