Cool. Then lets talk about those two transformers there.
Those two back to back transformers (L5 and L6) step up the impedance of the RX signal, couple between each other with a tiny capacitor, then steps the impedance back down. Inside L5 and L6, the larger windings have a capacitor in parallel with the inductor internally to form a resonant circuit, so instead of being broadband, they only pass a narrow band of frequencies. A capacitor naturally has a high Q since it has no resistive losses, so the Q of the overall tank circuit is mainly controlled by the Q of the inductor. Since the Q of an inductor is the inductive reactance divided by the ohmic resistance of the coil, the more turns it has (the more reactance) for a given wire diameter, the higher it's Q will be and the narrower the band of frequencies it will pass (when resonated with a capacitor). In order to take advantage of the high Q with a low source and load impedance, it has to step up the impedance in the middle where there are no low impedances to load down the tank and degrade the Q, hence two tuned transformers.
The reason I said it probably passes more noise is because, not only is that little toroid transformer unshielded allowing other signals to hop on it, I didn't see any parallel capacitor giving it a specific frequency response. Perhaps I was wrong about a parallel cap not being there, but if it's not, an untuned transformer is broadband and can pass a lot more stuff. So, when you have a 2kHz wide signal of interest and you have 5MHz of noise floor sneaking through, you get a worse signal to noise power ratio.
Edit: Another reason to really want that transformer shielded is because the next transistor, TR15, is a mixer, and if that toroid is picking up signals from the rest of the radio, they get mixed in where they shouldn't be.