In the fast moving world of digital electronics, I find it incredible that the vacuum tube — a piece of early 20th century analog technology — has managed to survive. It should have bitten the dust long ago but that just did not happen. This back-to-the-future one-tube radio is made with readily available parts, operates on 12 volts, and offers amazing performance.
Every signal begins with an oscillator — In ham radio, the oscillator is a key element in generating signals, mixing them together, and extracting the information from them. Let's see how to make an audio oscillator, plus learn about common RF types.
Previously, we learned what makes an oscillator do what it does, and tried a simple low frequency example. Now, it's time to move up — in frequency — to the oscillators which make the signals that drive the ham's wireless world.
Design and construction of a basic analog radio has changed drastically over the years. Radio architecture has evolved from multi-tube designs, to transistors, to integrated circuits, and now, today, to a single chip. Here's a look at how digital techniques have changed and improved analog radios.
I examined the almost perfect circle surrounding a stylized “M” (for Motorola) that was branded into the end of my index finger after touching the case of a power transistor to see if it was “warm.” This was my introduction to “heatsink selection for power semiconductors” I received as a young experimenter building a power supply — a lesson I have not forgotten several decades after the event.
The first project is a transformerless voltage doubler that takes a DC voltage from 12 to 30 volts and doubles it. Unlike most other voltage doubler circuits, this design can supply amps of current. The second project uses a power MOSFET in a linear (rather than switching) application.
A perfect wire should conduct a signal without adding noise, attenuation, or distortion. Whatever is electrically happening at one end of the wire should be happening at the other end exactly in the same form, no matter what the current, voltage, frequency, surroundings, or temperature. However, this isn't the case.
Electronic designers are familiar with the apparent perversity of Nature in the tendency of amplifiers to oscillate and oscillators to amplify. But even the beginning designer knows that questions of oscillation and stability involve feedback — that ubiquitous structure in natural systems and many man-made ones — whereby a fraction of the system’s output energy is fed back to the input to produce useful effects.
Understanding And Designing With The Ever-Useful CMOS Timer: Not as commonplace as the operational amplifier, the integrated circuit CMOS timer — such as the ICM7555 and TLC555 — has nonetheless found a secure niche in electronics. Why is this?
Crystals That Make The World Go 'Round: Strike a crystal goblet with a spoon, and you immediately have both the attention of your guests and the sympathetic resonance of other goblets on your sumptuous holiday table. What is happening here? Well, you have created a crystal oscillator that generates acoustic waves in the air.
