Catch Me If U Can !! on “SSTV”

A Experiment worth trying with a PC and a HF rig

Hi Everybody ! This is VU2UKR. I  would like to share a small experiment that will help you to get start sending and receiving colour pictures via Ham Radio using Slow Scan Tele Vision and introduce you to this fascinating mode,  so get a taste of it and above all enjoy.  I started fancying “SSTV” ever since  I got a Email from a YL Ham operator from Brazil  in 1998, asking me if I operate on SSTV… to get a contact with India on this mode !

I was very curious to go on the new  mode, sent back a reply asking for more info on SSTV, that YL “PT2TF” sent me some hyperlinks to help me catch the race on the WEB.  Since then when ever on the NET, I  search for “SSTV”. That was the beginning….!!!

In Simple words it’s the Exchange of “still” Pictures  using Amateur Radio and a Personal computer with sound card. A picture [ File like BMP, JPG ] in your Personal Computer is scanned line by line by a computer program and converted to corresponding Audio tones with respect to the color patterns and sending it over Radio as a RF  signal. The receiving station  on the other end  converts  the RF signals to Audio tones and sends it to the Personal computer and the  Program   loaded in the personal computer decodes the Audio tones and reconverts it to  Picture.

This mode is simply great because you are not only able to Communicate  or send and receive pictures but you can see the other operator when he/she sends his/her photograph respectively. 

You can  see pictures of Earth as seen  from  the Space station MIR via SSTV, as the cosmonauts who are HAMs use this mode to send and receive pictures. Usually they send  pictures of their control room of the spacecraft, or connect  the spacecraft’s front camera to SSTV. Usually they operate on VHF/UHF frequencies. Isn’t it  interesting, sitting at  home and downloading pictures from a spacecraft. 

All you need is a

a) Transceiver  [ Homemade or Commercial ]

b) Computer - Preferably  Pentium series with Sound Card

·         CPU, 80486-DX/2/66 or Pentium preferred.

·         RAM, 8mb minimum.

·         SOUND CARD, 16-bit + MICrophone +Software

                                                      [ to encode & decode pictures]

·         VIDEO, Resolution at 640*480 res. Or higher.

·         if “Dil Mange “ More then, the more power your PC has, the       

      better it will be!

c) A  32 “BIT” Patience    J  !!!!

For this experiment, No special hardware or  interface required.

There are several simple ways to get setup for slow scan TV, what I’m describing here is the VERY simplest, which use your computer and transceiver  with no Physical Interface [ that I ‘m currently using ]. There are many other ways to do it…using  OP-AMP interface.  The shareware software required for  SSTV can be downloaded from the Internet  site viz.,

http://www.mscan.com

What you need in your PC:-

1)  SSTV Software

2)  A Picture file to transmit [ say shack photograph ] [ BMP, JPG, PIC…etc ]

3)   Soundcard with Speaker + Mic ready

Frequencies :-

SSTV is always operated in the SSB segments of the HF bands. The SSTV calling frequencies are 14.230 MHz,  21.340 MHz, 28.680MHz.

The basics of SSTV  Receive  :-

Load SSTV  Program.

Tune Transceiver to SSTV  signal,  SSB mode .

Connect  an external speaker from your  RIG, preferably use the  small headphone  module,  removed from a  scrap stereo headphone. Place the  Mic  [ Condenser Mic ]  in front of the  Head phone module. If the RX signal is strong then the SSTV program starts decoding the picture automatically, else you can force it to decode manually.  The most common SSTV modes are "Martin 1" and "Scotty 1", and you will hear SSTV users announce the transmission mode before they transmit. Most software now automatically recognizes the correct mode. Some of the software’s are viz.,  Mscan, MultiMode, W95SSTV, FTV, EZSSTV, Chromapix etc .,

Another way is to directly connect the “line out” of the RIG to “Line in” of the sound card.  Sometimes the line out of the rig might not be sufficient for the SSTV program to decode in that case additional  small AMP is required. [ I have not tested ].

A little patience is required till you get your first picture on to your system, once you master the Magic then you will be rewarded. When I started this experiment I tried to decode  more than 50 sstv transmission, but the result was just a CLEAR PICTURE of COLOUR GRAINS !! HI ! .

Thanks to my XYL  for all encouragement , support  and  for her patience … watching me download,  screens full of color GRAINS  for hours and hours !!

The basics of SSTV  Transmit :-

Load the SSTV program.

Select the picture to send.

Set rig to SSB mode.

Click the transmit button.

Once  the transmit  button is pressed  the PC Speaker turns on and starts squeaking using different tones. The picture on the screen is scanned line by line and converted to Audible tones respectively.  The Microphone is placed before the  PC speaker,  [ Instead of PC Speaker here I used Big headphones connected to PC to avoid feedback tone ].  Keep the MIC of the Rig in front of the  Speaker or headphones connected to the  PC . If you have a VOX [ Voice operated Switch ] facility then  switch it on or else  press PTT.  Usually it takes about  One minute and a half to send a picture. The pictures are transmitted via Audio tones (1200-2300 Hz) over the air.

My first attempt to this mode was sending a Picture via SSTV  to OM Karan VU3GTF, who at the time was not ready for operating in this mode, so I asked him to receive the Tones I sent and record it on a Audio Tape. Then He retransmitted it to me  on SSB mode,  so as to simulate SSTV station from his end, to my surprise I could decode the audio tones that were recorded at his end, and got back  the picture I send earlier.

As things got hot  and results were encouraging  OM Raman VU3DJQ also joined me in the experiments and together  we made things work  better,  on 3^rd Dec 2000, It was a great day for me as  I had got my first DX on SSTV a station EU6TV from  BELARUS in Europe .

The  experiment was carried out  using the following :-

Here are the snapshots that were transmitted and received .

For a Homebrewer this mode may be of quite good use as one  can exchange  Circuits diagrams, schematics,  application data over the Air.

There are a lot of choices as to the selection of which SSTV system to start with. The SSTV hams are usually very willing to help other interested HAMS, SWLs or help you get started in slow scan.

Interface:-

With a  little bit of hardware interface  using OP-AMP ( IC741  or TL071 or TL084 )   one will  be able to get extremely high quality pictures. HAMCOMM ( A Simple interface software for RTTY and CW  transceiving ) The same  hardware circuit will also run several of the SSTV software.

If you don’t have an Amateur Wireless licence, then you can receive the pictures exchanged  by other HAMs, just as Short wave listening.

Hope that this fascinating mode of transceiving Pictures finds  a place in every VU HAMs shack. There are many other modes relating your PC + Sound Card and Amateur Radio like  the  PSK31, Hellscriber,  RTTY,   receive Weather FAX from satellites etc.,

Why wait , join the SSTV gang, and SSTV operators, just as other operators will be pleased to give a helping hand to setup your station. I would be pleased to help anyone to get on this new mode.

A Homemade Radio Transceiver and a PC  is just sufficient for  SSTV to begin with.

Catch me “on SSTV “ if you can ! 

73’s 

Sunil.U.K

de        VU2UKR  

ex: M / VU2UKR