Elecraft KAT500 Serial Command Reference - Manual (Page 16)

If fffff is zero or missing, the last Transmit frequency is used. If transmitting, the measured frequency is
used instead of fffff.
SM; is used by the KAT500 Utility Operate Page Memorize button.
SM with a frequency was introduced in firmware version 1.20.
SN (Serial Number, GET only)
GET format: SN;
RESPONSE format: SN xxxxx;
SN; reads the KAT500’s serial number, installed in EEPROM during factory installation of initial firmware
and will normally remain unchanged thereafter. Leading zeros may be omitted. EEINIT does not change
the serial number.
ST (SWR Threshold, GET and SET)
GET format: STbbt; where bb is the Band Number (see BN command) and t is a “type”
SET format: STbbtnn.nn; where nn.nn is a VSWR value.
The “types” are:

A for Auto tune VSWR threshold. When the KAT500 is in Mode AUTO and the current VSWR reaches
this threshold, the KAT500 will attempt to recall a prior tuner setting from its memory, or perform a
Full Tune as required to reach the Auto tune VSWR threshold. The default Auto tune VSWR
threshold value is 1.8. The minimum is 1.5. For example, to change the Auto tune VSWR threshold
for 20 meters to SWR 1.75:1, enter ST05A1.75; where 05 is the Band Number for 20 meters.

B for bypass VSWR threshold. During a “full tune”, VSWR is measured with the KAT500 in bypass,
with no inductors or capacitors in the RF path. If the bypass VSWR is less than or equal to the bypass
VSWR threshold, the desired (and memorized) tuner setting for this frequency is “use the bypass
relay”. The default bypass VSWR threshold is 1.2. For example, to change this threshold to 1.3:1 for
80 meters, enter ST01B1.3; where 01 is the Band Number for 80 meters.

K for amplifier Key interrupt VSWR threshold. If the VSWR exceeds this threshold, the amplifier key
interrupt relay is energized so that the amplifier is not keyed. The default amplifier key interrupt
VSWR threshold is 2:1. This threshold may be set as high as 99.99 to defeat the protection function.
The KAT500 Utility Edit Configuration dialog VSWR Thresholds tab supports setting these values
individually by band, or all at once for all bands.
VSWR values are encoded in an 8.8 binary format, so the least significant digit may change when
converting between binary and decimal representations.