Well, here we are – not so creatively titled HF-642 SSB Transceiver.
Summary Key Features:
- Dual conversion receiver.
- Independent TX/RX stages.
- IF Shift.
- RF Gain control
- IF Gain control
- DDS Oscillators.
- RF Speech Processor.
- Modular design.
- Through hole/discrete component design (where possible).
- HF, 50,70 and 144MHz coverage.
- USB, LSB, FSK441, JT6M and JT65 modes.
- 100W Transmitter PA.
The modular design approach has been chosen for this project to allow easy modification, expansion and maintenance. This project was never going to be a junk box delight, not keeping in-line with the QRP, traditional homebrew ethos however it was never about money saving – I could have went down the traditional basic, single conversion route and the project would probably be near completion now but as this rig will be my “daily runner” so I wanted it to be the best I could make it be within the limits of my skills.
The DDS and Control unit are in separate, equipment cases with all I/O exposed using multi-way connectors and SMA RF jacks for ease of assembly and interchangeability. Both of these units are large in foot print however compact design was not my goal – I will be building the transceiver in to a 19″ rack mount equipment case so it will be nice and spacious for future expansion and allow comfortable operating for my big hands and fat fingers.
Another advantage of the technologies chosen in this design means I can use the DDS and the Control unit to aid alignment of each stage, the AD9959 DDS has 4 independent channels and that means I can drive all the relevant stages with test signals, also having the luxury of a Spectrum Analyser I can use the tracking generator to sweep the filter stages and peak them for optimum resonance and performance.
Receiver Block Diagram
Proof of concept design
Here is a drawing of the target end result – all drawn to scale in Visio.
The main section of the IF stage was copied from the original design by Wes Hayward, W7ZOI, and Jeff Damm, WA7MLH using the Hybrid Cascode design as a base template, I made a few alterations to fit in with my overall design but much remains the same.