Homebrew Projects

Homebrewing an SSTV system used to be a formidable task. Back around 1983, Dr. Robert Suding, W0LMD, one of the great pioneers in this field, demonstrated his SSTV system at a local hamfest. I recently found the presentation handout and some notes tucked away in my filing cabinet.

It summarized: "This is a project by a serious amateur for the few other serious amateurs."

PC boards were not available so the builder had to hand wire about 140 integrated circuits! Parts cost alone was about $700.

It's a lot easier today. All of the projects here use a personal computer to do most of the work. All you need to build is some sort of interface to get audio in and possibly out of the computer.

In this chapter we'll take a quick look at several systems you can homebrew. In alphabetical order:

Those marked with an asterisk (*) use very similar simple interfaces connected to a serial port. Here is the simplest version:
        

                                U1 - top view
                        (pins pointing away from you)                25    9
                            notch on this end           J1    name   pin  pin
                            and/or dot near pin 1             ----   ---  ---

                                  +----U----+         +-----+
                                  | 1     8 |    +----|--O  |  DTR   20    4
audio from         | |            |         |    |    |     |
receiver    -------| |---+--------| 2     7 |----+    |     |
                   | |   |        |         |         |     |
                C1       |   +----| 3     6 |---------|--O  |  DSR    6    6
                        <    |    |         |         |     |
                         >   | +--| 4     5 |         |     |
                    R1  <    | |  +---------+         |     |
                         >   | |                      |     |
                        <    | +----------------------|--O  |  RTS    4    7
                         >   |                        |     |
                         |   |                        |     |
audio ground ------------+---+------------------------|--O  |  GND    7    5
                                                      +-----+


                                                Radio Shack
                                                part #           $
                                                -------        -----
        U1      741 or similar op amp           276-007         0.79
        R1      47K resistor                    271-1342        0.39
        C1      0.01 uF capacitor               272-131         0.49
        J1      DB25S                           276-1548        1.99
            or  DB9S connector                  276-1538        1.29
        -       Shielded cable for audio         ?               ?

There are many variations on this basic circuit. Others use diodes for reverse voltage protection, capacitors for power filtering, and/or audio transformers for breaking up ground loops. This is trimmed to the bare essentials but still seems to work well. 

E Z SSTV

This is the easiest to get up and running. That's why the name contains "E Z".

(The American pronounciation of E Z is like the word "easy". In other countries it sometimes comes out like "ee zed".)

Simply run the program and click on the "Recv" button or press the Enter key.

The first time you run it, it will ask about the type of interface (in plain English) and where the interface is connected. It even calibrates itself automatically from signals heard on the air.

More EZ SSTV information and download instructions.


JVFAX

This is a very popular program for WEFAX and SSTV developed by D???JV. It operates with a variety of interfaces including a single op-amp version. 

Micro Scan (MSCAN)

Need to get more details about this one.... 

Pasokon TV Classic

This system is described in the January 1993 issue of QST. The software is a copyrighted commercial product so it is not (or at least shouldn't be!!!) available on a BBS or Internet site.

Those with the ambition to homebrew a single interface for personal use will be rewarded with a copy of the software and a hardcopy manual from the author at absolutely no charge. Just send a photograph of the hand wired interface as proof.

Please note that this applies only to the "Classic" version as described in QST January 1993.  It does not apply to the later Pasokon TV Lite which uses a trivial interface.

More details are in the chapter on PC Based Systems.


VESTER

Ben Vester Vester K3BC wrote "An Inexpensive SSTV System" found in the January 1994 issue of QST. The software is written in BASIC and source code is available so experimenters can make their own modifications.

Software is available from the ARRL BBS at (203) 666 0578. 


ViewPort VGA

John Montalbano KA2PYJ describes "The ViewPort VGA Color SSTV System" in the August 1992 issue of 73 Magazine. This is a more substantial interface using an analog demodulator and crystal controlled tone generator.

The software can be obtained from the Cookie BBS at (419) 562 6327.

Kits are available from A & A Engineering mentioned in the chapter on PC Based Systems.


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(C) Copyright 1995 John Langner.
JohnL@world.std.com