Receiving ISS SSTV Live with an HT and a Phone

Before diving into decoding recorded SatNOGS audio, the most fun way to grab an ISS SSTV image is to catch the transmission live as the space station flies over your location. You don’t need a fancy radio setup — a handheld VHF/UHF radio (HT) and a smartphone are enough. Here’s how.

What You Need

• An HT capable of receiving in the 2-meter (VHF) band and/or 70-cm (UHF) band — the frequency depends on which ISS module is transmitting (see Step 3). Most dual-band hams already have a suitable radio: Baofeng UV-5R, Yaesu FT-60, Icom ID-51, etc.
• A roll-up J-pole, telescoping whip, or even the stock rubber duck antenna (better antennas = better images).
• A smartphone (iOS or Android).
• A free SSTV decoding app (see Step 1).
• A clear view of the sky during the pass — outside or near a window facing the pass direction.

Step 1: Install an SSTV App on Your Phone

Get this out of the way first so you’re not fumbling with app installs minutes before a pass.

iOS (iPhone / iPad):

• SSTV Slow Scan TV by Black Cat Systems — the go-to iOS app. Paid (a few dollars) but reliable.
• CQ SSTV — another option in the App Store.

Android:

• Robot36 – SSTV Image Decoder (free, by xdsopl) — excellent and free; despite the name it decodes most common SSTV modes including PD120 and Robot 36.
• SSTV Encoder / SSTV Decoder — there are a few free decoders; search the Play Store for “SSTV decoder.”

Install the app and give it permission to use the microphone. Open it once and poke around so you know where the record button and mode selector are.

Step 2: Confirm an SSTV Event Is Active — and Get the Frequency

ISS SSTV transmissions only run during scheduled ARISS events, typically a few times per year and lasting a few days at a time. Always confirm the event and its operating frequency before the pass — don’t assume.

• Upcoming events are listed at: https://www.ariss.org/upcoming-sstv-events.html
• Each event announcement specifies which ISS module will transmit and on which frequency:
  • The US / Columbus module (ARISS gear) transmits on 145.800 MHz FM (2 meters).
  • The Russian Service Module (MAI-75 experiments) transmits on 437.550 MHz FM (70 cm).
• The announcement also specifies the SSTV mode (PD120, Robot 36, etc.) — write it down.

If no SSTV event is active, you won’t hear anything no matter how perfect your setup is.

Step 3: Find Out When the ISS Will Pass Over

Use Heavens-Above to find pass times for your location:

1. Go to https://heavens-above.com.
2. Set your location using the link at the top right (city name, or latitude/longitude). Note: Heavens-Above only remembers your location between sessions if you create a free account and log in. Without a login, you’ll need to re-enter it each visit — or just bookmark the page after setting it; the URL contains the coordinates.
3. From the home page, click ISS under the “Satellites” section.
4. Important: the default view shows only visible passes (passes where the ISS is sunlit and the sky is dark at your location). For SSTV you can decode anytime the ISS is above the horizon, day or night — so change the dropdown from Visible passes to All passes to see every opportunity.
5. For each pass the table shows three key times — note all three:
   • AOS (Acquisition Of Signal) — the ISS rises above your horizon. This is when you should already be set up and listening.
   • Highest point (TCA — Time of Closest Approach) — the ISS is at maximum elevation. Strongest signal.
   • LOS (Loss Of Signal) — the ISS drops below your horizon. The pass is over.
   • Click any pass for a sky chart showing the path (start direction → highest point → end direction).
6. Pick a pass with maximum elevation greater than 45°. These high passes give the strongest signal, the longest decode window (~8–10 minutes), and the best chance of getting a clean image. Low passes (under 20°) are tough — terrain, buildings, and trees will eat the signal.

Step 4: Set Up the HT

1. Tune the HT to the frequency listed in the ARISS event announcement (145.800 MHz for US-module events, 437.550 MHz for Russian MAI-75 events).
2. Mode: FM (wide FM, the normal voice mode — not narrow).
3. Turn squelch all the way off (or to 0). SSTV tones won’t reliably break a normal squelch setting, and you’ll miss the start of the transmission.
4. Set volume to a comfortable listening level — about half. You don’t want it distorted/clipping, but you need it loud enough for the phone mic to pick up cleanly.
5. Optional but recommended: disable any battery-save / power-save mode so the radio doesn’t mute briefly between bursts.

If you have an external antenna, use it. A roll-up J-pole hung from a tree branch or stuck in a window does dramatically better than a rubber duck — especially on 70 cm.

Step 5: Set the Receive Mode

The ISS transmits in one of two common modes depending on the event:

• PD120 — the most common mode for recent ARISS SSTV events (each image takes ~2 minutes).
• Robot 36 — used for some events, including many Russian MAI-75 transmissions; each image takes ~36 seconds.

