HDCW V2.1 User Manual
Contents
1. 0100000 0000010 010011001 01111 010010001 111001 00011 110111000011 011010001 00 1011 111001 1 1110000111 0111 01 0011 101 0111 010110101 0 10001 1 01 10 10 bao je 4 11101 1101 011 01 010100110 11010 110110 O Oo Lop 4 001 101 01 H NKXIJISGHUAUAWVOWVOZREONG 1001 1101 100111 111011 a a gt Se oO 4 y D O O 0O O AO O O Oot OrREH gt 3 m 0 11110 00110 11110 11111011 L101 000101 001011 RR H Oe OT E EE ON OO 00101 001011 00011 00 01 00100 11010 111001 0110111 00 001101 1111 0101 0 0 000 0 001000010 oO O O NWO DWDANHDOHBWNEF CO Dog r O H O Oo 1010 L1000001 11001 1000010000 10011 0011 0011 011 0001 DULL 1001 00111 01011 111 0 0 10111 01 0 01 1 111 111000011 0 0 0 100100011 001 0011 10011 1000011 10101000 001110111010 0110110011001010 10 001101100 110001111 110111 000000000101 1110001001000010 101000111 0011011 00001100 00110110 00101111 101000102. ASK is slightly better If the PA is peak power limited and not mean power limited then FSK can transmit more energy per transmission In that case FSK yields the better SNR Of course FSK is the better choice in respect to Electromagnetic Compatibility EMC 1 3 Code Spreading radio channels as aurora FAI or RS usually change rapidly A rigid coding scheme as it is used in JT65 is not appropriate in that case The information entity which forms a codeword must be considerably smaller i e three two or one characters HDCW uses the characters of the following alphabet as the information entity ABCDEFGHIJKLMNOPORSTUVWXYZ 0123456789 Such a small entity enables fast dialogs as with CW or RTTY The drawback of a small information entity is a theoretical loss of 3 5 dB in respect to minimum usable SNR compared to 50 bits per information entity 1 2 An additional loss and source of errors in operator synchronization is caused by the necessity to communicate the changeover via the radio channel character A 1010111010 HDCW Code 0111000000 1010011 0100011 1011 01111 011101 011111 110100111 0011101001 00100000111 1110000001 1011 roOmaAoCANw H 1101 1100101 00011 100011111 000001010 011100001 001001100 0001 1101 001101001 00000101011 11110000001 01010111101 01011010001 000111110001 1011110110001 111000010111 0000 100 0001 10 10
3. Morse Code 4 pas opes j OoOOOrROOFrRF EF Oo Hm H pa H bE EAER p gt H 1O ea wy OOO O O RAO HH EY Os OrO 4 p H PRR EH I jay t 1101 1101 11100 10101 10101 10101 je jo 101 101 101 100 111 0 01000 1101000 000 1000 101000 1000 1110111000 101 111000 111 O 101 ELI 101 111 101 100 101 101 111 O 101000 1000 0 10111000 11101000 1010111000 1000 0 1000 111000 111000 101 111000 101 101 rFPoOoOOoOoaoOorOOCOCOrFrFOFOrFRFOCOOCOC OFF m 101 111 11101 a e i pes 11000 1000 O m O 101110111000 1110111000 101 101 f H 10111000 111000 101 101 OOO OrF CF 11010101 110111 110111 110111 110101011 111010111 110111 110101 10111 11101 ome 4 1000 B fo 1000 101000 1110101000 11011101000 1101000 010111000 01110111000 0111000 0101000 011101000 H nE a Ft OOOrFROrF OF OOO CCO Oo Pepe 0101 0101 0111 1101 Figure 1 HDCW uses an alphabet of 43 characters Each character is encoded by a binary codeword of 43 bits as shown in this figure Each codeword has 21 ones and 22 zeros All 903 possible pairs of different codewords differ exactly in 22 bitpositions If a received binary word of 43 bits is decoded by search for the codeword which differs in the lowest number of bit positions then
4. long Since the length of a bit is 2 samples k 5 12 see Chapter 1 4 the total length of the signal is m 43 2 samples After filtering and demodulation the signal is cut into m 43 pieces of 2 samples All these pieces are added like vectors After proper vertical scaling the result is displayed as the bit synchronization A good signal looks similar to a sine wave as in figure 3 a weak signal or pure noise leads to a noisy display as in figure 4 A sine wave is fitted into the display The position s of it s maximum is marked by a vertical red line The received bits are read as real values from the demodulated signal at the indices s i 1 2 with i 1 m 43 5 2 3 The Character Synchronization The principle of character synchronization is the same as that for HD43 which is described in 3 A significant synchronization is charaterized by a single peak out of 42 noise values Figure 5 shows a case of pure noise 5 2 4 The Decoded Text Display The primary receiver decodes the actual window at every incoming character As a consequence all characters will be decoded m times if m is the length of the decoder window This is descibed in figure 6 The horizontal axis of the display is time The actual time is inserted by vertical red lines at appropriate spacing The vertical axis is frequency f HDCW V2 1 by DJ5HG File Operator modulation ASK Character rate 8 rnin frequency spreading 700 rx band limits 9
