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FAX480 480 LINE FACSIMILE PROGRAM Dr. Ralph E. Taggart WB8DQT 602 S. Jefferson Mason, MI 48854 COPYRIGHT NOTICE The FAX480 program is copyrighted by Dr. Ralph E. Taggart. You are free to make copies of this software for your own use and to distribute copies to others, provided that no charge is levied for such distribution. ALL OTHER RIGHTS ARE RESERVED. You may not incorporate any elements of this program into other programs offered for commercial sale without written permission of the author. INTRODUCTION Since the publication of the original article on the 480 line fax standard in the February 1993 issue of QST, there have been additional enhancements to the release version of the FAX480 program that are worth noting: (1) The three image conversion utilities (BINFAX, FAXSSTV, and BINSSTV) have now been incorporated into the FAX480 program, providing more convenient use from within the FAX480 environment. (2) Two new 480 line display routines (one crystal-locked and one line-triggered) have been added to permit display of fax transmissions where you might have missed the start tone. (3) The synchronous AVT 94 video mode has been added to the SSTV receive options. (4) A synchronous 36 second SSTV receive routine has been added for the display of pictures transmitted by other FAX480- equipped stations. This mode, which depends on the extreme accuracy of the transmission rate from a FAX480-driven ViewPort interface, provides the same noise immunity enjoyed by the crystal-locked 480 line display mode while operating in the 240 line SSTV module. DISTRIBUTION FILE The FAX480.ZIP distribution file contains a total of six archived files: FAX480.DOC FAX480.EXE HOUSE.A HOUSE.B JEN.STV K4OVV.STV The FAX480.DOC file is this documentation file on the operation of the FAX480 program. The FAX480.EXE file is the complete software package for operation with the 480 line fax mode, using the modified A&A ViewPort VGA SSTV interface. The HOUSE.A and HOUSE.B files represent a sample 480 line fax image while JEN.STV and K4OVV.STV are sample SSTV image files. HARDWARE REQUIREMENTS The following hardware requirements must be satisfied for proper operation of the FAX480 program: (1) An IBM PC/AT/PS1/PS2 or compatible with a 10 MHz or faster clock speed and a minimum of 512K of RAM. (2) A VGA display adapter that is bios-compatible with the IBM VGA standard. Virtually all VGA adapters meet this requirement. (3) A monochrome or color analog VGA monitor. (4) A minimum of two 360K floppy disk drives, or a single 1.2 meg 5.25 or 1.4 meg 3.5 inch floppy drive, or a hard drive. The choice of drive options has no effect on the operation of the program but does impact the number of fax or SSTV images that can be stored as well as the speed with which images can be saved or loaded from disk. All things being equal, you will enjoy the program more if you have a hard-drive (a statement true for most software), but, if you lack one, there won't be any limitations on what you can do. (5) An optional Hewlett-Packard DeskJet or LaserJet printer for generating hard-copy printouts of fax images. The Laser printer must have sufficient memory to handle 300 dpi graphics. (6) An A&A Engineering ViewPort VGA SSTV interface, modified by the addition of a 4 MHz clock circuit as described in the February, 1993 issue of QST. (7) An available parallel printer port. INSTALLATION Hardware Installation is a simple matter of connecting the parallel port cable between the interface and your computer and making the needed audio connections. A shielded audio cable should be connected between the receiver audio output and the SSTV IN jack on the rear of the interface. A microphone is connected to the MICROPHONE IN connector on the front panel while a cable connects between the MICROPHONE OUT connector on the rear apron and your transceiver's microphone input connector. The two microphone connectors on the interface have the the following pin-outs: Pin Function 1 Microphone audio 2 PTT "hot" 3 PTT return/ground 4 Microphone ground A connector compatible with your transceiver input should be installed at the transceiver end of the cable between the interface and the rig. Consult the documentation for your transceiver for the equivalent pins on your transceiver's microphone connector. You can test the connections by operating your rig with the interface either on or off. In either case, the rig should key with normal microphone audio. The microphone patches through the interface at all times unless the interface is actually transmitting an image. The cable used to connect the parallel port of the computer with the DB-25 connector on the rear apron of the interface is a double-male and is usually sold as a "parallel cable". Such cables will have all connector pins wired. Similar-appearing cable, usually marked "serial cable", will not be fully-wired and will NOT function with the interface. Software If you have a hard drive, the best results will be obtained by operating the software from the hard disk. From your root directory, create a FAX480 subdirectory by typing: md\fax480 <ENTER> Switch to the new directory: cd\fax480 <ENTER> Now copy ALL the distribution files into this directory. In operation, you would enter the FAX480 subdirectory to execute the program and all image files would be stored in the same subdirectory. Image file capacity is limited only by available hard-disk storage. The FAX480 program can be operated from a floppy drive without any penalty other than the number of file images that can be stored on a single floppy disk. Copy the programs noted above on to a formatted disk for the drive in question. Operating from a floppy drive would normally involve booting the software from your program disk, after which you can remove the program disk and insert formatted disks for image file storage. Each fax image file requires 128K of available disk storage while SSTV image files use 64K, so you will have the following image capacity for various floppy drive configurations: Drive Fax Images SSTV Images 360K 2 5 720K 5 11 1.2 meg 9 18 1.44 meg 11 22 These figures assume that no other files are stored on the disks in question. OPERATION Booting the Program The SSTV portion of the FAX480 program inserts a small block in the upper left of all transmitted images that contains either <FAX480> or your call (six characters maximum), depending on how you boot the software. Assuming you are in the FAX480 subdirectory, or you are operating from the floppy drive with the program disk installed, to enable the call-sign option, simply type: fax480 urcall <ENTER> The call letters will appear in upper-case letters, irrespective of whether you type then in in upper-case or lower-case. If you don't care about using your call-letters, boot the program by typing: fax480 <ENTER> To make booting the software even move convenient in the future, you might consider using your word processor (in the non-document or ASCI mode) to create a batch file (FAX.BAT) in your root