Does the Aleis RFID race antenna / saleyard antenna have any null spot(s)?

No. The Aleis RFID race antenna for producers, race readers for saleyards and feedlots and fixed race readers have no null spot(s). A null spot is an area on an antenna where there is no activation and so tags or boluses may get through without being read. The Aleis race antenna design is exclusive to Aleis who hold a worldwide patent.