Spinelli MartaRoque, IanRazavi-Ghods, Nima2026-02-092026-02-092025Roque, I.L., Razavi-Ghods, N., Carey, S.H., Ely, J.A., Handley, W., Magro, A., Chiello, R., Huang, T., Alexander, P., Anstey, D. and Bernardi, G., 2025. Receiver design for the REACH global 21-cm signal experiment. Experimental Astronomy, 59(1), pp.1-30.https://doi.org/10.1007/s10686-024-09975-3https://hdl.handle.net/10566/21923We detail the REACH radiometric system designed to enable measurements of the 21-cm neutral hydrogen line. Included is the radiometer architecture and end-to-end system simulations as well as a discussion of the challenges intrinsic to highly-calibratable system development. Following this, we share laboratory results based on the calculation of noise wave parameters utilising an over-constrained least squares approach. For five hours of integration on a custom-made source with comparable impedance to that of the antenna used in the field, we demonstrate a calibration RMSE of 80 mK. This paper therefore documents the state of the calibrator and data analysis in December 2022 in Cambridge before shipping to South Africa.enRadiometerCalibrationInstrumentationNATURAL SCIENCES::Physics::Astronomy and astrophysics::CosmologyDark agesArticle