Why does the range figure given by the manufacturer not hold on a real site?
Catalogue ranges are measured in open field with line of sight, with the antenna properly positioned and in an environment with a low noise floor. On site, Fresnel zone violation, an antenna inside a metal enclosure, a 90° polarisation difference (20–30 dB in practice), 5 m of RG58 cable (~2.2 dB at 433 MHz) and a rising noise floor all come into play; every 6 dB of loss halves the range.
The number in the catalogue is not wrong; it is the number for a different condition. The figures given for AXI sets should be read with that qualification too: about 100 m for the SF100 and SF200, about 150 m for the ST100 and ST200, 100 m for the HCT400 and HCT402 — all of them belong to the open field, line of sight condition.
The reasons you fall below that value on site are items that add up:
- If the antenna is left inside a metal enclosure: tens of dB.
- If the remote control antenna is vertical and the receiver antenna horizontal: 20–30 dB in practice.
- A beam, container or vehicle entering the Fresnel zone at mid-path: 10–20 dB.
- A 5 m extension cable (RG58, 433 MHz): about 2.2 dB.
- An inverter or welding machine coming into service: a rise of more than 10 dB in the noise floor.
If only two of these items come together you reach 30 dB; given that 6 dB halves the range, a 150 m link drops to about 4.7 m.
The right approach is to treat the catalogue figure as an upper bound and, during installation, to verify the antenna placement, the polarisation match and the cable length one by one.
Full topic: 433 MHz or 2.4 GHz?