QSSTV on Linux — Complete SSTV Setup, Operating and ISS Reception Guide

What is SSTV and how does it work

Slow Scan Television (SSTV) is a method of transmitting still images over radio by converting pixel data into audio tones. Each line of the image is encoded as a sequence of audio tones ranging from 1500 Hz (black) to 2300 Hz (white), with sync pulses marking the start and end of each line. A receiving station decodes these tones back into pixels in real time, rebuilding the image line by line as the transmission arrives.

A complete SSTV image takes between 8 seconds (Robot 8, low resolution black and white) and several minutes (Scottie DX, high quality color) to transmit. The most popular modes — Martin M1 and Scottie S1 — produce a 320×256 pixel color image in about 110–114 seconds.

SSTV has a dedicated and passionate community. Operators exchange artwork, photographs, shack photos, and special event images on established frequencies worldwide. The International Space Station regularly transmits SSTV images during special events, making it possible for anyone with basic equipment to receive images from space.

Installation on Ubuntu and Debian

Ubuntu 22.04, 24.04 and Debian 11, 12

Install dependencies if missing

If the apt install fails due to dependency errors:

Build from source (latest version)

Raspberry Pi

QSSTV installs and runs on Raspberry Pi 3 and 4 via the standard apt method. It is slightly slow on older Pi models but perfectly usable for receive-only operation. A Pi with a cheap SDR dongle and QSSTV makes a capable SSTV monitoring station.

Verify installation

QSSTV opens its main window. If it fails to launch check the terminal for error messages regarding missing libraries.

Sound card and audio setup

QSSTV uses your computer's sound card to receive and transmit the audio tones that carry SSTV image data. The setup is the same as other digital mode programs — radio audio output to computer input, computer audio output to radio input.

Configure audio in QSSTV

Go to Options → Configuration → Sound and set:

• Input device — select your audio interface (USB audio adapter or radio's built-in USB audio)
• Output device — same device
• Sample rate — 48000 Hz recommended

Finding your audio device

Audio levels

QSSTV shows a receive level meter in the main window. When an SSTV signal arrives the meter should peak at 50–75% of full scale. If it clips at 100% reduce the radio's volume or the system capture volume via alsamixer. Clipped audio causes color distortion in received images.

PulseAudio

On modern Ubuntu systems select the PulseAudio device in QSSTV rather than the ALSA hardware device. This avoids conflicts with other applications using the same audio interface and allows volume control via the system mixer.

Radios with built-in USB audio

Radios like the Icom IC-7300 present as a USB audio device on Linux. Select the IC-7300 USB Audio Codec in QSSTV's sound settings. No external audio interface needed — one USB cable handles both audio and CAT control.

PTT and rig control

QSSTV needs to key your transmitter when sending. Configure PTT under Options → Configuration → PTT/CAT.

PTT methods

Hamlib rig control

For automatic frequency and mode control go to Options → Configuration → PTT/CAT and enable Hamlib. Select your radio model, serial port, and baud rate. With rig control active QSSTV can switch your radio to USB mode automatically when you start a transmission.

Serial port permissions

SSTV modes — Martin, Scottie, Robot explained

SSTV has many modes with different transmission times, resolutions, and color encoding methods. Choosing the right mode depends on band conditions and what the other station supports.

Which mode to use

• Martin M1 — use this as your default for HF operation. It is the most universally recognised and any SSTV operator worldwide will be able to receive it
• Scottie S1 — equally good alternative, particularly common in Europe
• Robot 36 — use when time is limited or when working the ISS — it is the standard ISS SSTV mode
• PD-120 or PD-180 — use when you want to exchange high-resolution images and both stations have agreed to the mode
• Scottie DX — use only when band conditions are excellent and there is no time pressure — the 4.5-minute transmission is very long for HF

How VIS codes work

Each SSTV mode starts with a VIS (Vertical Interval Signal) code — a sequence of tones that identifies which mode is being used. QSSTV detects this code automatically and switches to the correct mode without operator intervention. You do not need to manually select the receiving mode — just click Start and QSSTV identifies the incoming mode from the VIS code.

