# What is the maximum and minimum of antenna gap of dipole antenna?

Consider the picture below is a design of half wave length ($$\lambda$$) dipole antenna. I read some explanations saying that it is the best design to get the optimum transmit power. Or it is cut to $$0.47 \lambda$$ to $$0.48 \lambda$$ to get the optimum impedance (CMIIW).

But my concern here is, what is the minimum or maximum distance of the gap as in the picture? Gap between the two elements which the feeder line is connected? I expect that the explanation is in $$\lambda$$. But if you really need the used frequency, that just put 2,100 MHz.