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UPGRADEA.TXT
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1994-01-30
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319 lines
UPGRADES TO SSTV/FAX480/WEFAX SYSTEM
We have added a number of improvements to the soft-
ware-based system described in reference 1. A brief
outline follows with a much more extensive description
being included in the instruction manual which is includ-
ed in the new software.
(1) Since the Wefax pictures take up a lot of memory
space to store the whole thing, we have added the capa-
bility to save a portion of the image in FAX480 format.
This gives a "blow-up" of the area of interest, and
provides another source of FAX480 files. Figure 1 shows a
visual mode sample of this. Get out your magnifying glass
and look at the surprizing amount of ground detail avail-
able in these HF images when you have 64 shade process-
ing. If the recipient of the image has our system, he can
colorize the IR images to see cloud tops, ocean currents,
etc.
(2) Automatic recognition of the VIS codes has been
added as a mode in the receive program. The recognized
mode is printed out and the machine continues to copy in
that mode. Manual choice of a mode is available while in
Automatic if the VIS header got QRM'ed out.
(3) Another automatic mode is identical to (2) above
except it has an automatic SAVE added for every picture
copied, with the file names being sequential letters of
the alphabet. I use the Ramdisk as the recipient store
for these files while in unattended operation, as I'm
afraid I'll forget it's turned on and fill up my hard
disk. The VIS recognition doesn't pick up very weak
signals, so most of the images stored are not too noisy.
(4) We added an Automatic mode to the SLIDESHO
program. You set the dwell time you want for each slide,
and when running, just hit A(uto) to start a continuous
sequence of all the current directory files in the cate-
gory chosen. The slide sequence continues indefinitely
until you halt it.
(5) KY1S added a feature to his copy of the transmit
program (actually the View and Transmit program, VT.BAS)
that automatically provides a listing of all the file
names in the current directory which match the mode
chosen (ie,Scottie 1, etc.) after you activate VT.BAS.
You pick a file picture from this selection and it is
displayed for you to be sure it is the one you wanted.
This only took a few BASIC commands to implement, so I
added it. Since not everyone might want this feature, a
switch is provided in the CONFIGURATION list to turn it
on or off. Dennis has provided a perfect example of how
you can adapt the program to your own operating style
using the BASIC format.
(6) Since we found that 2-color files for the LABEL
program were more available from the multitude of Paint
programs in a PCX format, we added a PCXLABEL program.
(7) Some people objected to the "tone tick" audio
cue but were not satisfied with the loss of information
when they turned it off with the program switch. I find
this invaluable as a measure of the "heart-beat" of the
system. Since some computers have a fairly loud speaker,
you can combat the noise by inserting a resistor in
series with the speaker lead to reduce the volume. Some-
what reluctantly, I have added a visual screen cue that
will light when the machine is ticking if you must turn
off the speaker (lines 485-487 in RT.BAS).
(8) Since the program uses 262,144 color processing
and display, picture sources must support the high color
resolution. Some had difficulty finding image format
manipulation programs which offered an output in 24-bit
TIFF format to match my TIFCONV program. Listing the
people who have found solutions to this: KY1S reports
using Tempra and Photo-Finish 3; N9ARX reports using
Paint Shop Pro For Windows; WB7PAP reports using Graph-
ics Workshop 7.0 (he found this on the same Steve Rimmer
BBS listed in reference 1 as a source for video drivers:
416-729-4609). The last two of these are shareware pro-
grams. These programs accept different color resolution
files in GIF, PCX, etc. formats. The final SSTV files, of
course, have no more resolution than the source files.
(9) One unexpected result that has arisen as the
system has been tried on a larger number of systems is a
much wider dispersion of Time-of-Day clock frequencies in
many of the newer systems (mostly 486 systems). I chose
this source of system timing specifically because it was
generally held to close tolerances. Since the Time gets
updated from the battery-operated clock every time the
computer reboots, this tolerance apparently was let slide
due to competitive pressures. The line timing adjust-
ments, LT, in some cases required a larger correction
than expected, but most people handled that well. They
report that you only need determine one mode's line
timing experimentally, and all the others come right on
using the LT formula. I have added another simple formula
which makes the initial correction possible after copying
only one picture to ease the work if you have a system
which diverges from the mean significantly.
A somewhat more serious problem has arisen in some
of these systems, as the wider variation in frequency has
moved the transmit header frequencies (ie, the Frame
Sync) far enough to exceed the acquisition window of most
systems with automatic VIS recognition. This can be
adjusted out with a few judicious Pokes. To make this
easy we have added a 3 position switch to the SYSTEM
CONFIGURATION in VT.BAS which allows you to put the
system in a Test mode so as to measure and adjust the
header frequencies directly. In one extreme case, the
frequencies were far enough to break out of SYNC. This
adjustment should take care of such situations and also
satisfy those who want their signals "right on" frequen-
cy.
(10) Some of my sailing friends who use laptops with
only 16 gray shades displays wanted the improved process-
ing on Wefax incorporated into those programs. Also some
Wefax users prefer the 16 shade format since it uses only
1/2 the memory for storage. A collection of these pro-
grams including automatic scheduling for maps has been
included for those folks and others who only have 16
color display capability.
(11) Another problem which has shown up in a few
cases is noisy I/O cards. This shows up as noise in the
picture even with very strong signals. KY1S reported this
first and fixed it by replacing the offending card with
an older type he had around. Others have used the same
fix. I have no significant data on which brand cards are
faulty and more importantly which ones aren't. If those
who have encountered this problem and solved it will send
me the information, I will include it in later revisions
of the software for others to use. These cards are cheap
($10 to $15) so replacement shouldn't be burdensome.
(12) Other information gleaned from helping others
get the system working is included in the new instruction
manual, TVINFO.TXT.
The above additions are included in a new release
available on the ARRL BBS (tel: 203-666-0578) as file
VESTER-A.ZIP. By the time this gets published, the revi-
sion may be beyond -A.
Ben Vester, K3BC
4921 Bonnie Branch Road
Ellicott City, MD 21043
Reference:
(1)B. Vester, "An Inexpensive SSTV System", QST, Jan
1994, pp 27-29.