═══ 1. Introduction ═══ This program receives weather faxes and other radio faxes from a High Frequency (Short Wave) radio. The radio requires Single Side Band (SSB) or a Beat Frequency Oscillator (BFO). The computer requires OS/2 MMPM/2 and a supported sound card. To get started browse the following sections :  Physical configuration  Tuning the radio  Tuning the computer  Possible problems ═══ 2. Getting Started ═══ This program is designed for novice users. Jargon is kept to a minimum. The following sections should get you started in receiving the standard weather faxes. ═══ 2.1. Physical configuration ═══ Use either a microphone : Or an inline connection : to the microphone or inline socket of the sound card. When you first start this program a Set Initial Parameters dialogue should be displayed. If not then on the menu line, select Options, then select Set Initial Parameters. The Set Initial Parameters dialogue is displayed. Click on the appropriate Audio Input radio button. Click on OK ═══ 2.2. Tuning the radio ═══ Tune the radio to a weather fax frequency. Choose a single side band, usually upper, or tune the beat frequency oscillator, usually negative. You should hear a sound like crickets.  What radio fax sounds like ═══ 2.3. Tuning the computer ═══ On the menu line, select Window. Select Show spectrum. A small window will appear. This window displays the audio frequency spectrum of the incoming fax. Select Record. Select Start now. After a few seconds black lines appear in the spectrum window. The red line is the division between black and white parts of the incoming weather fax. There may be two peaks on the black lines if a fax is being received on the radio, one for black and the other for white. If a greyscale picture (an audio frequency between the black and white extremes represents a shade of grey) is being received, the black lines look like a blob shaped by the particular picture. Adjust the volume on the radio so that the VOL bar at the top of the spectrum window is about a third of the way across. This volume bar indicates the amplitude of the audio. Almost no bar indicates insufficient audio from the radio. A near full bar indicates too much audio and likely signal distortion. You may need an OS/2 mixer applet for your specific sound card to increase the Microphone or linein gain sufficiently. The aim of the next exercise is to position the red line between the two peaks (or somewhere within the blob for greyscale). If you have a BFO you can tune it to reposition the peaks around the red line. Or you can use the + and - keys to move the red line up and down. Note that the spectrum window only refreshes after every few seconds. If you want faster update select Record/Fast update. The best results may be got tuning the BFO so that the white peak is at 2300 Hz, the black at 1500 Hz and the red line at 1900 Hz. With the red line positioned between the two peaks, a picture should be unfolding in the main window. For a black and white picture, the foreground is usually black and the background white. If this is not the case the radio is tuned to the oposite side band. Select Record/Negative or Positive to correct the colours. The two peaks of the spectrum may be hard to see if there is some high frequency interference or computer generated noise. Move the red line up and down until you get the best picture; When you want to stop receiving, select Record then select Stop. Also refer to :  Alignment/Align  Record/Start on sync  Record/Auto sync and save ═══ 2.4. Possible problems ═══ Gaps between individual lines in the spectrum. The audio volume from the radio is too low. You may need an OS/2 mixer application, for your particular sound card, to set the input gain level. Adjust the gain and radio volume so that the volume bar in the Spectrum window is about one third the way across the window. Many peaks in the spectrum. The audio volume from the radio may be too high and clipping the signal. Adjust the input gain (mixer) and radio volume so that the volume bar in the Spectrum window is about one third the way across the window. Picture jumps horizontally. Buffers from the sound card occasionally disappear. I have seen this on Sound Blaster cards recording 8 bit samples. If you have a 16 bit Sound Blaster card set Bits per sample (Options menu) to 16. Picture looks noisy. Check that the input gain and radio volume is adjusted so that the volume bar in the Spectrum window is about one third the way across the window. Try selecting 64 greys in case the picture is grey scale. If the picture still looks noisy, listen to the monitor then compare to What radio fax sounds like. Noise could come from the computer, monitor, other appliance or atmospheric conditions. You should use an outside antenna and the lead connecting it to the receiver should be shielded. Message - Program not keeping up with Fax input. This message occurs when half the allocated memory for the transfer of sound information from the sound card to the program is used up. Try to reduces processor load and swapping activity from other applications. Try only using the spectrum when tuning, reducing the dots per line, reducing the sampling rate, reducing the grey scale or using black and white when grey scale pictures are not being transmitted. Radiofax