Gen hf

S9018 RF Oscillator — KiCad

An educational project of a compact RF oscillator based on a single S9018 NPN transistor. The PCB was designed in KiCad 10 and is intended for 9 V power supply, a trimmer capacitor, and an external wire antenna.

This project is intended for learning analog electronics and PCB design. The actual oscillation frequency depends on component values, tolerances, PCB layout, antenna length, parasitic capacitances, and assembly quality.

Features

• 9 V power supply
• S9018 transistor in TO-92 package
• RF resonant circuit using L1 and C4
• Frequency adjustment with trimmer capacitor C4
• 120 nH 0805 SMD inductor
• External antenna connector
• Manually routed PCB
• GND copper pour on the bottom (B.Cu) layer
• Closed board outline on the Edge.Cuts layer

Repository Structure

gen_hf.kicad_pro   KiCad project
gen_hf.kicad_sch   Schematic
gen_hf.kicad_pcb   PCB layout
gen_hf.kicad_prl   Local PCB editor settings
fp-lib-table       Custom footprint library table
README.md          Project documentation

The custom footprint for C4 must be stored in the library referenced by fp-lib-table. Before opening the project on another computer, make sure this library is included in the repository or replace it with a standard KiCad footprint.

Circuit Overview

Main components:

• Q1 (S9018) — RF oscillator transistor
• L1 + C4 — Tunable LC resonant circuit
• C1 — RF feedback capacitor
• R2 and R3 — Base bias network
• R1 — Emitter resistor
• C2 — Base bypass capacitor
• C3 — Power supply decoupling capacitor
• ANT1 — Antenna connector
• +9V1 — Power input

Bill of Materials (BOM)

Important Note About Q1

Always verify the S9018 pinout using the manufacturer's datasheet before assembly.

This project assumes:

Pin 1 — Emitter
Pin 2 — Base
Pin 3 — Collector

Connections

Power Supply

+9V1 Pin 1 → +9 V
+9V1 Pin 2 → GND

Antenna

ANT1 Pin 1 → ANT
ANT1 Pin 2 → GND

For initial testing, use only a short piece of wire as the antenna.

Do not connect a large external antenna until the oscillator frequency has been verified and local radio transmission regulations have been considered.

Opening the Project

1. Install KiCad 10 (or a compatible newer version).
2. Clone the repository:

git clone <REPOSITORY_URL>
cd <REPOSITORY_FOLDER>

3. Open gen_hf.kicad_pro.
4. If KiCad reports a missing footprint for C4, verify the path in fp-lib-table and add the custom footprint library.

PCB Verification

Before manufacturing, perform the following checks in the PCB Editor:

1. Run Inspect → Design Rules Checker (DRC).
2. Refill all copper zones by pressing B.
3. Verify that:
   • Unconnected items = 0
   • Shorts = 0
   • Clearance violations = 0
   • The Edge.Cuts outline is closed
   • The B.Cu copper zone is assigned to GND
   • All components are inside the board outline
4. Inspect the PCB using the 3D Viewer.

At the time of publishing, the project passes DRC with no errors after manual routing, board outline creation, and GND copper pour. Re-run DRC after every modification.

Gerber Generation

Open:

File → Fabrication Outputs → Gerbers

For a standard two-layer PCB, generate:

• F.Cu
• B.Cu
• F.Mask
• B.Mask
• F.SilkS
• Edge.Cuts

Then generate the drill files using Generate Drill Files.

First Power-Up

Before applying power:

• Inspect all solder joints.
• Verify the transistor orientation.
• Confirm component values.
• Check the trimmer capacitor orientation.
• Measure for shorts between +9 V and GND.

Power the circuit from a regulated 9 V supply.

RF Design Notes

This PCB is intended as an educational project.

For improved RF performance:

• Keep the LC tank components close together.
• Keep RF traces as short as possible.
• Use a continuous GND plane.
• Minimize loop areas.
• Use high-Q inductors and NP0/C0G capacitors.
• Place the decoupling capacitor close to the power input.

License

This project is provided for educational purposes.

Use it at your own risk.

Ensure compliance with local laws and regulations regarding RF transmitters before operating the circuit.