There is a fun activity called Parks on the Air ® (POTA) for international portable amateur radio operations that promote emergency awareness and communications from national/federal and state/provincial level parks. https://parksontheair.com/
I chose park K-6414 Mālaekahana State Recreation Area: https://dlnr.hawaii.gov/dsp/parks/oahu/malaekahana-state-recreation-area/
Here is a map of the other amateur radio operators I was able to contact. Some I spoke using SSB Mode with and others we used a digital mode called FT-8 to exchange contact info, signal strength and location. Band used were 17m, 20m.
My setup was "Hawaii-Go-Crate"™ by KH6ML All in one - Portable, Mobile, Field, and Home station.
Icom Ic-7300 Radio -100wMFJ-941E, TUNER, HF, 300w WITH MINI CROSS METER
Bioenno Power battery LFP (LiFePO4) 12V, 12Ah LFP Battery (PVC, BLF- 1212A)
2015 MacBook Pro Running boot camp windows 10 with a USB Cable BktTimeSync synchronizes PC w/ NTP server or GPS
MFJ Ultra-Lite Off-Center Fed Dipole Antennas MFJ-2010 300 W, 14 AWG, 67.0 ft. Length, Kit for 40, 20, 10, and 6 meters.