The most significant factor affecting RF performance for the CYRF8935 or any other over-the-air RF device is the antenna type, placement, and orientation. Antenna gain is normally measured with respect to isotropic, that is, an ideal radiator that sends or receives power equally to or from any direction. An ideal antenna choice for most low-power, short-range wireless applications, is the isotropic reference antenna. Unfortunately, these do not exist in practice. However, you should take care when placing the antenna, because dipole antennas have a radiation pattern where the null can be very deep.
For best operation, design the product so that the main antenna radiation is away from the body or at least not proximity-loaded by the human body or dielectric objects within the product.
Remember to keep the antenna away from clock lines, digital bus signals, and power supply; otherwise, harmonics of the clock frequency will jam certain receive frequencies.