The PRECISION CW Handbook 1. Table of Contents..............................4 2. Copyright......................................4 3. Warranty ......................................4 4. Acknowledgments ...............................4 5. Licence Agreements.............................5 5.1. Shareware Copies ......................5 5.2. Registered Copies......................5 6. Shareware......................................6 7. CCW, An Introduction ..........................7 8. PCW: The Program...............................9 9. PCW: How To Get Started ......................10 9.1. Minimum Hardware Requirements.........10 9.2. Data Interface........................10 9.3. How To Start The Program .............10 9.4. First Test............................11 9.5. Hints For Operation .................12 9.5.1. CCW Speed...................12 9.5.2. Frequency...................12 9.5.3. Timing......................12 9.5.4. Threshold...................13 9.5.5. Receiver Performance .......13 10. PCW: On Screen Display.......................14 10.1.The Status Window.....................15 10.2.The Buffer Window ....................15 10.3.The Decode Window ....................15 10.4.The Send Window.......................15 10.5.The Command Line Window...............15 10.6.The Function Key Menu.................15 11. PCW: Keyboard Commands.......................16 11.1.Character and Numeral Keys............16 11.2.Function Keys.........................17 11.2.1.Standard Functions...............17 11.2.2.Control Functions ...............18 11.2.3.Alternate Functions .............20 11.3.Special Keys ......................21 12. PCW: Command Line parameters ................25 13.PCW: Interfacing..............................25 13.1.CCW Input ............................25 13.2.CCW Output............................26 14. CCW and PCW: Some Theory of Operation .......27 15. PCW: Program Status Information .............30 16. PCW: Error Messages .........................31 17. Hot Line Support ............................31 The PRECISION CW Handbook 2. Copyright The PRECISION CW (PCW) program, its reference handbook and all supporting utilities are Copyright 1994-1995 by Ernst F. Schroeder, All Rights Reserved Worldwide. Shareware copies of PCW may be freely distributed subject to the restrictions detailed in this file. Registered copies of PCW are not to be copied or distributed, except as provided for in the Licence Agreement accompanying the registered version. 3. Warranty The author hereby disclaims all warranties relating to this software, whether express or implied, including without limitation any implied warranties of merchantability or fitness for a particular purpose. The author will not be liable for any special, incidental, consequential, indirect or similar damages due to loss of data or any other reason, even if the author or an agent of the author has been advised of the possibility of such damages. In no event shall the author's liability for any damages ever exceed the price paid for the Licence to use the software, regardless of the form of the claim The person using the software bears all risk as to the quality and performance of the software. 4. Acknowledqements The author of this program gladly acknowledges the work done by Bill de Carle VE21Q, who wrote the first computer coherent c.w. program under the name of COHERENT. Both COHERENT and PRECISION CW use an analogue to digital interface described by 8ill de Carle in QST for January 1992 and which has been reprinted in recent issues of the ARRL handbook. Special thanks go to Peter Lumb, G31RM, who did not only keep the CCW spirit alive for quite some time, but who also helped polishing the English in the PRECISION CW Program and in this document. 5. Licence Agreements Carefully read the following terms and conditions. Use of this product constitutes your acceptance of these terms and conditions and your agreement to abide by them: 5.1. Shareware Copies Ernst F. Schroeder, the author of this software, grants you, the end user, a nonexclusive personal Licence to use this software for a period up to 30 days in order to evaluate its suitability to your needs. After the evaluation period you must either register with the author or cease using the software. You may use the software on a single personal computer system and make as many copies as needed for backup and archives. You may also distribute the software, unmodified, in its entirety, to others who are interested in evaluating the software. You may not modify, alter, translate, disassemble, decompile, or lease the software or the reference manual. The Licence is effective until terminated. You may terminate it at any time by destroying the software. It will also terminate if you fail to comply with any term or condition of this agreement You agree upon such termination to destroy the software. 