Hi Joe,
The HF pileup QSO sequence that you suggested in your email is perfect for the normal case, when both parties copy each other
without problems, but some edge cases need to be discussed in more detail. The communication channel can fail at any stage
during the QSO, in one direction or another, and the QSO sequence must handle all such cases reasonably. Here is one case of
concern:
{
Note that VK9MA does not proceed to the next caller until receiving "RRR" and
logging the QSO. In the first sequence of example
QSOs, if Tx#4 is not received then #5 should instead be a repeat of #3. This message
should continue to be sent until the "RRR"
is received (or the VK9MA op gives up and calls someone else).
}
According to your description, the sequence is going to be like this:
1. CQ UP VK9MA QH72
2. VK9MA K1ABC FN42 | VK9MA W9XYZ -13
3. K1ABC VK9MA R QH72
4. VK9MA K1ABC RRR
5. K1ABC VK9MA R QH72
6. VK9MA K1ABC RRR
7. K1ABC VK9MA R QH72
8. VK9MA K1ABC RRR
9. W9XYZ VK9MA R QH72
How does K1ABC know if VK9MA logged the QSO with her or not? According to your description of the QSO sequence, VK9MA sends
message 9 in both cases. Should K1ABC log her contact or make another attempt? Those who are not active HF DX chasers cannot
imagine how much frustration such uncertainty will cause if not resolved properly. Please provide a way to make it clear if the
QSO was logged or not. We need some equivalent of the CW messages "TU UP" and "NIL UP". Can you suggest the best way of doing this?
This is not the only way how a QSO may end in an ambiguous state. One good way of making sure that all situations are handled
properly is to list all possible stages of the QSO and all possible messages (perhaps using a C++ Enum declaration), and develop
a table that defines what should be done in each stage if the given message is received, or if nothing is received. Two tables
will be needed, for the DX and for the caller. Such tables will be a good basis for the state machine that implements the QSO
sequence.
73 Alex VE3NEA
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