Weird display of frequencies when transmitting with WSJT-X

[JA9HWD]

When using WSJT-X, a strange phenomenon is occurring while continuously sending CQs.

shot_1 800_send_shift 2024-04-09 093647.png (234.82 KiB) Viewed 224 times

Shot_1 is when WSJT-X QRG is transmitted at 3.573MHz DF (audio frequency) 500Hz.
The VFO frequency actually transmitted is 3.572MHz and the DF (audio frequency) is 500Hz.
But why does the VFO display of Log4OM2 change to 3571.525KHz and is displayed 475Hz lower?

shot_2 800_recv 2024-04-09 094000.png (233.81 KiB) Viewed 224 times

Shot_2 is immediately after sending has finished and switching to receiving.
WSJT-X's QRG display and Log4OM2's VFO display have returned to 3573KHz correctly.

shot_3 800_send_shift_2 2024-04-09 094346.png (236.72 KiB) Viewed 224 times

Shot_3 will occasionally display differently from Shot_1 during continuous transmission. But this is correct as it is the actual VFO transmit frequency. This is more strange for Shot_1.


I haven't thought much about QSO logging, but I think Log4OM2 writes to the log at a frequency that is QRG plus DF. I think I read in another topic that logs are written using the frequency of VFO frequency + audio frequency.
In that case, if you specify split in the WSJT-X rig settings, the VFO frequency will change depending on the DF (audio frequency) as shown in the table below. However, there may be a calculation error somewhere in Shot_1. In the example, it is DF 500, so with a -1000Hz shift, the VFO frequency will be 3572KHz, the audio frequency will be 500Hz, and the log frequency will be 3572.5KHz.
Looking at the cluster and spot information, it seems that many logging software are miscalculating this and reporting the frequency, but I don't know what app they are using.

VFO shift frequency by DF with split specification
0000-499 -1500Hz
0500-999 -1000Hz
1000-1499 -500Hz
1500-1999 No shift
2000-2499 +500Hz
2500-2999 +1000Hz ... It's a pain so I'll stop here.

I don't know what kind of discussion there has been about this matter, but I would like to know why there is a difference in the display frequency in Shot_1.

Log4OM version: 2.32.1.0