5.2. Registered Copies Ernst F. Schroeder, the author of this software, grants you, the original purchaser, a nonexclusive personal Licence to use this software under the terms stated in this agreement. You may use the software on a single personal computer system and make as many copies as needed for backup and archives You may assign your rights under this agreement to a third party provided the third party agrees in writing to be bound by the terms of this agreement and you transfer all copies of the software to the third party, or destroy any copies not transferred. You may not copy, modify, alter, translate, disassemble, decompile, lease, or electronically transfer the software or the reference manual. The Licence is effective until terminated. You may terminate it at any time by destroying the software. It will also terminate if you fail to comply with any term or condition of this agreement. You agree upon such termination to destroy the software. 6. Shareware PRECISION CW is distributed as SHAREWARE. Shareware describes a method of distributing copyrighted software in which a user is allowed to evaluate fully the software before purchasing it. After an evaluation period, the user is required to register the product if she/he decides to keep using it. Shareware distribution addresses all the legitimate complaints that users have with commercial software? distribution Shareware allows a user to evaluate fully a product, free of charge, in his or her home, before deciding to buy it. Shareware programs can circulate freely on Bulletin Boards, through Shareware disk distributors, or through user groups. Because Shareware distribution reduces the need to advertise, Shareware is less expensive than commercial software. Shareware authors can often be more responsive to users' requests for help or bug fixes than large software companies. Shareware software, needless to say, is never copy-protected. In short, Shareware is a user's dream come true. Users show their appreciation to developers for this extremely flexible distribution scheme by registering their software. Without user registrations Shareware software would gradually disappear. It is not sufficient to simply let the "other guy" pay the registration. You are the other guy's "other guy". What SHAREWARE is not: Shareware is not "free" software. Shareware is not Public Domain software The fee that you may have paid to receive a Shareware program does not mean that the software has been paid for. This money was paid to a Shareware disk vendor, User Group, Bulletin Board Service or retailer to cover his cost of getting the program to you. Shareware software is paid for by registering your copy with the author. 7. CCW, An Introduction As you all will know, Morse code consists of dots and dashes arranged to represent letters, figures and punctuation marks. The basic element is the dot which has a predetermined length depending on the speed of transmission. High speeds require short dots. Hand sent Morse code and for that matter code sent with semi-automatic and automatic keys is random in nature and, even if the characters are correctly sent, the spaces can vary considerably. The standard speed for coherent c.w adopted by Ray Petit W7GHM when he designed the system was 12 words per minute. In actual fact it was the dot length which he decided should be fixed at 100 milliseconds. An element space was, therefore, also 100 milliseconds, a dash and character space were each equal to 300 milliseconds and all other spaces were multiples of the same 100 milliseconds. This timing is still in use today and is available on both the COHERENT and PCW programs available for coherent c.w. By connecting two computers together via the RS232 interfaces, one running COHERENT and the other running PCW, perfect communication can be achieved proving their compatibility. Only transceivers need be added at each end for on-the-air communication. Coherent c.w. depends entirely on accurate timing based on the element length. If you imagine two square waves both identical in timing but derived from separate oscillators and having the mark length equal to the space length and both these equal to 100 milliseconds it will be obvious that, if they both start together, they will stay in step indefinitely if the clocks generating them are perfectly stable. The original hardware coherent c.w. system was based on this principle and highly stable standard oscillators and transceivers were required at both ends of the contact. The difficulty of providing these is the major reason why coherent c.w. did not become popular. Modern computer programs have changed all that and now only reasonably stable transceivers and no frequency standards are required but it is obvious that the more stable transceivers and computers used in the system are the better will be the results. I must now return to our two square waves. These can be looked upon as strings of dots each dot and space being of a definite length. If we now arrange for one station to send a string of dots these will only be received accurately