Foundations of Amateur Radio

In 1958 The Kentucky Engineer published an award winning student article by Copthorne "Coppie" MacDonald. He described a Slow-Scan T.V. System for Image Transmission. If you get the opportunity, have a look for the link on his archived home-page which you can find from the Wikipedia SSTV page.

The purpose of this narrow band television idea was to be able to send images using cheaper equipment and less bandwidth than normal television. The idea caught on and it's still in use today.

In 1959 the idea of slow scan tv was used by the Luna 3 mission to transmit images from the far side of the moon. The NASA Apollo program also used SSTV to transmit images from Apollo 7, 8, 9 and from the Apollo 11 Lunar Module.

In 1968 SSTV became a legal mode for radio amateurs in the United States.

The International Space Station regularly uses SSTV to send images to radio amateurs across the globe.

The version of SSTV in use by radio amateurs today is different from the earlier grainy black and white images coming from the moon and if you're expecting a moving image, something that TV implies, you're going to be disappointed, since the popular SSTV modes send images one at a time, taking up to a minute or so to send. With a frame-rate of one frame per minute, watching anything other than grass grow is going to be a challenge.

That said, SSTV is a lovely and relatively simple way of sending images across the air.

In my quest for new adventures I like to play with things I know nothing about. I suspect that it's ingrained but it does keep me off the street. The other day I received an email from a local amateur, Adrian VK6XAM, who sent a message describing a new SSTV repeater he'd set-up for testing purposes. It's a local 2m repeater that waits for an activation tone, then it expects you to transmit an SSTV image and it will replay the image back to you. If you've familiar with a parrot repeater, this is a similar thing, just for SSTV rather than audio. The repeater is running on solar power and with the 100% duty cycle of SSTV, it's only available during daylight hours.

Technicalities aside, I couldn't resist.

So, I fired up QSSTV, a piece of Linux software that among other things knows how to receive and send SSTV images. After turning on my radio, tuning to the correct frequency, I received my first ever SSTV picture.

On a bright red background a yellow symbol appeared. At first I thought it was a hammer and sickle, but on closer inspection it was a micrometer and caliper, which absolutely tickled my fancy, having just taken delivery of some precision measuring tools - a Mitutoyo Test Indicator and a few other bits and pieces for another project I'm working on.

Had to learn how to drive QSSTV, make a template so you can overlay text on an image, learn what a signal report should look like, then when I figured all that out I triumphantly hit send and it made all the right noises, but nothing was happening.

More time looking at the inter-web taught me that if I want to use the rear connection on my FT-857d to send audio using FM, as opposed to SSB which is what most digital modes need, you need to set the radio to PSK mode and magically it starts to work.

My first ever SSTV image was sent an hour and a half after receiving my first image and the repeater dutifully sent it back. Then I got a picture from Keith VK6WK.

Of course the paint isn't even dry on any of this, so there's plenty more to learn, but the process is not too complex.

I will note a few things.

I had already set-up digital modes, that is, my radio was talking to my computer via CAT, that's Computer Assisted Tuning, essentially a serial connection that controls the radio and the audio was already being sent and received from the rear connector of my radio.

Getting SSTV running was really an extension on those activities, so if you're going to do this, take some time to make things work. I continue to recommend that you start with WSJT-X since it helps you get your levels and connections right.

Now I suppose I should start playing with SSTV over HF, but first I would like to figure out how to make the templates work better for me and how to actually seriously log an actual contact.

More adventures ahead!

Remember, have fun, play, get on air and make noise!

I'm Onno VK6FLAB