directory. This file would have the following format: cd\fax480 fax480 urcall cd\ with the batch file installed, simply typing: fax <ENTER> from the root director will move you automatically to the FAX480 subdirectoruy and boot the software with your call. When you exit the program, you will be back in the root directory. As the program boots, a "CHECKING PARALLEL PORTS..." message will be posted as the computer checks the three possible parallel port addresses looking for the interface. The interface unit should be connected and turned on PRIOR to booting the software. If the program doesn't find the interface unit, an error message will be posted, outlining the possible problems. You can continue at this point (type <C>) or exit the program (type <Q>). If you continue, all image file functions will be available to you but the program will not let you use the receive modes or transmit modes, since, lacking a connection to the interface, the program would "hang up" and require a keyboard or hard reset to get back on line. If the problem was a lack of power to the interface or failure to connect or switch the parallel port cable, simply hit the <T> key to repeat the port test. If you don't intend to use the interface for a particular operating session, hit <C> to continue. Almost all program functions will be available to you in such a case, except that the system will not let you display or transmit images. Typing <Q> will cause you to exit the program if your problem requires more in the way of thought or action. MAIN MENU This menu is the crossroads of the FAX480 program and provides access to all three of the primary program modules: <1> This will cause you to jump to the 480 line fax module <2> will route you to the SSTV module <3> will take you to the package of file conversion utilities <Q> will permit you to exit the FAX480 program, at which point you will be returned to your operating system. This menu illustrates a characteristic of all the primary functions of the FAX480 program. With the exception of file names that must be entered to load, save, or convert images, all menu commands are initiated by hitting a single alpha-numeric key. There is no need to use the <ENTER> key - one keystroke will accomplish each designated menu option. Alphabetical characters may be entered in either upper or lower case, so the keyboard shift status is irrelevant. Each of the three functional units will be described in the sections which follow. 480 LINE FAX OPTIONS Fax functions are organized into two columns - RECEIVE FUNCTIONS and OTHER FUNCTIONS. The former deals will the different options for receiving and displaying a 480 line fax image while the latter includes a variety of other functions. Note that the display also includes a real-time clock display that updates every minute. This is included as an aid in logging contacts. The display will be in local or UTC time, depending on how you have set your computer with the TIME function from DOS. For maximum utility, you should periodically reset the time from an accurate source. RECEIVE FUNCTIONS <1> Live Autostart This is the preferred receiving mode since image loading is initiated by the start tone and controlled by the crystal clock circuit, providing the maximum in noise immunity. This mode is used to display transmissions from other stations where the image is transmitted directly from the other computer ("live"). When you key <1> the image display screen will appear and the ** ACTIVE ** message will be posted to let you know that the system is attempting to load an image. You must enter this mode prior to the start of a transmission from the other station or just as the start tone is heard, as the system must receive a valid start tone to begin image display. If you entered the mode by accident, you missed the start tone, or there was a problem with the transmitting station, simply hit the <Q> key to exit. The ** ACTIVE ** message will be replaced by ** COMMAND **, at which point you can key <Q> to return to the Main Menu. See <3> and <4> below for how to display an image when you have missed the image start tone. Assuming image transmission proceeds normally, the received picture will be displayed, line by line, in the 512 x 480 display window. Reception can be aborted at any time by hitting the <Q> key, at which point the ** ACTIVE ** message will be replaced by ** COMMAND ** and you can use <Q> to exit back to the Main Menu. Assuming the transmission proceeds to completion, when the display window is filled with image data, the ** ACTIVE ** message will be replaced by ** COMMAND **. At this point, the received image will be retained and you have four options, as indicated by the menu on the left side of the screen: <S>ave Image <T>ransmit rint Image <Q>uit See the FAX POST-DISPLAY options for the use of these functions. <2> Recorded Autostart This option functions like <1>, except that it is used for transmissions that have been recorded on audio tape. This option does not have the noise-immunity of the clocked display mode (noise or interference can disrupt line-triggering) but does provide a useful tape-recording option. All display and post-display functions are similar to those described above. <3> Live Manual This option provides crystal-locked display if you have missed the image start tone. In all other respects, it is identical to the preferred Live Autostart option. <4> Recorded Manual This option provides for recorded display when the image start tone has been missed. In other respects, this routine is identical to the Recorded Autostart option. FAX POST-DISPLAY OPTIONS Any of the fax display options (1-4) will provide the following options when image display is complete: <S>ave Image <T>ransmit rint Image <Q>uit <S>ave Image Keying <S> will switch you to a screen prompting you for the name to be used for the image save. This name can be any valid DOS filename (8 characters max.) and should not incorporate any extensions. If you are using a floppy drive, be sure a disk is in the drive with enough capacity to hold the 128K image. Normally the file will be created in the default drive/directory. You can save to another drive/directory by including the appropriate path data in the file name you provide. NOTE: Files save to another drive/directory will NOT appear on the listing when you attempt to load images from the fax menu. If you want access to the image you have saved, the file must be transferred at a later time. See the IMAGE FILES section before attempting to do so. When the save is complete, you will be returned to the Main Menu. The received image will NOT be lost as it is retained in a RAM buffer and can be recalled at any time using the DISPLAY LAST IMAGE option from the Main Menu or by using the LOAD IMAGE FROM DISK option. <T>ransmit Hitting the <T> key will post the transmit menu display and send the image in memory. The system will key the interface and begin image transmission. When you use this option for the first time, you will need to adjust the MIKE GAIN control on the interface