IN general Omni Directional antennas are... ****.
As for the red wire. No clue. may have been for a different antenna. Do you have both of the cut ends? if so there is a way to hook it up safely.
Jumper the two cut ends as follows:
Get a License Plate Lamp socket and lamp from auto-parts-r-Us (generic name) I like the wedge based lamps for this and use a dash lamp instead of a license plate lamp
Use the two leads to "jumper" via the lamp
If you jumper into a short. the light comes on. Else it should stay off since the pre-amp draws a fraction of what it takes to light a license plate lamp. IF it lights very dim. use a bigger (license plate instead of dash) lamp.
THe light bulb becomes a self resetting protection device may be left in or removed.. I have a circuit on my RV protected that way.