MFJ-1270C/1274C MANUAL ADVANCED OPERATION
Page 66
before beginning transmission. This prevents repeated collisions of
transmissions by the same two stations. The random time is a multiple (0-15) of
the TXDELAY time.
The interval, in milliseconds, between the MFJ TNC detecting carrier-drop and
beginning to transmit is
Wait time = DWAIT * 10
for the first transmission of a packet. For subsequent transmissions of the same
packet the interval is
Wait time = DWAIT * 10 + ( r * TXDELAY ) * 10
where r is a random number from 0 to 15. Thus, if your MFJ TNC is forced to
re-transmit packets, you will occasionally hear a fairly long delay before
transmission begins.
Multiple packets may be transmitted before waiting for an acknowledgment.
This permits more efficient channel use when large amounts of data are being
transferred. The maximum number of packets which the MFJ TNC will send
before waiting for acknowledgment is specified by the command MAXFRAME.
This does not mean that t(e MFJ TNC will wait until several packets have been
entered before transmitting. MAXFRAME in combination with the command
PACLEN, which sets the maximum number of characters in a packet,
determines how much information can be sent in a single transmission. The best
combination for efficient data transfer is determined partly by the channel quality
and partly by the rate at which the terminal can process data. For a 1200 baud
terminal data rate, you should start with a combination that produces about 300
characters outstanding at one time.
Radio Baud Rate
The radio data transmission rate is selectable for 300 baud and 1200 baud. High
speed modem such as the MFJ-2400 and MFJ-9600 modem, if installed, can also
be selected with the dip switch on the back of the TNC.
Note that there is no
relationship between terminal baud rate and radio baud rate.
In order to communicate with another packet station you must
use the same radio
baud rates. The length of time required to send a given amount of information
increases as the baud rate decreases. For example, it takes four times as long to
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