fails while Grey definition is set to 16 Some VGA drivers have a problem processing 4 bit bitmaps (16 greyscale). Use 64 greyscales instead or try and obtain a recent video driver. Picture is skewed. The sound card and driver may not be sampling exactly as specified. Use Alignment/Skew to slope the picture back to the left or right while a picture is being received. ═══ 3. Menu items ═══ Only valid menu items will be enabled at a particular time. A few items, for which facilities is not yet written, are permanently disabled. ═══ 3.1. File/New ═══ Clears the current picture without saving it. The Record menu items will then be enabled. ═══ 3.2. File/Create viewing window ═══ Creates a new window titled "View Faxes" for the purpose of displaying saved faxes while a fax is being received in the primary window. Any number of these windows can be created. ═══ 3.2.1. View Faxes Window ═══ This window was created by the File/Create viewing window menu item. It is used primarily to display a saved fax (use File/Open) while the primary window is busy receiving a new fax. If you want to compare a number of pictures, create a number of View Faxes windows. ═══ 3.3. File/Open ═══ Displays a dialogue from which you can select one or more saved faxes from a list. The selected faxes will then be displayed in progression. If the disk is formatted with FAT then each list entry displays the long file name from the Extended Attribute followed by the FAT file name. Refer to Open Radio Faxes Dialogue. ═══ 3.4. File/Save ═══ Saves the fax, currently displayed in this window, on the hard drive. The file path from the current directory will be \RFAXES\FAX on 1995-01-25 at 02-30.BMP where :  1995 is the year  01 is the month, January  25 is the day of month  02-30 is the Coordinated Universal Time in hours(24) and minutes. This is the date and time the fax started. The date format enables the files to be listed cronologically when sorted in alphabetic order. This is an OS/2 HPFS long file name. If the disk is formatted with FAT then a file name FAXnnnnn.BMP is generated and the long name is stored in the extended attributes. ═══ 3.5. File/Save as ═══ Saves the fax, currently displayed in this window, on the hard drive. You specify the path and file name. You can use a long file name even if the disk is formatted with FAT. The long file name will be stored in the extended attributes. ═══ 3.6. File/Delete ═══ Deletes the saved copy of the fax, displayed in this window, from the hard drive. ═══ 3.7. File/Print ═══ Prints the displayed fax on the default printer. The height and width dimensions will be as displayed on the screen. You can change the dimensions selecting Window/Scale to window and resizing the window. Use the settings on your OS/2 print icon to change the default printer and the page orientation. ═══ 3.8. Alignment/Align ═══ This facility is required when the sync pulses have not been picked up at the start of the fax. After selecting this item the pointer is displayed in this window. Align the vertical line of the pointer where you want the left hand edge of the picture to be. Then click mouse button one. The picture will be re-aligned and the normal pointer restored. If you want to cancel the align, either hit Esc or select Align again. This facility also works while a fax is being received into the current window. ═══ 3.9. Alignment/Skew ═══ Usually a sound card has a slight inaccuracy in its sampling rates. This results in a picture that slants or skews to the right or left. Use this facility to correct this problem. While a picture is being received, select this item. The pointer icon will change. Position the centre of the icon on the top of a line that should be vertical and click mouse button one. Move the pointer down the line and click again. The picture should straighten up. If not quite right, do it again. This correction is remembered until the sampling rate, bits per sample or lines per minute is changed. ═══ 3.10. Record/Auto sync and save ═══ Select this item to automatically start, stop and save faxes. Select it again to revert to manual operation. This item can be selected while a fax is being received. It will then detect the end of the fax, stop recording, save it and wait for the next fax, commence recording and so forth. This will not work consistently for noisy pictures or incorrect tuning. Refer to Tuning the computer. ═══ 3.11. Record/Start on sync ═══ Waits for the sync pulses at the start of a fax and then starts receiving the fax. The fax will be correctly left aligned in the window. This will not work consistently for noise pictures. ═══ 3.12. Record/Start now ═══ This facility lets you start recording a fax after the transmission has started. It is useful for tuning in fax signals on the radio. It starts receiving now, irrespective of what is being received on the radio. Use the Alignment/Align menu item to align the fax in the window. ═══ 3.13. Record/Stop ═══ Stops receiving faxes. ═══ 3.14. Record/Fast update ═══ If this item is checked, the fax picture and the spectrum display will update more frequently. This will give faster feedback for tuning in a picture but possibly less clarity. ═══ 3.15. Record/Negative or Positive ═══ If the radio is tuned to the wrong side band (for black and white, the