Assuming the same transmitter and RF output power are used, what is the effect of changing the transmission line from RG-213 coaxial cable to RG-58?

RG-213 and RG-58 are both common 50-ohm coaxial cables, but they differ significantly in physical size and signal loss characteristics. RG-213 is a thicker cable with much lower attenuation, while RG-58 is a thinner cable that exhibits significantly higher loss per meter. When you replace a low-loss cable (RG-213) with a higher-loss cable (RG-58), more of the transmitter's RF power is dissipated as heat within the cable itself. Consequently, less of the original RF power reaches the antenna to be radiated. Changing the cable type does not change the impedance match at the antenna feedpoint itself, meaning the SWR at the antenna remains unaffected, which makes the SWR-related distractors incorrect.