MFJ-1270C/1274C MANUAL ADVANCED OPERATION
Page 64
Amateur radio equipment varies greatly in the time delays required in switching
from receive to transmit and from transmit to receive. If the MFJ TNC starts
sending data before the transmitter is operating or before the receiver has had
time to switch from transmitting and lock up on the incoming signal, the packet
will not be received properly. The delay between transmitter keyup and the
beginning of data transmission is controlled by the command TXDELAY.
During the time the MFJ TNC is keying the transmitter but not sending data, it
will transmit a synchronizing signal (flags).
If you are transmitting packets through an audio repeater, you may require a
considerably greater keyup delay than is required for direct communications.
Furthermore, the extra keyup delay is not required if the repeater has not had
time to "drop" since the last transmission. The command AXDELAY allows you
to specify an additional keyup delay to allow the repeater receiver and
transmitter to lock up. The command AXHANG sets the time the MFJ TNC
will assume is required for the repeater to drop. If the MFJ TNC has detected
channel activity recently enough that the repeater transmitter should still be on, it
will wait only the TXDELAY time before sending data, rather than adding an
AXDELAY time as well.
The commands TXDELAY, AXDELAY, and AXHANG all set times in units
of 10 ms. If AXDELAY is in effect the total keyup delay will be
Keyup delay = (TXDELAY + AXDELAY) * 10
in milliseconds. If channel activity has been heard more recently than
AXHANG*10 ms ago, the keyup delay will only be
Keyup delay = TXDELAY*10
in milliseconds.
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