There are many options when you need to splice wires. In addition to formal two-piece connectors, there’s the widely used ...

The 3BR Garmin GPS Cables are made from genuine Garmin cable stock. The cables are then modified to be used with one of the 3BR Powersports Baryl Plug barrel connector at the power outlet end and they ...

Pretty sure there is a fair amount of loss on those connectors, although 1 dB does sound like a lot to me. 1 dB seems like a decent guess for a coupler / cable joint through a barrel connector though.