EMEpsk User Guide
Contents
1. 6 2 Manual Entry of Callsigns and Report You can enter a callsign into the field ToCall This is possible only in AutoQSO mode manual Pressing the normal button or the contest button will generate the corresponding Standard Procedure for the entered call A Standard Procedure can be deleted by pressing the button only in AutoQSO mode manual The report usually is generated automatically by a double click on a decoded line It can only be altered in AutoQSO mode manual EMEpsk uses thee possible reports W eak M edium L arge They mean W SNR lt 26 dB M SNR lt 23 dB L SNR gt 23 dB 6 3 Mixed Normal Contest QSOs If a station runs contest mode it sends contest reports Reception of a contest report forces the QSO automatic to reply with a contest report even if it runs in normal mode If a contest station is called with a report it replies with a contest report without roger A manual operator should do the same 6 4 Manual QSOs Set the AutoQSO mode to manual You can select any individual message of the Standard Procedure by clicking the line The EMEpsk program does not accept messages that violate the correct sequence if the AutoQSO mode is not manual Therefore you cannot send RRR before something like RW has been received from the other station At the other end the EMEpsk receiver even will not decode a message which is outside the defined order of the Standard Procedure The manual option only was imple2. demodulated signal By this reason the polynomial degree should be adapted to the properties of the actual radio channel EMEpsk therefore offers the following options also see Chapter 12 selection degree maximum number of fading minima no fading 6 1 medium fading 30 7 fast fading 80 20 flutter 200 50 3 3 4 NoiseBl A simple noise blanker NB can be switched ON and OFF It is a powerful tool for reading signals in pulse like non Gaussian noise In absence of pulse noise the NB should be set to OFF 3 3 5 BirdieBl A simple birdie blanker BB can be switched ON and OFF It is a powerful tool for finding and reading signals in birdie like non Gaussian noise Since the EMEpsk signal does not show any carrier in the input signal it is not cleared by the BB Therefore weak signals can be identified and decoded even if strong birdies are present In absence of birdies the BB should be set to OFF 3 4 The Sychronization Displays AZ 174 3 EL 17 5 Doppler 36 4Hz 3 4 1 The Normal Display The output of the synchronization in time relative to the expected value within the allowed time interval 6 s 6 s is diplayed on the left side The corresponding synchronization within the frequency interval 2 Hz 2 Hz is displayed on the right side Peaks within the gray background are not confident The confidence is given by the vertical scale The peak height 21 of the TimeSync means that pure Gaussian noise will generate suc
3. Synchronization One of the main problems of amateur weak signal communication is to detect the transmitted packets in time and frequency domain PSK raises a second problem the phase of the received signal must be determined from this signal EMEpsk interleaves the 664 bits of codewords with a binary address pattern of 332 bits such that every 3rd bit of a block bits 1 4 7 10 991 994 is known to the addressed receiver These bits are used for phase recovery and for block detection There are two types of addresses 1 a specific binary pattern of 332 bits used as a general broadcast address for CQ QRZ QST and 2 a unique binary pattern for each callsign 2 6 Code Formats In all cases three nested codes are used The outer convolutional code the channel code is for error correction The inner code is for detection of remaining errors It is mainly this code that prevents from display of garbage The third code is the source code which translates the bit arrays into displayed text output There is a plausibility check at this stage which refuses the display of callsigns that do not comply with the syntax of callsigns 99 9 of random texts are invalid There are several coding schemes for different message types Here only a brief overview is given For details see the EMEpsk documentation 2 6 1 General Messages CQ QRZ QST These three messages communicate a callsign of up to 10 characters in case of CQ or QRZ or som
4. The actual parameters FreqTol Fading NB BB must be adequate to the saved file You can try to adapt these parameters 4 Differences between the original decoding and the decoding of the saved file may be caused by different parameter settings but also by the compression to only 8 bits per sample in the record 5 General messages CQ QRZ QST will always decode 6 QSO messages will only decode if ToCall is set to the callsign of that QSO and if AutoMode is set to manual 7 Decodes of saved files are displayed in dark green color 8 Except from the displayed color there is no difference to real time decodes It is therefore not a good idea to decode files while an actual QSO is in progress The displayed times may be corrupted and the AutoMode also reacts on the decodes of stored files this gives the opportunity to test the reaction in special situations
