This appears to be a ham radio transmission. Here's a breakdown of the message:

* "00:23" is the time of day (12:23 AM).

* "JR4ARN/P" is the call sign of the amateur radio operator making this transmission. The "/P" indicates that they are operating portable.

* "on JP-0023" refers to the grid square location of the antenna, which in this case is in Japan's Setonaikai National Park area (grid square JP-0023). Grid squares are used to define geographic locations for amateur radio operations.

* The various suffixes "JP-EH, JP-FO, ..., JP-YC" are likely additional grid square coordinates for nearby areas that the operator can also be heard in. These might indicate their propagation range or areas where others have reported seeing their signal.

The rest of the message:

* "7043 FT8 TNX" is a transmission report:

+ "7043" is the date (July 4, 2023).

+ "FT8" refers to the digital mode being used for this transmission. FT8 is a popular amateur radio mode that uses subaudible tones to transmit data.

+ "TNX" is an abbreviation of the word "thanks," indicating appreciation for someone else's reception or reporting of their signal.

The final part, "[JP3HIW]", suggests that JP3HIW was the other station with whom JR4ARN/P made a QSO (a two-way communication) using the FT8 mode.