Why should DC power for a 100-watt HF transceiver not be supplied by a vehicle’s auxiliary power socket?
The socket is not wired with an RF-shielded power cable
The socket’s wiring may be inadequate for the current drawn by the transceiver✓Correct answer
The DC polarity of the socket is reversed from the polarity of modern HF transceivers
Drawing more than 50 watts from this socket could cause the engine to overheat
Explanation
An auxiliary power socket and its wiring are typically sized and fused for something in the 10 to 15 ampere range, whereas a 100 watt HF transceiver draws around 20 amperes on transmit peaks. The wiring would overheat and the fuse would open, which is why a direct connection to the battery is used instead.