5. contents Strong birdies can lead to the all zeros codeword which is decoded to QST fi fC PIAL LS This message is forbidden by the program and never displayed False decodes of the type mycall de falsecall with a correct MyCall but false calling call with or without report also can occur at a rate of 1 in 10 years of continuous operation An automatic reply then starts a QSO with an alien It will stuck at your reply and never lead to a confirmed QSO You should set the parameters StopTX and StopQSO appropriately to limit such wasted operation 10 2 Fatal False Decodes A fatal decode is a decode which leads to a confirmed but invalid QSO Such false decodes in principle can occur but it hardly should happen while the universe exists 12 Fading EMEpsk uses Phase Shift Keying as it s modulation The demodulation requires a phase recovery This phase recovery is possible only when the phase changes caused by the radio channel are much slower than those made by the PSK itself The number of fading minima within one period of EMEpsk may roughly be 10 medium fading The loss of sensitivity is about 4 dB if the Rayleigh fading has 20 minima fast fading see Figure 5 If the fading is even faster then incoherent communication modes are better i Ni id 4 fi kan i i 5 10 15 20 25 30 35 40 45 time s 1 period Figure 5 Example for fast fading The upper figure shows the real part blue and the imaginary
6. exe and this helpfile EMEpsk_ UserGuide pdf 3 5 2 The Period Button This Button selects the first or the second period as the TX period First means even minutes second means odd minutes This entry Ist 2nd is not relevant in AutoQSO mode reply The receiver then listenes in every period and will automatically change this entry if necessary 3 5 3 The AutoQSO Button There are four different modes of automatic operation manual means that operation has to de done manually QSO means that the EMEpsk program will run the Standard Procedure automatically after the user had started a QSO manually reply means that EMEpsk will automatically start and finish a QSO if it records a call to this station CQ means that this station will automatically call CQ after a QSO has been finished The further behaviour is as in mode reply 3 5 4 The StopTX Button This Button is colored with red background if the TX is transmitting see Figure 2 Pushing the button then immediately will stop the TX The TX can be switched to ON again by a click into the corresponding line of the Standard Procedure 3 5 5 The Doppler Elimination WSUWA The precise computation of the actual Doppler shift needs the knowledge of the 144 123 actual frequency Therefore the section shown here is inserted between the two synchronization displays The frequency must be entered in MHz If the Doppler shift absolutely is more than 1000 Hz which can occur on fr
7. start 8 1 EMEpsk exe This is the EMEpsk program to be executed on your computer At it s first start it will be unpacked internally which may take a while please be patient 8 2 decodedtext txt This text file prints all messages which are decoded by the EMEpsk program in chronological order The line format is as follows time At Af SNR address de call report locator QSO no PWR ANT T3236 2 00 0 50 30 dB DJ5HG de SM2CEW rep RW KP15CR 1233 200W 18dB time isin UTC at is the time offset of the decoded block is the offset of the decoded signal to the nominal carrier frequency 1000 Hz The SNR is derived from the reconstructed block It heavily depends on the quality of the phase recovery The received report consists of a possible R and one of the letters WML which stand for weak medium and large 8 3 log txt EMEpsk automatically gererates a logfile with lines of the following format startconnect conf stop callsign rptsent sent rptrcvd rcvd locatr pwr ant distance 14 22 14 25 14 29 14 30 GW4WND M RW 136 I082KM 500W 15dB 932km 8 4 EMEpsk_parameters mat This is used to save the actual parameters If you delete this file EMEpsk will start using the default settings If EMEpsk does not start please delete this file or rename it for later restauration and try to start EMEpsk again 8 5 EMEpsk_UserGuide pdf This is the document you currently are reading 8 6 records This folder contains all wav
