Kantronics KPC-4 - Page 22

PERSIST
the
TNC
will
transmit.
If
it
is
larger
it
will
wait
another
SLOTTIME
and
then
generate
another
random
number
and
again
decide
whether
to
transmit
or
not.
When
using
PERSIST
and
SLOTTIME
you
should
set
DWAIT
to
0,
since
both
will
be
used
if
specified.
As
an
example,
let's
assume
that
PERSIST
is
set
to
63,
and
SLOTTIME
is
set
to
10.
This
value
of
SLOTTIME
results
in
a
random
number
being
generated
every
100
milliseconds.
When
the
TNC
sees
that
the
channel
is
clear,
it
waits
100
ms,
then
generates
a
random
number
between
0
and
255
(inclusive).
If,
in
our
example,
the
number
was
83,
then
the
TNC
would
not
start
the
keyup
of
the
transmitter
since
83
is
greater
than
the
63
PERSIST
value.
Instead,
it
would
wait
an
additional
100
ms,
and
if
the
channel
is
still
clear,
generate
a
new
random
number.
This
time,
let's
say
it
comes
up
with
the
number
27.
Since
this
is
less
than
the
PERSIST
value,
we
now
start
the
keyup
of
the
transmitter
to
send
the
packet.
Txdelay
TXDELAY
should
be
adjusted
to
allow
your
radio
sufficient
time
to
switch
from
the
receive
mode
to
transmit
and
develop
full
power
output.
If
the
TNC
sends
the
packet
before
the
radio
is
at
full
power
the
beginning
of
the
packet
will
be
lost
and
no
one
will
be
able
to
decode
it.
It
is
a
good
idea
to
allow
a
little
extra
time
for
this
parameter
to
allow
the
station
you
are
talking
to
sufficient
time
to
switch
from
his
transmit
mode
back
to
receive.
This
is
not
usually
necessary
if
you
are
connected
through
a
digipeater,
but
if
you
are
connected
direct,
this
could
make
the
difference
between
successful
communications
and
no
communications.
The
TNC
sends
flags
during
this
period,
so
if
someone
has
this
set
extra
long
you
will
hear
a
repetitive
sound
at
the
beginning
of
the
packet.
Frack
Frame
acknowledgment
time.
If
the
TNC
expects
an
acknowledgment
of
a
packet
it
has
sent,
it
will
wait
FRACK
seconds
for
the
acknowledgment.
If
the
acknowledgment
is
not
received
it
will
either
send
a
poll
or
retransmit
the
packet,
depending
on
the
setting
of
AX25L2V2.
When digis are used
extra time
is allowed
for
each
transmission
using
the
following
equation:
FRACK * ((2 * n) + 1) seconds
where n is the number of digipeaters. The lower the baud rate (HBAUD) the longer
this parameter should be set, because everything is slower. The length of the
transmission (determined by PACLEN and MAXFRAME) also needs to be taken into
account when deciding how to set FRACK. Longer packets (and more of them) require
more time to be transmitted, more time to be repeated by the digipeater, and so on
down the line. The FRACK timer begins when PTT is released (the packet has
been sent) and is suspended when data carrier from the radio is present, or
when your station is transmitting.
16 PACKET
: © Copyright 1989, 1990, Kantronics, Inc. All Rights Reserved.
Version 3.0 Aug 13, 1990 Duplication of this manual or the firmware without
Operations Manual permission of Kantronics, Inc. is prohibited.