for at RF output reading on your transceiver that is between 1/2 and 2/3 of the PEAK reading normally observed with voice transmission. Keeping the audio level down will reduce distortion and the possibility of over-driving the transmitter. It is also important since fax transmission (like SSTV) involves a 100% duty-cycle and you do not want to overheat your final amplifier stage(s). Using a dummy load to make the gain adjustment is highly recommended. The setting of the MIKE GAIN control has no effect on normal microphone audio, which is normally set by a level or gain control on your transceiver. If you change this control, readjustment of the MIKE GAIN control will probably be required. Transmission can be aborted at any time by hitting the <Q> key, at which point the interface will drop out of the transmit mode and you will be returned to the fax menu. When transmission is completed (normally about 2 minutes and 8 seconds, the interface will drop out of the transmit mode and you will return to the Main Menu. rint Image Hitting the key lets you print a hard copy of the displayed image provided you have a compatible printer. Refer to the PRINTING IMAGES section prior to using this function for the first time. OTHER FUNCTIONS <R>ecall Last Image If you have previously received an image or loaded one from disk, that image will be scrolled into the active window of the display screen. When scrolling is complete (** ACTIVE ** switches to ** COMMAND **), you have the same options available to you as described under the receive modes. If you have not loaded or received an image since the program was booted, a black screen will be displayed. IMPORTANT NOTE: Although unlikely, if you do something that causes the program to abort, you can usually save the image by immediately rebooting the program and calling up the DISPLAY LAST IMAGE option. This is due to the fact that DOS does not normally use the RAM area allocated for the image buffer. If you reboot/reset the computer, however, the image will be lost since a reset will cause the buffer area to be over-written as part of the power-on system test (POST). While such image recovery is valid for system operating under DOS, I cannot tell you what the results will be using WINDOWS or any other GUI operating system. You can test this option by exiting the program and then rebooting the FAX480 program. If the image was corrupted, you may want to operate the program from the DOS environment. <L>oad Image From Disk When you key <L> to invoke this function, the names of all FAX480 image files on the default directory/drive will be displayed. Each of these will have an ".A" extension (see the section on FAX IMAGE FILES). Enter the name of the file to load (less the .A extension) and the image file will be loaded, the system will switch to the image display screen, and the image will be transferred to the screen. Any of the secondary functions (<S>ave, <T>ransmit, rint, or <Q>uit can be used if desired. Note that you can save the image to the default directory/drive under a different file name or you can save to another directory/drive with the save or a different file name. This provides a convenient way to copy interesting images to a floppy for backup purposes or to another disk to provide to another fax/SSTV operator. <G>rayscale Display Keying <G> will fill the entire screen with a 16-step grayscale display that is ideal for adjusting the brightness and contrast of the VGA display or for setting camera exposures for taking photographs (see PHOTOGRAPHING THE DISPLAY). Hitting any key will return you to the Main Menu. <A>dd Label to Image This option lets you add a single line of text (60 characters max.) to the bottom of the image. Any text or numerical character is acceptable but some punctuation (period, for example) or characters (" quotation marks) are not. You will get a RE-DO FROM START message if your text entry contains an illegal character. Also, although the 480 line format will resolve lower-case characters, you may want to use upper-case to retain maximum readability under less-than-optimum conditions. If you enter Q instead of a text line, the routine will return you to the Main Menu. Assuming you have entered a text line, the routine will jump to the image display screen and show you the image with the label overlaid on the bottom. Note that the text, no matter how long the line, is centered with respect to the image. This label is now in the video RAM buffer so will go out with the image if you transmit it. Also, if you Save the image at this point, it will be saved along with the image. As a general rule, you may want to Save received images before experimenting with labels so an un- labeled version can be recovered if desired. If the image is save using the original file name, the labeled version will replace the unlabeled one. If you don't like your label, it can be replaced by keying <Q> to exit the display screen, followed by an <A> from the Main Menu to do another label. Any new label will completely overlay any previous one. Labels on previously saved images can be replaced or edited using this feature. If you want to eliminate any label, reload the image in question, provided it was saved without a label.. The label feature can perform several functions. You may wish to label an image just prior to transmission with information specific to that contact: WB8DQT TO W1AW 20M 1830Z 20 JULY 1992 You may also wish to label received images in a similar manner, thus permitting your image files to serve as an image log. Labels can also be used as captions to "explain" images that are less- than-obvious in terms of the subject. <S>STV Options Keying this option will route you to the SSTV menu to be described in a later section. <C>alibration Tone This routine causes your interface to transmit one of three possible calibration tones (1200 Hz Sync, 1500 Hz Black, or 2300 Hz White) to assist the other station in precision tuning your signal. You select the tone, depending on the needs of the other station. For communicating with other FAX480 stations, use the 1500 Hz (Black) option. The calibration tone will be sent continuously until you press the <Q> key. Generally, 5-10 seconds will be adequate to allow the other station to make tuning adjustments. <T>une Display Proper grayscale rendition in both fax and SSTV modes requires accurate tuning/carrier insertion at your receiver. Usually you can achieve sufficient accuracy by tuning for natural voice quality, but this can be ambiguous at times. The tune display provides a graphic aid for precision tuning. Two vertical, parallel lines define the range from 1200 Hz (Sync) at the top of the display to 2300 Hz (White) at the bottom. If you are uncertain about the accuracy of your tuning, request that the transmitting station transmit a 1500 Hz (Black) calibration tone prior to sending an image. Key <T> for the tone display and you will note a horizontal line between the two vertical lines. Carefully adjust the receiver tuning (use the RIT control in the case of a