  The Simons Observatory (SO) is a ground-based cosmic microwave background
(CMB) survey experiment that consists of three 0.5 m small-aperture telescopes
and one 6 m large-aperture telescope, sited at an elevation of 5200 m in the
Atacama Desert in Chile. SO will utilize more than 60,000 transition edge
sensors (TES) to observe CMB temperature and polarization in six frequency
bands from 27-280 GHz. Common to both the small and large aperture telescope
receivers (LATR) is the 300K-4K Universal Readout Harness (URH), which supports
up to 600 DC bias lines and 24 radio frequency (RF) channels consisting of
input and output coaxial cables, input attenuators and custom high dynamic
range 40K low-noise amplifiers (LNAs) on the output readout coaxial cable. Each
RF channel can read out up to 1000 TES detectors. In this paper, we will
present the design and characterization of the six URHs constructed for the
initial phase of SO deployment.

Instrumentation and Methods for Astrophysics;Instrumentation and Detectors