DroidSSTV - SSTV for Ham Radio

DroidSSTV - SSTV for Ham Radio is an Android application that enables amateur radio operators to send and receive Slow Scan Television (SSTV) images directly from their mobile device. This app is a practical solution for portable ham radio enthusiasts, effectively turning an Android smartphone or tablet into a self-contained SSTV transceiver. Users of DroidSSTV - SSTV for Ham Radio can decode incoming audio signals into images or encode their own pictures for transmission over the air. It eliminates the need for a dedicated computer, offering a streamlined, on-the-go method for this unique form of visual communication.

Decoding Incoming SSTV Signals with Audio Input

To decode signals, users first connect their device’s microphone to a radio’s audio output, either via cable or by placing the device near the radio’s speaker. After launching DroidSSTV - SSTV for Ham Radio, they tune their HF or VHF transceiver to a known SSTV frequency, such as 14.230 MHz. The application’s built-in spectrum analyzer provides a visual aid for precise tuning. As the modulated audio is received, the software automatically detects the transmission mode (e.g., Scottie 1, Martin 2) and begins drawing the image line by line on the screen. The final decoded picture is automatically saved to the device’s gallery for later review or sharing.

Transmitting User-Selected Images as SSTV

For transmitting, users begin by loading an image from their device’s storage into the gallery within DroidSSTV - SSTV for Ham Radio. The app provides tools to adjust the image’s contrast, brightness, and saturation to optimize it for the limitations of SSTV transmission. Once the image is prepared, the user connects their device’s audio output to their radio’s microphone or auxiliary input. After keying their transmitter, they press the transmit button in the app. DroidSSTV - SSTV for Ham Radio then encodes the picture into the appropriate audio tones, which are played out and broadcast over the air.

Utilizing Pre-Loaded Templates and Macros

This function allows for the rapid creation of standardized images, like contact information or contest exchanges. Users start by creating or importing a template image, which serves as a background. Within DroidSSTV - SSTV for Ham Radio, they can then define editable text fields over this template. During operation, users select the desired template and fill in the macro fields with relevant text, such as their call sign or signal report. The app seamlessly merges the text onto the template image, creating a new, customized picture ready for immediate transmission without needing external editing software.

Managing and Sharing a Received Image Library

All pictures successfully decoded by DroidSSTV - SSTV for Ham Radio are automatically saved to a dedicated folder on the device’s SD card or internal storage. The application provides a built-in gallery view to browse this collection of received images chronologically. From this gallery, users can perform several actions: they can review past transmissions, delete unwanted images, or select a specific picture to share. The share function integrates with the Android OS, allowing users to directly email an image, upload it to cloud storage like Dropbox, or post it to social media platforms, all without leaving the app.

Adjusting Audio Levels for Optimal Performance

Successful decoding requires a clear audio signal at the correct level. The DroidSSTV - SSTV for Ham Radio interface displays a real-time level meter that responds to the incoming audio from the radio. Users monitor this meter and adjust their radio’s audio output volume or the device’s microphone gain to keep the input level within the optimal range, indicated on the meter. This ensures the software can cleanly decode the audio tones without distortion. Proper level adjustment is a critical step users perform before and during reception to guarantee image quality.

Automated Mode Detection and Synchronization

This core feature handles the technical complexities of signal processing automatically. When an SSTV transmission begins, DroidSSTV - SSTV for Ham Radio first listens for the Vertical Interval Signaling (VIS) code, a digital tone that identifies the specific mode. The app decodes this VIS tone and automatically configures its decoder to the correct protocol. Throughout the reception, the software continuously performs auto-synchronization and slant correction, compensating for minor timing differences in the received signal to keep the image perfectly aligned and straight as it is drawn on the screen.