Hmmm ?? A construction project!! Or, is it a recipe?

Start with a 48 inch length of stainless steel 1/16 inch diameter rod.

Add a new coil at one end to be tapped for a 50 ohm match at 146 MHz.

Add a new capacitor connected in parallel with the coil.

Adjust capacitor and inductance to achieve 146 MHz resonance.

Using an antenna analyzer locate and solder a tap coil for 50 ohm match.

Seal all with a strong weather proof sealant.

Install in mount provided at point of sale.

Install on vehicle.

After failure, replace with commercial 146 MHz antenna

Deacon Dave, W1MCE