TECHNICAL SPECIFICATION - PUA43 MODE Preliminary Issue 0.1 21 January 2001 Bob Larkin, W7PUA 1-Introduction - The PUA43 Mode uses a slow speed code that is suitable for very weak-signal communication. There are several options and the full designation for the mode should incude that information. The code is compatible with "Message Estimation" as used in the DSP-10. The message is of a fixed length and transmitted as a multiple frequency-shifted sine-wave. Randomization of the frequency is used to reduce coherent interference. It is intended to be used with Long Term Integration to improve the effective signal-to-noise ratio. Historically, the use of this general type of code goes back at least to the Piccolo system of the 1950's. Since that time other systems besides this have implemented the use of Multiple FSK. WARRANTY: OF COURSE, THERE IS NO WARRANTY FOR THE USE OF THIS CODE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. THIS CODE AND THIS SPECIFICATION ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE IS WITH YOU. SHOULD THE CODE SYSTEM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. THE DOCUMENT AND THE SPECIFIC IMPLEMENTATION OF THE CODE IS THE ORIGINAL WORK OF THE AUTHOR, AND NOT BELIEVED TO INFRINGE ON ANY INTELLECTUAL PROPERTY RIGHTS. HOWEVER, THIS MAY NOT BE THE CASE, AND IN USING THIS CODING SYSTEM FOR ANY PURPOSE, ONE ASSUMES THE RESPONSIBILITY OF ENSURING THAT THEY HAVE THE RIGHT TO DO SO. Ownership: This code system is fully "open" and made available for use by any amateur or commercial individual or organization. The idea is to encourage experimentation with this type of communication. In order to have a common standard, the code is specified by this document which is copyrighted by the author. Permission is granted to copy or reproduce this document freely, as well as to disseminate it in any way. However, one may not change the content of the document. One may wrap it inside of another document. -------------------------------- SPECIFICATION -------------------------------- Designation - The term PUA43, followed by two parameters specifies the coding/modulation system. The first parameter is a frequency spacing parameter, carried by a letter 'A', 'B' or 'C', as folows: A - 9.375 Hz symbol spacing. B - 18.75 Hz symbol spacing. C - 37.5 Hz symbol spacing. The second parameter is the message length of either 14 or 28 symbols. A typical complete designation would be PUA43-B28 Modulation: - Each symbol translates into a unique code frequency F, by the formula F=F0 + DF x mod43(R + S) where F0 is the base frequency 450 Hz DF is the symbol spacing 9.375, 18.75 or 37.5 Hz, depending on the first code parameter R is a random stir value between 0 and 42, inclusive, that is specified below S is a number between 0 and 42, inclusive, that corresponds to the symbol being sent. mod43 operator take the value if it is between 0 and 42 and subtracts 43 if it is not. The frequency, F, is normally added to a "base" RF frequency to determine the actual transmission frequency. Each symbol has one or two times within the minute that it is sent. Both message lengths start at the beginning of the minute. The 14 symbol message repeats after 28 seconds. At 56 seconds after the start of the minute, a 4 second "dead" period is assigned to allow identification in an alternate code, such as Morse code. The identification should not overlap spectrally with the PUA43 code. A Morse code identification at 400 Hz is recommended, but not required. Symbols - There are 43 symbols, that have numerical value of 0 to 43, called S. The value can represent the following items: Numbers 0 to 9 for S=0 to 9, in order. '.' the period S=10 ',' the comma, or other agreed upon meaning S=11 ' ' a space S=12 '/' forward slash S=13 '#' means "previous message received", or other agreed upon meaning S=14 '?' question mark S=15 '$' shift to modify the maeaning of a single following symbol S=16 (shifted characters are undefined at this time) Letters A to Z (or a to z) for S=17 to 42, in order. Modulation - The code frequency, F, is added to a "carrier" frequency that is not specified here. This sine-wave is keyed on and off with a rise/fall-time of 10 msec, or less, and remains on at a constant amplitude for at least 1.9 seconds. The rise/fall-time and shaping should be selected as in a CW waveform to minimize "key-clicks". Random Stir - There are 1440 random numbers corresponding to each minute in a day. Each number takes a value form 0 to 42 and is called R in the coding formula. The first of the 1440 values applies to the minute from 0000 to 0001 UT. Each subsequent value applies to subsequent minutes, in order. The values are 29 12 13 6 25 ... 1334 more values ... 26 where the entire list is contained in the attached ASCII file, UHFA_43A.RND, that is part of this specification. Timing - The timing of the pulses should be synchronized to UT with an accuracy of 30 milliseconds or better. Frequency Accuracy - The final transmitted frequency accuracy shall be better than First parameter A: .5 Hz First parameter B: 1 Hz First parameter C: 2 Hz.