1. Signal source
The source can be the browser audio output, an ESP32 PWM output, an AD9833 module, a DDS board or a dedicated RF oscillator.
DIY Hardware
DIY frequency hardware guide.
Explanations for using audio, ESP32, DDS, PWM, amplifiers, coils, plasma tubes and RF hardware with the site.
Blocks
How a DIY setup is normally built
A reliable project is easier when each stage has one job.
2. Level and isolation
Use level control before amplification. Isolation protects the computer or phone from external circuits.
3. Driver and amplifier
The driver conditions the signal. The amplifier provides current or voltage for the chosen output device.
4. Output load
The load might be a speaker, transformer, coil, electrode test load, plasma tube coupler or antenna system.
Audio
Browser audio output
The simplest output is the audio tone from the browser.
Direct listening
Use speakers or headphones for low-risk audio testing. Keep volume low, especially with headphones and high tones.
Feeding an amplifier
A headphone output can feed an audio amplifier input. Start with the website volume and amplifier gain low.
Audio transformer
An audio transformer can provide isolation between the computer audio output and an experimental circuit.
Bluetooth link
A Bluetooth receiver can keep the computer physically separate from the hardware, but it may add delay and audio processing.
ESP32
ESP32 and CYD generators
ESP32 boards are useful for portable signal generation and user interfaces.
PWM output
ESP32 PWM can generate simple square-wave or filtered control signals. It is easy to control but needs filtering for smoother waveforms.
CYD screen projects
CYD boards add a touch screen for choosing programs, setting time, changing intensity and showing status.
Bluetooth audio
An ESP32 audio receiver can receive sound from a phone or computer and pass it to a driver stage.
Pin checks
Always match the sketch pins to the exact board. TFT, touch, SD card, PWM and audio pins can vary between boards.
DDS
AD9833 and DDS modules
DDS modules create more stable sine, square or triangle waveforms than basic PWM.
AD9833
The AD9833 is controlled by a microcontroller and can generate accurate low-level waveforms. It usually needs buffering before driving anything larger.
Buffer stage
A buffer protects the DDS module and gives a stronger, lower-impedance output for the next stage.
Amplitude control
Use a controlled attenuator, gain stage or amplifier volume control. Avoid overdriving the DDS output.
Carrier and modulation
For carrier systems, keep the oscillator, modulation stage and amplifier separate so each can be tested safely.
Amplifiers
Drivers and amplifiers
An amplifier must match the signal type and load.
Audio amplifiers
Use audio amplifiers for speaker-range signals. They are not automatically suitable for RF or coil loads.
MOSFET drivers
MOSFET drivers switch gates quickly for PWM and coil driver circuits. They need correct supply decoupling and layout.
RF amplifiers
RF amplifiers expect correct impedance, filtering and load matching. Do not run them into unknown or badly matched loads.
Dummy loads
Test amplifiers into a suitable dummy load before connecting coils, tubes or antennas.
Plasma
Plasma tubes, gas tubes and coils
Gas tubes need electric field strength, coupling and safety spacing, not just a frequency number.
Capacitive coupling
A tube with no terminals can be coupled using external plates, foil bands or coils, depending on the driver type.
Resonant step-up
Coils and tuned circuits can increase voltage, but tuning changes with tube size, nearby objects and grounding.
SSTC systems
Small solid-state Tesla coil systems use a resonant secondary and a switching driver. Keep logic electronics isolated from the high-voltage section.
Brightness and heat
Run tubes gently. Excess brightness, heating or arcing means the setup is being pushed too hard.
RF
RF, modulation and antennas
RF projects need matching, filtering and legal operation.
Carrier
The carrier is the high-frequency signal. Audio or low-frequency data can modulate it using AM, gating or another modulation stage.
AM modulation
AM changes carrier amplitude. A clean modulator is usually better than trying to force modulation at the final amplifier output.
Low-pass filtering
Use the correct filter after RF amplification to reduce harmonics and unwanted emissions.
Antenna matching
An ATU can help match the antenna system, but it does not make every load safe or efficient.
Safety
Safety rules
High voltage, RF and coils can cause burns, shocks, interference and equipment damage.
Keep computers isolated
Never connect high-voltage or RF stages directly to USB, laptop audio or phone ports.
Start low
Begin with low voltage, low power and a dummy load. Increase only after measurements look correct.
Use enclosures
Cover live terminals, coils and driver boards. Add fuses and strain relief where power enters the build.
Watch interference
RF can trip electronics, alarms, breakers and medical devices. Keep experimental RF away from people and sensitive equipment.