Receiving SSTV images

Receiving SSTV is largely automatic once QSSTV is running with correct audio input.

Step-by-step receive procedure

1. Tune your radio to an active SSTV frequency in USB mode — 14.230 MHz for 20m
2. Set the radio volume so the audio level meter in QSSTV shows 50–75% of full scale during signals
3. In QSSTV click Start in the receive panel
4. QSSTV listens continuously — when it detects a VIS code at the start of a transmission it automatically identifies the mode and begins receiving
5. Watch the receive window as the image builds line by line from top to bottom
6. Completed images are saved automatically to your configured image directory

Reading the SSTV signal on the waterfall

QSSTV includes a waterfall display showing the received audio spectrum. SSTV signals have a characteristic appearance — a fuzzy band of audio energy moving slowly across the spectrum as the image tones sweep through frequencies. You do not need to click on the signal as you would in Fldigi — QSSTV detects it automatically from the VIS code.

Saving received images

Configure the automatic save directory under Options → Configuration → Misc → Received images directory. QSSTV names files automatically with date and time. You can also manually save any displayed image via right-click on the receive window.

Receive quality indicators

Common quality issues in received images and what causes them:

• Correct but noisy image — weak signal or band noise. Normal on HF — try again when conditions improve
• Slanted image — sample rate mismatch between transmitting and receiving stations. Fix with the slant correction slider
• Partial image — tuned in mid-transmission, VIS code was missed. Wait for the next transmission
• Color cast or color bars — audio clipping. Reduce receive audio level
• Scrambled or inverted image — sideband is wrong. Verify USB mode on radio

Transmitting SSTV images

Step-by-step transmit procedure

1. Load an image in QSSTV's transmit panel via File → Open or drag and drop
2. Select your SSTV mode from the Mode dropdown — Martin M1 is a safe default
3. Listen on the frequency for at least one full image cycle to confirm it is clear
4. Optionally announce on SSB voice: "CQ SSTV [your callsign] going to image"
5. Set your radio to USB mode and ensure PTT is configured correctly
6. Click Transmit — QSSTV keys PTT, transmits the VIS code, then sends the image
7. Watch the progress bar — the image transmits line by line
8. When transmission completes QSSTV releases PTT and switches back to receive

Transmit audio level

Correct transmit audio level is critical for good image quality at the receiving end. The ALC on your radio should show zero or minimal deflection during SSTV transmission. Any ALC action means you are overdriving the radio's input and causing signal distortion that degrades image quality at the receiving station. Start with low audio output and increase slowly until ALC just touches zero.

Radio mode for SSTV transmission

Always transmit SSTV in USB (Upper Side Band) mode. Some radios have a DATA or USB-D mode — use this if available, otherwise plain USB. Never use FM for HF SSTV — the FM deviation characteristics are completely wrong for SSTV audio tone encoding.

Bandwidth considerations

SSTV occupies about 2.3 kHz of bandwidth in USB mode. Make sure your radio's IF filter is wide enough — at least 2.4 kHz. Some radios with narrow CW filters active will cut off high frequency SSTV tones and degrade transmit quality significantly. Use the widest available SSB filter when operating SSTV.

Operating guide — making contacts on 14.230 MHz

Listening before transmitting

SSTV transmissions take 90–270 seconds depending on the mode. Starting a new transmission on top of an in-progress QSO destroys the image for both the transmitting and receiving station. Always listen for at least one full image cycle — about 2 minutes — before transmitting to confirm the frequency is clear.

A typical SSTV QSO

1. Tune to 14.230 MHz USB and listen for SSTV activity — the characteristic warbling sound is unmistakable
2. Wait for a clear frequency — watch QSSTV's receive window until no image is in progress
3. Optional voice announcement — briefly say "CQ SSTV [callsign] going to image" on voice before transmitting
4. Transmit your image — send one image in Martin M1 or Scottie S1
5. Switch to receive — watch for a reply image from another station
6. Reply with another image — send a second image acknowledging receipt
7. Exchange continues — a typical SSTV QSO consists of 3–6 image exchanges