background is black and the foreground white) select Negative. Select Positive to revert to normal. ═══ 3.16. Record/Monitor ═══ If this item is checked, the sound card will output whatever is input. This is useful while you are tuning. ═══ 3.17. Record/Auto tune from sync pulses ═══ Select this option to automatically reposition the red dividing line between the frequencies of the black and white signals as determined during the syncronizing pulses at the beginning of each picture. Warning,choosing this option when reception is poor can cause the red dividing line to be positioned incorrectly. If reception is good, this option is useful for radios that drift in frequency. ═══ 3.18. Image/Rotate 180 ═══ The picture is rotated 180 degrees. ═══ 3.19. Image/Rotate 90 ═══ The picture is rotated 90 degrees clockwise. ═══ 3.20. Image/Negative ═══ White is changed to black and black to white. The greys are also reversed. ═══ 3.21. Image/Crop ═══ This facility cuts out a rectangle from the picture and makes it the new picture. After selecting this item, a vertical and a horizontal line follow the pointer. Position them on two sides of the intended rectangle and click mouse button one. Now move the pointer until the intended rectangle is boxed and again click mouse button one. Hit Esc to cancel the operation. Note, when the pointer exits the window the picture will scroll. ═══ 3.22. Image/Undo all crops ═══ Restores the picture to before the cropping operations. ═══ 3.23. Options/Set initial parameters ═══ Presents a dialogue to sets basic configuration parameters. Refer to Set initial parameters dialogue. ═══ 3.24. Options/Set parameters ═══ Presents a dialogue to set parameters such as lines per minute and dots per line. Refer to Set parameters dialogue. ═══ 3.25. Window/Scale to window ═══ Rescales the picture to fit the size and shape of the window. Therefore the whole fax can be seen. Using this facility, the window frame dimensions can be adjusted to change the vertical and horizontal proportions of the picture. This facility is not enabled while the fax is being received. Select again to disable scaling. ═══ 3.26. Window/Show spectrum ═══ Creates a small window to display the audio frequency spectrum of the incoming fax. Select again to delete the window. Refer to Tuning the computer for use of the spectrum window. ═══ 3.27. Show/Pause ═══ Select to pause a slide show type presentation of faxes. Select again to continue the presentation. Refer to Open Radio Faxes Dialogue. ═══ 3.28. Show/Forward ═══ Displays the next fax in a slide show type presentation. Refer to Open Radio Faxes Dialogue. ═══ 3.29. Show/Backward ═══ Displays the previous fax in a slide show type presentation. Refer to Open Radio Faxes Dialogue. ═══ 3.30. Show/Continuous ═══ Presents the current slide show continuously. ═══ 3.31. Show/Replay ═══ Re-starts the current slide show type presentation from the beginning or the end depending on whether forward or backward were selected. Refer to Open Radio Faxes Dialogue. ═══ 4. Set Initial Parameters Dialogue ═══ Sets basic configuration parameters. ═══ 4.1. Audio Input ═══ The sound card input has a Line in and a Microphone jack. Choose as you have cabled. ═══ 4.2. Set Coordinated Universal Time ═══ Set the time difference between the time set in the computer's clock and the Coordinated Universal Time. If you are located east of the International Date Line and west of Greenwich, England then you are ahead of UTC. Otherwise you are behind. ═══ 4.3. Save compressed bitmaps ═══ Check this to save compressed bitmaps. This will save considerable disk space. However, be aware, I have found one video driver which was unable to read compressed bitmaps. ═══ 5. Set Parameters Dialogue ═══ Sets parameters that describe the basic characteristics of the incoming fax. ═══ 5.1. Lines per minute ═══ Most weather faxes come at 120 lines per minute. This rate is exact and is used to align the picture down the screen. Other radio faxes may have other rates. ═══ 5.2. Dots per line ═══ The audio out of the radio is a continuous signal. It is represented on the screen and printer by a finite number of dots. It is up to you how many dots you want to use. More dots provide more accuracy, but require more computer overhead. Also if the Scale feature is off, a high number of dots yields a picture too wide for its height. You can experiment with this parameter. ═══ 5.3. Index of Correlation ═══ You may set the index of correlation to create a picture (if the scale feature is off) that has the correct horizontal and vertical dimension. Weather fax usually use an index of correlation of 576. Note, this can create a large picture using much memory and disk space. ═══ 5.4. Max lines in picture ═══ Sometimes, due to noise, the end of the fax is not detected. This parameter stops the fax reception after the set number of lines. ═══ 5.5. Grey definition ═══ The number of shades of grey the signal is translated too. Warning,choosing 256 greyscale on a display that is limited to 256 colours will turn the rest of the desktop to greys while the picture is displayed (or re-displayed in the future). Warning, some VGA drivers have problems with 16 greyscale. Choose 64 greyscale or try to obtain a recent video driver. ═══ 5.6. Bits per sample ═══ Sample