Table Of Content

PACTOk wf e odiwanvearN envAO FaHtaD EfEixtive Commnnication Protocol aiv DataGommllnicatio~ ruetalna oidar Only the MA!STER corrects his Receive LlsiIlgHFfre hasrecentlybecome Pb- more effective and enjoyable due to a new A long series of tests conducted by co-cation protocol called PACTOR DL6MAA and DF4W have shown that PACTOR was developed by two for operation in rapidly changing enterprising German amateu~~,DIhMAA conditions, it is not a good policy to adjust and DF4KJL This arkle is based on the packet length automatically. Simulations information provided by these gentlemen on-the-air testing the optimum in their various writings. HF packet length to be about one second. PACTOR Features To compensate for varying conditions, PACTOR varies the number of data tub seodton PACTOR was designed to overcome the characters in the data block, egnah cyna shortcomings exhibited by both packet and of the synchronous timing ANlTOR in HF operation while remaining parameters. PACTOR determines the affordable for the average amateur broper baud rate to use based on the operator. ‘accuracy of bit transitions and the link error statistics. - Error-free data transmission (less than 1 x 10-S) Data blocks have CRC-16 checking as is done in AX25 packet. This is much more True binary data transmission robust than the parity bits FEC used in Efficient use of channel capacity AMTOR. Good interference tolerance The data field of the PACTOR packet can contain any digital information; the format Requires only 600 Hz channel bandwidth of the codes is specified in the status byte. Complete visibility of sending and At the present trme the choice is between receiving callsigns 8 bit ASCII and Huffman compressed 7 bit ASCII. Whv PACTOR? Authorization HF propagation is characterized by multipath propagation which induces ‘bit The US FCC regulations specify that stretching’ and phase distortions, fading, Baudot or ASCII codes may be used for and impulse noise, interference by other data transmission, The 8 bit ASCII text stations, among other obstacles to transmitted by PACTOR is closer to erup‘ comIIlunication, ASCII’ than the bit-stuffed HDLC used by so there should be no AX25 packet, The PACTOR mode is similar to AMTOR ytilage lfo siht .edomehT question of the which is good for ordinary HF compressed PACTOR data mode uses commumcation. Both use half duplex ASCII characters encoded in a channel- ARQ; packets (blocks) of data carrying the capacity-enhancing format which still information are acknowledged with short meets the intent of the regulations. The ‘receipt’ signals by the receiving station. regulations regarding amateur When errors occur, the receiver can transmissions require that there be no request the repetition of a packet with intent to obscure the data transmitted. The relevant control signals. * emehcs si dehsilbupsa Huffman encoding PACTOR uses a MASTER/SLAVE an appendix to this article. It seems phasing like AMY’TOR. The SLAVE clock tganhitdocne reasonable to me to consider 1s synchronized to the h4ASTER timing. 62 for spectrum efficiency using a widely throughput in good conditions is up to four pubhshed encoding scheme shows no times as greaL During the poorest of mtent to encrypt the content of the data conditions, throughput is considerably transmkion and is therefore allowable better than AMTOR because of the under US regulalions. CRC-16 error checking and Memory-ARQ capabilities. ecnamrofreP :xidneppA ROTCAP namffuH PACTOR achieves good throughput code during poor HIF conditions by a variety of tech.quesXheactualbaudrateiskept l!itdbm coding is relativelv indifferent to low-thesameasAMTORThisisone differences be6een red &d theoretical thirdtherateoftyphNWAX25packet alphabet character fpequencies, so that operation. From another point of view, similar good results are obtained in AMTOR and PACTOR bits are three German and Englglish plain text. The