SSTV – Slow Scan Television

Intro to SSTV (Slow Scan Television)

My goal in this article is to give a very basic overview of SSTV (Slow Scan Television), explain why this technology is useful and a brief tutorial that explains how you can use it to your advantage with items you likely already have. If you have a ham radio, an Android phone, 10 minutes and a little bit of patience you can be working stations like a semi-pro today.

Slow Scan TV was developed in the 1960s and is used by amateur radio operators all over the world. The technology used in transmitting is very similar to Analog television but at a smaller bandwidth. Just to give you an idea of how small, Analog broadcasts used a 6Mhz channel to transmit lines at 25-30 frames per second. SSTV uses only 3khz of bandwidth at most. Transmission time depends on the method that you use but my experience has been a transmission time of between 30 seconds and 2 minutes to send a single image. Because the images are transmitted over the air, parts of the image can be lost resulting in imperfections in the image.

Now that you know when it was developed and the limitations you may be thinking why not just use the internet or my cell phone? I always like to answer that question with another question. What if your cell phone or the internet stops working? We all know if major communication breaks down, ham radios and their operators will be worth their weight in gold.  You can use slow scan to send images of maps, weather patterns that you download from satellites, schematics or other technical data that would be easier to represent with a picture.  Although there are some serious use cases for slow scan, during the net we like to take the time to share images that we enjoy or think others enjoy.  Being active in slow scan is not only fun but will also make you a more capable operator.

You should now have a basic overview of slow scan and it’s capabilities.  If I still have your interest you can follow the tutorial below to learn how to receive and transmit using your radio and an Android phone.  It is possible to receive and transmit on an iPhone and using a computer (Windows/Linux/Mac OS) but we are focusing on Android for now because it is the cheapest mobile option.

Receiving Transmissions

To receive transmissions you will need to download an application called Robot 36 on the GooglePlay Store.  Make sure the application is in auto mode.  This automatic mode will allow the device to determine and decode the transmissions without interaction by you.  Any images that are decoded are automatically saved to your device.  With the software running, make sure the microphone of your Android device is as close as possible to the speaker of your radio.  No cables are needed using this method.  There is a tutorial below that shows me installing and setting this up on my phone.

Transmitting SSTV

Transmitting images is a simple process overall.  You will need to download an application called Slow Scan SSTV on the Google Play Store.  With the application open, you can select an image by clicking on the portrait at the top of the application.  Center your picture in the box by dragging and two finger pinch to zoom.  Click the three dots in the top right corner to select your mode.  On the Anderson Radio Club Slow Scan Net we will use Robot36 as the standard mode.  To add your call sign, click on the screen and a menu will open.  Type in your call sign in the text box.  To move your text around on the image, double press and drag where you would like the text to be.  To erase the text, click on the text and erase and save the text box in the menu and click the button in the top right to save.  When you have the image that you desire in the box in the center of the app using the Robot36 mode you are ready to transmit.  Key and hold your radio mic and press the play button at the top of the slow scan app.  Hold your Android speaker up to your radio microphone while you transmit.  For best results, increase the volume on your Android device to max volume.  There is a tutorial below that shows e installing the app and transmitting a test image.

Below are some of the images that have been received since we have started the Anderson Slow Scan net.  Special thanks to Colin (KO4DZT) for being active, setting up the net and for just being an all around swell amateur operator.