8. 00 times the amplitude of the signal occurring within one period lead to a loss of 2 dB 50 birdies within 1 kHz of each 6 times the signal energy also cause a loss of 2 dB 3 The EMEpsk Graphical User Interface The Graphical User Interface is shown in Figure 2 The different parts of the GUI are exlained here top down and right left 3 1 The Decoder Window address sender received information 16 24 0 05 0 10 30 dB co de smM2cew 16 26 0 05 0 10 30 dB CQ de sm2cew 16 28 0 05 0 00 31 dB DJ5HG de SM2CEW rep w 16 30 0 05 0 00 30 dB DI5HG de sm2cew RRR The upper half of the GUI figure displays the decoded messages including some meta data Lines belonging to a QSO are printed in red color The window scrolls when the lower line is reached A single left click on a text pastes the line into the clip board A double click on a CQ generates the standard procedure CTRL amp click clears the decoder window 3 2 The Time And Volume Display The actual sound input volume is displayed to the right of the date time display below the decoder window It is colored red if the volume is too high and black if it is too low In the latter case the decoding process stops To the right there is an edit bar to enter messages that shall be searched for by correlation See Chapter 3 4 3 for explanation 3 3 The Parameter Buttons FreqOffset FreqTol Fading NoiseBl BirdieBl ED oe oe 3 3 1 FreqOffset This is a toggl
9. Klaus von der Heide 1 Introduction EMEpsk is a very sensitive digital mode for Earth Moon Earth EME operation It uses fixed RX TX periods of 1 minute A rate of 50 correct decodes is reached at 30 dB The disadvantage of PSK is that it rapidly degrades in case of fast phase changes by libration fading EMEpsk is identical to PSK21 SlowPSK with 1 minute period with two exceptions 1 It corrects the Doppler shift caused by the relative motion between the operator s location on the Earth surface and the Moon and 2 SlowPSK by default uses an audiocarrier of 1000 Hz while it is 1500 Hz in EMEpsk 2 Properties of the EMEpsk Mode 2 1 Demands 1 EMEpsk needs very stable frequencies of TX and RX with a frequency drift less than 2 Hz within the selected period 2 The errors of the samplerate 8000 for sound input and sound output must be determined such that the samplerates are known at an accuracy of 1 Hz 2 2 Modulation EMEpsk uses binary Phase Shift Keying at rate of 20 8333 bits s The pulse shape is a sinc function The result is a minimum energy modulation not a constant amplitude modulation 2 3 Signal Spectrum As a consequence of the sinc pulse the spectrum of the transmitted signal has a rectangular shape with a total bandwidth of 21 Hz Stations can be spaced by only 25 Hz without causing interference 2 4 Code Words EMEpsk transmits binary blocks of 996 bits The length of the transmissions is 48 s 2 5
10. ameter Gui Now repeat the test 5 4 The TX should go on air in the chosen TX half periods The EMEpsk signal does not have a constant amplitude The TX output power therefore must be adjusted to an SSB level if the PA is peak power limited most solid state PAs 6 Making QSOs 6 1 Starting QSOs There are two ways to get active a Wait for a decoded CQ call in the decoder window A double mouse click on the decoded line will generate all entries of the Standard Procedure and it will automatically select the reply to this CQ as the next transmission If you select the AutoQSO mode QSO or higher the QSO now will run automatically b Start a CQ call by clicking the CQ line in the Standard Procedure If the AutoQSO mode reply is selected replies to your CQ will generate the Standard Procedure automatically and the QSO runs automatically Otherwise the reply only is displayed Here double click on the decoded line to generate the Standard Procedure for the calling station As in 1 the QSO will now run automatically if the AutoQSO mode QSO is selected You can change the AutoQSO mode at any stage of the QSO Select the AutoQSO mode manual if you want to send a special private message edited in the last line of the Standard Procedure section Such a message will only be decoded at the other end if you are in a QSO i e if the other station got a message of line 3 or line 4 of the Standard Procedure and actually runs your call as it s ToCall
