R-390A/URR · Restoration reference The R-390A Mechanical Filters: Selection, Sources and Testing Four Collins filters, six bandwidths, one capacitor that can destroy them — and where to buy, repair and test them in 2026 The R-390A/URR gets its reputation for…
VK6ADA Technical Reference · Boatanchor Files The Collins R‑389, R‑390 & R‑390A Development, deployment, and a practical operator’s guide to the finest HF receivers of the vacuum-tube era — written for amateur radio operators and shortwave listeners, fact-checked against the…
Choosing an SDR Front-End for the R-390A: A Comparison Matrix A field guide for pairing the Cold War’s finest analog HF receiver with a modern spectrum display. The R-390A/URR was the most precise general-coverage HF receiver the US military ever…
vk6ada.com.au • Collins R-390/URR Technical Series R-390/URRFailure Prevention Kit — Component & Modification Design A complete engineering analysis of the ten predictable R-390/URR failure modes, with a structured two-tier component replacement kit and four preventive circuit modifications. The R-390/URR is…
VK6ADA vk6ada.com.au • r-390a.net Collins Military Receiver Restoration Series R-390/URR ReceiverRestoration Guide A complete field guide to the cosmetic and mechanical restoration of the Collins R-390/URR military HF communications receiver — covering disassembly, the critical green gearwheel procedure, cabinet refinishing,…