A λ/2 center fed dipole mounted several λ from other metallic objects, and if the feedline is brought off at right angles from the center of the dipole, has a theoretical balanced feedpoint impedance of 73Ω.
When feeding it with 50Ω coax (unbalanced), you can do various things:
1. Hook the coax center conductor to one leg, and the shield to the other. Practically this works, and it is done all the time. It has two problems. Due to the unbalanced feed line, currents in the dipole legs are unbalanced, therefore the antenna has asymmetry in its radiation pattern, and the current on the outside of the coax also radiates in the vertical plane, adding to the pattern distortion. The losses attributable to the slight mismatch of connecting a 50Ω feedline to a 73Ω antenna are so slight as to be insignificant.
2. Use 70Ω CATV coax, and diddle the transmitter to match 73Ω. You still have the unbalance dipole currents/feed line radiation, but lower SWR losses.
3. Use a 1:1 balun between the 50Ω coax and the dipole. This straightens out the radiation pattern and eliminates the coax radiation. However, the balun loss wipes out any improvement. The mismatch loss in the coax is uneffected.
4. Use 75Ω balanced twin lead to feed the antenna. This requires moving the balun to the transmitter end of the feedline. Most transmitters can be retuned to match 70Ω by adjusting the Π-network output tuning. Gets rid of the feedline radiation, and balances the currents in the dipole. Twin lead has lower losses than coax. This is the preferred solution.
5. Use 300Ω balanced twin lead to feed a "folded dipole" with a 300Ω feed-point impedance. Need a 1:4 balun at the transmitter. Even lower feedline losses. This is the way analog TV antennas used to work.
Any "improvement" in range by choosing method 1-5 is apt to be so slight (~1 or ~2db) that you will be hard pressed to notice the difference.