SSTV operating etiquette

• Never start a new image while one is in progress — wait for the frequency to be clear
• Keep transmissions reasonably spaced — give other stations a chance to reply or transmit
• Include your callsign on every image — it is standard practice and required in many jurisdictions
• Acknowledge received images — if someone sends you an image, send one back
• On crowded frequencies take turns — do not monopolize the frequency with multiple rapid transmissions
• If band conditions are poor, switch to a faster mode like Robot 36 rather than insisting on Martin M1

Finding SSTV activity

SSTV activity varies by band conditions, time of day, and day of the week. Weekend afternoons in UTC tend to be most active on 20m. During poor propagation try 40m or 80m for more regional activity. Special events and contest weekends sometimes generate bursts of SSTV activity across multiple bands simultaneously.

Logging SSTV contacts

Log SSTV contacts the same as any other mode — date, time, callsign, frequency, and mode (SSTV). For award purposes SSTV is usually logged as an image mode. Many operators collect the images themselves as a visual log of their SSTV contacts — the received image from a contact is a more interesting record than a log entry.

Receiving ISS SSTV transmissions

The International Space Station runs SSTV transmissions during special events, typically using Robot 36 mode on 145.800 MHz FM. Receiving ISS SSTV images is one of the most rewarding experiences in amateur radio — images from space, received with basic equipment.

Equipment needed for ISS SSTV

• Radio — any FM radio covering 145.800 MHz. A cheap handheld like the Baofeng UV-5R works perfectly
• Antenna — a simple 2m vertical or even a rubber duck antenna is sufficient during good passes. A yagi improves results on lower passes
• Audio connection — headphone output from the radio to your computer's line-in
• QSSTV — set to Robot 36 mode before the pass begins

Finding ISS pass times

Use the Predict tool on this site or Heavens-Above (heavens-above.com) to find when the ISS will be above your horizon. For ISS SSTV you need passes of at least 20 degrees maximum elevation — higher is better. A pass directly overhead (90 degrees) gives the longest visibility window and strongest signal.

Step-by-step ISS SSTV receive

1. Check the ARISS website (amsat.org/ariss) or the ARISS Facebook page for active SSTV event announcements — the ISS only transmits SSTV during specific events, not continuously
2. Find the next suitable pass for your location using Predict or Heavens-Above
3. Tune your radio to 145.800 MHz FM about 2 minutes before the pass begins
4. In QSSTV select Robot 36 mode (or leave on Auto to detect automatically) and click Start
5. As the ISS rises above the horizon you will hear SSTV audio — QSSTV begins receiving automatically
6. Watch the image build as the ISS crosses overhead — a 10-minute pass typically delivers 3–5 images
7. Signal strength peaks when the ISS is at maximum elevation and fades as it sets

Digipeating through the ISS APRS

The ISS also runs an APRS digipeater on 145.825 MHz. This is separate from the SSTV transmissions. During a pass you can transmit APRS packets using a path of ARISS and they will be digipeated by the ISS, potentially being received by stations across a wide area. This requires a Direwolf or hardware TNC setup — see the Direwolf guide for details.

Uploading ISS SSTV images to the gallery

ARISS maintains a gallery of ISS SSTV images received by operators worldwide. Upload your received images to the ARISS SSTV gallery (spacecomms.uk) to contribute to the collection. Include your callsign, date/time, location, and equipment details when submitting.

Preparing images for best quality

The quality of your transmitted SSTV image depends as much on image preparation as on your equipment. A well-prepared image looks dramatically better after transmission than an unoptimized one.

Resolution and aspect ratio

SSTV modes have specific resolutions — transmitting an image at the wrong size causes stretching or cropping. QSSTV resizes images automatically but pre-resizing in an image editor gives better results:

• Martin M1, M2, Scottie S1, S2, DX — 320×256 pixels
• Robot 36, 72 — 320×240 pixels
• PD-120, PD-180 — 640×496 pixels

Color and contrast optimization

• Boost contrast — SSTV transmission reduces apparent contrast. Increase contrast 10–20% before transmitting
• Increase color saturation — colors desaturate slightly in transmission. Boost saturation 15–25%
• Avoid very dark areas — shadow detail is lost in transmission. Lift shadows in your image editor
• Use bold colors — subtle gradients and pastels look washed out after SSTV transmission. Strong primary colors survive better
• Sharpen slightly — SSTV adds slight blurring. A small amount of sharpening pre-transmission compensates

Adding your callsign

Including your callsign on every SSTV image is both good practice and required by regulations in many countries. Use large, high-contrast text — dark text on a light background or light text on a dark background. Place it in a corner that does not obscure the main subject. Many operators use a consistent callsign overlay template for all their SSTV images.

