It seems the BNC connector on the subject radio is not a standard size??!! I just installed an outdoor discone and am feeding my radios with RG6 and F connectors. This requires the use of a an F to BNC adapter. This adapter fits very loosly on the 400's BNC connection preventing the signal from getting to the radio. It seems to be the female connector on the radio has too large of a hole in it...the very small hole inside of the connector. And, the outside diameter of the connector itself seems smaller than normal creating an all around loose fit. The adapter works fine on my AOR receivers so it is clearly the conector on the GRE. Close inspection of this connector shows it to be one of sub-quality which kinda surprises me. Anyone else had this problem? I guess I'm off to my local electronic supplier to find a chassis mount, female BNC to make the swap.