The 7K's aren't much more DC voltage dependent than any other mobile HF radio, IF the poorly designed fuse holders on the factory DC power cable are replaced with good quality 30 amp holders that bite through the fuse blades' surface oxidation that builds up over time.? Cleaning the fuse blades will help temporarily, but the fuse holders have an inherent design flaw, compared to typical automotive-style ATC fuse holders.? Of course there can be other sources of voltage drops that all add up in a mobile or battery-powered installation.? There should be less than 500 millivolts drop from the battery terminals to the TUNER port pins 3-4 under load in a proper installation.
A properly adjusted 7K will operate down to 10.9 VDC (as measured across the TUNER port pins 3-4 while transmitting with the TX PO=100%).? The output power will decrease by 50-60% compared to 13.8 VDC.
Below about 10.5 VDC the radio will do a reset of the CPU, mainly designed to protect the radio during a power-up cycle until the supply voltage is stable.? IC1301 is the reset control IC for the CPU.
Transmitting at 100W on just battery power (without the engine running) is not good practice.? Adding a battery booster just makes a bad situation worse for? battery life.? Dropping the TX PO to 50W only decreases the received signal by 3 dB, but can quadruple battery run time typically.
Steve, W3AHL
Steve W3AHL