FT8 / Technical Articles

A Look at Maintaining Proper Etiquette in FT8 Mode

Compared to the classic amateur modes of CW, SSB, and RTTY, WSJT-X modes such as FT8 are very structured with constrained message protocol. They are not suited for rag-chewing, and one would think that operating etiquette would not be an issue. However, there are three things to consider to be a “good” FT8 QSO partner, and all of them are specific to the unique characteristics of FT8.

To start, make sure to install a PC time manager and have it running in the background to ensure your computer clock is in sync with UTC. All QSO partners need to do this because the FT8 software depends on everyone starting transmission and decoding at precisely the same time. The delta should be less than a second, though the software can sometimes cope with larger discrepancies. It is easy to be exact, so download one of several freeware time sync programs. I use Network Time on all my computers. It is small, unobtrusive, and runs unattended in the background. Another favorite is Meinberg Time Server, although it is more complicated to set up.

Next, recognize that FT8 is designed to operate best in split mode—that is, each station transmits on a fixed audio frequency within the 3 kHz passband that is hopefully free of QRM. Since everyone copies all stations transmitting everywhere in the passband, there is no need to operate simplex or zero-beat with your QSO partner. This minimizes QRM and offers the best chance that signals will be copied clearly. In the WSJT-X main window, check the box for ‘Hold Tx Freq’; there is an equivalent setting in other derivative software like MSHV or DigiRite.

Interestingly, one of the biggest problems in FT8 communication is one QSO partner not logging the apparent contact. The problem typically results from one partner expecting what I call the “superfluous third acknowledgment.” Here is a typical FT8 QSO:

          Tx 6: CQ K1XYZ FN37

          Tx 1:  K1XYZ KN4ABC EM82

          Tx 2: KN4ABC K1XYZ +01

          Tx 3:  K1XYZ KN4ABC R-03

          Tx 4: KN4ABC K1XYZ RRR

          Tx 5:  K1XYZ KN4ABC 73

The QSO is complete with the reception of Tx 4 and should be logged by both parties. However, the automatic message sequencer in WSJT-X triggers the logging function only after Tx 5. The operator can override the sequencer to log the QSO after Tx 4, but most let the automatic sequence play out. After nearly four years of extensive FT8 operation, I have found that many operators expect, and indeed require, that Tx 5 be sent and received before logging the QSO. 

This breaks with decades of amateur QSOs in the classic modes where a QSO is considered complete after each station sends and receives:

  1. Both call signs, and
  2. An exchange, e.g., a signal report, and
  3. Acknowledgment of 2

Thus, all conditions are met with FT8 message Tx 4.  But due to the WSJT-X automatic message sequencer and several years of precedent, the de facto standard for FT8 QSO completion includes the third superfluous acknowledgment of Tx 5.

Unfortunately, it is probably too late to revert the FT8 QSO definition back to the long-standing and proven amateur QSO protocol that omits Tx 5. Perhaps the saying, “If you can’t beat ‘em, join ‘em,” is good advice for this situation. Sending Tx 5 probably maximizes the probability that both QSO partners log the contact, thus exhibiting good QSO etiquette despite the unnecessary Tx 5 that lengthens each QSO. This is more of an issue in FT4/8 contesting where minimum QSO times are desired.

Proponents of the Tx 5 third acknowledgment argue that it is needed to confirm receipt of the Tx 4 RR73 message. The flaw in this assertion is that it applies equally well to the “need” to confirm the Tx 5 message. As you can see, this logic goes on forever (confirming receipt of Tx 5, etc.). For those who want to explore this acknowledgment phenomenon further, Google the “Two General Paradox,” which describes the classic computer science problem popularized back in 1972.

A pragmatic solution to this endless acknowledgment dance is the QSO context. In standard practice for amateur contacts, when you do not receive the expected response, you resend your last transmission until you get that response. After a few retries it is customary to abort the QSO and move on. In an FT8 QSO, you can be pretty sure your Tx 4 message was received if your QSO partner does not repeat the Tx 3 message. And it is nearly 100% certain your partner received your Tx 4 message if the next transmission is a CQ or a call to another station. In other words, Tx 5 is not required to assure QSO completion with high confidence.

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