Receiving SSTV Images on Ham Radio: ATS Mini V4, RTL-SDR, and Decoding Software

Our SDR getting-started guide covers RTL-SDR basics broadly, and our ATS Mini V4 content covers the radio itself in depth, but neither walks through one of the more rewarding beginner ham radio activities you can do with either device: receiving Slow Scan Television (SSTV). SSTV encodes a still image as an audio tone sequence transmitted over standard voice radio bands - no special hardware beyond a receiver and a way to feed audio into decoding software. It's how amateur radio operators (and periodically, astronauts aboard the ISS) transmit pictures over the air, and it's one of the more satisfying "I can't believe that worked" moments in the hobby.

How SSTV Actually Works

An SSTV transmission encodes an image line by line as a sequence of audio tones - pitch corresponds to brightness and color, with a sync pulse marking the start of each line. A receiving station just needs to capture that audio accurately and feed it into decoding software, which reconstructs the image by mapping tone frequency back to pixel color over time. Several encoding modes exist (Martin M1, Scottie S1, Robot 36, PD120 among the most common), each trading transmission time against resolution and color fidelity - the decoder auto-detects the mode from the sync pattern in most cases.

What You Need

• A receiver capable of SSB reception in the ham bands where SSTV activity happens - most commonly 14.230 MHz (20m) for HF SSTV, though VHF/UHF SSTV nets exist regionally, and the ISS periodically transmits SSTV on 145.800 MHz FM during scheduled events.
• Audio output from the receiver - either a physical 3.5mm audio cable from the radio's headphone jack into a computer or phone's microphone/line-in, or (for SDR-based reception) the demodulated audio stream from the SDR software itself.
• Decoding software - MMSSTV or QSSTV on a PC, or Robot36 on Android/iOS for phone-based reception via the microphone.

Option 1: ATS Mini V4 + Phone App

The ATS Mini V4's SSB capability, covered in our SSB tuning guide, makes it a legitimate SSTV receiver despite being a pocket radio rather than a dedicated ham transceiver. This is the lowest-friction path to your first decoded SSTV image:

1. Tune the ATS Mini V4 to 14.230 MHz USB (upper sideband) - this is the most active HF SSTV calling frequency, most reliably occupied during contest weekends and scheduled SSTV events.
2. Use the fine-tuning steps from our SSB guide to get the tone centered and crisp - SSTV decoding is far more sensitive to mistuning than voice communication, since the decoder is reading precise audio frequencies as color and brightness data.
3. Position your phone's microphone near the ATS Mini's speaker (or better, use a 3.5mm cable from the ATS Mini's headphone jack directly into the phone if your phone/adapter supports audio-in), and open Robot36 or a similar SSTV decoder app.
4. Wait for a transmission - you'll hear the distinctive rising SSTV calibration tone, and the app will begin drawing the image line by line in real time as it decodes.

Direct cable connection into the phone beats holding a microphone near a speaker by a wide margin - any room noise or speaker distortion shows up as visible artifacts (color speckling, torn lines) in the decoded image.

Option 2: RTL-SDR + PC Software

An RTL-SDR dongle paired with SDR# or SDR++ and a virtual audio cable gives you more control and generally cleaner decodes than a phone microphone setup, at the cost of more moving parts to configure:

1. Tune your SDR software to the target frequency in USB mode, same frequency guidance as above.
2. Install a virtual audio cable (VB-Audio Cable on Windows, or a PulseAudio/JACK loopback on Linux) to route the SDR software's demodulated audio output directly into your SSTV decoder's input, rather than looping audio through physical speakers and a microphone.
3. Open MMSSTV or QSSTV, set the input to the virtual audio cable, and let it auto-detect the incoming mode once a transmission starts.
4. For the clearest signal, use a proper HF antenna (see our RF and antenna fundamentals guide) rather than the RTL-SDR's stock antenna, which is optimized for higher frequencies than 20m HF.

Receiving ISS SSTV Events

NASA and ARISS periodically schedule SSTV transmissions from the International Space Station on 145.800 MHz FM, commemorating anniversaries or events - these are announced in advance on ARISS and ham radio community sites and are a great target because the ISS is a strong, predictable signal source with a known pass schedule. This requires VHF reception (not the ATS Mini's typical shortwave/HF focus, though check your specific unit's band coverage) and tracking the ISS pass times for your location, since you're only in range for the several minutes the station is overhead.

TargetFrequencyModeBest Receiver HF SSTV (general ham activity)14.230 MHzUSBATS Mini V4 or RTL-SDR with HF antenna/upconverter ISS SSTV events145.800 MHzFMVHF-capable receiver or RTL-SDR with VHF antenna Regional VHF/UHF SSTV netsVaries by regionFMCheck local ham radio club schedules

Troubleshooting Poor Decodes

• Torn or skewed image lines: usually mistuning - fine-tune in small steps until the sync tone sounds crisp and consistent rather than drifting.
• Color banding or wrong colors entirely: often an audio level issue - too hot an input clips the tones, too quiet loses the low end. Most software shows a level meter; aim for consistent peaks without clipping.
• No lock/mode detection at all: confirm you're actually on USB, not LSB or AM - SSTV is conventionally transmitted USB regardless of HF band convention, and a mode mismatch will produce audio that never resolves into a recognizable sync pattern.

Safety and Legal Notes

Receiving SSTV requires no license anywhere - you're just listening, the same as tuning a shortwave broadcast. Transmitting your own SSTV images does require an amateur radio license appropriate to the band you're operating on, and licensing requirements vary by country. This guide covers receive-only operation, which is legal for anyone with a capable radio.

SSTV reception is a genuinely good project for exactly the audience this site already serves with ATS Mini and SDR content - it turns a receiver you already own into something that produces a tangible result (a decoded image on your screen) rather than just audio, and it's a natural next step once you're comfortable tuning SSB.