11. ate of significant false correlations c is not negligible Without the error detecting code the second code of EMEpsk there would be a considerable amount of false decodes and that would render the AutoQSO mode impossible But EMEpsk uses the error detecting residual code of r 15 13 bits in CQ calls QSO messages That reduces the rate of false decodes down to about c 2 lt 0 00001 These false decodes produce 10 characters of random text as the calling callsign On the average only one out of 1000 such textstrings can pass the plausibility check So the rate of displayed false CQ calls is about 0 00000001 This is no more than one false CQ in 100 years of continuous operation The correlation with QSO messages and messages entered into the Correlate entry may display false results because there is no no error correction and no error detection These displayed results with the exception of the SNR are not information which has been received via the radio waves 10 1 Non Fatal False Decodes The most probable false decodes are of the type TOCALL de MYCALL free text of 10 characters In the automode they have no relevance In manual mode such messages also have no relevance because it is extremely improbable that they display senseful text Also false QSTs like QST L 7NCD6ADRF can occur QSTs are messages to all operators They do not carry any QSO information and they are simply displayed by the EMEpsk program without notice of their
12. e general message of 10 characters in case of a QST The selection between CQ QRZ and QST is encoded by two bits Callsigns and general messages are restricted to text of 10 characters of the EMEpsk alphabet They are translated into binary patterns of 54 bits So with the two selection bits we have a total of 56 source information bits The inner code adds 15 check bits for final error detection resulting in 71 bits The channel code encodes the 71 bits by a rate 1 8 convolutional code of constraint length 13 tail ended The resulting codeword has 664 bits These bits are interleaved with the general address pattern giving the transmitted block of 996 bits After the receiver recorded a hit with the general address pattern the 664 soft bits are decoded by the Viterbi algorithm resulting in a binary pattern of 71 bits The first 56 bits are used to generate the 15 check bits If any of these generated check bits differs from the received check bits bits 57 71 then the message is discarded The probability to get correct check bits out of wrong received data is 1 32749 To get the rate of displayed false decodes from pure noise the rate 1 32749 has to be multiplied with the rate of valid random callsigns 0 001 So the amount of displayed garbage is very small lt 0 00000003 The codes used in EMEpsk are unmodified linear codes Therefore the all zeroes word is a correct codeword It would decode to QST This specia
13. e button If it is OFF with gray background the frequency offset is 0 i e the output carrier frequency is at the nominal value of 1500 Hz and the expected input carrier is 1500 Hz too and no automatic QSY is made If FreqOffset is set to ON white background color automatic QSY is activated The actual frequency offset is displayed in Hz See Chapter 14 for recommended operation 3 3 2 FreqTol The computational effort of searching for relevant signals is proportional to the search space in frequency This effort can considerably be reduced by setting the frequency tolerance to an acceptable low value FreqTol 20 means that the carrier of the signal to find must be within 20 Hz of the nominal carrier frequency 1500 Hz The sensitivity decreases with FreqTol gt 2 The background of the FreqTol button then is colored pink Large values 100 200 are for search of signals The search is sensitive to any BPSK signal Therefore care must be taken in using a value as large as 200 because a PSK31 signal may be selected as the biggest one while a weaker EMEpsk signal then is ignored If automatic QSY is activated gray background on the FreqOffset button then the frequency offset is adapted to the first received signal of the other station in a QSO and FreqTol is set to an appropriate low value The frequency offset is set to 0 and the previous value of FreqTol restored when a QSO ends Options PSK Spectrum Simulation help SNR address s
14. e files automatically recorded Operating Parameter SAVE or manually taken with the save button audio and all screenshots taken with the save button graphic of the EMEpsk GUI All records are taken mono with samplingrate 8000 and 8 bits per sample The filenames start with EMEpsk rec followed by the ISO 8601 date in the format yyyymmddTHHMMSS 9 Resuming a QSO after Program Failure EMEpsk is a complex program with many different options It is impossible to test such a program under all situations Several probable problems with the soundcard are eliminated by automatic failure detection and restart But surely many bugs remained undetected If the program fails please try to characterize what had happened If the failure occured within a running and not completed QSO do the following 1 Restart the program 2 Select AutoQSO mode manual 3 Type the callsign of the other station into the field of ToCall 4 Select the same report as before 5 Click the appropriate button Mormai or BOntest to generate the Standard Procedure messages 6 Select the right message of the Standard Procedure to be sent next Be aware that you are in manual mode now If the QSO traffic is running again in both directions you can select a different AutoQSO mode of your choice for example QSO 10 The Rate of False Decodes EMEpsk only tries to decode a received signal when there is a significant correlation with one of the two addresses The r