if the timing at the receiving end corresponds to our identical second square wave. Assuming that perfect timing exists at both ends the only thing that will stop correct reception is the relative phase of the two square waves If the rising edge of one square wave occurs at exactly the same time as the rising edge of the other the signals will be synchronized (coherent) and all following transitions will correspond. Using the original Petit hardware filter this was achieved by the transmitting station sending a string of dots and the receiving station adjusting a phasing control until the string of dots was received clearly and distinctly. Once this was done and, assuming perfect timing, the stations would stay in step indefinitely. Dots and dashes transmitted would be received at the other end of the contact and as spaces no matter how long were all multiples of the element length. a dot or dash received after a space would still occur on the rising edge of the receiver clock This is a somewhat simplified explanation of how coherent cw works but it will give you some idea of the principle behind the system. Let me repeat that in order to ensure correct operation all oscillators had to be exceptionally accurate and, above all, stable. The need for stable oscillators has been overcome in the PC programs available for CCW operation. Automatic synchronization has been included so there is no need to have phasing controls. If the program receives a string of coherent c.w. dots it will automatically synchronize. Computer clocks and all but the best transceivers can drift a little and provision is made for the automatic correction of frequency drift. Any transceiver will receive coherent c.w. as it is exactly the same as c.w. with the exception that it is timed extremely accurately and is, therefore, "perfect" Morse code. This means that anyone hearing it can easily assume that ordinary c.w. is being sent. If you are prepared to receive the signal from the other station as c.w. you can, of course, make contact. In order to indicate that you can operate coherently it is necessary to include something in your call to this effect. You can send a string of dots (by pressing $) followed by CQ CCW DE and possibly more dots. This will enable another coherent station to synchronize and call you. If you do not send the string of dots the calling station will have to send them to enable you to synchronize. You are sure to receive calls from c.w. stations even though you indicate that you are using coherent c.w. They either will not know what CCW means and assume that you have a funny way of calling CQ or they may be curious to know what CCW is all about. Please take the opportunity to tell them. Unlike some of the digital modes where it may be a little difficult to decide which type of signal is being received, coherent c.w. is easy to recognize by its perfect timing and string of preliminary dots. Even so you will have difficulty finding stations as there are not many stations active at the time of writing. For some time now it has been the practice of coherent operators to use one frequency. Various frequencies have been tried. At one time frequencies one kilohertz up from the usual QRP frequencies were used as it was thought that QRP operators had the most to gain from coherent c.w. and they may be tempted to make enquiries. This did not prove to be the case. It is now suggested that thirty five kilohertz up from the bottom of each band be used. There is sure to be some interference whichever frequencies are chosen but coherent c.w. with its accurate timing and very narrow bandwidth stands a good chance of being heard. For the time being please use these frequencies and watch for any announcement of changes, e.g. in the Digital Journal. I will try to ensure that other magazines are notified of any changes. I hope you will enjoy using coherent c w. and that we will have more activity in the near future. 8. PCW: The Proqram Welcome to PRECISION CW (PCW)! This is a DOS shareware program, to be used for reception and transmission of CW signals with precision timing, also called 'COHERENT CW' or CCW. This mode of communication was first described by Ray Petit, W7GHM in 1975 The idea lay dormant for quite a while, until it was revived by Peter Lumb, G31RM, who started issuing his CCW Newsletter in 1989. The first decoder circuits, based on standard CMOS logic ICs, were difficult to build and operate. This situation changed considerably, when Bill de Carle, VE21Q introduced his 'COHERENT' software, which operates CCW on a PC with only a simple hardware interface for signal input. Now PRECISION CW is the next step, which offers you a choice of input centre frequency, detection bandwidths, Morse speeds, Morse decoding, and an enhanced user interface. CCW uses standard Morse code with precision timing for transmission, and the 'matched filter' concept or 'correlation detection' for reception. Initially the single speed of 60 cpm or 12 wpm had been used for CCW. Now PRECISION CW offers three CCW speeds: 40, 60, and 120 characters per minute, corresponding to 150, 100, and 50 ms duration of the basic signal. The corresponding minimum detection bandwidths are +/- 6.7, 10, and 20 Hz, which can be adjusted between 300 and 1200 hz. The program needs the A/D converter as described and distributed by VE2IQ, to enter input data via one of the PC serial communication (com) interfaces. CW output is available on the RTS line of the same COM interface. 