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I thought I had seen a spec from an NEC datasheet stating the 2SC2150 had a ~5dB nf. Of course that was a max rating.
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I've still got my classic and probably quite rare 1989 NEC databook for high frequency devices and I was quite surprised that the 2SC2148, 2SC2149 and 2SC2150 BJTs were included in it.
The datasheet graphs show about 3.5dB noise figure at 1.85GHz at 15mA bias current for the 2SC2150. My old notes for the IF1 module showed that I measured about 1dB gain and just over 6dB noise figure for the complete IF1 module after I repaired it. If there is 2dB loss in the directional filter and maybe 0.8dB in the LPF and the 2SC2150 manages a 3.5dB noise figure then this does stack up to be just over 6dB NF for the IF1 module at 2.05GHz.
This old NEC databook really is a very good book with all kinds of application notes in the back for BJT and MOSFET LNA design. It also has app notes for diode ring mixer design and TV tuner design from the 1980s. It has datasheets and lengthy circuit app notes for all the classic low noise devices like the 3SK88(A), 3SK74, the wonderful 2SC3355/6/7 BJT and others like the 2SC2026. It even has about 10 pages devoted to homebrew diode ring mixers using various Schottky diodes.
It is one of my most valued databooks. NEC have added a very strange front cover to this databook showing a drawing of a teddybear sat on a beach ball. I've always called it my teddybear book...
I haven't seen it online anywhere but I keep looking and hoping.