Date: Tue, 12 Apr 1994 13:50:25 -0400
From: johnl@world.std.com (John W Langner)
To: bowen@cs.buffalo.edu
Subject: replacement for ancient /pub/ham-radio/sstv...

			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Some outdated and just plain wrong information keeps getting passed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.