Amazon! Has a 10 ft RG-58U cord tho so the actual output is more like 4.1 when you do the math. Good if you need to get it high up or far away, though, and don’t want to use a big old white fiber glass guy.
Here’s a link: Waterproof Replacement 5.8dBi Strengthen Magnet Base Pure Copper 915MHZ LoRa Gateway Antenna with 3M/10FT Cable for Helium Hotspot RAK Nebra Bobcat 300 SenseCAP M1 Hotspot HNT Finestra Miner, Eifagur https://www.amazon.com/dp/B09MRGDTPZ/ref=cm_sw_r_cp_api_glt_i_QB2AT85SHV6A50MJQ994
i’m using this antenna. i’m thinking it’s 5.8dbi https://www.amazon.com/dp/B09MRGDTPZ/ref=cm_sw_r_cp_api_i_T0HR8V041HRP8WN42PS0