5. sendtext OJ0 XY5ABC OJ0 XY5ABC DJ5HG DJ5HG 52A 52A KKK the call and report were entered into the corresponding edit fields Then the text to call was clicked two times then my call two times then report amp two times and cho lt once 5 3 The Transmitter 5 3 1 The Change Over Button Whenever the green button receiving is pushed it will change into red color and transmit the text content of the bottom line of the HDCW GUI in the mode specified by the actual parameters see figure 4 There is no effect if the send text field only contains blanks or nothing 5 3 2 Composing a Message The send text can simply be entered by setting the cursor into the line and then typing on the keyboard There are seven additional text fields The three fields for my CQ my Call and my locator are predefined by the menu and cannot be edited directly Instead they are pushbuttons Any mouseclick on such a button appends the corresponding text at the end of the send text line Alternatively you can click on the text above the buttons my CQ etc The fields to call etc can be edited Therefore these are not buttons The contents only can be appended to the end of the send text line by mouse click on the text to call etc Figure 8 gives an example of text composition The special symbols amp lt do not belong to the HDCW alphabet If they are used in one of the text e
6. with the input from the soundcard HDCW starts in this mode 4 1 4 Decode Record Select this item to specify a wave file which then will be decoded with the actual receiver settings If you are not sure set the bandlimits to 500 2500 Hz the modulation to ASK and try all speeds All standard samplerates 8000 11025 16000 22050 32000 44100 48000 are supported 4 2 Set Local Parameters 4 2 1 Operator Select the menu option Operator and the submenu item set call amp locator A small window will pop up You should place this window somewhere outside the main window of HDCW Then enter your call and locator and quit by clicking the ok button Do the same with the submenu item preferred CQ call within the menu option Operator This entry should contain the complete transmission including possible repetitions the changeover and the final character as a command for changeover 4 3 Set Operating Parameters 4 3 1 Modulation Select the modulation ASK or FSK with the menu option modulation FSK uses a fixed shift of 1000 Hz for spreading channels or four times the bitrate see 1 4 for none spreading channels 4 3 2 Characters per Minute The transmission rate is selectsd with the menu option Characters per minute 87 is a good value for your first tests since it is similar to the usual CW speed 4 3 3 Frequency Spreading of Channel The menu item Frequency Spreading of Channel offers 5 options ranging betwe
7. 1010001f 1011101000 DJ 11101010001011 01110111000101010101000101010100011101f 101000 Figure 2 In rapid fading conditions a dash of the Morse code may be read as two dots or two dots as a dash which in most cases cannot be detected as an error This figure shows the author s callsign in Morse code upper line and the twelve single bit errors of this type In contrast the HDCW code can correct up to 10 faulty bits in each binary word at the price of nearly three times the number of bits 1 4 Transmission Speed HDCW implements seven different transmission speeds between 349 and 5 5 characters per minute The precise values are 60 8000 43 2 with k 5 12 The value 87 characters per minute may be the most adequate for normal QSOs It is similar to usual CW speed The corresponding bitrates are 8000 2 with k 5 12 The bitlength is 2 samples at samplerate 8000 HDCW V2 1 by DJ5HG Characters per minute Frequency Spreading of Channel Rig Parameters modulation FSK Character rate 87 min frequency spreading 125 rx band limits 9 00 1300 tx frequency 1050 decoder window 12 buffer size 3 audio level 6 B spectrum and filter responses LN aiden ee bit synchronization character synchronization 21 Nov 2012 1640 50 Figure 3 HDCW GUI The two lines at the bottom are for transmitter input and control All above thes
