I've never tried the 75ohm coax connector always use the RCA connectorsand my pic Quality is very good! how ever many things besides wireless devices will effect its reception Any metal, microwaves just a few .Play with the antenna and try the cam next to it to see if it is a bad unit but use the RCA jacks as jay148 suggested as well and try the other codes a,b,c,d on the bottom ,on the cam the switch is under the rubber stopper!