Setup: Si5351 RF generator (@ 28 MHz) ➔ GSD-Hacks-v5 ➔ 7th order LPF ➔ {COAX-UNDER-TEST} ➔ Digital RF power meter ➔ Dummy load

Results at 13.8V drain:

Coax TypePower Reading
RG-58 (7 meters)4.5W
RG-316 (7 meters)3.9W
RG-188 (7 meters)3.9W

Results at 15V drain:

Coax TypePower Reading
RG-58 (7 meters)5.4W
RG-316 (7 meters)4.7W
RG-188 (7 meters)4.7W

These measurement results seem to match the ones from Eric, WD8RIF.

For ultra-portable HF field operations (POTA / SOTA / others), carrying a roll of RG-58 coax can be challenging.

Using RG-316 (light but a little stiff) and RG-188 (flexible and lightweight) for bicycle-portable or man-portable operations can be a decent option if we are willing to tolerate some RF power losses.

Also, RG-58 with PL-259 connectors is pretty mechanically rugged in comparison against RG-316 and RG-188 - another factor to keep in mind.

References: