6.3 RF, IF amplifiers, selectivity

Enhancing Receiver Performance

In this chapter, participants will explore the functionalities and significance of RF and IF amplifiers and understand the concept of selectivity in superheterodyne receivers. The course will provide detailed explanations for 11 key questions, starting with understanding the ‘noise floor’ of a receiver (Question A-006-003-001) and its impact on signal detection. The role of the first IF amplifier stage in improving selectivity and gain (Question A-006-003-002), and the appropriate gain levels for RF amplifiers (Question A-006-003-003) will be examined, giving insights into how these components influence receiver sensitivity and performance.

Learners will also delve into the primary purpose of RF amplifiers in improving noise figure (Question A-006-003-004) and how receiver sensitivity is often expressed for UHF FM receivers (Question A-006-003-005). The concept of ‘dynamic range’ in receivers (Question A-006-003-006), the effect of lower noise figures on receiver sensitivity (Question A-006-003-007), and the origin of noise in well-designed receivers (Question A-006-003-008) will be covered, providing a comprehensive understanding of receiver noise management.

Further, the course will discuss why very low noise figures are less critical for high-frequency receivers (Question A-006-003-009) and define the term ‘dynamic range’ in the context of signal amplitude levels during reception (Question A-006-003-010). Lastly, the role of the preselector in front-end selectivity (Question A-006-003-011) will be explored, highlighting its importance in filtering and signal reception.

Through this chapter, participants will gain a thorough understanding of the key components in superheterodyne receivers and how they contribute to optimizing receiver performance, especially in the realm of amateur radio