Epson Multi-mode Data Controller MFJ-1278B - Manual (Page 51)

MFJ-1278B MULTI-MODE BASIC OPERATION
Unsuccessful Connections
Sometimes you will initiate a connect sequence that can't be completed. The station may not
be on the air, or it may not be within range of your station. You may have even mis- typed
the other call sign. If the MFJ-1278B does not get a response to its first connect packet, it
will try again. You can control the number of attempts the MFJ-1278B will make with the
command RETRY. The default number of retry attempts is 10. If the MFJ-1278B does not
get an answer after this number of transmissions, it will give up and display the message:
*** retry count exceeded
*** DISCONNECTED
The retry count is also used once the QSO has started. Each transmission sent to the other
station is "acknowledged," or ACKed by the other station, and vice versa. The ACK means
that the packet was received and that the CRC checksum indicated that it was received
without errors. This is the means by which packet radio can ensure error-free
communications. Sometimes a packet will not be received correctly by the other station,
either because of accidental interference from another packet station (a collision), or because
of other channel noise.
If the MFJ-1278B does not get an ACK soon enough, it retransmits the packet and
increments the retry count. If the count set by RETRY is exceeded, the MFJ-1278B will
automatically disconnect and display the same message:
*** retry count exceeded
*** DISCONNECTED
The automatic disconnect feature keeps a MFJ-1278B from indefinitely retransmitting a
packet and tying up the channel under hopeless conditions. For example, an intermediate
digipeater might have been shut down, or the RF channel might have deteriorated to the point
of being unusable. The other operator might have even turned off his station without
disconnecting. If you are operating under special conditions, such as a marginal HF channel,
you can set RETRY 0 to disable all automatic disconnects (the retry limit is never reached).
Monitoring Channel Activity
The MFJ-1278B can monitor packet activity on the channel while connected to another
station. You can "read the mail," displaying packets between other stations. The MFJ-
1278B will also keep track of stations heard during a session. This section will describe
some of the monitor functions.
Monitoring is enabled or disabled by the MONITOR command. You can try this out in
digital loop-back mode while disconnected. Type:
cmd: MONITOR ON
cmd: CONVERS
This is a test packet.