15. e report and there will be no correlation if a callsign is wrong 3 4 3 Correlation with a Known Message EMEpsk also can correlate with non QSO messages There is a text entry see 3 2 for such messages These messages must not contain a report The callsigns may be arbitrary but must be different from the own callsign If this text field is not empty the correlation is tried only after the decoder failed and the correlation with expected QSO messages did not succeed message at 34 dB DAHS de T 1211 2MM RRR AZ 186 8 EL 17 3 Doppler 9 7HZ Figure 3 A message below the sensitivity level could not be synchronized by the 332 address bits blue lines But correlation with the 996 bits of the complete block was successful red lines A new phase recovery based on the new synchronization and a following decode again failed otherwise there would not be the red colored text The left figure is the result of correlation of an expected message within a QSO while the right figure shows a correlation with a message entered into the correlation text entry see 3 2 3 5 The Operation Parameters Save Save Period AutoQSO EA A E oe 3 5 1 The Save Buttons audio Save the audio signal of the actual receiving period or the last when transmitting graphic Save the actual GraphicalUserInterface as a bitmap file The saved files are stored in the folder records which is located in the same folder as EMEpsk
16. ender received information CQ contest de 12 1212 mmM CQ contest de 12 1212 mm DISHG de 12 1212 mmM rep w 000001 3JO53IM 500w 15dB DI5HG de 12 1Z1Z mmM RRR FreqOffset Mable Fading ROEG s BirdieBl To Call tisa ort Generate Standa cQ contest de DJ5HG aad ee Bo d Rew TX Period Au 0 Ommam ensema O e _az 1z1z mm de vasta o Figure 2 The Graphical User Interface GUI of EMEpsk Decoded messages are displayed in the decoder window The lower half of the GUI shows the actual Standard Procedure to the right here contest procedure and signal displays and control buttons to the left The GUI can be resized The fonts then are resized too for ex try full screen A single mouse click on a line in the decoder window copies the line into the clipboard A double click on a decoded CQ generates the Standard Procedure SHIFT amp click transfers the Af of the line to the actual FreqOffset which leads to zero beat with that station This figure is from a simulation with generated SNR 31 dB atthe other end 3 3 3 Fading The carrier phase of a received block is modelled by a complex polynomial of degree d This polynomial therefore has 2 d 1 real parameters which have to be derived from the signal additionally to the binary information Since the information content of the signal is limited by the noise choosing a large value of d leads to a better phase recovery but it increases the noise in the
17. equencies above 500 MHz then the audio frequencies leave the SSB bandwidth EMEpsk should not be used in that case Doppler 11 1Hz The Moon parameters are only for information TX Perio 3 6 The Standard Procedure To Call MC CISCICRSCUCce sccm The Standard Procedure of a QSO is XYZ AB1CDE w v normal contest controlled by three colored buttons normal pushing this button i generates the last 6 lines of the Standard Procedure for a normal QSO pushing this button generates the last 6 lines of the Standard Procedure for a contest QSO The cQ de DI5HG QRZ de DISHG XYZ ABLCDE de DJ5HG XYZ AB1CDE de DJ5HG rep W 000017 3053IM 100w 15dB XYZ ABLCDE de DJ5HG rep RW 000017 3053IM 100w 15dB XYZ ABLCDE de DJ5HG RRR XYZ ABLCDE de DJ5HG TNX 73 QSO numberis updated XYZ AB1CDE de DJ5HG automatically clears the entry of ToCall and the last 6 lines of the Standard Procedure The ToCall can be entered manually into the edit field A double click on a decoded CQ call in the decoder window will set ToCall and generate the Standard Procedure If this is done while a QSO is running a non modal warndialog demands for a user decision between abort the running QSO or do not start a new QSO 3 6 The Menu Bar The menu bar is self explaining The file Exit option of the menu guarantees a clean exit from EMEpsk but it may take a while because it stops all concurrent processes in an ordered sequence Opti
