Elecraft KAT500 Serial Command Reference - Manual (Page 17)

T (Start Full Tune, SET only)
SET format: T;
RESPONSE format: FT; when full tune completes.
This command is equivalent to pressing the front panel TUNE button. T; is equivalent to FT; (Full Tune).
VFWD (Forward coupler voltage ADC count, GET only)
GET format: VFWD;
RESPONSE format: VFWD nnnn; where nnnn is 0 through 4095. Leading zeros may be omitted.
VFWD; returns an Analog-to-digital conversion (ADC) count of the VFWD voltage from the KAT500’s RF
coupler. VFWD and VRFL are used to compute the VSWR. VFWD is also used for safety thresholds.
VRFL (Reflected coupler voltage ADC count, GET only)
GET format: VRFL;
RESPONSE format: VRFL nnnn; where nnnn is a number between 0 and 4095. Leading zeros may be
omitted.
VRFL; returns the ADC count of the reflected voltage at the coupler, using the same units as VFWD.
VSWR (Voltage Standing Wave Ratio, GET only)
GET format: VSWR;
RESPONSE format: VSWR nn.nn; Range is VSWR 0.00; to VSWR 99.99; for 99.9 to 1 or higher VSWR.
VSWRB (Voltage Standing Wave Ratio in Bypass, GET only)
GET format: VSWRB;
RESPONSE format: VSWRB nn.nn; Range is VSWRB 0.0; to VSWRB 99.99; for 99.99 to 1 or higher VSWR.
VSWRB is the VSWR of the antenna, as measured at the KAT500 coupler, when the KAT500’s bypass
relay was released; without any KAT500 inductors or capacitors in the RF path.