MFJ MFJ-1270C, Системное руководство

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MFJ-1270C/1274C MANUAL ADVANCED OPERATION
Page 91
ACKPRIOR ON|OFF
This enables prioritized acknowledgments if turned on.
If ACKprior is turned off and SLots (see below) is set to 0, this modification of
the AX.25 protocol is effectively disabled. The MFJ TNC will behave like
normal AX.25 protocol.
Prioritized acknowledgments and slotted channel access can be enabled or
disabled independently of one another. So you could if you wished run normal
AX.25 with slotted channel access or the new protocol without slotted channel
access.
DEADTIME 0 - 250 (each increment represents 10 milliseconds)
This is the time between when a remote TNC has pressed PTT and when the
local TNC can reasonably be expected to detect this fact.
This must be set to a value that accounts for the slowest acceptable station on the
channel. It includes the time required for the remote station's radio to come on
the air properly after assertion of PTT (TXDelay) and the time required for the
local station's squelch (if used) and TNC DCD circuits to allow generation of a
"DCD true" signal in the local TNC. Ideally, once the proper value for this timer
is ascertained, all stations on the channel will use the same value.
Very preliminary testing done here on VHF indicates that measurements of the
above delay times should be multiplied by 1.5 for use as the DEAdtime
parameter. We had carefully measured the times for all stations participating in
our tests. This gave us a worst case delay total of 210 milliseconds. When we
ran the test, we were still getting about a 5 percent collision rate on the
acknowledgments. We were required to increase the DEAdtime parameter to 30
(300 milliseconds) to completely eliminate collisions with ACKs.
The current default for this parameter is a ridiculously short 30 milliseconds.
This represents only the worst case delay for the TNC's DCD circuit and
completely ignores the radio delays.
A much more reasonable value for this timer on VHF NBFM 1200 baud AFSK
is 300 milliseconds (DEAdtime 3et to 30). This represents a relatively safe time
for a radio that is usable for serious packet work.