18. h a peak once in 10 periods Therefore this peak of a signal at 28 dB is very confident The figure shows a typical signal of SNR 30dB 3 4 2 Correlation with Expected QSO Messages If you are in a normal QSO then the number of possible messages expected to be received from the other end depends on the actual QSO state It is 3 if it should contain a report or 1 if you are waiting for RRR and 73 If a received period cannot be decoded within a QSO the possible blocks are generated and correlated with the received signal If this leads to significant peaks in time and frequency the phase synchronization is based on this correlation and a digital decode is tried again If that results in a decode the printed textline is marked by an asterisk If it fails the synchronization is displayed in red color and the corresponding message is printed into the time synchronization display The message does not show up then in the decoder window because there is no error correction and no error detection By this reason it is never used in an automatic QSO Nevertheless it surely is interesting for the operator to know how many dBs the received signal is below the decoder level Figure 3 left gives an example In a manual QSO the correlation may be used if the peaks in both displays are very significant both peaks must be at least as good as in the right part of Figure 3 The information corresponds to the short messages of JT65 But EMEpsk includes th
19. ing in AutoMode reply then the caller does not know it s QRG accurately The sleeping station should run with FreqTol 50 The caller can correct his QRG when a reply was decoded Fading should match the actual conditions of libration fading NoiseBI setting depends on the local conditions BirddieBI usually can be set OFF The PC clock must be set at a precision of about 2 seconds Transceiver Bandwidth can be reduced such that the audio range 1000 FreqTol 1000 FreqTol Hz is in the passband In EME this is not as critical as on HF In case of pulse like QRM a large bandwidth may be better because the NoiseBlanker then can eliminate the pulses more accurate TX Power must be limited to the value used in SSB mode Never drive full power with a transistor PA USB should be used normally But LSB also is possible without loss of sensitivity The dial then must be set exactly 2 kHz higher For example 14068 kHz used on USB will appear on 14070 LSB The procedure concerning QSY by the df value mentioned above needs inverted correction in this case df 27 8 gt QSY 28 Hz down instead of up EMEpsk can decode saved audiorecords Please note 1 The basic parameter samplerate must be normal If you use the option 48000 the records are saved with 8000 samples of 8 bits mono the same as in the normal case of 8000 samples s 2 The basic parameter carrier normal 1500 should be the same as that of the recording 3
20. l output is caught and never displayed It only occurs at random if heavy birdies are present and not blanked out by the birdieblanker 2 6 2 Private Messages Private messages are transmissions addressed to a specific callsign Four message type bits allow 16 different message types within this group including contest messages with QSO number Maidenhead locator etc The information is encoded into 54 bits of source code The 4 message type bits and 13 check bits are added to finally reach 71 bits Other than above the check bits are derived from the concatenation of the 54 source code bits plus the bit pattern of the addressed callsign and plus the bitpattern of the sending callsign if an R or 73 is sent This is important because active callsigns may be very similar Then the address correlation could show hits from similar callsigns These hits are discarded when the check does not succeed The channel code is the same as above 2 7 Automatic Operation Decoded information is immediately discarded if any of the check bits differs As a consequence displayed garbage is extremely rare see Chapter 10 The protection of communicated information is so powerful that a station can run EMEpsk in an automatic mode where EMEpsk automatically replies to incoming calls and runs the QSOs to the final 73 without any interaction by the operator 2 8 Sensitivity 2 8 1 The Block Error Rate of EMEpsk The most critical elements in a PSK recei
