I've been fascinated with sending pictures ever since I was licenced as a ham 10 years ago (am I that old!?) I was surprised to discover just how easy it was. With today's technology it couldn't be easier. Armed with a radio, computer and a set of images one can get a SSTV station going for a very modest amount.
Lets make some assumptions. As a radio ham you'll have a radio. As long as you know of someone else whom has a radio that can hear you (or you can hear him) any old radio will do. You will also have a computer. I use an IBM PC clone but anything will do just make sure that you can get software for it.. You'll also need an modem. A modem 'modulates' data into tones and 'demodulates' tones into data. Yes, I know that sounds technical and the SSTV puritans wouldn't call it a modem but that's what it is.
I lied. With modern PC's you don't need a modem. Just about every PC I have seen lately is equipped with a sound card. A sound card is equipped with a thing called a Digital Signal Processor. For our purposes we'll assume that this DSP is the modem. Its actually much more than that. It can be used to shape the signal as well as to decode it and a whole host of other things too.
| So here what I used to build my first SSTV station based around my PC. At the time
there was a lack of sound card software so I built the good old HamComm interface complete
with the TX mods so that it would send. Click here
to see the circuit diagram of the one on the right. This one was ok but I later built a
'basic+' HamComm interface. This greatly improved things as it treated both the
transmitted and received audio to some proper shaping and filtering etc. Click here to see the circuit diagram. So as you can see its quit a simple interface. If you went to Radio Shack to buy the parts they should cost no more than about $5. Click here to view the Radio Shack parts list for the HamComm interface. I finished the circuit off by building it into a box with all the fittings needed for my radio and computer. |
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Sound card use is much simpler, well, on receive anyway. Simply plug the output of your receiver into the soundcard and run your software (assuming it supports sound cards).
Ok, so now that we have an interface/modem/whatever we need some software for our computer. I use EZSSTV as I find it very simple to use and it has some built in test pictures that can get you going in a hurry. Its available here. When looking for software try to get some that allows not only reception of the pictures but also re-transmission of pictures too. You never know when you might want to send your buddy his own pictures. You should also get some that allows you to write messages on top of the pictures.
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Alright then. We have an interface/modem/whatever and some software for our PC. Now
all we need is some material to send to our friends. This is the tricky part. Firstly it
must be 'suitable' material. I've seen all sorts of stuff in my time and most of it was
pornographic. Its a shame really, SSTV doesn't really do the models justice ;-} These days there's all sorts of ways you can get pictures into your PC. I used a capture card to grab images from a CCIR security camera. I 'acquired' the card from a sales rep whom wanted me to start selling them at the firm I worked at. I rescued the camera from a CCTV 'sensor'. Click here to view the first camera. As it happens, this camera was also the first LoftyCam. I took the picture of me on the left with this arrangement. Note the 'suitable' t-shirt ;-} You could also use a scanner or even a digital camera as a picture source. If you don't own any of these you can get your photographs convered onto CD-ROM at your local film processing shop. Kodak charges and extra $5 if you have it done at the same time as the film is developed. |
And that all there is to it. You might think that I've over-simplified things a bit but you'll see when you do it yourself that its not all that hard.
Get your iron going and have some fun. If you 'see' me on air, give me a shout.
SSTV links ...
Download some software here
I use this DOS software
I've started to use this too
The SSTV Handbook
© & ® Mark A Phillips, G7LTT 1997/8/9/2000
This page was last updated Wednesday, February 16, 2000 12:46:49 -0000
