General Introduction

        There are plenty of other sites where full information about SSTV is available, so wont go into that here in any detail, except to say SSTV involves sending a single frame picture over a normal voice capable radio channel using audio. All that is required is a computer, radio and linking cable(s) or interface between the two. Receive and transmit audio is via the radio accessory socket connector, as can be TX keying, but manual TX keying is simple and easy. Perfectly satisfactory RX audio can be taken from the earphone jack on radios without an accessory socket, e.g. a scanner, if just reception is required. If physical connection between radio and computer is not practical, a microphone (even webcam mic) into the computer will work, placed near the radio's speaker, obviously the less ambient noise the better.

        In our area, the most popular computer program is MMSSTV (see note below) on 144.500MHz, FM. Several other programs are available. RX-SSTV is very straightforward for RX only. Antenna polarisation is normally vertical.

        There are currently three replay stations operating on 144.500MHz analogue in the UK, a manned system (not 24/7) by G4OAX in Frinton-on-Sea, Essex, MB7TW south Birmingham and an occasional MB7TF just north of Cambridge. More detail on these systems and how to use later.

        Of course MMSSTV can be used on other frequencies and modes, including HF/LF. MMSSTV is very popular on 14.230MHz USB. There are also many variants (see note below), one such is EZ which although triggered by a radio signal, actually sends the picture via the internet. More info is available elsewhere.

        These programs are some years old and may run better on older computers, so a good use for that old Widows XP machine maybe? The older computers also often had a serial port for easy TX/RX control, especially if 'homebrewing'.

        NOTE: Most OpenWeb and KiWi SDRs via the internet have a build in analogue SSTV decoder in the 'Extension' drop down list, so if using an SDR you don't need a separate decoder (or even a radio come to that!!).

    MMSSTV

         This is the most popular program to use, is freely available, and ideal to get started. No particular explanation is required, although a couple of tips to get set up initially without wading through the help files might prove useful. This analogue system will copy surprisingly weak signals, all be it with a lot of noise if very weak.

        As already mentioned, the picture is sent as audio 'tones', full details and specifications can be found elsewhere. Briefly, the audio is FM modulated onto an audio subcarrier with sync at 1200Hz and the video between 1500 - 2300Hz, black being at 1500Hz and peak white at 2300Hz. The widest RF bandwidth on the radio appears most suitable.

        A quick and easy start is to get the program up and running in RX, connect audio from your receiver to your computer line in, level adjustment may be required under 'Option'. The level is indicated to the left of the waterfall, when receiving a signal it should be green and averaging around the line between the waterfall and the orange box above, or slightly more.

        An initial issue most users encounter is how to get the slant of the picture correct. Receive a picture which is known to be correct e.g. the replay station, click on the 'Sync' tab above the picture, below the picture you should see a yellow smiley face, click on this then click on 'Mem' to the right. Go back to the 'RX' tab and the picture should be straight, this setting corrects both TX and RX, so no further adjustment should be required.

        The file MMSSTV.TXT within the program under the 'Help' tab is quite comprehensive.