Most apps have an Auto mode that detects which one is in use from the leader tones. If your app has Auto, use it. Otherwise set the mode manually based on what the ARISS announcement specified.

Step 6: Decode the Pass

About a minute before AOS:

1. Take the HT and phone outside (or to a window facing the AOS direction shown on Heavens-Above).
2. Open the SSTV app and start it listening / set it to record.
3. Hold the phone microphone right up against the HT speaker — about an inch away. Try to keep it steady. Some folks rest both on a flat surface, speaker pointing at the phone mic.
4. Keep ambient noise to a minimum — no music, no conversation. Wind is the enemy.
5. As the ISS climbs toward the highest point, you’ll hear the warbling SSTV tones. The app will detect the leader tones and start drawing the image line-by-line on your screen.
6. Don’t move the phone or radio while an image is decoding — even small bumps create horizontal slip lines in the picture.
7. Signal will be strongest around the highest-point time and will fade as the ISS approaches LOS.
8. A single high-elevation pass usually yields 1–3 complete images depending on the silence cycle (see below). The app saves each one to your camera roll / photo gallery automatically.

Expect Silence Between Images — Keep Listening

The ISS transmits in a ~2 minutes on, 2 minutes off cycle. The “off” period gives the transmitter time to cool down between images. If you don’t hear anything, that’s normal — keep listening. The next image will start about 2 minutes after the previous one ended. Don’t shut down or move things around just because you’re hearing dead air; another image is coming.

(Robot 36 events on the Russian module are even more spread out — about 36 seconds on, 2–3 minutes off.)

Tips for Better Images

• Maximum elevation matters more than anything else — chase the >45° passes.
• The signal is weakest at AOS and LOS, strongest near the highest point.
• An external speaker / earphone-to-phone cable can replace acoustic coupling and dramatically improve quality, but acoustic coupling works fine for a first try.
• If the image is rolling or slanted, the app’s sample-rate calibration may be off — most apps have a slant-correction slider.
• Russian MAI-75 events on 437.550 MHz are more affected by Doppler shift than 145.800 MHz events — you may need to nudge the HT up ~10 kHz at AOS and down ~10 kHz by LOS for best audio.

Once you’ve grabbed a few live images this way, the SatNOGS recording workflow below is great for catching passes you missed or that happened on the other side of the world.

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Decoding ISS SSTV Images from Recorded SatNOGS Audio

Receiving SSTV images from the GCARC SatNOGS site uses recorded satellite audio files (typically .ogg format) from their ground station observations. You download the audio, play it through Audacity (routed via a virtual audio cable), and decode the Slow Scan Television (SSTV) signal in real time with MMSSTV software. This method works offline after downloading the file and produces high-quality decoded images, especially useful for ISS SSTV events or other satellites captured by the station.

The GCARC (Gloucester County Amateur Radio Club) SatNOGS station is publicly accessible and often records SSTV transmissions (e.g., from the ISS). No radio hardware is needed—just your computer, the free software below, and an internet connection to download the audio files.

1. GCARC SatNOGS Site (Audio Source)

• Description: This is the web-based observation page for SatNOGS ground station #223 (W2MMD / GCARC Clubhouse in Mullica Hill, NJ). SatNOGS stations record satellite passes and upload lossless audio files (.ogg format) along with waterfall plots. You browse past observations, filter for SSTV-mode passes (e.g., ISS SSTV events), and download the raw audio to decode locally.
• How to access:
  1. Go to the station page: https://network.satnogs.org/stations/223/
  2. Click the Observations tab (or go directly to the network observations and filter by station 223 and mode SSTV).
  3. Find a relevant observation (look for ones with “SSTV” in the description or strong waterfall signals during known events like ISS SSTV).
  4. On the observation page, click the download icon for the audio file (named something like satnogs_XXXXXX.ogg). Save it to your computer.
• Tip: SSTV audio is usually in the 145.800 MHz range for ISS. The .ogg files play fine in most software; no conversion is required for this method.

2. Virtual Audio Cable (VB-Audio VB-CABLE)

• Description: Free software that creates a virtual audio loopback device on your PC. It lets you route audio output from one program (Audacity playing the .ogg file) directly into the input of another program (MMSSTV) without using speakers or physical cables. This enables clean, real-time decoding with no loss.
• How to download:
  1. Go to the official VB-Audio site: https://vb-audio.com/Cable/
  2. Scroll to the download section and click the latest VBCABLE_Driver_PackXX.zip (e.g., VBCABLE_Driver_Pack45.zip – about 1.3 MB, supports Windows XP to Windows 11, 32/64-bit and Arm64).
• How to install and set up:
  1. Extract the ZIP file.
  2. Right-click VBCable_Setup.exe (or the setup file) and select Run as administrator.
  3. Follow the installer prompts and reboot your computer when finished.
  4. After reboot, open Windows Sound settings (right-click speaker icon → Sounds or Sound settings):
     • You will now see two new devices:
       • CABLE Input (VB-Audio Virtual Cable) – Use this as the output/playback device for Audacity.
       • CABLE Output (VB-Audio Virtual Cable) – Use this as the input/recording device for MMSSTV.
  5. (Optional but recommended) Set the cable volume to 100% in the Windows Volume Mixer to avoid low signal levels.