8. 800 2500 tx frequency decoder window buffer size audio level bit synchronization O o character synchronization 21 Nov 2012 15 35 20 CQ CQ DJ5HG DJSHG DJSHG KKK Figure 4 Example of a simulation with a weak aurora signal in ASK at 12 dB The green spectrum display indicates the weak signal around 1000 Hz Three receivers are running with overlapping filters separated by 500 Hz The bit synchronization is not good but the character synchronization shows a significant peak The receiver sees a signal of 13 dB HDCW V2 1 by DJ5HG File modulation ASK Character rate 174 min frequency spreading 250 rx band limits 900 1200 tx frequency 1050 decoder window 16 buffer size 3 audio level 9B Spectrum and filter responses bit synchronization 21 Neiv 2012 15 42 10 21 Ney 2012 15 42 30 Character synchronization CQ CQ DJSHG DJSHG DJSHG KKK Figure 5 The spectrum range is restricted to the input range here The character synchronization does not show any significant peak Indeed this is a result of pure noise nothing sent in the simulation Let the transmitter send the text TEST SIGNAL OF HDCwW and let the decoder window be m 8 characters When the receiver has gotten half the signal then the actual signal contains TEST SIG The receiver evaluates the bit synchronization and finally decodes the sequence of letters and displays it One letter later the recei
9. HDCW V2 1 User Manual Klaus von der Heide DJSHG 1 General Aspects 1 1 General Application Area HDCW was designed as an RTTY type mode for use on radio channels with great frequency spreading as in aurora If the frequency spreading is as low such that PSK31 decodes then these coherent digital modes outperform HDCW But also on none spreading channels HDCW may be very useful by two reasons 1 it is very robust against QRM and 2 it decodes all incoming signals within the usual SSB bandwidth in parallel HDCW is not a pure digital mode because there is no final decision in the receiver which character is to be displayed All characters are displayed at all places in time But their visibility is an analog function of their confidence Therefore only those with acceptable confidence are visible at all It remains the operators s decision what has been received Pure noise produces a noisy text see figures 3 7 As a consequence the displayed output can only be stored as an image not as a text 1 2 Modulation HDCW uses optionally ASK or FSK Since HDCW receives the audio signal from an SSB transceiver the bandwidth is limited to about 2 5 kHz Therefore FSK is not useful if the frequency spreading is as large as 2 kHz or near to it The spreading of aurora depends on several parameters especially on the frequency band and on the beamwidth On 144 MHz FSK with a shift of 1 kHz should work well In respect to total transmitted energy
10. If the operator does not append further send text in time HDCW will automatically change over after three added blanks in sequence 5 3 4 Editing while Transmitting The send text to the right of the grey progress bar can still be edited while the transmitter is on But editing near to the progress bar is not recommended Time is inexorable and probably faster than you expect This may lead to corrupted text at the other end 5 3 5 Clearing the Send Text The send text is cleared by pushing the CLT button 5 3 6 CW Identification If the D button is pushed before a change over to transmit then the station call will be sent in normal CW on the specified tx frequency directly before the next HDCW transmission If the ID button is pushed while a HDCW transmission is running the CW identification will be appended at the end of the transmission The CW identification is disabled in simulation mode 6 References 1 K von der Heide DJSHG Possibilities and Limitations of Forward Error Correction in Minimal QSOs Proceedinds of the EME Conference W rzburg 2006 2 K von der Heide DJSHG Digital Weak Signal Communication for Minimal QSOs DUBUS vol 38 1 2009 pp 36 46 3 K von der Heide DJSHG HD43 a new digital mode for very weak signals DUBUS vol 38 4 2009 pp 47 57
11. a decoding error occurs when the received word has at least 11 faulty bits otherwise the correct character will be decoded In contrast the Morse code has different length and no error correcting capability at all see figure 2 Figure 1 specifies the complete HDCW code and compares it to the Morse code All HDCW codewords mutually differ in 22 bit positions So a false decode only occurs when more than 10 bits are inverted In contrast single bit errors in CW can corrupt the information This is demonstrated at the example of the author s callsign in figure 2 DJ5HG 111010100010111011101110001010101010001010101000111011101000 J5HG 1ff1010100010 11011101110001010101010001010101000111011101000 J5HG 11101ff100010 11011101110001010101010001010101000111011101000 DIBSHG 1110101000101fJf1011101110001010101010001010101000111011101000 DJBHG 111010100010111011 01110001fJ10101010001010101000111011101000 DJBHG 11101010001011 01110111000101f 101010001010101000111011101000 DJBHG 11101010001011 0111011100010101f 1010001010101000111011101000 DJMHG 11101010001011 011101110001010101f 10001010101000111011101000 DJ5SBG 11101010001011 011101110001010101010001f 10101000111011101000 DJSBG 11101010001011 01110111000101010101000101fJ101000111011101000 DJ5M G 11101010001011 0111011100010101010100010101fJ1000111011101000 DJ 11101010001011 011101110001010101010001010