Recommended image subjects

Common and well-received SSTV image subjects:

• Your shack — antenna tower, operating position, equipment
• Local scenery and landscapes
• Special event graphics and commemorative images
• Wildlife photography (bold, high-contrast subjects work best)
• Astronomical images — moon, planets, star fields
• Digital art created specifically for SSTV

Active SSTV frequencies worldwide

HAMDRM digital SSTV

HAMDRM is a digital SSTV mode built into QSSTV that transmits image data using DRM (Digital Radio Mondiale) encoding with forward error correction. Unlike analog SSTV where any noise in the audio directly degrades image quality, HAMDRM can correct errors introduced by noise and interference — producing a perfect image even when the signal is partially corrupted.

HAMDRM vs analog SSTV

Setting up HAMDRM

Configure HAMDRM in QSSTV under Options → Configuration → HAMDRM. Both stations must be using HAMDRM mode simultaneously — coordinate via voice or a brief analog SSTV exchange first. HAMDRM uses about 2.4 kHz bandwidth so check your local band plan before using it.

Troubleshooting image quality problems

Received image is slanted or skewed

Slanting is caused by a sample rate mismatch between your sound card and the transmitting station's. The image tilts left or right depending on whether your rate is slightly fast or slow.

• Use the Slant correction slider in QSSTV's receive panel — small adjustments of 0.001–0.005 are usually enough
• Positive slant correction moves the image right, negative moves it left
• Set the correction incrementally while watching the image — a correctly adjusted image has perfectly vertical edges
• Once you find the correct value for your sound card it stays consistent — save it in preferences

Image has color bars or heavy color cast

• Receive audio level is too high — clipping the input causes color encoding errors. Reduce radio volume or system capture level
• Check that the radio is in USB mode — FM or LSB cause characteristic color distortion in received images
• Ground loop hum adds bias to the audio signal — use audio isolation transformer or switch to USB audio interface

Image starts partway through

• QSSTV missed the VIS code at the start of the transmission — you tuned in mid-image
• Wait for the next transmission — QSSTV will detect the VIS code automatically and receive the complete image
• Increase receive audio level slightly so QSSTV detects the VIS code more reliably from a weaker signal

Noisy or grainy received image

• Weak signal — normal on HF. Try the same station at a different time when propagation may be better
• QRM (interference from other stations) on the frequency — nothing to do except wait or try a different frequency
• Local noise from computers, switching power supplies, or other electronics — try an external antenna well away from noise sources

My transmitted images look poor at the receiving end

• ALC is deflecting during transmission — reduce transmit audio level until ALC shows zero
• Radio is in wrong mode — must be USB, not FM, LSB, or AM
• IF filter too narrow — use widest available SSB filter (at least 2.4 kHz)
• Speech processing or compression enabled — disable all audio processing when using digital modes
• Transmit audio level too low — receiving station gets a noisy image. Increase until ALC just touches

QSSTV won't detect incoming SSTV signals

• Verify audio input is selected correctly in Options → Configuration → Sound
• Check audio level — too low and VIS codes are not detected
• Make sure the radio is in USB mode
• Try clicking Start in the receive panel if it is not already running
• Run arecord -l to verify your audio device is available to the system

ISS SSTV signal weak or intermittent

• Low elevation pass — passes below 20 degrees elevation have short windows and weaker signals. Wait for a higher pass
• Antenna pointing — for very low passes a directional antenna pointed at the horizon helps significantly
• Doppler shift — try tuning ±5 kHz from 145.800 MHz if audio quality is degraded at pass start or end
• ISS transmission may have ended — check ARISS announcements for scheduled transmission times

Frequently asked questions

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