transceiver) until the horizontal line is lined up with the two arrows. These arrows are positioned at the 1500 Hz point on the frequency display. When the line is properly aligned with the arrows, your are precisely tuned for image reception. To use the tune display for SSTV, you have several options. If the other station can transmit a short calibration tone (all stations using the FAX480 software can do so), ask them to transmit a black (1500 Hz) tone and tune as noted above for fax. Stations can also be tuned while transmitting SSTV. If you can note the bar at the top of the display that corresponds to sync (1200 Hz), tune to the point where this is positioned JUST at the top. Multiple bars should also be noted in the range between the arrows (black) and the bottom of the display (white). The black threshold can usually be noted because of the clustering of bars. If you can see the black threshold, carefully adjust tuning to it aligns with the two arrows. The rapidly shifting frequency of an SSTV signal results in the bars, corresponding to the individual frequencies, being fairly faint. They may not be readily visible on a laptop computer with an LCD screen because of the slower response time of such a display. LCD displays will work well with the single-tone tuning aid. No matter what your tuning mode, hitting the <Q> key will return you to the fax menu. <Q>uit 480 Line Fax This keystroke will cause you to exit the fax module and return to the Main Menu. FAX IMAGE FILES Although I have referred to image files in the singular, each image is actually contained in two 64K binary files. This strategy allows for fast loads and save of the image data. The file name is made up of the name you selected plus the extension A for the upper half of the image and B for the lower half of the image: filename.A filename.B Within the FAX480 program this two file structure is transparent to the user but it must be considered if you wish to copy or delete files from the DOS environment. The wildcard option is useful in both cases. Use delete filename.* <ENTER> to remove a specific image file or copy filename.* <ENTER> to copy an image file. PRINTING FAX IMAGES The rint Image option from the display menu allows very high-quality printing from displayed images. The routine supports LaserJet compatible printers, including the H-P DeskJet. Laser printers must be equipped with sufficient memory to handle a full page of 300 dpi graphics (typically 1 megabyte). The DeskJet requires no ancillary memory for printing. The printer must be connected to the computer using a parallel printer cable. This presents a practical problem since the ViewPort VGA interface is also connected to the parallel port. An A/B switchbox can be used to facilitate switching between the interface and the printer. The switch MUST be set to the interface when the FAX480 program is booted and when you desire to receive or transmit a picture. When you want to print an image, you must switch to the printer prior to invoking the print routine. Hitting the key will initiate the printing process. The screen will clear to white and the display image will be repositioned to the center of the screen. Printing a picture will require several minutes with a typical printer while the time required with the DeskJet will be significantly longer. In either case, the result is a printout of very high quality compared to other printing routines. If you operational computer is not linked to a laser printer, you can copy the FAX480 program and any desired image files to floppy disks and print out pictures on any other computer that does have the proper printer. You will get the error message when you boot the software because you will not have the A&A interface connected but that will not inhibit loading images from disk and printing them. SSTV OPERATION The basic fax functions have so much in common with SSTV that it made a lot of sense to add an SSTV option to the basic FAX480 program. The program will receive and display the following formats using a high-quality 64-step grayscale: 8/8.5 second B&W 36 second B&W 12 second Robot color 36 second Robot color 76 second Robot color Scottie 1 color Scottie 2 color AVT 94 color In addition, the system will transmit image in either the 8 or 36 second B&W format. Since the ViewPort VGA system comes with a color SSTV operating program, you might well ask why bother with a piece of software that only displays monochrome images? For someone who wants to get on every once and a while and operate SSTV, there are a couple of very good reasons why you may wish to use this part of the program: IMAGE QUALITY - if your VGA monitor will only display 256 color values, the quality of the color image display is marginal. If the received signal is slightly-mistuned, you will also get undesirable color tints on your images. That same monitor (or a monochrome VGA monitor or a VGA laptop) will do an excellent job of displaying grayscale images. Mistuning will only cause subtle shifts in the grayscale display - not a color tint! CONVENIENCE - there is no configuration file to play with since everything is clocked and all operations are independent of your CPU and its clock speed. This program is also much easier to use since almost everything works from a single menu. IMAGE STORAGE - all images stored with the ViewPort VGA program require 123K of disk space. Monochrome images are stored in color format and will be over-laid by color when called back up from disk. This program stores all images in 64K disk files and save and load almost instantly with no color tint. In addition, information on the original image format is automatically stored in the image disk file. ESCAPE - With the ViewPort VGA software, you can get trapped in a receive routine if the system doesn't get a valid sync pulse. This program features single key exit from any routine without the need to re-boot the computer. The program is simple to use and the high-quality monochrome image display will typically generate a nicer image with a standard VGA display system then will the color option. You may well find the program to be your preferred operating system unless you become a "hard-core" SSTV operator. Of course, the ViewPort VGA software can be used at any time for color display and transmission and the fax clock modification will have no effect on the operation of the interface with the ViewPort software. SSTV MENU The SSTV Menu is organized like the fax menu, supporting both receive and other functions. RECEIVE FUNCTIONS The Main Menu provides seven receive display modes. They all share a number of operational features in common. When a mode is selected, the screen will format for SSTV display, an abbreviation of the operating mode will appear along the left edge, as will a small white square in the lower left of the display. This square indicates that the program is actively processing an image. If display completes in the normal fashion, the square will disappear. In a direct sense, the square functions to perform the same