12. a large bandwith with these visible gaps may be sufficient for monitoring 2 or is it better to monitor a small bandwidth without gaps or something between Choose the band limits correspondingly The receivers are invoked one after the other In the case of figure 7 running through all 63 receivers lasts about 50 seconds As a consequence each of the receivers can decode only one window of in this case 16 characters every 50 seconds In contrast the selected primary receiver runs permanently as is obvious in figure 7 So if this situation happens in a QSO that does not affect the contact if the correct frequency was selected as the primary frequency HDCW V2 1 by DJ5HG File Operator ji Characters per minute Frequency Spreading of Channel Rig Parameters modulation FSK character rate 44imin frequency spreading 62 5 rx band limits tx frequency decoder window buffer size audio level Spectrum and filter responses wi AA Ht DD SHG DJS G CQ D 5HG DJ5HG character synchronization Figure 7 Effect of overloading the processor by too many receivers Note that the selected primary receiver is running permanently 44 characters per minute no spreading full bandwidth while the others get the processor at so large timesteps that they only can decode about 15 of the signal JO53IM 0J0 XY5ABC OJ0 XY5ABC OJ0 XY5ABC DJ5HG DJ5HG 52A 52A KKK Figure 8 To compose the
13. d changeover The button CLT clears the lowest line The button ID adds the station call in CW 2 User Interface The Graphical User Interface GUI of the HDCW program is shown in figure 3 The two lines at the bottom are controls for the transmitter Everything above belongs to the receiver Only the menu bar is for control of both receiver and transmitter 2 1 Menu Bar The menu bar has 8 items File a wave file can be selected as input to the receivers instead of the sound Operator input of station callsign Maidenhead locator and preferred CQ call Modulation choose ASK or FSK Character per minute choose the character rate 349 174 87 44 22 11 5 5 characters minute Frequency spreading choose appropriate value between 500 and 2500 Hz or no spreading Rig Parameters set several important parameters as tx frequency bandlimits of receiver etc Simulation set simulation on off or set channel type and SNR Help display short instructions on HDCW 2 2 Receiver Output and Transmitter Input This is explained in figure 3 A detailed description follows in Chapter 4 2 3 Graphic Renderer On some systems the OpenGL renderer does not correctly display the generated graphic HDCW starts with the zbuffer renderer by that reason But the OpenGL renderer usually is better and faster You can toggle between both renderers by a double click on the gray background surrounding the grahic text field 3 The Decoding Process Th
14. dit fields they are replaced by the contents of the corresponding text field The same send text of the example in figure 7 would result by typing into the send text field the shortcuts amp amp lt There are two additional special symbols This forces the HDCW transmitter to change over to reception Everything right from a will never be sent gt This symbol forces the HDCW transmitter to repeat the send text to the left of it until the transmission is stopped manually via the receiving sending toggle button Everything right from a gt will never be sent This symbol does not work in simulation mode Leading and trailing blanks of the send text are deleted before changing over to transmit If there are only blanks in the send text field the transmitter will not switch on 5 3 3 Progress of Transmission If the transmitter is running it puts the generated signal character by character into the buffer between the HDCW program and the sound card A grey bar over the send text field indicates the progress which characters of the send text already went into the buffer In the example of figure 4 the CQ call completely went through the buffer with the exception of the last K Since the buffer size in that example is 2 the buffer only contains the preceding KK and the CQ call already was sent When the transmitter reaches the end of the send text but does not find a change over symbol then the transmitter transmits a blank