21. mented to cope with computer program rig problems If everything works well then at least the AutoQSO mode QSO should be used because it s operation is more reliable than a human can be 7 The AutoQSO Mode There are four levels of automatic operation The first level manual corresponds to the usual operation of other modes In this level you have to interpret the decoded information of the decoder window by your own to support your decision on which line of the Standard Procedure should be sent next Be careful with your decision because out of order messages will not be decoded at the other end The second level QSO allows the fully automatic operation of the Standard Procedure after a QSO has been started manually The third level reply allows the EMEpsk program to generate and operate the Standard Procedure after a specific call to this station had been recorded It is not necessary to call CQ in this level It is sufficient that some other station starts calling you on the right QRG and with the right period In the fourth level CQ EMEpsk will call CQ whenever it is not in a QSO Replies to the CQ lead to automatic operation of the corresponding Standard Procedures 8 Files All files used and generated by EMEpsk are located in the same folder The location depends on the system you use Usually it is something like your private folder documents MATLAB EMEpsk The path to some files are printed into the DOS window at program
22. ng degrades If the samplerate factors are set correctly then no degradation occurs The sampleratefactors can be determined with the program samplingrates by DJSHG The CW ID is sent by keying the EMEpsk signal This is not a clear tone CW signal but the EMEpsk receiver can well decode interrupted signals So the time while the ID is sent is not lost for a QSO You can transmit the CW ID never or at intervals of 1 2 5 or 10 minutes The options of SAVE are none QSO decoded all decoded and all The save audio button in the main GUI is colored audio when the actual recording will be saved All audio recordings are WAV files at sample rate 8000 and mono with 8 bits per sample The options for samplerate are normal 8000 samples s and 48000 samples s Avoid 48000 if possible It costs about a million floatingpoint operations per second on your PC 4 2 Parameters for Automatic Operation STOP TX sets the maximum number of TX periods for the same message This timeout only is activated in automatic operation STOP QSO sets the maximum number of TX periods of a QSO This timeout only is activated in automatic operation 73 sets the number of periods you want to send the 73 message after having received the final RRR It is convenient to send 73 or CQ to inform the other end that the QSO is complete 4 3 Contest Parameters If Contest Mode is set to ON then a QSO is started by a call of the other station without report If one stati
23. on runs contest mode and the other runs normal mode then the other station automatically is enforced to run the QSO in contest mode too The QSO number for the next QSO can be set here It is incremented automatically if a QSO is run in contest mode So you need not to enter it every QSO Power and Antenna Gain can be selected for the contest format These values should be set in any case because a call could enforce you to run in contest mode 5 Checking the Interaction of EMEpsk with the TRX Hardware 5 1 Parameters Set the parameters in the Parameter GUI according to the previous Chapter 4 Choose the right soundcard ID and set the AutoMode to manual 5 2 Computer Clock Check the computer clock The difference to the UTC minutes should be much less than the value chosen for TimeTol 5 3 Test Received Audio Switch your rig ON and adjust the volume such that the value of the input volume display in the EMEpsk GUI is between 10 dB and 10 dB letters not black or red 5 4 Test Signal Output Connect your earphones to the selected sound output of your computer Choose the period to 1min Ist or Imin 2nd Click on the standard message QRZ de YourCall Then check whether EMEpsk switches the output signal ON when the selected line of the Standard Procedure is switched to yellow color 5 5 Test TRX Control Connect the PTT of your TRX with the RS 232 interface Choose the appropriate values for COM port and PTT in the Par
24. ons basic parameters opens a GUI to set basic parameters see next Chapter Options Moon Position opens a window showing the Moon position over time of the current day Options save GUI position saves the actual size and location of the EMEpsk window Options default GUI position restores the default position of the EMEpsk window Exit and start EMEpsk again PSK Spectrum opens a new window which shows possible locations of BPSK signals over the frequency range 1500 df FreqTol 1500 df FreqTol The displayed information is similar to a spectrum It is a nonlinear combination of three sources 1 the original spectrum 2 the spectrum filtered by a matched filter and 3 the spectrum of the squared signal Simulation is discussed in Chapter 13 4 The Parameter GUI Some basic parameters are set via a parameter GUI It is shown below in Figure 4 If this GUI is not already open then select options in the menu bar of the main GUI parameters on green background may be changed in a running QSO Basic Parameters Automatic Operation callsign DJ5HG Stop TX 5 locator JO53IM Stop QSO 30 UTC clock 2 73 3 COM port COM3 PTT RTS input ID 0 Mikrofo output ID 0 Lautsp input corr 1 0001 output corr 0 9998 Contest Mode OFF CW ID 5min QSO number 97531 save all decoded TX power 500W samplerate normal Ant Gain 15dB Contest Parameters Figure 4 Window with standard parameters Some parameters may be entered a
