SSTV TX transmits Slow Scan Television images from .BMP files stored on the SD card, in the standard SSTV tone range (1,500–2,300 Hz), as FM on VHF/UHF or SSB on HF. Every transmission starts with the calibration header and VIS code, so receivers can recognise the mode by themselves.

This is an external app (.ppma file on the SD card).

Controls

• File — Selects the .BMP file to transmit from the SSTV/ directory on the SD card.
• Mode — Selects the SSTV transmission mode. Default: Scottie 2.
• Mod — How the tones go on air:
  • Auto (default): USB below 30 MHz, FM from 30 MHz up. The field shows what Auto chose, Auto USB or Auto FM, also when the frequency is changed in the transmitter bar.
  • FM, USB or LSB: always that one. SSTV on HF is sent in USB on all bands.
• Frequency, Gain, AMP — Standard RF controls. Default gain: 12 dB.
• ▶ — Starts transmission. A progress bar shows the current scanline.

Supported Modes

Mode	VIS Code	Lines	µs/pixel
Scottie 1	60	256	432.0
Scottie 2 (default)	56	256	275.2
Scottie DX	76	256	1080.0
Martin 1	44	256	457.6
Martin 2	40	256	228.8
SC2-180	55	256	734.4
Robot 36	8	240	275 (Y), 137.5 (colour)

All modes transmit 320 pixels per line. Robot 36 sends the top 240 lines of the 320 × 256 image, in BT.601 YCbCr: the luminance of each line, then R-Y on even and B-Y on odd lines, at half the pixel time, each after a separator tone (1500 Hz before R-Y, 2300 Hz before B-Y). It is the mode most phone apps (such as Robot36 for Android) decode.

The PD modes can be received by SSTV RX but are not transmitted.

Modulation

• FM: the tones frequency-modulate the carrier, as on VHF/UHF.
• USB / LSB: SSB of a single tone is that tone as a carrier offset; the transmitter sends the tone directly at +f (USB) or −f (LSB) from the dial frequency. Set the dial frequency the way an SSB transceiver shows it (e.g. 14.230 MHz USB).

Image Requirements

• Format: 24-bit uncompressed BMP (.bmp)
• Size: exactly 320×256 pixels
• Location: SSTV/ directory on the SD card

Images that do not match the required resolution are not listed.

RF Parameters

Parameter	Value
Sample rate	3.072 MSps
Baseband bandwidth	1.75 MHz (fixed)
Frequency step	10 kHz

Settings Persistence

Settings, including Mod, are saved to tx_sstv.ini.

Legal notice

Transmitting requires a licence for the frequency used (for SSTV usually an amateur radio licence). Use low power or a dummy load when testing.