1. AMATEUR RADIO TRAINING
Transmitters & Receivers
v1.11 © essexham.co.uk

2. Transmitters & RECEIVERs
Block Diagrams
Modulation Types
Station Setup

3. Transmitter Basics A 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

4. Transmitter Block Diagram1 2 4 3
1: Audio Stage
2: Modulator (More on this shortly)
3: Frequency Generator (also referred to as an Oscillator)
4: RF Power Amplifier

5. Receiver Basics A 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

6. Receiver Block Diagram1 2 3
1: Tuning and RF Amplifier
2: Detector (Also referred to as a “De-modulator”)
3: Audio Amplifier

7. Amplitude Modulation (AM)
Audio Signal
Carrier
Modulated signal

8. AM Transmitter Block Diagram
Modulator
Audio Stage
RF Power Amp
Frequency Generator

9. Frequency Modulation (FM)
Audio Signal
Carrier
Modulated signal

10. FM Receiver Block Diagram
Tuning & RF amp
Detector
Audio Amplifier

11. AM vs FM
Audio Signal
AM Signal
FM Signal

12. Transmitting
At 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”.

13. Station Setup Microphone Power Supply
Transceiver (transmitter & receiver)
SWR Meter
RF Filter
ATU
Antenna

14. Summary Block Diagrams Modulation Types Station Setup
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

15. TRANSMITTERS & RECEIVERS
Any questions?
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