3. Audacity (Audio Player)

• Description: Free, open-source, cross-platform audio editor and recorder. Here you open the downloaded SatNOGS .ogg file, adjust playback if needed (e.g., trim to the SSTV portion), and send the audio through the virtual cable.
• How to download:
  1. Go to the official Audacity website: https://www.audacityteam.org/download/
  2. Click Download Audacity (current version is around 3.7.x). Choose the Windows installer (avoid third-party sites).
• How to install and set up:
  1. Run the downloaded installer (.exe) and follow the prompts (no special options needed).
  2. Launch Audacity.
  3. Go to Edit → Preferences → Devices (or use the device dropdowns in the main toolbar).
     • Set Playback Device to CABLE Input (VB-Audio Virtual Cable).
     • (Input device doesn’t matter for playback.)
  4. Open your downloaded SatNOGS .ogg file: File → Open.
  5. (Optional optimization) If the audio is very long, use the selection tool to highlight just the SSTV transmission portion (visible as the characteristic SSTV tones in the waveform). You can also check the sample rate (Edit → Preferences → Quality); 44100 Hz or 48000 Hz works fine.

4. MMSSTV (SSTV Decoder)

• Description: Free Windows software specifically designed for Slow Scan Television (SSTV). It decodes audio signals into color images in real time. It supports all common SSTV modes (Scottie, Martin, PD120, etc.) and has an automatic mode detector.
• How to download:
  1. Go to the official HamSoft page: https://hamsoft.ca/pages/mmsstv.php
  2. Download MMSSTV113A.exe (full version, ~2.5 MB, last updated 2010 but still the standard and fully functional for amateur use).
  3. (Optional modern fork) A community-updated version called MMSSTV-YONIQ is also available on the same site or at radiogalena.es/yoniq if you prefer a refreshed interface.
• How to install and set up:
  1. Run the .exe file and follow the installer (it’s straightforward).
  2. Launch MMSSTV.
  3. Go to Option → Setup MMSSTV (O)…
  4. In the Sound Card or Miscellaneous tab:
     • Set Sound Input (or RX sound card input) to CABLE Output (VB-Audio Virtual Cable).
     • Leave other settings at defaults initially.
  5. In the main MMSSTV window:
     • Set RX Mode to Auto (recommended for ISS SSTV, which often uses PD120 or similar).
     • Enable the waterfall/spectrogram view if desired (it helps visualize the signal).
     • Adjust the Volume slider (green bar) so the signal level peaks nicely without clipping (watch the level meter).

Full Step-by-Step Process to Decode an SSTV Image

1. Download the .ogg audio file from a GCARC SatNOGS observation as described above.
2. Make sure VB-CABLE is installed and your PC is rebooted.
3. Open the .ogg in Audacity and set its Playback Device to CABLE Input (VB-Audio Virtual Cable).
4. Open MMSSTV and set its Sound Input to CABLE Output (VB-Audio Virtual Cable). Set RX mode to Auto.
5. In Audacity, press the Play button (spacebar or play icon). Start from the beginning of the SSTV tones (you’ll hear the characteristic “beeps” and tones).
6. Watch MMSSTV: The signal should appear in the frequency graph/waterfall, and decoding will begin automatically. Images build line-by-line in the RX window.
7. When finished, you can save the decoded image via File → Save Picture in MMSSTV.
8. (Troubleshooting tips)
   • No signal in MMSSTV: Double-check device selections and cable volumes. Try restarting both programs.
   • Distorted/poor decode: In Audacity, resample the track (Tracks → Resample) to 11025 Hz or 48000 Hz if needed, then re-export temporarily as WAV if direct playback fails.
   • Low volume: Increase the CABLE volume in Windows Sound settings or Audacity playback level.
   • Mode mismatch: Manually select the known SSTV mode (e.g., PD120 for recent ISS events) instead of Auto.

This setup is reliable, widely used by the amateur radio community for replaying SatNOGS recordings, and completely free. Once you have it working with one file, you can decode any SSTV observation from the GCARC station (or any other SatNOGS station) instantly. Enjoy the space pictures!