A Direct Conversion HF Tranceiver

This is a project that I have been wanting to work on for some thirty years, but some how something always seemed to take the time. The concept of a direct conversion transceiver is a very simple, and with some of the DDS chips now available the possibility of building a simple transceiver is within reach. Where possible I have used various kits to save the need to build printed circuit boards, and also to get around the issues associated with finding the necessary components.
The key bits on the project are:
1. DDS VFO
2. Direct Conversion Receiver
3. Direct Conversion Transmitter
4. RF Amplifier
5. RF Filtering
6. S Meter circuit
Putting them all together we have a simple QRP Direct Conversion transceiver ...

1. DDS VFO
The cost of DDS chips has dropped considerably in recent years and make the construction of a stable local oscillator with a digital readout a relatively simple exercise. This project was my first experiment with DDS and a easier approach of purchasing a kit was taken. The kit used is a DDSV4 VFO kit from KangaUS. This DDS kit is an oscillator based on the Analog Devices AD9859 DDS numerical oscillator and an Atmel ATMEGA16 microcontroller. It arrives pre-assempled with the microcontroller already programmed.

2. Direct Conversion Receiver
The transceiver actually started with the  ...

3. Direct Conversion Transmitter
4. RF Amplifier
5. RF Filtering
6. S Meter circuit