If the amplifier in Question 4 has a noise figure of 10 dB but a...

When calculating the total noise figure of cascaded components, Friis' formula is used:

F_total = F1 + (F2 - 1)/G1 + (F3 - 1)/(G1 × G2) + ...

Where:

F_totalis the total noise factor (linear, not in dB).

F1, F2, ...are the noise factors of the individual stages.

G1, G2, ...are the gains of the preceding stages (linear, not in dB).

In this scenario, the amplifier has a gain of 0 dB, which corresponds to a linear gain of 1. A noise figure of 10 dB corresponds to a noise factor of 10. Assuming the cable and filter have negligible noise contributions or are passive components with minimal loss, their impact on the total noise figure is minimal.

Applying Friis' formula:

F_total = 10 + (1 - 1)/1 = 10

Converting back to dB:

NF_total = 10 × log10(10) = 10 dB