9 PCW: How To Get Started 9.1. Minimum Hardware Requirements The following minimum configuration is needed: Computer: Industry-Standard PC CPU: 80286 or higher Clock: 16 MHZ or faster Operating System: DOS 3.1 or higher The use under the Windows(g) operating system is not recommended! 9.2. Data Interface Input and output of CCW data is performed via a serial communication (COM) port of the PC in connection with the VE21Q hardware interface. Without this interface PRECISION CW cannot be used for CCW data input, but CCW Morse output is still possible. You have to connect the VE21Q interface to a free COM port of your PC via an appropriate cable for serial data with 9-pin or 25-pin Sub-D connectors. Any of the four COM1 ... COM4 can be used, but in case you have your mouse e.g. on COM1, then you can only use COM2 or COM4 without provoking an interrupt conflict. CCW output is available from the PC loudspeaker and from the RTS line of the chosen COM port. This line is active high. Please note that only in rare cases this line will be suited for direct keying of a CW transmitter. Generally a special keying interface will be needed. One example which can easily be used together with the VE21Q interface is given in paragraph 13.2. 9.3. How To Start The Program You can start PRECISION CW either from a hard disk or from a floppy disk by simply typing 'pcw' at the DOS prompt. Even without the input A/D interface you can exploit most of the various features. Pressing gets you to the help menu for further information. The (ESC) key always brings you back to the main level and cancels messages and special prompts. You leave PRECISION CW by pressing ~F10> and 'y' ('z' on German keyboards, if you did not use the 'kbdd' parameter). For proper installation of PRECISION CW you have to tell the program which COM port you have chosen on your PC. This is done by adding a COMx parameter on the command line. Furthermore, you have to tell PRECISION CW which keyboard layout you are using. The US English (qwerty) keyboard is default, but when you want to use the UK English keyboard, you have to add the parameter kbdg; likewise 'kbdd' for the German (qwertz) keyboard. EXAMPLE: when using COM2 and the German keyboard you should type at the DOS prompt: pcw com2 kbdd After this the PRECISION CW screen will appear with an introductory message showing your callsign The clock in the upper right corner should be running and displaying your local PC time. Now vou can exPloit the various functions ansi especially the HELP menu . 9.4 First Test Connect the VE21Q interface and start PRECISION CW as previously described. After start-up no warning message should appear in the command window (see paragraph 16 for warnings and error messages) and some rapidly changing numbers should appear for MARK and SPACE in the status window. Even with no analogue audio input to the VE21Q interface, there should be occasional beePs from the loudspeaker after a short while. Please remember that you can switch the loudspeaker off and on again by pressing the key. The loudspeaker is on, when the third field in the function key window shows 'SPKR' in white on red backaround. For a test of the transmitting functions, first switch off the RECEIVE function with . Now every keystroke should be reflected within the send window by the corresponding letter, the loudspeaker should sound the Morse code, and any transmitter connected to the data interface shouid be keyed accordingly. As a next test you should enter some text into the Morse buffer ( text ~F6>), watch how the display for buffer-length changes, and send that message by pressing . Now you are even ready for BEACON operation: Write a short message into the buffer, set the BEACON parameters to some simple values like 'every 1 minute; at each full minute' ( 1 ~RTN> ), and watch how the program automatically sends out this message on each full minute of the system clock, which is shown in the upper right-hand corner. For testing the receiving and decoding functions it is probably best first to record a considerable length of CCW on a simple cassette tape recorder. The recording can simply be made by using the PC loudspeaker and a microphone connected to the cassette recorder. The easiest way to produce a long message is to fill the buffer with a message of just under 1 minute length, and then let the program send it over and over using the BEACON function described above. For easy synchronization you should