ter 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 num
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ber. This time, let’s say it comes up with the number 27. Since this is less than
the PERSIST value, we now start the key-up of the transmitter to send the packet.
Txdelay
TXDELAY should be adjusted to allow your radio sufficient time to switch from
receive mode to transmit mode 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. TXDELAY also allows the station you
are talking to sufficient time to switch from transmit mode back to receive mode.
The TNC sends flags during the TXDELAY period, so if someone has this set ex-
tra 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 us-
ing the following equation:
FRACK * ((2 * n) + 1) seconds
where n is the number of digipeaters. The lower the baud rate (HBAUD) the
higher 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 re
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leased (the packet has been sent) and is suspended when data carrier from the ra
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dio is present, or when your station is transmitting.
Retries AX.25 Level 2, Version 1 vs. Version 2
The way retries are accomplished depends on AX25L2V2 being OFF or ON. To
explain this we will follow a conversation through its path. First let’s assume sta
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Packet Modes of Operation Overview of Packet Communication
User’s Guide 152 KAM’98 v 8.3
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