Mini-Circuits ZFRSC-42-S+ Power Splitter/Combiner
DC to 4200 MHz
See the last two photos for results of measurements of attenuation from the S port to ports 1 and 2 respectively.
low insertion loss, 0.1 dB typ. above 6 dB
excellent amplitude unbalance, 0.02 dB typ
https://www.minicircuits.com/pdfs/ZFRSC-42+.pdf