The achievable RF range is affected by many factors as listed below.
- Transmit power and TX antenna gain
- Receive sensitivity and RX antenna gain
- Frequency: It is related to the gain and effective area of the antenna. It can simply translate into that the lower frequency the link operates at the better RF range can be achieved.
- Antenna radiation pattern: The best RF range can be achieved if the TX and RX antennas are facing to each other in their maximum radiation lobes. There could be some directions where the antennas' radiation patterns do have minimum notches and thus the RF range could be poor in these directions.
- Interference, noise: Any in-band noise does have severe negative effects on the range since it can mask out the wanted signal at the RX side (see the co-channel rejection parameter). But, stronger out-of-band noise can also degrade the RF range based on the receiver's ACS and blocking performances.
- Frequency offset between TX and RX: It can become more critical in narrow-band systems where the exact carrier frequencies must correctly be set.
- Final product placement and enclosure: The antenna performance can be affected by any material in the close proximity of the antenna and by the antenna placement. In order to avoid any de-tuning effect (and thus RF range degradation) make sure about the recommended antenna (or i.e. module) placement and clearance.
- Environment: Ideal case is an outdoor environment where there are no reflections (e.g. no walls, big obstacles, trees, houses) and there is a direct line-of-sight (LOS) between the TX and RX and there isn't any obstacle in the Fresnel ellipsoid too (see online calculators for the Fresnel zone/ellipsoid). Less ideal case is an urban area, or when there is no LOS between the TX and RX. The worst situation is an office indoor environment where there is typically no LOS and there are walls, obstacles and thus reflections. Propagation constant can describe the environment which is typically 2.5...3.5 in an outdoor environment with LOS between the TX and RX nodes, while can even be 4...6 in an indoor environment.
- Transmitter and receiver heights: This is also related whether there is any obstacle, e.g. ground, in the Fresnel ellipsoid. If so, the RF range is negatively affected. Thus, the higher the nodes are placed at the bigger RF range can be achieved.
See a related KBA link on this topic below which describes an example estimator/calculator for the RF range.