SSTV Information 
   ---------------- 
 
Slow Scan Television has been around for a few decades but it never 
got very much attention.  The reason is that commercial equipment was 
very expensive and and it was much too complicated for most people to 
homebrew.  The situation has changed radically in the last couple years. 
Rather than using expensive special purpose hardware, most of the newer 
systems are using personal computers to do most of the work.  There is  
now a wide assortment of free software that uses very simple interfaces  
and ready-to-use commercial systems at affordable prices. New people are  
showing up on SSTV everyday. 
 
Although SSTV activity has exploded during the last couple years, it's 
still hard to find much modern information.  The most recent SSTV  
handbook published in the U.S. (that I know of) is now almost 20 years old. 
Technology has changed quite a bit since then.   
 
A very popular introductory book about Ham Radio (no names mentioned 
but it's available at Radio Shack) devotes only a few sentences to SSTV 
and describes it as 8 second black & white pictures.  It's been nearly  
all color pictures for many years. 
 
The CQ 1994 Equipment Buyer's Guide lists only two SSTV products and 
neither is manufactured anymore. 
 
Here is one of my attempts to help combat this lack of information. 
This file contains some background on SSTV, a list of equipment available, 
and pointers to other sources of information.  
 
Detailed specifications and prices have been avoided because that could 
be considered advertising.  This file is being distributed over the 
Internet and Ham Radio Packet BBSs where advertising is not appropriate. 
 
Some outdated and just plain wrong information keeps getting passed 
back and forth between various lists of SSTV equipment.  A couple months 
ago I sent letters to 29 different suppliers asking about their SSTV and  
related products.  Some letters were returned as undeliverable.  Most  
of those who did not respond have been dropped from the list.   A couple  
that didn't respond are still listed because the products are believed  
to be still available. 
 
As with anything else, there are some good products available and some 
real junk being sold with deceptive advertising.  Just get on the air 
and ask what people are using and how they like it.  Caveat emptor! 
 
Please send additions and corrections to johnl@world.std.com and I'll  
distribute a new version occasionally. 
 
Let me know where you saw this file; I'd be interested in knowing how 
far it gets propagated. 
 
 
   Version of January 1994. 
   ------------------------ 
 
 
Background 
---------- 
 
There are several different ways to send images over ham radio: 
 
1. RTTY art - Remember when people made pictures from characters? 
 
2. FSTV (Fast Scan TV - Also called ATV) - Similar to broadcast TV. 
 Full motion, color, sound, etc.  Restricted to UHF and up because 
 a signal requires several MHz of bandwidth. 
 
3. WEFAX (weather facsimile) - Very high resolution gray scale images 
 sent by audio tones over a period of minutes. 
 
4. SSTV (Slow Scan TV) - Low to medium resolution still images sent  
 through audio channels over a period of several seconds to a few 
 minutes.  Mostly color these days. 
 
5. Digital SSTV - We have the technology but I haven't seen any proposals  
 yet.   
 
 
Transmission Modes 
------------------ 
 
The original 8 second SSTV transmission mode (around 1958) had the following  
characteristics: 
 
 black = 1500 Hz 
 white = 2300 Hz 
 gray levels in between 
 120 scan lines 
 15 lines per second 
 5 mS of 1200 Hz for horizontal sync 
 30 mS of 1200 Hz for vertical sync 
 
Since that time many more modes have been invented, sometimes to add new 
capabilities, sometimes the result of Not Invented Here syndrome. 
 
The major groups are: 
 
 Robot - Introduced with the Robot scan converters (California). 
 Wraase - Introduced with the Wraase scan converters (Germany). 
 Martin - Developed by Martin Emmerson (England). 
  First available as replacement PROMs for Robot 1200C. 
  Scottie - Developed by Eddie Murphy (Scotland). 
  First available as replacement PROMs for Robot 1200C. 
 AVT - Developed by Ben Blish/Williams (Montana). 
  First available in the AVT system. 
 