function as the <**ACTIVE**> and <**COMMAND**> indicators for fax. If you need to abort display for any reason, simply key <Q> and the square indicator will disappear, leaving you in the equivalent of the fax COMMAND mode. See the section on Post-Display Options for what you can do with the displayed image. Reliable SSTV display requires that the station be accurately tuned. Results will depend on noise and interference levels. Mis-tuning will result in varying degrees of line mis- triggering, as will noise or QRM (depending on the strength of the SSTV signal. Absent interference, the noise generated by your computer system (on HF) will set the noise floor. My Zenith lap- top, for example, requires an S4-S5 signal to overcome the effect of computer generated RF (see the section on COMPUTER NOISE SUPPRESSION). <1> 8/8.5 Second B&W This is the standard low-resolution SSTV image format. While the images are limited in detail, they are acceptable if the subject is chosen with care and have the advantage that they can be transmitted very quickly. They are also compatible with virtually every SSTV system ever built, including early analog equipment. This receive mode will also display Robot 12 second color images. <2> 36 Second B&W <S> This is the high-resolution (240 line) monochrome display mode. This format provides a combination of the highest available SSTV resolution in the shortest possible transmission time. Note the <S> following this mode. If you are ready to receive another FAX480-equipped station, key <S> when the image starts instead of <2>. This will lock the display to the crystal clock and completely avoid the possibility of false line triggering. You can only use this option with other FAX480 stations since other SSTV stations employ slightly different clocking schemes. With most other SSTV systems, the clock is far enough off to result in a "tilt" to the picture that can range from mild to severe. Under difficult band conditions, you can use the synchronous option is the slant is not too bad. Some individual SSTV units will be almost on the right frequency and the results will be quite satisfactory. With other FAX480 systems, the images will be perfectly synchronized if the clock has been adjusted with reasonable care. <3> 36 Second Robot Color This is a popular format because it allows the transmission of 240 line images in a short period of time. Image quality is distinctly lower, however, that with either the 36 second B&W or 72 second Robot Color format. <4> 72 Second Robot Color This is the highest quality display in the Robot Color system and the resulting image will be equivalent to the 36 line B&W format. Having the other station send a 36 second B&W image will save time, but most operators will wish to transmit color for the benefit of others on the frequency. <5> Scottie 1 This is a popular color display mode that requires about 2 minutes for the display of a 240 line image, with resolution equivalent to the 36 second B&W and Robot 72 second color modes. <6> Scottie 2 This mode provides results comparable to or slightly better than the 36 second Robot Color mode. The main advantage, compared with Scottie 1. is the shorter transmission time. In general, Scottie 1 will provide the better quality. <7> Amiga AVT 94 This is a synchronous system that is difficult for most non-Amiga systems to handle because the format does not employ sync pulses and clocking requirements are quite stringent. The FAX480 hardware clock is sufficiently accurate, when tuned with care, and the software compensates for the different clock rates, yielding essentially perfect synchronization. If you want optimum image noise immunity when working stations equipped with Amiga, Pasokon, or up-graded Robot systems, this is the mode of choice. When working other stations using the FAX480 software, the synchronous 36 second B&W option will provide equivalent image quality in about 1/3 the transmission time. Reception of AVT94 images requires that the transmitting station be tuned VERY accurately if the software is to lock properly to the image header. Tuning errors of only 100 Hz will result in image display being aborted. If the system has locked on to the header properly, you will see the display start at the top of the screen. You should key up the mode just as the VIS data ends and the 5 second header begins for best results. If the system fails to lock on to the header data, the square block in the lower left of the screen will go out without the image being displayed. There is no way to display the image if the receiver was mis-tuned during the header interval and the <Q> key should be used to return you to the SSTV Menu. OTHER FUNCTIONS <R>ecall Last Image Whenever you use the <Q> key to exit the display screen (see POST DISPLAY OPTIONS), the image is not lost but is saved to disk as a 64K file (TEMP.STV). This image can be retrieved at any time using the <R> key. The complete range of functions described in the section on POST DISPLAY OPTIONS are then available. <L>oad Image from Disk When you key <L> to invoke this function, the names of all SSTV image files on the default directory/drive will be displayed. Each of these will have an ".STV" extension (see the section on IMAGE FILES). Enter the name of the file to load (less the extension) and the image file will be loaded, the system will switch to the image display screen, and the image will be transferred to the screen. See the POST DISPLAY OPTIONS for what you can do at this point. <G>rayscale Display Keying <G> will fill the entire screen with a 16-step grayscale display that is ideal for adjusting the brightness and contrast of the VGA display or for setting camera exposures for taking photographs (see PHOTOGRAPHING THE DISPLAY). Hitting any key will return you to the Main Menu. rint Files Printing files takes a fair amount of time, using the high- resolution image printing routine and it makes little sense to devote an entire page to SSTV images. This routine is a batch printing routine that will place up to four SSTV images on a sheet of paper. When you activate this option with the key, you will get a display of the available SSTV image files and you will be requested to supply four file names in sequence (no extensions). Any image can be skipped by hitting <ENTER> at the request. In effect, you can print from one to four images. Printing four at a time is a better investment, in terms of printing time, but the choice is yours. If the format of the four images is important to you, image 1 is in the upper left, image 2 is in the upper right, image 3 is in the lower left, and image 4 is in the lower right of the printed page. Once file names have been selected, the four images will be formatted on the screen. This will take several minutes, followed by the actual printing routine. You will find the resulting prints quite satisfactory, compared with other SSTV image print routines. <C>alibration Tone This routine causes your interface to transmit one of three possible calibration tones (1200 Hz Sync, 1500 Hz