start the message with a '$' character, which introduces a string of 150 dots. Rewind the tape and plug the input of the VE21Q interface into the headphone output of the tape recorder. Switch the RECEIVE function back on again with ~F1>. Now upon playback of the tape you should be able to copy the recorded message, as each decoded dot or dash is reproduced by the PC loudspeaker. Finally you should switch on the DECODE function with ~F2>. Now the text decoded from the received CCW Morse signs should appear in the decode window. Of course, the playback of CCW signals at a comfortable level is not a tough task for precision CW, but you can use it for getting acquainted. Finally, you may want to experiment with lower signal levels different parameters, or with adding noise and other interference. 9.5. Hints For Operation Generally for CCW operation several parameters have to be watched, set, or agreed upon. These are: 9.5.1. CCW Speed This is one basic parameter which has to be agreed upon before a QSO. All previous CCW experiments have been made with a CW speed of 12 wpm (words per minute) or 60 cpm (characters per minute), which, according to general agreement in the world of amateur radio, corresponds to a duration of 100 milliseconds for each basic mark or space. PRECISION CW provides two additional speeds at 40 cpm (150 ms) and 120 cpm (50 ms). CCW will only work when transmitter and receiver are set to the same speed. 9.5.2. Frequency Because of the very narrow bandwidth of the CCW decoding filter, there has to be a very close match between the frequency of the CCW transmitter and the frequency of any receiver. PRECISION CW has been designed to simplify this problem by providing optional larger detection bandwidth and the AUTOTUNE function. The larger bandwidth can be used for initial spotting of the wanted signal, while the AUTOTUNE function can help to cope with frequency drift of receiver or transmitter. 9.5.3. Timing The mutual relative timing between transmitter and receiver for dots and pauses is not known at the beginning of each transmission, but one of the main requirements of CCW reception is, that transmitter and receiver use the same time framing. It is therefore essential for a receiver to acquire and to maintain synchronization of framing. For this task PRECISION CW is able to shift its decoding cycle in increments of 5 ms. This can either be done by pressing the and cursor keys, or most of the time better by the AUTOTRACK function. Increments of 5ms at a CCW speed of 60 cpm translate into 20 possible positions This is the information given by the PHASE parameter in the status window The AUTOTRACK function works best for large initial deviations, if a longer string of dots is received. This is the reason for the habit of having a string of dots at the beginning of each CCW transmission 9.5.4. Threshold In order to be able to decide, whether the signal present in the passband and in the last 100ms time frame is a dot (mark) or no signal (space), the program uses a decision level, which is constantly updated according to the past decisions The actual decision level is called the 'threshold' level. This level can either be increased or decreased manually by pressing the or cursor buttons, or can be adjusted automatically by the AUTOTHRESHOLD function When using AUTOTHRESHOLD, the value of threshold always tends to zero, unless a signal larger than the current threshold, i.e. a mark, has been detected. Three different time constants of adaptation are available: slow, medium. and fast. 9.5.5. Receiver Performance The CCW detection method by itself is able to cope with a variety of adverse conditions and interference from the transmission medium. The input to the CCW decoder is in the 800Hz frequency range, therefore the SW or VHF receiver itself should ideally react like a means for distortion-free frequency translation in reality, a typical amateur radio receiver can only approximate such behavior. Nevertheless, a good receiver with low intermodulation and a good CW IF filter will perform adequately. As the receiver gain control (AGC) and the AUTOTHRESHOLD function will interact, it may be better to be able to switch off the receiver AGC entirely. 10.1. The Status Window The uppermost part of the screen is occupied by the status window It contains all relevant information on the program flow, which has to be available all the time. The first line shows the program name and version number, as well as the current system clock. SPEED gives the current Morse speed in characters per minute (cpm) BW shows the current detection bandwidth in Hz. CYCLE is a parameter giving information on the relative CCW time framing between transmitter and receiver. MARK shows the level of the last detected 'signal present' condition. SPACE shows the level of the last 'no signal' condition. THRESHOLD shows the current value of the decision threshold. F gives the current center frequency of the detection filter in Hz. dF gives the estimated frequency deviation in Hz of the last detected signal with respect to the current center frequency. BEACON displays the beacon parameters. If the analogue input signal to the VE21Q interface is too large, then the blinking red message 'CLIPPING' will appear in the status window. The PC's system time in 24h format (hh:mm:ss) is displayed in the upper right-hand corner 10.2. The BufferWindow Just below the status window is the buffer window. It shows the current contents of the transmit buffer. The time, which is needed to send the contents of this buffer using the current CCW Morse speed, is displayed above the buffer window. 