S21RC
S21RC's personal blog: DIY projects, shack insights, and operating experiences from Bangladesh.
Description
Documents S21RC's construction of an impedance transformer harness for a VHF/UHF cross yagi, utilizing 20m of RG179 cable. Details the creation of a DIY RF sampler with a -50dB sampling output, primarily for measuring HF radio PA section output with a Spectrum Analyzer, also applicable for Pure Signal transmission.
Chronicles the deployment of a 200m long beverage antenna for the S21DX IOTA operation in 2022, positioned 2m above ground. Discusses the construction of a 3-element short beam for 10m to replace a previous 2-element antenna, with assistance from S21DW. Provides guidance on operating cheap PA-70 and PA-100 type Chinese SSPAs using IRF530 MOSFETs, emphasizing the necessity of a final LPF.
Outlines the design and construction of a fully isolated interface for radio-to-computer connections, supporting various digital modes with isolated ground, audio transformers for IN/OUT, optical isolation for CAT/CIV, and isolated PTT/COS lines. Includes a log of software updates, such as the HMI/TFT for NX8048K070 and 2.1.14 Lite release with bug fixes for PEP hold and gradual watt decay.