Timewave PK-900, Operating Manual

Page: 157 / 392

CHAPTER 11
PACTOR OPERATION
11.1 Overview
PACTOR is a relatively new amateur data communications mode. It was
developed in Germany by Hans-Peter Helfert, DL6MAA and Ulrich Strate,
DF4KV. PACTOR combines some of the best features of both AMTOR and
packet as well as providing a few new features. PACTOR operates at
100 bps or 200 bps depending on radio conditions. PACTOR also
contains a 16 bit CRC to provide near error-free operation and can
also selectively use a data compression scheme (Huffman encoding) to
increase the throughput when transmitting text. PACTOR uses an 8-bit
word, allowing the use of the full ASCII character set. You should
use both upper and lower case in your PACTOR transmissions.
When data blocks are repeated in the case of an error, the receiving
unit can often combine the information in the repeated blocks to
provide a good block without the need of receiving a perfect block.
This scheme is called memory ARQ.
Like AMTOR and packet, PACTOR has two basic modes of operation, an ARQ
mode (Automatic ReQuest for reception) and a non-linked mode used for
CQ calls and roundtable operation.
o ARQ PACTOR is a handshaking protocol that allows two stations to
communicate in a near error-free fashion. A PACTOR ARQ exchange
consists of a 0.96 second burst of data from the information
sending station followed by a short burst from the data receiving
station that is an acknowledge (ACK) or non-acknowledge (NAK).
The NAK is sent by the receiving station when the CRC data test
indicates an error in the data block. Like packet, PACTOR is
mark-space polarity independent, although for different reasons.
The PACTOR protocol alternates the data polarity with every
transmission to reduce the effects of interference on the
received signal.
o The unproto(col) mode of operation is a non-linked type of
operation. It is used for roundtable operation or for calling
CQ. The unproto mode repeats the data blocks a selectable number
of times and can use either 100 or 200 bps. It also uses the CRC
error check.
11.2 Where to Operate PACTOR
Before you can operate PACTOR, you must first know where the activity
occurs. Most PACTOR operation occurs on the 20-meter amateur band
between 14.065 and 14.085 MHz. PACTOR activity can be found on the
other HF amateur bands as well and is most often located between 65
and 90 kHz up from the bottom of the band as it is on 20 meters.
On 80 meters, most PACTOR will be found between 3660 and 3690 KHz.
PACTOR is not sensitive to to the sideband used, but we recommend
using LSB as in RTTY and AMTOR operating modes.
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