It appears you've provided a log entry from a amateur radio operator's activity, specifically in the form of a Morse code transmission.

Here's a breakdown of what the message likely means:

- **JL3AMK/3**: This is the amateur radio call sign (also known as a "handle") of the operator. The format "XYZZ" indicates:

- "XY" represents the country code, which in this case is Japan.

- "ZZ" are the suffix letters that uniquely identify the individual amateur radio license holder within their country.

- **3**: This refers to an operating frequency or mode, likely meaning the transmitter was operated on a third amplifier stage (a way to increase power output) at VHF frequencies, but given the context of CW operation and specific location mentioned, it could also hint at the use of a repeater system accessed via a "3" prefix or suffix indicating a specific band (like 2-meter amateur radio band in this case).

- **JP-1509(Hattori Ryokuchi Prefectural Park, JP-OS)**: This is the location from which the transmission was made. The format is:

- "JP" denotes Japan.

- "OS" likely refers to a geographic or administrative division within Japan, possibly indicating a park or other public area, but given the specific mention of a prefectural park, it could also imply another type of landmark.

- **10111.0 CW QRT**: This is the transmission content:

- "01" represents hours (1 AM) followed by "20", which is the minute (20 minutes past an hour).

- "111.0" is likely a frequency but in this context seems to be a part of the time or sequence rather than a precise frequency.

- **CW** means the transmission was made using Morse code.

- **QRT** indicates that the operator has ended their transmission.

In summary, this log entry suggests that an amateur radio operator with the call sign JL3AMK/3, operating from Hattori Ryokuchi Prefectural Park in Japan, transmitted a message on CW mode at some point past 1 AM.