10.3. The Decode Window This window contains the past results of the Morse decoding function 10.4. The Send Window This window contains the past Morse transmissions from the keyboard 10.5. The Command Line Window In this line special prompts and messages are displayed 10.6. The Function Key Menu This line displays short mnemonics for the functions performed by the function keys. For some functions their state is shown by a change of color or text. Two further menus can be reached by pressing and holding down either the ~CTLz or the ~ALTz key. 11. PCW: Keyboard Commands 11.1. Character and Numeral Keys The following character and numerical keys are supported and used for the generation of CCW Morse output: characters: a ... z (lower case or upper case) O .. . 9 numerals the space key introduces a timing delay of 4 time units into Morse transmissions (i.e. 0.4 sec for 60 cpm) (full stop) (comma) (slash) (question mark) (on a German Keyboard the n is identical to '?' i.e.you do not need the shift key to get a '?') - - produces a sync pattern of 150 dots (|.e bU sec tor bu cpm) produces a pattern of 8 dots (1.6 sec for 60 cpm) Both $ and % do not end with a key-up period of three dots length, therefore they can be concatenated to produce longer strings of dots. Any different following character should be separated by a space. 11.2. Function Keys The ten function keys F1...F10 are used by PRECISION CW for access to the main parameters. Three levels of menu are provided for these function keys. The first level is reached via the function keys alone, the second level is reached by pressing the ~CTL> key together with the function key, and the third level is reached by pressing the key together with the function key. Some functions switch states which are immediately displayed on the function key menu, others provoke a prompt for more input on the command line. All functions are now described in detail. 11.2.1. Standard Functions Toggles the RECEIVE function on and off. The RECEIVE function is on when the REC field is displayed white on red, it is off when it is displayed black on light grey. Toggles the Morse DECODE function on and off. The DECODE function is on when the DEC field is displayed white on red, it is off when it is displayed black on light grey. Toggles the internal SPEAKER on and off. The SPEAKER is on when the SPKR field is displayed white on red, it is off when it is displayed black on light grey. The speaker is used to signal incoming data as well as outgoing Morse code. No Function When the key field displays SEND in black on light grey, hitting 'F5> will send out the contents of the transmit buffer window. When the transmit buffer is empty an error message will appear. If any Morse transmission either from the transmit buffer window or from the send window (keyboard direct) is under way, then the function key field will display ABORT in white on red. Then either hitting 'F5> or ~ESC> will cancel all transmissions. Hitting 'F6> will switch the keyboard input to the transmit buffer. The cursor will jump to the transmit buffer window and any text up to 3x80 characters can be entered and edited with the (BACKSPACE> key. This function is ended either by pressing again or by pressing . If the transmit buffer is not empty at the beginning, then a message will appear asking for confirmation of overwriting the current contents of the transmit buffer. The key starts a sequence of inputs for the BEACON mode. Each input has to be terminated by the key. The key cancels all inputs for the beacon mncir 1 st input:set the time difference in minutes between successive BEACON transmissions. 