Black, or 2300 Hz White) to assist the other station in precision tuning your signal. You select the tone, depending on the needs of the other station. For communicating with other FAX480 stations, use the 1500 Hz (Black) option. The calibration tone will be sent continuously until you press the <Q> key. Generally, 5-10 seconds will be adequate to allow the other station to make tuning adjustments. <T>une Display Proper grayscale rendition in both fax and SSTV modes requires accurate tuning/carrier insertion at your receiver. Usually you can achieve sufficient accuracy by tuning for natural voice quality, but this can be ambiguous at times. The tune display provides a graphic aid for precision tuning. Two vertical, parallel lines define the range from 1200 Hz (Sync) at the top of the display to 2300 Hz (White) at the bottom. If you are uncertain about the accuracy of your tuning, request that the transmitting station transmit a 1500 Hz (Black) calibration tone prior to sending an image. Key <T> for the tone display and you will note a horizontal line between the two vertical lines. Carefully adjust the receiver tuning (use the RIT control in the case of a transceiver) until the horizontal line is lined up with the two arrows. These arrows are positioned at the 1500 Hz point on the frequency display. When the line is properly aligned with the arrows, your are precisely tuned for image reception. To use the tune display for SSTV, you have several options. If the other station can transmit a short calibration tone (all stations using the FAX480 software can do so), ask them to transmit a black (1500 Hz) tone and tune as noted above for fax. Stations can also be tuned while transmitting SSTV. If you can note the bar at the top of the display that corresponds to sync (1200 Hz), tune to the point where this is positioned JUST at the top. Multiple bars should also be noted in the range between the arrows (black) and the bottom of the display (white). The black threshold can usually be noted because of the clustering of bars. If you can see the black threshold, carefully adjust tuning to it aligns with the two arrows. The rapidly shifting frequency of an SSTV signal results in the bars, corresponding to the individual frequencies, being fairly faint. They may not be readily visible on a laptop computer with an LCD screen because of the slower response time of such a display. LCD displays will work well with the single-tone tuning aid. No matter what your tuning mode, hitting the <Q> key will return you to the fax menu. <F>ax Menu Keying <F> will return you to the fax menu. <Q>uit SSTV Hitting <Q> will cause you to exit the SSTV program and return to the Main Menu. SSTV POST-DISPLAY OPTIONS When an image has been received, recalled, or loaded from disk, you will note letters arrayed vertically along the left side of the display: <S> <T> <Q> <C> <R> The five letters correspond to your options at the point - <S>ave, <T>ransmit, <Q>uit, <C>ontrast expansion, and <R>epair. <Q>uit Keying <Q> will return you to the SSTV menu. The received image will NOT be lost and can be recovered at any time using the <R>ecall Last Image option from the SSTV menu. <S>ave Image Keying <S> will switch you to a screen prompting you for the name to be used for the image save. This name can be any valid DOS filename (characters max.) and should not incorporate any extensions. If you are using a floppy drive, be sure a disk is in the drive with enough capacity to hold the 64K image. Normally the file will be created in the default drive/directory. You can save to another drive/directory by including the appropriate path data in the file name you provide. NOTE: Files save to another drive/directory will NOT appear on the listing when you attempt to load images from the Main Menu. If you want access to the image you have saved, the file must be transferred at a later time. See the IMAGE FILES section before attempting to do so. When the save is complete, you will be returned to the Main Menu. <T>ransmit Image Hitting the <T> key will cause the screen to clear and you will be presented with the following transmit options: <1> 8/8.5 Second B&W <2> 36 Second B&W <Q>uit Transmit Keying <Q> will cause you to exit the transmit menu and the image will be re-posted. Keying either <1> or <2> will cause the image to be re-posted, the interface will key up, and the current image will be transmitted in the selected format. When you use this option for the first time, you will need to adjust the MIKE GAIN control on the interface for at RF output reading on your transceiver that is between 1/2 and 2/3 of the PEAK reading normally observed with voice transmission. Keeping the audio level down will reduce distortion and the possibility of over-driving the transmitter. It is also important since fax transmission (like SSTV) involves a 100% duty-cycle and you do not want to overheat your final amplifier stage(s). Using a dummy load to make the gain adjustment is highly recommended. The setting of the MIKE GAIN control has no effect on normal microphone audio, which is normally set by a level or gain control on your transceiver. If you change this control, readjustment of the MIKE GAIN control will probably be required. Transmission can be aborted at any time by hitting the <Q> key, at which point the interface will drop out of the transmit mode and you will be returned to the Main Menu. When transmission is completed (in either 8.5 or 36 seconds), the interface will drop out of the transmit mode and you will return to the Main Menu. Both transmit image formats incorporate the standard Robot VIS codes in the vertical sync pulse. This means that Robot 400C, 450C, and 1200C scan converters, Amiga AVT systems, the Pasokon system for the IBM, and any other display systems which use the VIS codes will be able to automatically switch to the proper mode with the receipt of your vertical sync pulse. Those with display systems that require manual display mode selection need to know what mode you will be using, so you should clearly state your option prior to beginning transmission. Even those whose systems normally trigger on the VIS-coded may need the mode to manually trigger their system if noise or QRM disrupts the VIS interval. <C>ontrast Expansion Some SSTV images you will encounter will have relatively poor contrast. This may be because of the nature or the original subject, poor lighting or other factors at the transmitting end, or slight mistuning at your end. Regardless of the cause, keying <C> from the post-display menu will give you the option to look at the pixel distribution of the image and correct contrast deficiencies if you wish. The option takes a little time, so I suggest you use it for images you have saved to disk, rather than attempting to adjust pictures while you are on the air. When you key <C> the system will BEEP, indicating that the command was recognized. NOTHING else will happen for the next few minutes but be patient. When analysis is complete, the screen will clear and you will be presented