25. part red of the signal The very fast phase changes are from the modulation 996 bits The lower figure shows the amplitude of the signal EMEpsk can decode this but at a loss of 4 dB 13 Simulation The simulation mode of EMEpsk is activated by entering some value for the SNR If the SNR is not empty the specified noise in 2500 Hz bandwidth is added to the TX signal If fading is specified other than none then the fading is generated prior to the noise addition A frequency offset can be specified too The selected line to be sent in simulation mode is colored in pink Two computers can communicate via crossed audiocables The callsigns used on both computers must be different but the Maidenhead locators must be equal or near to each other The frequencies entered should absolutely be equal but with different sign one with negative frequency This compensates the Doppler elimination 14 Recommended Operation FreqOffset ON A double click on a decoded CQ then applies the observed frequency offset of the other station automatically to the own station which leads to zero beat The own FreqTol parameter is set to 2 or lower The CQ caller can run with this FreqTol value from the first FreqTol must be set with care It is less critical on VHF But on HF QRM dominates and must be made inert by a FreqTol as small as possible If you set FreqTol manually do not forget to increase FreqTol after the QSO If a station is sleep
26. s an editable text callsign and QSO number for example others may be selected in a pulldown menu Parameters shown on light green backgroud may be changed within a running QSO 4 1 Basic Parameters Here enter your actual callsign possibly including guest prefix or P etc The maximum length of the callsign is 10 characters The locator is the full Maidenhead locator like JO53IM UTC clock means UTC minus computer clock in hours So it is negative if you live at least one hour east from Greenwich You can select the COM port for TRX control with the COM port parameter The PTT parameter offers the choice of the DTR or the RTS lines choose DTR or RTS for inverted levels There are pulldown menues for the soundcard IDs for both input and output These IDs are not the same as in other programs which use the soundcard You have to try it out The samplerate correction factors input corr and output corr must be set as precisely as possible While the PC clock determines the start and end of the TX and RX periods it is the samplerate which determines the actual length of a packet If the sample rate is correct then the length of a packet is 996 20 833 47 808 s It is shorter if the samplerate is larger If the difference of the samplerates used at both ends of a communication path is so large that the length of the packet sent differs by about one bit or more from what the receiver defines as it s packet length then decodi
27. ver are 1 the block localization in frequency and time and 2 the phase recovery If the radio channel severely distorts the signal phase then the rate of failure of the phase recovery is high at marginal conditions The utmost sensitivity only is reached if there is no or very slow fading Medium fading causes a loss of 2 dB fast fading gt 20 minima in period even leads to a loss of 4 dB See Chapter 12 for more information The block error rates of PSK21 were determined with a channel simulator As mentioned above PSK21 is the same as EMEpsk with the exception of the Doppler elimination The results are given in Figure 1 block error rate no fading r medium fading fast fading confident correlation 10 I T I I jt i j i i i i i i j 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 SNR in bandwidth 2500 Hz dB Figure 1 Block error rate of PSK21 as a function of the SNR in a bandwidth of 2500 Hz GPS sync means frequency error lt 0 1 Hz and time error lt 0 5 s otherwise frequency error lt 10 Hz and time error lt 2 s solid lines successful digital decode dashed line confident detection of an expected message by correlation Compared to the phase distortion additive non Gaussian noise like birdies or spikes from electrical machines can hardly jam a PSK reception if the receiver uses a noise blanker and a birdie blanker 100 pulses of 10
Download Pdf Manuals
Related Search