A node’s antenna performance is determined by several factors:
- The RF circuitry and impedance matching on the board.
- The type, RF characteristics, quality and position of the antenna.
- If monopole antenna the inclusion of a good ground plane in the design is essential.
- The quality and characteristics of the antenna cabling and connectors.
A monopole antenna is actually the half of a dipole antenna. The other half is formed by the ground plane. Without a good ground plane a monopole antenna will have suboptimal to bad performance.
A good ground plane is determined by several factors and designing good antennas is not simple.
Often the quality of these (Chinese) quarter-wave-length monopole antennas is not very high and not optimal for the frequency used. Together with the ground plane this has significant impact on the antenna’s performance. Another aspect is that the IPEX/U.FL antenna connectors have a specified lifetime of rather limited number of insertions and removals. These connectors must be inserted and removed with care, but in practice are often handled worse which lowers their quality and lifetime.
Your setup initially lacked a (good) ground plane and you have now added some ground plane, which makes your antenna more like a real dipole. The two halves of true dipoles are normally positioned in the same axis opposite of each other (not in 90 degree angle). For best results a node’s antenna should be positioned upright (which is related to its radiation pattern).