with a histogram showing the distribution of pixel values from black at the left to white on the right. The further the lines extend down from the baseline, the more pixels have that particular value. If the vertical lines are relatively widely spaced and about 16 in number, the original image was probably transmitted with 16 grayscale steps. If you key <Q> at this point, you can exit without changing the image. Otherwise, proceed as follows. The first step is to indicate where you want the new black cutoff to be. You will notice a short vertical line extending above the baseline at the far left. Pressing the <+> key will move this mark toward the right (white end of the grayscale) while pressing <-> will move it back toward black (assuming it is not already at the far left. If there are few pixels at the black end of the grayscale, move the marker to the right (using the <+> key, until you get to a point where the number of pixels begins to increase - then press the key to mark the new black threshold. If there is a good clustering of pixels at the left side of the display, simply key with the marker positioned at the far left. Once you have keyed , the marker will re-appear at the white (right) end of the display. Move the mark ( using <+>/<-> to the point where you want the white cutoff be be and key <W> to mark the white threshold. At this point the display will clear and the original image will re-appear. As you watch, it will be overwritten using the new pixel distribution. When complete, you can save the image or quite in the normal manner. If the contrast-expanded image is superior, save the image using the original file name. If you aren't sure, save it with another name and compare the two using the Disk Image Load routine. For those of you with some image processing background, this routine performs a "pixel slide" to the black threshold, followed by a pixel expansion keyed to the new white threshold. <R>epair One of the common ways in which an image can be degraded is improper line triggering. This can be caused by improper tuning or by interference or noise. Commonly, the line or lines will be offset to the right. The <R>epair routine allows you to reposition such offset lines, greatly improving the appearance of the image. The routine takes a bit of time, but is worthwhile in the cases where you want the best possible appearance for a significant image. When you key <R> a short white line will appear at the top and to the left of the image. This line marks the line to be repaired. Keying <D> will move the reference line DOWN while keying will move it UP. When the marker is positioned opposite an offset line (look CAREFULLY), pressing the <A> key will cause the line to be offset to the LEFT by one pixel. The <A> key can be pressed as often as desired to properly align the offset image line. The or <D> keys can then be used to move the scribe to other lines, where the process can be repeated. When the lines have been repositioned to your satisfaction, hitting <Q> will terminate the repair routine. At this point, you will be prompted for whether you want the repaired image to replace the original image file. Keying <Y> will replace the original image while keying <N> will retain the original disk file. At that point you will be returned to the normal SSTV post- display screen. If you elected NOT to replace the original image, it can be save to another file-name using the <S> routine. SSTV IMAGE FILES All images are saved as 64K binary files, permitting extremely fast loads and saves. Each image is also labeled with an .STV file extension. Image files can be deleted, copied, or re-named, just like any other data file. If you rename a file under DOS, be sure to add the extension to the name. If you fail to do so, the image will not appear on the image directory listing when you load a file. FILE CONVERSION MENU Keying <3> from the Main Menu will route you to the File Conversion Menu. Prior to discussion of the various file conversion options, some discussion is in order regarding sources of images and steps preparatory to conversion. Lets Start with the latter. SCREEN IMAGE CAPTURE The key to all the conversion options is the ability to capture computer images from various sources into a form the conversion programs can manipulate. This is accomplished with a family of programs called "screen capture" software. As noted in the original article on the fax standard, I prefer the VGACAP program available on the DRIG BBS (see the February 1993 issue of QST for information on this system). This is a TSR program that sits in the background until you have an image displayed, at which point you invoke the "capture" by keying <Alt-F4). At this point, VGACAP takes over and converts the screen image (without altering it) to a binary data file. If the image was in the 640 x 480 x 16 format (suitable for fax), the result will be a 307K binary file containing all the data for the screen image. This file will reside in the current directory and will be names: screenxx.raw where xx is a number from 01 to 99, depending upon how many screen captures you have executed since booting VGACAP. There will also be a matching palette file (screenxx.plt), which we do not need. Other capture programs will operate in a similar manner, but I would suggest the use of VGACAP for the most predictable results. The file conversion routine has one option for converting these 307K files to 480 line FAX480 files. If the original image was in the 320 x 200 x (16, 64, or 256) format, the result will be a 64K binary file with the same name convention as the larger 307K files, but with the extension ".bld" instead of ".raw". The file conversion module contains a routine for converting these 64K files to FAX480 SSTV image files. IMAGE VIEWERS Many image options (see below) will support full-screen display of images they create, but if this is not the case, they will support conversion of the images to one of several popular formats (.GIF, .PCX, .TIF, .IMG, or .TGA). In such cases, you need a viewing program that will import the image files and provide the full-screen display needed for capture as noted above. There are many programs that will do this, but one I have had good success with is VUIMAGE, a shareware package available on the DRIG BBS. This is an excellent program supporting .GIF, .PCX, and .TIF display, a wide range of monitor modes, and a very wide range of scaling options. Most of my images, from a variety of sources, are displayed using VUIMAGE to execute the actual screen capture. I set the mode to 640x480x16 for high resolution images I intend to capture for fax files, or 320x200x256 for generating 64K files for direct conversion to SSTV format. By adjusting the scale, I can get just the screen display I wish to capture, gaining considerable control over the dimensions and coverage of the ultimate image file. SOURCES OF IMAGES Hand scanners and flatbed scanners can also be used to generate images and most of these devices come with programs that support the 640 by 480 x 16 