Thanks please read owners manual. The KL 503 is a 12V linear amplifier for use in the frequency range 25 - 30 MHz, with a drive power of 1 to 6 W in all modes.
The KL 503 features a six-position power selector via a a front panel knob and a RX preamplifier with electronic switching, which can be activated via a switch on the front panel. Power Supply : 13.8VDC+/- 1V 40A. Input Power: 1W - 6 W. Input VSWR: 1.1 - 1.5:1.
Fuse : 3x 10A Fast 5×20mm. Dimensions : L 300 W 190 H 67 mm.