General Licensing Class

General Licensing Class Your Receiver Lake Area Radio Klub Spring 2012

Amateur Radio General ClassElement 3 Course Presentation • ELEMENT 3 SUB-ELEMENTS(Groupings) • 1 - Your Passing CSCE • 2 - Your New General Bands • 3 - FCC Rules • 4 - Be a VE • 5 - Voice Operations • 6 - CW Lives • 7 - Digital Operating • 8 - In An Emergency • 9 - Skywave Excitement

Amateur Radio General ClassElement 3 Course Presentation • ELEMENT 3 SUB-ELEMENTS(Groupings) • 10 - Your HF Transmitter • 11 - Your Receiver • 12 - Oscillators & Components • 13 - Electrical Principles • 14 - Circuits • 15 - Good Grounds • 16 - HF Antennas • 17 - Coax Cable • 18 -RF & Electrical Safety

Your Receiver • The simplest combination of stages that implement a superheterodyne receiver is HF oscillator, mixer, detector. (G7C07) Simple Generic Superheterodyne Receiver

Your Receiver detector mixer HF oscillator Simplest combination

IF Amplifier Stages Your Receiver • A mixer is the circuit used to process signals from the RF amplifier and local oscillator and send the result to the IF filter in a superheterodyne receiver. (G7C03) Single conversion receiver Dual conversion receiver

Your Receiver • A product detector is the circuit is used to combine signals from the IF amplifier and BFO and send the result to the AF amplifier in a single-sideband receiver. (G7C04) • Heterodyning is another term for the mixing of two RF signals. (G8B03) Very simple mixer

Your Receiver In a receiver the Mixer stage combines a 14.250 MHz input signal with a 13.795 MHz oscillator signal to produce a 455 kHz intermediate frequency (IF) signal. (G8B01) A Mixer circuit is used to process signals from the RF amplifier and local oscillator and send the result to the IF filter in a super heterodyne receiver. • In this mixer the output is the sum and the difference of the two applied signals: • The sum would be 14.250 + 13.795 or 28.045 MHz • The difference would be 14.250 - 13.795 or 0 .455 MHz 14.250 MHz 455 kHz First IF amp. Mixer Local oscillator 13.795 MHz Filtering removes the undesired frequency

Your Receiver • If a receiver mixes a 13.800 MHz VFO with a 14.255 MHz received signal to produce a 455 kHz intermediate frequency (IF) signal, a 13.345 MHz signal will produce an image response in the receiver. (G8B02) • To prevent this many receivers use a tuned preamplifier before the mixer input (sometimes called a preselector). • An advantage of a receiver Digital Signal Processor IF filter as compared to an analog filter is that a wide range of filter bandwidths and shapes can be created. (G4C12) • The following is needed for a Digital Signal Processor IF filter. (G7C09) • An analog to digital converter • A digital processor chip • A digital to analog converter All of the choices are correct.

Your Receiver • One use for a Digital Signal Processor in an amateur station is to remove noise from received signals. (G4C11) • Digital Signal Processor filtering is accomplished by converting the signal from analog to digital and using digital processing followed by converting back to analog. (G7C10) Basic Digital Signal Processing (DSP) System DSP speaker

Your Receiver • One reason to use the attenuator function that is present on many HF transceivers is to reduce signal overload due to strong incoming signals. (G4A13) Dual function switch: Pre-amp & Attenuator. Icom 7000

Your Receiver • The purpose of the "notch filter" found on many HF transceivers is to reduce interference from carriers in the receiver passband. (G4A01)

Your Receiver • A Digital Signal Processor (DSP) filter can perform automatic notching of interfering carriers. (G4C13) • A discriminator circuit is used in many FM receivers to convert signals coming from the IF amplifier to audio. (G7C08) • FM receivers have different types of circuits than the superheterodyne receivers designed for AM, CW and SSB. Discriminator circuit Frequency to voltage conversion

Your Receiver • An S meter is found in a receiver. (G4D06) • Most commercial receivers have an S meter. • An S meter measures received signal strength. (G4D04) “S” Meters are based on S9 representing 50uV

Element 3 General Class Question Pool Your Receiver Valid July 1, 2011 Through June 30, 2015

G7A07 What is the simplest combination of stages that implement a superheterodyne receiver? RF amplifier, detector, audio amplifier RF amplifier, mixer, discriminator HF oscillator, mixer, detector HF oscillator, pre-scaler, audio amplifier

G7C03 What circuit is used to process signals from the RF amplifier and local oscillator and send the result to the IF filter in a superheterodyne receiver? Balanced modulator IF amplifier Mixer Detector

G7C04 What circuit is used to combine signals from the IF amplifier and BFO and send the result to the AF amplifier in a single-sideband receiver? RF oscillator IF filter Balanced modulator Product detector

G8B03 What is another term for the mixing of two RF signals? Heterodyning Synthesizing Cancellation Multiplying

G8B01 What receiver stage combines a 14.250 MHz input signal with a 13.795 MHz oscillator signal to produce a 455 kHz intermediate frequency (IF) signal? Mixer BFO VFO Discriminator

G8B02 If a receiver mixes a 13.800 MHz VFO with a 14.255 MHz received signal to produce a 455 kHz intermediate frequency (IF) signal, what type of interference will a 13.345 MHz signal produce in the receiver? Local oscillator Image response Mixer interference Intermediate interference

G4C12 Which of the following is an advantage of a receiver Digital Signal Processor IF filter as compared to an analog filter? A wide range of filter bandwidths and shapes can be created Fewer digital components are required Mixing products are greatly reduced The DSP filter is much more effective at VHF frequencies

G7C09 Which of the following is needed for a Digital Signal Processor IF filter? An analog to digital converter A digital to analog converter A digital processor chip All of the these answers are correct

G4C11 Which of the following is one use for a Digital Signal Processor in an amateur station? To provide adequate grounding To remove noise from received signals To increase antenna gain To increase antenna bandwidth

G7C10 How is Digital Signal Processor filtering accomplished? By using direct signal phasing By converting the signal from analog to digital and using digital processing By differential spurious phasing. By converting the signal from digital to analog and taking the difference of mixing products

G4A13 What is one reason to use the attenuator function that is present on many HF transceivers? To reduce signal overload due to strong incoming signals. To reduce the transmitter power when driving a linear amplifier. To reduce power consumption when operating from batteries. To slow down received CW signals for better copy.

G4A01 What is the purpose of the “notch filter” found on many HF transceivers? To restrict the transmitter voice bandwidth. To reduce interference from carriers in the receiver passband. To eliminate receiver interference from impulse noise sources. To enhance the reception of a specific frequency on a crowded band.

G4C13 Which of the following can perform automatic notching of interfering carriers? Band pass tuning A Digital Signal Processor (DSP) filter Balanced mixing A noise limiter

G7C08 What type of circuit is used in many FM receivers to convert signals coming from the IF amplifier to audio? Product detector Phase inverter Mixer Discriminator

G4D06 Where is an S-meter found? In a receiver In a SWR bridge In a transmitter In a conductance bridge

G4D04 What does an S-meter measure? Conductance Impedance Received signal strength Transmitter power output

General Licensing Class