sound at 8 bit or 16 bits per sample. Generally choose 8 bit for lower overhead. One sound card loses data on 8 bit (picture jumps horizontally) but works on 16 bit. ═══ 5.7. Samples per second ═══ The rate at which the audio sound from the radio is sampled into digital amplitude values. The higher the rate, the greater the processor overhead. You can experiment with this. ═══ 6. Open Radio Faxes Dialogue ═══ Displays faxes saved on disk. You can select the disk and directory. One fax can be selected from the list (double click the entry). Or several faxes can be selected from the list (hold down the Ctrl key while selecting) for a slide show type presentation. ═══ 6.1. Select the disk ═══ Select from the drop down list. ═══ 6.2. Select the directory ═══ Select from the drop down list. ═══ 6.3. Select one or more ═══ Highlight one or more faxes from the list then click OK. ═══ 6.4. Delay in seconds ═══ The time, in seconds, between each fax shown in the slide show type presentation. ═══ 7. General information ═══ The following sections give a simple description of facilities used in weather faxes. ═══ 7.1. Weather faxes ═══ Weather faxes are weather maps, cloud maps and other charts that are transmitted by meteorological departments around the world, for ships and aircraft and others affected by air and sea conditions. ═══ 7.2. Weather fax station frequencies ═══ Listed are a few frequencies (MHz) on which fax transmissions can be found. Other frequencies and transmission times may be found by contacting your local Meteorological bureau or on CompuServe or Internet. ┌────────────┬───────────────────────┐ │Argentina, │5.7775, 11.48 │ │BuenosAires │ │ ├────────────┼───────────────────────┤ │Australia, │5.1, 11.05, 13.92, │ │Melbourne │20.469 │ ├────────────┼───────────────────────┤ │Australia, │2.628 │ │Canberra │ │ ├────────────┼───────────────────────┤ │Australia, │5.755, 7.535, 10.555, │ │Darwin │15.615, 18.060 │ ├────────────┼───────────────────────┤ │England, │2.374, 3.652, 4.307, │ │London │6.446, 16.912 │ ├────────────┼───────────────────────┤ │China, │7.42, 11.42, 18.94 │ │Shanghai │ │ ├────────────┼───────────────────────┤ │Japan, Tokyo│3.365, 5.404, 7.305, │ │ │9.438, 9.970, 13.597, │ │ │18.22 │ ├────────────┼───────────────────────┤ │New Zealand,│5.8066, 9.4586, │ │Auckland │13.5501, 16.3401 │ ├────────────┼───────────────────────┤ │Reunion, │8.176, 16.335 │ │SaintDenis │ │ ├────────────┼───────────────────────┤ │USA, Norfolk│3.357, 8.08, 10.865, │ │ │15.959, 20.015 │ ├────────────┼───────────────────────┤ │USA, │4.346, 8.682, 12.73, │ │SanFrancisco│22.527 │ └────────────┴───────────────────────┘ ═══ 7.3. SSB/BFO ═══ Faxes comprise audio frequencies of 1500 Hz for black and 2300 Hz for white, and in between if there are greys. The audio signal modulates a high frequency (short wave) carrier producing an amplitude modulated (AM) signal. An AM signal contains the carrier frequency and two side bands. For transmission, one side band and the carrier are suppressed, resulting in a single side band (SSB) signal. Therefore, to regain the 1500 and 2300 Hz audio, the radio receiver must re-insert the carrier and other side band. This is done using a Beat Frequency Oscillator (BFO) or Single Side Band (SSB) mode. ═══ 7.4. Makeup of a fax ═══ The audio tones from the radio, if tuned precisely, will be 1500 Hz for black and 2300 Hz for white, and in between for greys. The fax begins with about 60 sync pulse lines. Each pulse is a line of black terminated by a short period of white. The left hand edge of the picture is the start of the black. Most Weather faxes are sent at exactly 120 lines per minute. Each line takes exactly half a second. The picture after the sync pulses is aligned based on this. If you tape record the audio and play it back to this program, you will find the slight inaccuracy in the speed of the tape will cause the picture to skew. The fax is terminated by a few lines of alternate black and white spaces. ═══ 7.5. How the program works ═══ The sound card samples the analogue audio input into 8 or 16-bit digital values at the specified rate (22050/sec by default). One thread of the program uses MMPM/2 playlist to fill buffers. Another thread takes each buffer, breaks it up according to the number of dots per line, determines audio frequency and whether each dot is black or white, and updates a shadow bit map. A third thread updates the window on the screen from the shadow bit map. A fourth thread displays the frequency spectrum. ═══ 7.6. Coordinated Universal Time (UTC) ═══ Is the time in Greenwich, England. It is sometimes referred to as Greenwich Mean Time (GMT). It is used as a worldwide standard time for worldwide facilities such as short wave radio. Most times displayed on the faxes will be UTC. ═══ 7.7. High Frequency (Short Wave) ═══ Is the range of radio frequencies that most easily travel long distances by bouncing off the ionisphere and the ground. However they are subject to noise interference, echoes (signals travelling different paths and arriving at different times), and diurnal variations. Meteorological stations transmit on a number of HF frequencies. Choose the best one for the time of day. These stations also transmit maps for determining the best frequency to use for a location and time.