---
tags: [radio, ham-study]
---

# Radio transmitters and receivers

## Transmitters

![The radio transmission process](../img/radio-transmission-process.png)

Radio transmission comprises four stages:

1. Audio stage or "amplification"

- The weak signals from the microphone are amplified

2. Frequency generation via an oscillator

- The [carrier wave](./Frequency_modulation.md) is generated

3. Modulation

- The carrier wave and audio signal are combined

4. RF power amplification

- The combined signal is increased and fed through to the antenna

The following are important considerations:

> Incorrect setting of the oscillator can result in operation outside of the
> amateur band and cause interference to other users

> The microphone gain should not be set too loud as this will cause distortion.
> Furthermore, too loud a signal causes **over-modulation** on AM and
> **over-deviation** on FM which again could cause inteference.

> The RF power amplifier must be connected to a correctly matched antenna to
> work properly. If not, damage can be caused to the transmitter.

## Receivers

![The radio reception process](../img/radio-receiver-process.png)

Radio reception comprises three stages:

1. Tuning/RF amplifier

- The receiver is tuned to the required frequency and the weak incoming signal
  is amplified so that it can be used

2. Demodulator

- Extracts the original audio signal from the modulated radio signal, separating
  the signal from the carrier.
- Each type of modulation type (FM, AM, SSB etc) has its own demodulator

3. Audio amplifier

- Amplifies the recovered signal and feeds it to a loudspeaker or headphones