bill.meara
We went with just four boards, four subcircuits: Bandpass filter. Mixer. RF Oscillator, Audio Amplifier.
Understanding these four circuits allows students to understand almost all RF devices.
Circuits were chosen for their simplicity and understandability: Nothing exotic or overly clever.
Students were required to actually BUILD the circuits.
This was a challenge. This was not easy.
This was NOT a kit-build. Students would layout their own boards and acquire parts from a central parts source.
The receiver they built is a real receiver, capable of real long-distance communications. It has been used on the airwaves in a two-way contact.
Prior to this build, most of the students obtained their amateur radio licenses.
This build project was part of a larger global effort: There were similar group builds in Hyderabad, India and Munich, Germany. Radio amateurs as far away as Australia helped build and test the receiver circuit prior to the project.
Students in Hyderabad India with the receivers they built
About 28 blog posts describing the details of this project can be found here:
Cuthbert Nibbles
yashiro
Steve Schuler
This is intentionally an analog electronics project, not a programming project or even a digital electronics project. The students have many outlets for those skills including robotics and even a cube sat project. We chose to have them build an all analog, discrete component receiver expressly to provide the students a foundation level understanding of RF engineering concepts. It is also why we chose to use large, through-hole components, resistors, capacitors, transistors, diodes, and yes even toroid transformers that the students wound themselves. Every step in the process - including the decision to use Manhattan style construction was intended to teach and reinforce fundamental concepts like the difference between and inductor and capacitor or the importance of a good ground plane when working with RF circuits. The students were able to see the shape of the filter on a VNA and gain an intuitive understanding of what happens when they compressed or spread the turns of the transformer - changing the inductance. As they built the analog variable frequency oscillators, they were able to experience directly what it means to have a resonant tuned circuit. In the audio stage they learned why layout is important and how amplifiers can easily become oscillators if you are not careful. We are working from the principal that there is an intuitive level of understanding that can be gained from this kind of hands-on work that you simply don't get from a software project. And this intuitive level of understanding will benefit them as they go on to bright technical careers in an all-digital world. And they will have the advantage of having, at least once, built something complex and technical from scratch, where they can identify the purpose and function of each and every component in the circuit.