The RF output power of RR9 series readers is 1W or 4W. Is this a random choice or a deliberate decision?
For HF tag’s process, the higher RF output power of the reader is favorable especially dealing with small tags. But the RF power is definitely not “the higher the better”. The choice of RF power relates to the following issues:
(1)  Though 13.56MHz radio wave is harmless to human body, the excessive RF power will still be not friendly to other nearby electronic equipments especially taking the reader’s RF frequency drifting and spectrum purity into consideration. There are some regulations covering this issue in domestic and international standards.
(2)  The tag’s effective distance is a combination result of the reader’s RF output power, receive sensitivity, S/N ratio and other environmental factors. It will not work efficiently to extend the effective distance by solely increasing RF power. Excessive RF power will do harm to the tag’s durability when tag is operated close to the reader’s antenna. Practically, the choice of reader’s RF power is 1W or 4W and it meets the requirements of most applications