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     RTTY RECEPTION:
     
     To receive RTTY I suggest that you first try and decode the BAUDOT
     transmissions at 50 bits per second speed, as this is very common on the
     shortwave bands. Try the following frequencies:- 13.563, 15.637, 19.171,
     11.536, 14.452, 13.583, 13.660, 8.151, 14.764, 14.547, 14.595, 14.609.
     
     You will have to set the RADFAX2 program using HARDWARE TIMING, and the
     120 LPM DELAY value that was supplied with the program should not have
     been changed by more than +/- 2 %. If your computer cannot use HARDWARE
     TIMING, or you had to change the 120 LPM DELAY value (to receive correct
     120 LPM fax pictures), then this indicates that your computer's 8253
     timer chip or associated crystal  is not compatible enough to receive
     RTTY using the RADFAX2 program. To my knowledge only some of the AMSTRAD
     models have this problem. FAX and MORSE reception will still work on
     these models of AMSTRAD.
     
     The next problem is to tune into the RTTY signals correctly. This is
     difficult if you only use the LED indicator on the RADFAX decoder, as it
     is too wide and can be alight even if you are not quite on the station.
     A better turning method is to look at the RTTY signal while using the
     RADFAX2 program in 120 LPM FAX RECEPTION MODE. While in this mode turn
     the FINETUNE or the BFO control on your radio until you can see little
     black and white horizontal bars forming on your computer screen. Adjust
     your radio until the smaller black bars are about the same length as the
     smaller white bars. The changing black and white bars can only be seen
     while the RTTY station is transmitting characters, and not just an idol
     tone which would appear as either an all black or all white signal.
     These little bars represent the START, STOP and/or  DATA BITS of the
     signal. The higher the baud rate the shorter these bars will appear. If
     2 or 3 bits of the same logic level are sent side by side then the bar
     will look twice or three times as long as the smaller bars (ignoring
     noise).
     
     If you continued to let the program run in 120 LPM FAX MODE while
     receiving RTTY characters you will begin to notice little columns
     forming on your video monitor, These columns will most likely be oblique
     but may sometimes be vertical. As the program is receiving at 120 LPM it
     therefore takes .5 of a second to scan across the video monitor, and if
     you can count 24 or 25 columns across your monitor then you can assume
     the RTTY station is transmitting at 50 baud (bits per second), as the
     columns usually represent individual bits stacked on top of each other.
     
     If your signal is poor you might notice tiny specs (or not so tiny) of
     white on the black bits and vice versa. This can be sometimes be
     remedied by setting the BAUD RATE control on your RADFAX DECODER to 45
     BAUD. If it doesn't fix the problem then this station might be too noisy
     to receive correctly. You might also try the BANDWIDTH control. The
     narrower it is the less noise will be received, but if it is too narrow
     you will also loose your RTTY signal. If you change the BANDWIDTH
     control you might also have to retune your radio.
     
     Alright lets assume we now have a good signal and its well tuned, lets
     have a go at decoding it. Switch the RADFAX2 program back to the
     TELETYPE MENU and select SPEED 2 (50 BAUD) then press the <B> key to
     decode RTTY (BAUDOT CODE).














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     Also it might be handy to know that the BAUBOT CODE is transmitted as 1
     START BIT, 5 DATA BITS and 1.5 STOP BITS. The 5 data bits can represent
     32 individual codes or characters. As this is just enough for 26
     alphabetical characters, CR, LF and Space, and  some control codes,
     where do the numbers (0-9) fit in. Well the numbers 0-9, and all the
     punctuation characters  reuse the same 32 codes. The CR, LF, Space, LTRS
     and FIGS codes are the same in both sets of CODES. The LTRS and FIGS
     codes are used to switch between both sets of codes. If the station is
     transmitting LETTERS (A-Z) and it wants to send a number it must first
     send a FIGS codes (Figure shift) then the receiving station will know to
     print a Figure (number) instead of a Letter. Both stations will usually
     stay in the Figures case until a LTRS code (Letters Shift) is sent and
     received. Sometimes a transmitting station will always revert back to
     the LETTERS CASE after sending a Space, LF or CR code, (even if it
     hasn't send a LTRS code). A receiving station can still decode this
     station if it has an UNSHIFT ON SPACE mode, or the operator manually
     tells the receiving station to revert back to the LETTERS CASE (not very
     good as characters are bound to be lost), by pressing a LTRS key.
     
     If the sending station is sending characters of the LETTERS CASE and the
     receiving station thinks it is receiving characters of the FIGURES CASE
     (or visa versa) then rubbish will appear on your screen. You can remedy
     this by first knowing what the problem is and then switching to the
     proper CASE by using the <L> LTRS or <F> FIGS keys.
     
     Sometimes the bit pattern is sent inverted,  or all the 0 bits are
     transmitted as 1's and all the 1 bits are sent as 0's. This problem can
     be solved if your decoder or program can do the same. If you can't read
     the characters it is reasonable to assume this is the case so switch to
     the opposite sense by pressing the <I> key.
     
     You can expect to see foreign languages being transmitted on RTTY but
     English and French are very common. The Russians sometimes transmit copy
     in the Cyrillic alphabet and this will appear as rubbish. The program
     can't decode AMTOR which is also common on the shortwave bands.
     
     If you were getting good copy and after a time is degenerated into
     rubbish then it could be that your radio is drifting off the station
     frequency. Try and retune again using the 120 LPM FAX MODE as an
     indicator. Best results will be achieved when the small white bars are
     the same length as the small black bars.




























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