15. e lines is receiver output Only the menu at the top is for both receiver and transmitter control a The upper left field shows the most important actual parameters The fields below show b The actual spectrum and the bandpass responses of the running receivers c The quality of the bit synchronization which is perfect here d The quality of the character synchronization which also is perfect here The large field to the right shows the decoder output one line per running receiver The corresponding center frequency f is given in the vertical bar with actual frequency offset df and SNR df of the 1050 Hz receiver says that the received signal probably is about 2 Hz lower which is below the accuracy of frequency detection The 1050 Hz receiver is colored red It was selected by a mouseclick as the primary receiver The primary receiver has priority while the others are computed as far as the computer s processors can do the job The figures for bit synchronization and character synchronization are from the primary receiver The button CLR clears the decoded text the button SAV saves the HDCW window as a JPG image The large green button is for change over The lowest line is a text input line for text to be sent Some buttons CQ station call and station locator are for pasting this information into the text line This also is possible with free text written into the edit fields for to call report scratchpad an
16. ecoder window specifies the length of the input signal If you choose m characters the receiver will analyse the last n incoming samples where n m 43 2 with k 5 12 asin Chapter 1 4 Especially the bit synchronization and the character synchronization is based on the sequence of these n samples If the received message is considerably shorter than m characters then noise from outside the message can prevent synchronization If on the other hand a very weak message is longer than m characters then the actual synchronization does not utilize all energy of the complete message and may fail by that reason A window of 12 characters probably is a good compromise for most purposes 4 4 5 Buffer Size The output signal is generated and sent to the sound card character by character The advantage is that the text to be transmitted can be written and even corrected while the transmitter is running The drawback is the necessity of a buffer between the sound card and the send text of the GUI even worse the drawback is that this buffer can run empty while your computer is busy doing windows updates anti virus checks or something else other than putting the next character into the HDCW output buffer The HDCW program does not abort if the buffer runs empty It tries to evaluate the number of samples the soundcard output was interrupted throws away these samples fills the buffer with samples to be sent from the actual moment or better what the progra
17. en 500 Hz and 2500 Hz If FSK is used then spreading of 1500 and 2500 Hz is disabled A further option is no spreading In that case the receiver uses a narrow band filter of four times the bitrate In this case the FSK shift is 1000 500 250 125 62 5 31 25 16 125 Hz for the character rates 349 174 87 44 22 11 5 5 per minute 4 4 Set Rig Parameters Parameters which are set only once or are rarely changed are collected under the menu item Set Rig Parameters These are 4 4 1 Tx Audio Frequency Set the audio carrier frequency which is the input to the SSB transmitter A warning will be given if this frequency is outside the specified receiver band limits But working in split mode may be very useful in pile ups or in aurora with it s huge Doppler shift In FSK mode tx frequency and rx frequency too generally is the lower audio carrier Make sure to use USB with your transceiver 4 4 2 Rx Audio Band Limits Set the two frequencies for lower and upper band limits in Hz both within 500 Hz and 2500 Hz You could leave these values at their default values 500 Hz and 2500 Hz But in no spreading mode this can lead to a large number of receivers which may overcharge the computing capability of your PC 4 4 3 Delta F The computation of the frequency shift the df value needs considerable computing power If you are not interested in it at large spreading for example you shoud set Delta F to OFF 4 4 4 Decoder Window The d
18. ere is an important difference between the HDCW decoding and digital receivers as PSK31 RTTY JT44 or FSK441 The HDCW receiver converts the incoming noisy signal into an outcoming noisy text stream As a consequence the final decision stage is the operator himself as in reading CW Figure 3 gives an impression The confidence of the letters is gray tone coded So most of the output is more or less gray colored garbage But typical noise also produces isolated significant output While this may be very irritating in JT65 with it s complete and senseful message templates the isolated bold letters in HDCW are easily identified as noise peaks Of course the gray color could simply be changed into white But the author feels that the visibility of the noise offers more insight into the process of information transfer A drawback of this analog output is the difficulty to store the decoded information in a usual textfile At the moment only the option to store the whole GUI as a JPG image is implemented SAV button 4 The Menu Bar of HDCW 4 1 File Besides the exit HDCW this menu item offers three options 4 1 1 Set Record Folder HDCW uses a folder with a fixed path for records If you want to generally store the records and screenshots somewhere on your computer then specify the folder here 4 1 2 Saveas PDF This offers the possibility to store the HDCW GUI as a PDF file 4 1 3 Decode Sound Input This is the normal operation mode
