1. AMATEUR RADIO TRAINING
Transmitters & Receivers
Release: v1.22
hamtrain.co.uk

2. Transmitters & RECEIVERs
Block Diagrams
Modulation Types
Station Setup

3. Transmitter Basics A radio transmitter has four basic stages:
1. Audio Stage
Gets and amplifies weak signals from the microphone
2. Frequency Generator
Creates the radio signal on the right frequency
3. Modulator
Mixes the radio and audio signals together
4. 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:
1. Tuning / RF Amplifier
Tunes into the required frequency
Amplifies the weak signal so that it can be used
2. Detector
Extracts the audio from the radio signal. Often called “demodulation”
There are different types of detector for each modulation type
3. Audio Amplifier
Amplifies the audio and feeds it to a loudspeaker or headphones

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

7. Modulation AM FM

8. Amplitude Modulation (AM)
Audio signal
Carrier
Modulated
signal

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

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

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

12. AM vs FM
Audio Signal
AM Signal
FM Signal

13. Morse & Data CW Audio CW Signal CW: Tones generated using a Morse key
Data: Audio tones generated via a computer soundcard or a TNC (Terminal Node Controller)

14. Transmitting
At Foundation, you can only use commercially-purchased transmitters (no construction)
You must only transmit on allocated frequencies and must not exceed permitted power levels
‘Over-modulating’ or ‘Over-deviating’ may result in interference to to adjacent frequencies as well as poor audio quality. Take care with audio levels (microphone gain, shouting, data signals from a computer)
You must stay in-band, not cause interference, and test your transmitters “from time to time”.

15. HF Station Setup 12V PSU (Power supply)
Transceiver (transmitter & receiver)
Microphone / Morse Key / Data Interface
RF filter
SWR meter
ATU
Antenna

16. Summary Remember the diagrams for transmitters and receivers
Block Diagrams
Remember the diagrams for transmitters and receivers
Don’t just learn the numbers – learn the meanings
Modulation Types
Amplitude Modulation
Frequency Modulation
Transmitter usage
Take care with audio levels, so you don’t over-modulate or over-deviate
Test equipment to ensure it stays in-band

17. TRANSMITTERS & RECEIVERS
Any questions?
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