Epson Multi-mode Data Controller MFJ-1278B - Manual (Page 63)

MFJ-1278B MULTI-MODE BASIC OPERATION
As indicated in the preceding paragraph, the usual terminal/radio/modem parms are available.
As in Packet, Pactor also contains COMMAND and CONVERSE modes. Please note that
switching between them is modeled on the "NEWMODE ON" procedures in packet. The MFJ-
1278B is in COMMAND mode, if the p_cmd: prompt is on the computer screen. To switch
to CONVERSE mode from COMMAND mode the K key followed by an <ENTER> is issued
by the user. The CMDCHR character switches the MFJ-1278B from CONVERSE mode
back to COMMAND mode. The CMDCHR character is defined as CTRL-C. Once
connected, the link acts much like AMTOR.
The station originating the connection is the master and he remains in transmit mode until he or
the slave initiates a changeover. Either station may reverse the direction of the link by issuing
a control-Y changeover (^Y) in converse mode.
PACTOR FEATURE DEFINITIONS
DIGITAL MEMORY ARQ
The MFJ-1278B's Pactor incorporates a Digital Memory ARQ mode. Digital Memory
ARQ enables reconstruction of a good packet from a bad packet. A bad packet is one
repeatedly received with on or more bit errors. Digital Memory ARQ accumulates the bit
value, 1 or 0 derived from the RF port during successive reception of the same error-laden
packet. These bit accumulations are sent to the receiver shift register. Thus a good packet is
reconstructed from 2 or more "bad" packets.
The MAXSUM parameter controls the number of accumulations performed for each bit.
Larger MAXSUM values increase the effectiveness of the Digital Memory ARQ scheme, but
only to a certain point. The reception of an almost perfect packet will be inadequate to
overcome the accumulated noise, if MAXSUM is too large. Also the presence of excessive
QRM, QRN, or QSB effects the reception of good packets. On the other hand, if MAXSUM is
too small the accumulation of samples will be too few to correct for moderate error rates. The
factory setting for MAXSUM represents a good compromise--feel free to play with it.
FEC UNPROTO
Unproto: "FEC/UNPROTO" packets are transmitted UREPEATS+1 times. Selecting larger
values of UREPEATS reduces throughput, but enhances reliability. To transmit in UNPROTO
mode, issue the appropriate unproto command and type away. When done, break out to
"p_cmd:" mode and type 'D' or 'DD' to terminate transmission.
MONITORING
Monitoring unproto: If MONITOR is ON the MFJ-1278B is always in listen mode,
except when connected to another station. There are other situations occur that prevent the