Electronics

Tech / 19 Sep 2026 / 5 min read

What Actually Receives a Radio Signal: Antenna, Tuning, Detection, and Amplification

A radio receiver does not begin with a transistor. It begins at the antenna terminals, where an electromagnetic field produces a small RF voltage and current that the rest of the circuit can process. That distinction matters in discrete-transistor projects. An antenna, a tuned network, a detector, and an amplifier perform different electrical jobs. Combining their names into “the radio circuit” hides the boundary that determines whether a receiver can select a station, recover its modulation, and produce enough output to hear.

Electronics Radio

Tech / 19 Sep 2026 / 8 min read

What a DT-9205A Digital Multimeter Can Measure and Where Its Limits Matter

The DT-9205A is a manual-ranging digital multimeter built around a 3½-digit LCD, typically displaying values up to 1999 counts. Its rotary switch selects both the measurement function and the range, so the meter depends more heavily on correct setup than an autoranging instrument. The DT-9205A name is used by multiple manufacturers and sellers. Functions and maximum ranges can differ between versions, even when the front panels look similar. The markings on the actual meter and its supplied manual therefore take precedence over specifications found for another DT-9205A variant.

Digital Multimeter DT-9205A

Tech / 19 Sep 2026 / 5 min read

The Same 100 Ohm Resistor Behaves Differently at 3 V and 5 V

A 100 Ω resistor is still a 100 Ω resistor whether it is connected to 3 V or 5 V, provided it remains within its specified operating conditions. What changes is not the nominal resistance but the electrical state around it: current, voltage drop, and power dissipation. That distinction matters because a resistor does not generate an output voltage on its own. Its voltage and current are determined by the surrounding circuit.

Electronics Resistor

Tech / 19 Sep 2026 / 7 min read

Measure Electronic Components with a Digital Multimeter

A digital multimeter combines several electrical measurements in one instrument, but each mode answers a different question. A resistance reading can confirm that a resistor is near its marked value. A diode test can show a plausible forward-voltage drop. A voltage measurement can reveal whether a circuit node is being powered. None of those readings, by itself, proves that an entire circuit is healthy. That distinction matters when testing electronic components. A multimeter is excellent for static and low-frequency checks, especially when the expected electrical condition is known. It is much less informative when the fault depends on waveform shape, switching behavior, noise, timing, or operation under load.

Electronics Multimeter

Tech / 19 Sep 2026 / 6 min read

Infrared Sensors Measure Different Physical Effects

An infrared sensor is not a single measurement technology. “IR sensor” can describe a reflective proximity detector, a PIR motion detector, a non-contact temperature sensor, an optical encoder, or an infrared receiver. They all operate with radiation outside the visible spectrum, but the quantity being measured is different. That distinction determines what the sensor can detect, how far it can work, and which environmental conditions can produce false or weak readings.

Infrared Sensors

Tech / 19 Sep 2026 / 6 min read

Electrolytic Capacitor ESR Turns Ripple Current Into Heat

An aluminum electrolytic capacitor does not behave like an ideal capacitor. Its internal foil, electrolyte, tabs, and contacts add resistance, represented in a simple model as equivalent series resistance, or ESR. When AC ripple current flows through that resistance, the capacitor dissipates real power as heat. For power-supply filtering, this mechanism can matter as much as capacitance and voltage rating. A capacitor may have the expected number of microfarads and still run too hot if its ESR is too high for the ripple current imposed by the circuit.

Electronics Capacitor