RSSI - 73

Hi, really need some help. I installed my camera on a brick wall at the back of my property but no more than 20 feet from an excellent sky fibre router. I'm getting a weak signal and an RSSI of -73. I've looked at the help pages on here and done some research and dont want to pay another £49.99 for a ring chime that by reading comments on here and on amazon are very hit and miss. Any advice? many thanks