The Robot, Wraase, Martin, and Scottie modes are all closely related. 
They all use the tones above for black, white, and gray levels. 
They all have 1200 Hz horizontal sync, although some Martin and Scottie 
implementations rely on accurate crystal oscillators and ignore the 
horizontal sync once synchronized.  Color is generally transmitted by sending  
each scan line 3 times, once each for red, green, and blue components.   
Robot is different from the rest in that it encodes colors with  
luminance (Y) and chrominance (R-Y and B-Y) instead of R,G,B.   
 
Each of these modes has a few different speeds, usually providing 120 or 240  
scan lines and varying degrees of horizontal resolution.  (Actually some send 
128 or 256 lines but the top 8 or 16 are always a fixed gray scale,  
leaving 120 or 240 usable lines.)   In general, the trade-off is time vs. 
image quality: the modes with the best image quality require the most time. 
 
The Robot modes have a much longer vertical sync (called VIS) containing 
7 bits of information and a parity bit.  This identifies the format of the 
following image so manual selection is not required on systems that  
recognize it.  Everyone else has adopted the Robot VIS coding and assigned  
themselves unused codes in the original specification.  Unfortunately, 
Scottie DX and one of the AVT modes use the same VIS code due to a 
lack of cooperation among developers. 
 
The AVT mode is radically different from the rest.  It has no horizontal 
sync at all; very accurate crystal oscillators are required to prevent 
slanted pictures.  After 3 repetitions of the usual Robot VIS code,  
it has a digital header with 32 repetitions of the transmission mode, and 
a sequence number.  It is only necessary to receive one of the 32 groups 
correctly to achieve synchronization.  For more details see the AVT article 
in CQ-TV mentioned in the bibliography. 
 
 
Frequencies 
----------- 
 
By convention, SSTV operation is generally found on only a few frequencies. 
 
 3.845 
 3.857 
 7.171 
 14.230 
 14.233 
 21.340 
 28.680 
 144.5 
          
 
Nets 
---- 
 
Two different Slow Scan nets meet on Saturdays at 15:00 and 18:00 UTC  
on 14.230 MHz. 
 
 
Scan Converters 
--------------- 
 
A scan converter is a device that converts images in one TV standard to 
another.  In this case we interested in converting between SSTV (for 
transmission with voice radios) and NTSC/PAL so we can use Camcorders, 
TV monitors, etc. for creation and display of images. 
 
A couple years ago anyone who was serious about SSTV had a Robot 1200C. 
 
It is a complete system dedicated to SSTV.  Just connect it to 
 - Color TV camera (either NTSC or PAL). 
 - Color TV set or monitor. 
 - Speaker and Mic connectors of a transceiver. 
 - Tape recorder for picture storage. 
 
It has 4 black & white modes (one compatible with original 8 second) and 
4 color modes with different transmission times and resolutions. 
 
It displays images with 256 x 240 resolution with 18 bits per pixel. 
That's more than 250,000 colors. 
 
 Robot Research 
 5636 Ruffin Road 
 San Diego, CA 61927 
 
It also has a parallel port for connection to a home computer.  Several  
different programs for transferring images to/from the 1200C and for  
performing various other functions are available. 
 
    ART (Amiga Robot Terminal - for Amiga computer) 
 Tom Hibben KB9MC 
 Mule Hollow Road 
 Box 188 
 DeSoto, WI 54624 
 (608) 648 2033 
 
    GEST 
 Torontel 
 174 Bellamy Rd. N. 
 Scarborough, Ontario 
 Canada M1J 2L5 
 (905) 888 9054 
       or 
 Royal Electronics (Canada) 
 336 Goodram Drive 
 Burlington, Ontario 
 Canada L7L 2K1 
 (905) 637 9622 
 
    Hi-Res (for IBM PC) 
 Tom Jenkins N9AMR 
 5968 S. Keystone Ave. 
 Indianapolis, IN 46227 
 (317) 784 6118 
 
    Robot Helper 
 William Montgomery VE3EC 
 482 Townsend Ave. 
 Burlington, Ontario 
 Canada L7T 2B3 
 (416) 681 0509 
 
