How does thermal noise affect receiver sensitivity and how can it be mitigated in the field?

• A. It improves sensitivity; use wider bandwidth
• B. It has no effect; ignore
• C. It only affects transmit side
• D. It sets the noise floor; mitigate with low-noise receivers, shielding, and reducing external noise sources

Answer: (D)

Thermal noise sets a fundamental background level in every receiver. It comes from the random motion of electrons in resistive parts and is proportional to temperature and the bandwidth you’re listening with. Because the received signal has to stand out against this background, the receiver’s sensitivity is effectively limited by the noise floor created by this thermal noise. In practical field use, you control it by choosing a front end with a low noise figure, shielding the receiver and interconnects from external RF noise, and reducing external noise sources such as nearby transmitters or EMI. Narrowing the bandwidth to what is actually needed also lowers the total noise entering the detector. So the best approach is to use low-noise receivers, implement good shielding and grounding, and minimize external noise sources to push the noise floor down and improve sensitivity.