amateur radio training transmitters & receivers v1.11 © essexham.co.uk
TRANSCRIPT
AMATEUR RADIO TRAINING
Transmitters & Receivers
v1.11 © essexham.co.uk
TRANSMITTERS & RECEIVERS
• Block Diagrams• Modulation Types• Station Setup
Transmitter BasicsA radio transmitter has four basic stages:
Audio Stage• Gets signals from the microphone
Frequency Generator• Creates the radio signal on the right frequency
Modulator• Mixes the radio and audio signals together
RF Power Amplifier • Increases the combined signal and feeds to the antenna
Transmitter Block Diagram
1: Audio Stage
2: Modulator (More on this shortly)
3: Frequency Generator (also referred to as an Oscillator)
4: RF Power Amplifier
3
1 2 4
Receiver BasicsA radio receiver has three basic stages:
Tuning / RF Amplifier
• Tunes into the required frequency
• Amplifies the weak signal so that it can be used
Detector
• Extracts the audio from the radio signal. Often called “demodulation”
• There are different types of detector for each modulation type
Audio Amplifier
• Amplifies the audio and feeds it to a loudspeaker
Receiver Block Diagram
1: Tuning and RF Amplifier
2: Detector (Also referred to as a “De-modulator”)
3: Audio Amplifier
1 2 3
Amplitude Modulation (AM)
Audio Signal
Carrier
Modulated signal
AM Transmitter Block Diagram
Audio Stage RF Power Amp
Frequency Generator
Modulator
Frequency Modulation (FM)
Audio Signal
Carrier
Modulated signal
FM Receiver Block Diagram
Tuning & RF amp Detector Audio Amplifier
AM vs FM
Audio Signal
AM Signal
FM Signal
TransmittingAt Foundation-level, only commercially-purchased transmitters can be used (no construction)
You must only transmit on allocated frequencies and at permitted power levels
‘Over-modulating’ or ‘Over-deviating’ may result in interference to other channels as well as poor audio quality. Take care with audio levels (microphone gain and shouting)
You must stay in-band, not cause interference, and test transmitters “from time to time”.
Station Setup• Microphone• Power Supply• Transceiver (transmitter & receiver)• SWR Meter• RF Filter• ATU• Antenna
Summary• Block Diagrams
• Remember the diagrams for transmitters and receivers
• Modulation Types
• Amplitude Modulation
• Frequency Modulation
• Station Setup
• Setting up a station correctly is one of the Foundation practicals
TRANSMITTERS & RECEIVERS
Any questions?
essexham.co.uk/train