I’m working on getting my extra class license. Here are a few things I have found that help. Even with a background in electronics and years of being a ham I still score about a 50% on any practice test I take. Here are several places to get study guides and take sample tests. I use my phone to take practice test ofter. Check out Dave Casler, (KE0OG) youtube videos. These are very nice and a great resource. »
Start here: http://sdr.w5tsu.net:8073 ( Kiwi SDR ) http://sdr.w5tsu.net:8074 ( Kiwi SDR ) http://sdr.w5tsu.net:8075 ( OpenWebRX ) This includes both HF, VHF, and UHF I have a new radio. I picked up a KiwiSDR (http://kiwisdr.com/) receiver from Seeed. (https://www.seeedstudio.com/KiwiSDR-Kit-p-2725.html). The KiwiSDR was developed by the Funkamateur John Seamons ZL / KF6VO, is a branch of the OpenWebSDR project and realy started life as a kickstarter project. This is the best HF (10kz-30mz) receiver I own. »
M17 is a digital radio modulation mode, like DMR, D-Star, or Fusion, developed by Wojciech Kaczmarski (SP5WWP) in 2019. Unlike other protocols, M17 has every part of the protocol open source. See: M17Project.org. OpenRTX is an open-source project used to replace the firmware in commercial amateur radios. See: OpenRTX.org. OpenHT is a hardware project working to build and Open Hardware Handy Talkie. It is based on FPGA design - a complete Lattice Radiant project for the LIFCL-40-7SG72C. »