Module freq 

Core radio methods: frequency, mode, power, squelch, S-meter, TX/RX, firmware, power status, ID, band control, VFO/memory mode, FM radio, fine step, function type, and filter width.

Band capabilities (per Operating Tips §5.9, §5.10)

• Band A: 144 / 220 (A only) / 430 MHz amateur operation
• Band B: 0.1-524 MHz wideband receive, all modes (FM, NFM, AM, LSB, USB, CW, DV, DR)
• TH-D75A TX ranges: 144-148 MHz, 222-225 MHz, 430-450 MHz
• TH-D75E TX ranges: 144-146 MHz, 430-440 MHz

IF signal output (per Operating Tips §5.10)

Menu No. 102 enables IF (Intermediate Frequency) signal output via the USB port: 12 kHz center frequency, 15 kHz bandwidth. This is intended for SSB/CW/AM demodulation by a PC application. Single Band mode is required for IF/Detect output. A band scope can be driven via a third-party PC application using the BS command.

FQ vs FO

The D75 has two frequency-related command pairs:

• FQ (read-only): returns the current frequency and step size for a band. Writes are rejected by the firmware — use FO for frequency changes.
• FO (read/write): returns or sets the full channel configuration for a band, including frequency, offset, tone mode, CTCSS/DCS codes, shift direction, and more. This is the primary command for tuning the radio via CAT.

VFO mode requirement

Most write commands in this module (FO write, MD write, SQ write, FS write, etc.) require the target band to be in VFO mode. If the band is in Memory, Call, or WX mode, the radio returns ? and the write is silently rejected. Use set_vfo_memory_mode to switch to VFO mode first, or use the safe tune_frequency() API which handles mode management automatically.

Tone and offset configuration

CTCSS tone, DCS code, tone mode, and repeater offset are not configured through dedicated commands. Instead, they are fields within the ChannelMemory struct passed to set_frequency_full (FO write). Read the current state with get_frequency_full, modify the desired fields, and write it back.