Frequency & Modes

This page covers the commands used to control VFO frequencies, select operating modes, change bands, and configure DATA sub-modes on the K3/K3S. For the complete alphabetical command listing, see the K3/K3S/KX3/KX2 CAT Command Reference.

VFO Frequency Control

The FA and FB commands read and set the frequency of VFO A and VFO B respectively. Frequencies are expressed as 11-digit values in Hz, zero-padded on the left.

FA00014200000;       Set VFO A to 14.200000 MHz
FB00007050000;       Set VFO B to 7.050000 MHz

To read the current frequency, send the command with no parameter:

FA;                  Query VFO A frequency
                     → FA00014200000;

The valid frequency range is 0.5 MHz to 54 MHz on the K3/K3S. Exact upper and lower limits depend on the installed band modules and transverter configuration.

VFO Stepping

The UP / DN commands step VFO A up or down by the current tuning rate. UPB / DNB do the same for VFO B.

UP;                  Step VFO A up by the current rate
DN;                  Step VFO A down by the current rate
UPB;                 Step VFO B up
DNB;                 Step VFO B down

Band Selection

The BN command queries or sets the current band by number.

BN;                  Query current band → BN07; (15m)
BN05;                Switch to 20m band

Band numbers map as follows:

Number	Band	Number	Band
00	160m	08	12m
01	80m	09	10m
02	60m	10	6m
03	40m	11	Transverter 1
04	30m	12	Transverter 2
05	20m	13	Transverter 3
06	17m	14	Transverter 4
07	15m	15	Transverter 5

Band Change Sequence

The recommended pattern for changing bands and confirming the result:

Operating Modes

The MD command reads or sets the operating mode. Each mode is represented by a single digit:

Value	Mode	Value	Mode
1	LSB	6	DATA
2	USB	7	CW-REV
3	CW	9	DATA-REV
4	FM
5	AM

MD;                  Query current mode → MD2; (USB)
MD6;                 Switch to DATA mode
MD3;                 Switch to CW mode

Use MD$ to target VFO B / sub receiver mode instead of VFO A / main receiver.

Mode Transitions

The diagram below shows the available mode transitions and the commands that trigger them:

DATA Sub-Modes

When the operating mode is DATA (MD6) or DATA-REV (MD9), the DT command selects the DATA sub-mode:

Value	Sub-Mode	Description
0	DATA A	Default, uses MIC/LINE audio input
1	AFSK A	Audio FSK
2	FSK D	Direct FSK keying
3	PSK D	Direct PSK

DT;                  Query DATA sub-mode → DT0;
DT1;                 Switch to AFSK A sub-mode

Linked VFOs

The LN command links or unlinks VFO A and VFO B:

LN1;                 Link VFOs (A and B track together)
LN0;                 Unlink VFOs
LN;                  Query link state → LN0; or LN1;

When linked, changing VFO A frequency also changes VFO B to the same frequency. This is useful for simplex operation where both VFOs should remain on the same frequency.

VFO A/B Operations

Several commands control VFO swapping, copying, and TX/RX assignment:

Swap and Copy

SWT19;               Emulates A/B button tap — swap VFO A and VFO B
SWT20;               Emulates A=B button tap — copy VFO A to VFO B

TX and RX VFO Selection

The FT command selects which VFO is used for transmit. The FR command selects which VFO is used for receive.

FT0;                 VFO A transmits
FT1;                 VFO B transmits (split operation)
FR0;                 Receive on VFO A
FR1;                 Receive on VFO B

Practical Patterns

Setting Frequency and Mode

A typical sequence to configure the radio for FT8 on 20 meters:

FA00014074000;       Set VFO A to 14.074 MHz (FT8 frequency)
MD6;                 Set DATA mode
DT0;                 Set DATA A sub-mode

Reading Current State

Query all relevant frequency and mode parameters in one burst:

FA;                  Query VFO A → FA00014074000;
MD;                  Query mode → MD6;
DT;                  Query DATA sub-mode → DT0;
BN;                  Query band → BN05;