This appears to be a radio transmission, specifically a Morse code message in the format used by amateur radio operators. Let's break it down:

* "10:51" indicates the time of day (10 hours and 51 minutes).

* "JK1JXP/1" is a call sign, which identifies the transmitting amateur radio station.

+ "JK1" is the prefix for Japan.

+ "JXP" is the suffix for a specific amateur radio license holder.

+ The "/1" indicates that the transmitter is located on the operator's home QTH (QTH = Station), rather than being mobile or operating from a different location.

* "on JP-1238(Johoku-Chuo Prefectural Park, JP-TK)" refers to the location of the transmission:

+ "JP-1238" likely indicates a specific grid square or geographic location within Japan (using the Nippon 100km x 100km grid system).

+ "(Johoku-Chuo Prefectural Park, JP-TK)" provides additional information about the location, including the name of the park.

* "1851 SSB" likely refers to:

+ "18" is the frequency band in MHz (e.g., 18m band)

+ "51" is the specific frequency within that band

+ "SSB" stands for Single Side Band, a type of radio transmission where only one sideband (upper or lower) is transmitted.

The message "[JK1JXP]" likely indicates that this call sign belongs to the transmitting station.

This format appears to be in accordance with Japanese amateur radio conventions.