times as long as 300 baud HF packet bits, compression factor attained with ASCII thus providing much increased protection amoW to about 1.7, resulting in an from the bit smearing caused by multipath average of 4.5 bits per character. A retaerg propagation, compression factor would require considering the statistical relationships A doubling of the throughput compared to sretcarahc vokraM( AMTOR results ffrom sending longer between the individual encoding). blocks of data (but still short enough to cope with most fades) thus reducing the Code in order of frequency, LSB tnes( percentage of overhead carried. In first) on the left: addition, the ability to automatically Character ASCII double the data content of each block EMYfIIlm under favorable conditions provides a space 32 10 considerable increase in efficiency. e 101 011 n 110 0101 Finally, encoding ASCII text (7 bit characters) using Huffhan codes increases i 105 1101 throughput by an average of at least 70 r 114 1110 percent. t 116 00000 S 115 00100 Memory-ARQ ’ d 100 00111 a 97 01000 A sigpificant feature of PACTOR is u 117 1111.1 Memory-ARQ. Copies of the repeated 1 108 000010 reception of the same packet which fails h 104 000100 the CRC are aggregated in memory and 103 000111 are summed individually for each bit. The g aggregate of all unsuccessful transmissions m 109 oololl is decoded which effectively increases the <CR> 13 001100 signal to noise ratio by about 15 dB. This <LF> 10 00’1101 PACTOR feature is hardware dependent 0 111 OlOOlO and prevents the proper implementation of c 99 010011 PACTOR as a software- only upgrade to b 98 0000110 packet or Ah4TOR equipment. f 102 0000111 119 0001100 The combination of the above factors W provides a protocol which can provide a D 68 0001101 throughput nearly equal to HI? packet in k 107 0010101 122 1100010 the best of conditions, and much better Z throughput than packet during typical 46 1100100 conditions. Compared to AMTOR, the 44 1100101 63 S 83. 11’11011 39 11or001101:110 A 65 00’101001 w- 95 111100001z00 E 69 llooooo0 49. 38 111100111001 P 112 11m10 + 43 111100111110 V 118 11m11 > 62 111100111111 0 48 l1.sDoolll @ ooo101011-moo F 70 lmolloo 36 4#)0101011:1001 B 66 11001111 < 60 ooo101011:1010 C 67 lllloool X 88 ooo101.0111011 I 73 11’110010 # 35 001~01ooo1 lo1 1 T 84 11’110100 Y 89 001010001z0101 0 79 ocm01ooo 59 111100001’10100 P 80 ooo101100 934 11110000110101 II 1 49 00’101oooo 91 001010001l01000 I R 82 1m oooo10 93 001010001101001 ( 40 110011011 127 110001101111000 ) 41 110011100 126 110001101111001 L 76 110011101 125 110001101’1111010 N 78 1111ooooo 124 110001101’111011 Z 90 111100110 123 110001101111100 { M 77 111100110 Y 96 110001~01111101 9 57 ooo1010010 A 94 110001101111110 W 87 ’ cKMI1010100 32 110001101111111 >su< 5 53 ~01010101 <GS> 29 11.1100001101100 Y l21 0001010110 9 ESC > 27 111100001101101 2 50 0001011010 <EM> 25 111100001101110 3 51 0001011011 <CAN> 24 111100001-101111 4 52 01)010111oQ <ETB> 23 111100001110000 6 54 0001011101 exN> 22 111100001110001 7 55 0001011110 <NAK> 21 111100001110010 8 56 ooo1011.111 <DC4> 20 111l00001110011 H 72 0010100010 <DC3> 19 111100001110100 J 74 1100000110 <DC2> 18 111100001110101 U 85 1100000111 cDCl> 17 111100001110110 V 86 1100011000 <DLE> 16 111100001110111 <FS> 28 1100011001 <RS> 30 113100001111000 X 120 1100011010 <SI> 15 111100001111001 K 75 1100110100 <so> 14 111100001111010 3 63 1100110101 4cl+ 12 113100001111011 -- 61 1111000010 <VT> 11 113100001111100 4 113 1111010110 <HT > 9 11l100001111101 Q 81 1111010111 CBS> 8 113.100001111110 J 106 00010100110 <BEL> 11-l.100001111111 G 71 00010100111 <ACK> 6 1111.00112000000 45 oco10101111 <EN@ 5 11n100111000001 58 00101000111 <EOT> 4 11l100111000010 ?. 33 11110011101 <ETX> 3 1111001-l1000011 47 11110011110 4TX> 2 113100111000100 / 15 42 001010001100 <SOH> 1 1’1.:1100111000101 34 1l0001101100 CNUL> 0 11.1200111000110 37 110001101101 <SUB> 26 11l100111000111 64