    SCAN  
 Bert Beyt W5ZR 
 301 Tampico St. 
 New Iberia, LA 70560 
 (318) 365 5263 
 
 
Replacement PROMs are available to give the 1200C other transmission modes  
such as Wraase, Martin, Scottie, and AVT.  PROMs available from: 
 
 Martin Emmerson G3OQD 
 6 Mount Hurst Rd. 
 Hayes, Bromley 
 Kent BR2 7QN 
 England 
 
See "SSTV with the Robot 1200C Scan Converter and the Martin Emmerson 
EPROM Version 4.0" in the July 1991 issue of 73 Amateur Radio Today for 
more details. 
 
The 1200C was discontinued late 1992. 
 
A 1200C equivalent is available: 
 
    DFM 1200 USA Scan Converter 
 Felipe Rojas AB4QC 
 3475 Shady Woods Circle 
 Lawrenceville, GA 30244 
       or 
 Donald Lucarell K8SQL 
 265 Outlook 
 Youngstown, OH 44504 
       or 
 Muneki Yamafuzi JF3GOH 
 2-3-2, Ohyodonaka Kitaku 
 Osaka 531 
 Japan 
 
  Semi-kits containing 3 PC boards and the hard to find 
  components. 
 
The newest scan converter is the SUPERSCAN 2001.  It is similar to the 
Robot 1200C but a more modern design with several improvements. 
It can hold four 256 x 240 images with about 250,000 colors.  New features 
include mouse support, titling without a computer, both parallel and 
serial interfaces, and a CMOS RAM with battery backup to save parameters. 
 
Now available are: 
 * Semi-kit with 3 printed circuit boards, an EPROM developed 
  by Martin Emmerson, and instructions. 
 * High stability crystal oscillator. 
 * Interface card for IBM PC. 
 * Packages of hard-to-find components. 
 
The builder must gather up all the other components which go on the boards. 
 
 Jad Bashour 
 55 Hampton Road 
 London N15 3SX 
 England 
 Tel. 081 889 0486 
 
 
Digital Signal Processing 
------------------------- 
 
Digital Signal Processing (DSP) could be the next major breakthrough in 
improving SSTV reception while maintaining compatibility with existing 
equipment.  DSP uses an Analog to Digital (A/D) converter to sample the  
audio signal.  After that it's all software. 
 
DSP can simulate analog circuitry or do types of processing not even 
possible with the analog approach.  DSP isn't magic and it doesn't 
guarantee superior performance.   It all depends on the skill of the 
person writing the DSP software. 
 
Wyman Research, a major manufacturer of FSTV equipment, showed a prototype 
system at the Dayton '93 SSTV Forum.   We are all anxiously awaiting more 
information on progress. 
 
 
Home Computers 
-------------- 
 
Now that most home computers have plenty of memory and excellent color 
graphics, the most cost effective method is to use a computer with a 
suitable interface and software. 
 
Note that if you want to send a picture of anything real, you will also 
need a frame grabber which will add a few hundred more $ to the total 
system cost. 
 
 
Amiga 
----- 
 
The AVT Master system was once very popular during for both SSTV and WEFAX.   
It is composed of an interface that attaches to the parallel port and  
software. 
 
It has images with up to 4096 colors, all the popular transmission modes,  
builtin graphics editor, text generation, image processing techniques to  
clean up noisy pictures, and loads of other features. 
 
It was discontinued Fall 1993 when AEA dropped all of its Amateur  
Television products. 
 
 
IBM PC 
------ 
 
When I first typed up this file, there was only a very crude B&W  
system available. 
 
The situation has changed dramatically in the last year or two.  There are  
now several PC-based color SSTV systems available.   
 
    Pasokon TV 
 Absolute Value Systems 
 115 Stedman St. # B 
 Chelmsford, MA 01824-1823 
 (508) 256 6907 
 
  See QST, January 1993 for details. 
 
