50 Ω dummy load
A transmitter test load in several power versions, with the drawings and instructions needed to assemble it.
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Build, experiment and equip your station with these electronics projects.
HF antenna tuner
Several tuner versions for matching an HF antenna to your station, with circuit diagrams and construction files.
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LM386 audio amplifier
A compact audio amplifier for listening to the low-level audio signals from a receiver.
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NE555 timers and oscillators
Progressive NE555 circuits for exploring timing, oscillation and pulse generation through practical builds.
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1 kHz audio signal injector
An adjustable square-wave audio generator for tracing signals and troubleshooting audio circuits.
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Six-band HF preselector
Six HF receive sub-bands and a switchable attenuator for selecting signals at the receiver input.
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QRP power and SWR meter
An instrument requiring calibration to display forward and reflected power and the standing wave ratio.
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Iambic CW keyer
An A/B keyer with adjustable speed from 5 to 40 words per minute, sidetone and an isolated output.
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Disclaimer
These dossiers are supplied as is for educational and experimental purposes. Calculations, simulations and file checks are neither measured performance nor certification or qualification of the assembled device.
The person building or using the device must check the schematics, components, connections and protective measures, follow manufacturer instructions and applicable regulations, and have the completed device validated before use. Depending on the device, electrical voltages, radiofrequency energy and heat can cause electric shock, burns or fire. Tests must be conducted by a competent person, starting at low power with suitable protective measures.
To the extent permitted by law, ON4CRD and the contributors do not guarantee fitness for a particular purpose or results, and disclaim liability for damage arising from construction, modification or use. This notice does not limit any mandatory rights or any liability that the law does not allow to be excluded.