VGA mode. Programs such as VGACAP can be used to capture the screen images as described above. TV frame grabbers can be used if they support high resolution image capture. Most inexpensive boards will only capture 240-256 video lines. In such cases, it makes little sense to transmit these as fax, since 240 line SSTV formats will match the resolution of the captured images. Such images can be captures directly from the application or using a viewer (320x200). Higher quality frame grabbers will capture a 512 line image (using both interlaced frames that make up a TV picture). A high quality black and white camera will typically produce sharper images than a comparable color camera. These high resolution frame grabbers usually support 640 x 480 VGA display so programs like VGACAP can capture the images. Other sources, such as paint programs, image libraries, BBS sources, etc. can all provide images suitable for conversion to either fax (if the original has a high-enough resolution) or SSTV. COLOR VS. MONOCHROME Image conversion is quite predictable with monochrome images and most unpredictable with color. B&W hand-scanners and TV image capture boards generate such monochrome images automatically and present no problems when used with viewers such as VUIMAGE. Color images must be converted to monochrome prior to screen capture is acceptable results are to be obtained. Many viewing programs allow color images to be displayed with a monochrome palette (VUIMAGE, despite its other useful qualities, does NOT!), in which case you can screen grab with good results. Lacking other options, color images can be converted to monochrome using the ViewPort VGA software that comes with your interface, provided the .PCX, or .TGA images have the correct resolution to start with (see your program documentation). Assuming the VGACAP program is resident, follow the steps below: (1) Boot the ViewPort software (2) Use the <ESC> key to get the OTHER OPTIONS menu. (3) Load the image (<F7> for .TGA or <Shift-F7> for .PCX) (4) Once the image has loaded, use <ESC> to get back to the OTHER OPTIONS menu. (5) Use <F10> to get to the test and diagnostic routines (6) Key <Y> to display the Luminance data (7) Key <Alt-F4> to capture the screen Images captured in this way will produce 64K binary files suitable for SSTV conversion. All of this sounds very complex to start with, but you can't hurt anything by experimenting. Once you have played with grabbers, viewers, and images for a bit, it will all become second nature. IMAGE CONVERSION OPTIONS The Image Conversion menu supports three options (in addition to <Q> to exit the conversion menu). All share some common characteristics on that they will ask for the name of the file to convert and the name for the converted file. The three options are: <1> 307K binary files to 480 line fax This program will convert the 307K screen binary files to FAX480 fax image files. Be sure to specify the entire name of the file to convert (ex. screen05.raw), as well as directory and/or path data if the source image file is not in the FAX480 directory. Conversion will take several minutes but image line numbers will be posted to let you know how the process is proceeding. When complete, you can retreat to the fax menu and view the new image. To save disk space, the routine erases the original 307K binary file when conversion is complete. <2> 480 line fax to SSTV This routine will create an SSTV image file from a FAX480 fax file. The original fax image file is retained and the SSTV image is posted on the screen as conversion proceeds. <3> 64K binary files to SSTV This will convert 64K binary screen grab files directly to SSTV format. The SSTV image is displayed as conversion proceeds and the original binary file is erased when conversion is complete. Note that routines <1> and <3> do erase the original binary files (307K and 64K, respectively, but they don't so anything with the smaller palette files (.plt extension). You should periodically sweep your directories and erase such files. The erase screen*.* command should do the job as long as you have no un-converted screen files in the same directory. PHOTOGRAPHING IMAGES Photography provides another way to archive images you have received. A 35 mm camera, equipped with a close-up or macro lens and black and white film, will do the job if positioned on a tripod. The display image on the VGA monitor should be framed and focused with the camera so that it fills most of the field of view. To avoid a diagonal artifact on your pictures, caused by the camera focal plane shutter, set the exposure time to 1/4 to 1/2 second. The f-stop can be adjusted for the proper exposure using the grayscale display from the main menu and your camera's built-in light metering. When making photographs, keep the ambient light level low so you don't "wash out" the screen. You also need to be sure that bright objects such as windows or lamps are no reflecting off the monitor screen as viewed in the camera viewfinder. Due to the high resolution of the fax format, the resulting photographs will tolerate a high degree of enlargement (typically up to 8 x 10 inches) while retaining acceptable image sharpness. FUTURE OPTIONS When I first created the FAX480 program, it supported only 480 line fax operation. When I realized how effective the system was going to be, I added a few basic SSTV options to make the program more attractive. The present for of the SSTV module reflects added features I wanted when I actually put the system on the air. It is safe to say that the SSTV module has grown far beyond that which I had originally intended. Since the program is being made available as freeware, you cannot expect be to be quite as aggressive in adding new features as I would be if I were selling the program. None-the-less, there are a few options that are likely candidates for future upgrades: (1) HF fax receive modes The ViewPort interface provides all the hardware resources needed for reception and display of wirephotos and weather satellite photos and charts transmitted on HF. No transmission in these modes will be supported since all are too long, in terms of the time required for transmission. (2) Amiga AVT fax modes The Amiga AVT system supports a 640 x 400 fax mode which could be added without too much difficulty. The extent to which I do upgrades is dependent on two factors - the size of the program user base and the enthusiasm of users for specific features. If lots of folks are using the program and I get comments on-the-air or through my BBS (517-676- 0368), I will be more prone to make upgrades available. One thing I won't do is mess with color display. The whole intent of this project was to make an affordable system available for high-resolution imagery, with the SSTV features added as a bonus. John Montalbano is doing an excellent job in providing color options using the ViewPort interface and I can see no point in re-inventing the wheel, particularly since his software is exceptionally reasonable in terms of price. Mason, MI January 1993