    PC SSTV 5.0 
 Software Systems Consulting 
 150 Avenida Cabrillo, "C" 
 San Clemente, CA 92672 
  
    SSTV Explorer  (Receive-only) 
 Radioware Corp. 
 P.O. Box 1478 
 Westford, MA 01886 
 (508) 452 5555 
 (800) 950 9273 
 
  Product review in QST, April 1994. 
 
    ViewPort VGA (developed by KA2PYJ) 
 A & A Engineering 
 2521 West LaPalma, Unit K 
 Anaheim, CA 92801 
 
  Construction article in 73, August 1992. 
 
All the systems have some kind of hardware interface (modem or just 
demodulator) and software that runs on the PC.  All require a VGA display. 
But there the similarities end. 
 
Interestingly, much different approaches were taken with the hardware. 
Pasokon TV uses an interface that fits into an expansion slot inside the 
computer.   ViewPort VGA uses an external interface that connects to the 
printer port.   PC SSTV and SSTV Explorer use small interfaces that  
plug into a serial port. 
 
Software varies quite a bit in terms of SSTV modes implemented, support 
for super VGA cards with more than 256 simultaneous colors, ease of use, and 
other features.   
 
 
HiRes 32 is a new version of the popular HiRes program.  It is a paint 
program designed specifically for use with the PC-based SSTV systems. 
It has fancy text and a wide variety of special effects. 
 
    HiRes 32 
 Tom Jenkins N9AMR 
 5968 S. Keystone Ave. 
 Indianapolis, IN 46227 
 (317) 784 6118 
 
Most of the recent growth of SSTV activity has been from the use of low 
cost interfaces and software on personal computers rather than expensive 
dedicated hardware.  The next logical step is to use other common hardware 
which wasn't even intended for to be used for this purpose. 
 
    SLOW SCAN TV for the SOUND BLASTER 
 Gene Harlan WB9MMM 
 Harlan Technologies 
 5931 Alma Drive 
 Rockford, IL 61108 
 (815) 398 2683 
 
  As the name implies, it uses the popular Sound Blaster 
  sound card from Creative Labs. 
 
  A demo version is available through Compuserve: 
  GO HAMNET 
  Library 6 
  SLOWSCAN.ZIP 
 
 
Multimode Systems 
----------------- 
 
The MFJ-1278B, primarily intended for packet radio, RTTY, AMTOR, Morse 
code, etc. is also capable of SSTV with the optional MultiCom software. 
 
 MFJ Enterprises, Inc. 
 P.O. Box 494 
 Mississippi State, MS 39762 
 (601) 323 5869 
 
The AEA DSP-2232 has DSP modem software for SSTV.  I talked to someone 
in sales there about a month ago.  They have no plans to complete the 
other half: the PC software to make the modem useful. 
 
The BMK-MULTY is software for sending and receiving AMTOR, RTTY, WEFAX, 
SSTV, etc. 
 
 Schnedler Systems, AC4IW 
 25 Eastwood Rd. 
 P.O. Box 5964 
 Asheville, NC 28813 
 (704) 274 4646              
 
Mac 
--- 
 
Many people have asked many times and there doesn't seem to be  
anything available. 
 
 
Others 
------ 
 
There have been SSTV implementations for other machines such as the Radio 
Shack COCO and the Atari computers.  (See Bibliography, below.)  CQ-TV also  
mentions SSTV for machines we never heard of in the USA.  
 
 
Free Software 
------------- 
 
There are several free SSTV programs available that will receive, and 
perhaps transmit, with very simple interfaces.  Look around the ARRL BBS 
(phone (203) 666 0578 or e-mail to info@arrl.org), Internet archives 
(ftp to world.std.com, ftp.cs.buffalo.edu, oak.oakland.edu or other 
SimTel mirrors), or the ham radio sections of other on-line services 
or BBSs.   
 
Look for file names resembling: 
 JVFAX??.ZIP 
 SLOWSCAN.ZIP 
 SSTVDEM?.ZIP 
 SSTVFAX2.ZIP 
 VESTER.ZIP 
 
Naturally, these don't offer all the features of some of the commercial 
systems but they are a wonderful way to get a taste of SSTV with little 
or no cost. 
 
