Securing the antenna connector to the V4 or V5 is sufficient by hand. Do not over tighten with any tool such as a spanner as it may damage the threads of the connectors.
Technically, it should finger-tight and the torque of about 1.7 to 2.3 Nm. This means that if you are using your thumb and index finger for the turning action, once you feel the physical stress and pain, that is enough.
If you really need to use a spanner, use a small size spanner. Use minimal turning force and once you reach the resistance point, a little nudge on the end of your spanner with your index finger is more than sufficient.