19. m believes to be that moment and starts the soundcard again But the author cannot guarantee that this procedure never goes into nirvana after itself again was interrupted several times by windows To avoid such problems choose an appropriate value for the buffer size on your computer For normal QSO mode and character rates of 87 or lower the buffer size 2 should be sufficient At higher speeds use 3 or 5 Real buffer problems may occur in simulation mode because the receivers generate a heavy workload in parallel to the transmitter The delayed transmission caused by a large buffer size is not a problem in a simulation 4 4 6 COM Port Here you can select a COM port for transceiver control 4 4 7 PTT Options for the PTT are RTS RTS inverted DTR DTR inverted 4 4 8 Sound Input ID HDCW detects all activated sound input devices of your computer By default the device ID 0 is chosen If you want to use a different device select it here You must quit then HDCW and start it again to activate the change 4 4 9 Sound Output ID Similar to the sound input also the device ID for the sound output can be chosen Different IDs for sound input and sound output are allowed If you change the ID you must quit HDCW then and start it again The output ID may be different from the input ID of the same device Sorry names of the output devices are not available 4 5 Simulation HDCW has an inbuilt simulation capability which is controlled via
20. the menu item simulation with 3 submenus 4 5 1 ON OFF Here you can toggle between simulation ON and simulation OFF If the simulation is on the transceiver control via the COM port is disabled 4 5 2 Channel Options of this submenu are no fading fading 1s fading 0 2s aurora 4 5 3 SNR Here you can set the SNR value for the simulation 5 Details of the HDCW GUI 5 1 General Features of the GUI The HDCW GUI has no fixed format The fontsize and the fontpitch automatically are adapted to the actual size of the GUI The user should change the GUI size to optimize the readability of the decoded output in respect of his personal needs 5 2 Interpretation of the Receiver Output 5 2 1 The Spectrum Display The spectrum of the received signal is colored green as in figures 3 and 4 The filter responses of the receivers are colored blue ASK and lower frequency in FSK and magenta upper frequency in FSK I the frequency spacing of the receiver coincides with the frequency shift as in figure 3 then the blue lines overwrite the magenta lines Therefore only the upper frequency responses of the two receivers at the higher band limit are visible A simple mouse click into the spectrum display toggles between the full scale of 0 3000 Hz and the close view restricted to the interval defined by the band limits 5 2 2 The Bit Synchronization Let the decoder window be m characters Then the signal to analyse is m 43 bits
21. ver again is invoked Now it gets EST SIGN the next time ST SIGNA and so on Each time the decoded text is displayed The earlier is not erased The decoded letters are written on the decoded text display exactly where they are seen by the receiver depending on the bit synchronization and on the character synchronization Each character is decoded m times So it is printed m times nearly at the same horizontal place if the character synchronization is the same The position then only varies because of possible differences in the bit synchronization If the character synchronizations of the m overlapping decodes differ then different characters are printed at shifted positions This leads to the typical garbage of HDCW as seen in the decoded text below left and right from the decoded TEST SIGNAL OF HDCw 8 R G T ST SI GNAL OF HDCW NYH B08 YH R Figure 6 The nature of garbage and decoded text in the HDCW display 5 2 5 Consequences of Low Processor Power Any PC should be sufficient for QSOs in HDCW But differences will be evident in simulation mode and especially in monitoring the whole 2 kHz Bandwidth in no spreading mode Figure 7 gives an example of unacceptable overload by running 63 receivers with DF switched ON If you see these white space bands diagonally running over the decoded text display then first switch Delta f to OFF Then you have to decide between the options 1 Is it better to monitor
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