2nd input:set the minute within a 1 h period, on which each BEACON transmission will start. This value cannot be equal to or larger than the first value. No function. Help function. CCW operation will be stopped and a menu will appear. A prompt will ask for further input. Pressing ~ESC> will cancel the command. Termination of program. A prompt will appear asking for confirmation. Pressing upper case or lower case 'y' will terminate PCW, any other key will cancel the command. (If a German keyboard is used without the KBDD command line parameter, the program is terminated by pressing (F10> and the 'z' Key.) 11.2.2. Control Functions This level of function menu is reached by pressing and holding the ~CTL) key. The current state of functions is shown on the function key menu.; Actual 'functions are reached by holding the ~CTL> key and pressing the function key. This function allows you to set the center frequency of the CCW filter manually. A numerical value can be entered via the keyboard. This value is limited to the range between 300 Hz and 1200 Hz. Toggles the AUTOTUNE function on and off. AUTOTUNE is on when the A-TUNE field is displayed white on red, it is off when it is displayed black on light grey. AUTOTUNE will try to adjust the center frequency of the CCW detection filter to the estimated frequency of the past 'mark' signals. Adjustment is made in steps of 1 Hz. Toggles the AUTOTRACK function on and off. AUTOTRACK is on when the A-TRACK field is displayed white on red, it is off when it is displayed black on light grey. AUTOTRACK will try to keep CCW framing in synchronism between transmitter and receiver. Adjustment is made in steps of 5 ms. No function The following four functions switch parameters of the AUTOTRESHOLD function. The current state is displayed by showing the corresponding field in white on red AUTOTHRESHOLD off. No automatic adaptation of the decision threshold. AUTOTHRESHOLD slow. Slow automatic adaptation of the decision threshold. AUTOTHRESHOLD medium. Medium fast automatic adaptation of the decision threshold AUTOTHRESHOLD fast. Fast automatic adaptation of the decision threshold. Displays program status information in the command line. See paragraph 16 for d~?ts Displays program information and either the registered callsign or a registration message. 11.2.3. Alternate Functions This level of function menu is reached by pressing and holding the ~ALT> key. The current state of functions is shown on the function key menu. Actual functions are reached by holding the ~ALT> key and pressing the function key. Decrease the center frequency of the CCW filter by 1 Hz. Increase the center frequency of the CCW filter By 1 Hz Decrease the chosen CCW Morse speed Available values are 120, 60, and 40 cpm. Increase the chosen CCW Morse speed. Available values are 120, 60, and 40 cpm. Decrease the CCW decoding bandwidth. Available values are 200Hz, 100Hz, 40Hz, 20Hz, and 10Hz or 6.67 Hz, depending on the chosen Morse speed. Increase the CCW decoding bandwidth. No function No function. Saves the contents of the transmit buffer as shown in the buffer window to a DOS file. The prompt on the command line asks for the file name. Loads the transmit buffer with the contents of a DOS file. The prompt on the command line asks for the file name. The new contents of the transmit buffer are shown within the buffer window. 11.3. Special Keys Retards receiver CCW framing by 5 ms, decreases the value of the CYCLE parameter Advances receiver CCW framing by 5 ms, increases the value of the CYCLE parameter. Increases the value of the decision threshold Decreases the value of the decision threshold. The following special keys perform functions identical to some function keys Increase the chosen CCW Morse speed. Available values are 120,60, and 40 cpm < End> Decrease the chosen CCW Morse speed Available values are 120 60 and 40 cpm Increase the CCW decoding bandwidth. Available values are 200Hz,100Hz, 40Hz 20Hz and 10Hz or 667 Hz, depending on the chosen Morse speed Decrease the CCW decoding bandwidth 12. PCW: Command Line Parameters PRECISION CW uses default values for a number of parameters, which can be adjusted by keyboard commands after start-up. In addition, many of these parameters can be preset or switched at start-up time via the DOS run string command. At the DOS prompt type 'pcw and an appropriate string of characters before hitting the key. The string may comprise one or more keywords, which are separated by blanks Letters within the keywords can be either lower or upper case. Example C \> PCW com1 KBDG tune+ threshO All available run string commands are now described. The fixed part of the strings is given in capital letters and the subsequent lower case letters have the following meanings c a single character n a single numerical character nnn a decimal number X either the '+' or the '-' character COMn n is in the range 1 .. 4 default is COM1 This command switches the input port to the desired communication interface COM1 ... COM4. As DOS only defines COM1 and COM2, the addresses and interrupts shown in table 12-1 are assumed for COM1 ... COM4. These are the settings found on most PC serial interface cards. No. of serial Address of interrupt interrupt interface Interface used switched off _ by KINT+ COM1 $3F8 INT4 INT3 COM2 $2F8 INT3 INT4 COM3 $3E8 INT4 INT3 COM4 $2E8 iNT3 INT4 Table 12-1 Addresses and Interrupts for COM Interfaces INTn n is in the range 3 ... 4 default setting depends on the COMn command (see table 12-1). This command switches the interrupt which will be used for data input via the selected COM interface It is only needed when non-standard installations have to be covered.