Active Splitters, Distribution Amplifiers & Preamps
Overview
Active RF distribution networks — MMIC LNAs, masthead preamps, and multi-port distribution amplifiers — replace the 6–12 dB passive-split loss with active gain, enabling one antenna to serve many receivers while maintaining adequate signal level at each port. This dive covers MMIC LNA selection (Mini-Circuits PSA4-5043+, SAV-541+, Analog Devices ADL5523), the noise-figure case for mounting gain at the antenna (Friis cascade: first stage dominates), active distribution amplifiers (Stridsberg MCA204, DX Engineering SP4-100), bias-T powering over coax, gain-budget management to keep the front end out of IP3 compression, and T/R switching to protect LNAs during transmit. DIY builds are a SAV-541+ MMIC LNA on a 0.1–2000 MHz substrate and a 4-way distribution amp with masthead bias-T; commercial buys range from $50 Nooelec LANA to $2000 Bonito DA300U.
Context
The Friis cascade equation is the governing principle: the first amplifier in the chain dominates the system noise figure, so an LNA placed at the antenna feedpoint sets the system NF regardless of downstream feedline loss and passive-split loss. This makes masthead LNA placement mandatory for satellite work, weak-signal DXing, and any wideband SDR receive chain where the feedline run exceeds a few meters. This dive closes the matching-network cluster and hands off to the physical-deployment cluster; the receive-loop active-preamp designs in the Receive-Only Loops sub-project cross-link back here for the MMIC selection and noise-figure budgeting sections.