 
Publications 
------------ 
 
Modern information on SSTV is very scarce.  The only recent handbook is: 
 
 Slow Scan Television Explained 
 by Mike Wooding G6IQM 
 (available from BATC) 
  
The only other SSTV handbook, that I know about, was written by Don Miller  
W9NTP and Ralph Taggart WB8DQT about 20 years ago. 
 
There is a good SSTV overview in the January 93 issue of QST. 
 
There are a few magazines that specialize in Amateur Television.  These are 
mostly oriented toward fast scan TV but SSTV and WEFAX are mentioned  
occasionally.   
 
 (Regular column on 'Satellites, Facsimile & Slow-Scan TV 
 Imaging' by Fred Sharp W8ASF) 
 The SPEC-COM Journal 
 P.O. Box 1002 
 Dubuque, IA 52004-1002 
 
 (Frequent column 'SSTV Revisited' by Roland Humphries G4UKL) 
 CQ-TV 
 British Amateur Television Club 
 Dave Lawton G0ANO 
 Greenhurst, Pinewood Road 
 High Wycombe, Bucks HP12 4DD 
 England 
 
 Amateur Television Quarterly  
 1545 Lee St. 
 Suite 73 
 Des Plaines, IL 60018 
 
 Amateur TV Today! 
 QCD Publications 
 1492 Highway 30 
 Tipton, IA 52216-9335 
 
Booklets of old ATVQ and A5 articles are available from: 
 
 ESF Copy Service 
 4011 Clearview Dr. 
 Cedar Falls, IA 50613 
 
A newsletter devoted to SSTV: 
 
 VISION 
 International Visual Communications Association (IVCA) 
 P.O. Box 140336 
 Nashville, TN 37214 
 
 
Bibliography 
------------ 
 
I've purposely excluded the scores of articles describing modifications 
to the Robot 400 (an early Black & White only system) because they're all  
in the booklets from ESF and of little interest to someone without a  
Robot 400. 
 
 
Abrams, Clay K6AEP & Taggart, Ralph WB8DQT, "Color Computer SSTV", 73,  
Nov-Dec 84. 
 
Cameroni, Giuseppe I2CAB & Morellato, Giancarla I2AED (translated by 
Jim Grubbs K9EI), "get on SSTV - with the C-64", ham radio, Oct. 86, P. 43. 
 
Churchfield, Terry K3HKR, "Amiga AVT System", 73 Amateur Radio, Jul 89, p. 29. 
 
Goodman, Dick WA3USG, "SSTV with the Robot 1200C Scan Converter and the 
Martin Emmerson EPROM Version 4.0", 73 Amateur Radio Today, Jul 91, p. 46. 
 
Langner, John WB2OSZ, "Color SSTV for the Atari ST", 73 Amateur Radio,  
Dec 89, p. 38, Jan 90, p. 41. 
 
Langner, John WB2OSZ, "SSTV - The AVT System Secrets Revealed", CQ-TV 149 
(Feb 90), p. 79. 
 
Langner, John WB2OSZ, "Slow Scan Television - It isn't expensive anymore", 
QST, Jan. 93, p. 20. 
 
Montalbano, John KA2PYJ, "The ViewPort VGA Color SSTV System", 73, Aug 92, 
p. 8. 
 
Pagel, Paul N1FB, "Radioware SSTV Explorer" (product review), QST, Apr 94, 
p. 80. 
 
Schick, Martin K. KA4IWG, "Color SSTV and the Atari Computer", QST, Aug 85. 
 
Taggart, Dr. Ralph E. WB8DQT, "The Romscanner", QST, Mar. 86, p. 21. 
 
Vester, Ben K3BC, "An Inexpensive SSTV System", QST, Jan. 94, p. 27. 
 
 
Conclusion 
---------- 
 
Most hams are scared away from trying SSTV because they still think it HAS TO 
be expensive.  That WAS true but it's not anymore.  SSTV activity has  
exploded in the last year with the introduction of low cost IBM PC-based 
SSTV systems.