Which of the following direct, fused power connections would be the best for a 100-watt HF mobile installation?
Why A 100 W HF transceiver draws roughly 20 to 25 amps on peak, so the feed has to be short, heavy gauge and fused at both ends to keep voltage drop and fire risk down. Connecting directly to the battery gives the lowest impedance source and lets the battery act as a large filter capacitor that smooths out alternator whine and other vehicle electrical noise. Tapping the accessory or fuse-panel wiring instead usually means undersized wire and a sagging supply voltage that distorts your transmit audio.
Watch out Running to the alternator or generator puts you right at the noise source with no battery smoothing, and balanced transmission line is meant for RF feedlines, not DC power runs.
100 W HF pulls ~20 A: heavy wire straight to the battery, fused. Battery = built-in noise filter.