[Scott Harden] has been working through a design for a variable inductor to use as a PTO, or permeability tuned oscillator. What you see above is the most recent fruit of these efforts. The variable ...

A tuned circuit formed by a capacitor and an inductor is a familiar enough circuit, and it’s understood that it will resonate at a particular frequency. As that frequency increases, so the size of the ...

VARIABLE condensers are now so commonly employed in radio receivers to tune circuits including a constant inductance that the use, some years ago, of variable inductances or variometers with fixed ...

Although the ubiquitous LM386 IC was designed to be used as an audio amplifier, it has a number of undocumented characteristics that can be exploited to create simple radio receiver circuits that ...

Superheterodyne receivers have been mass-produced since around 1924, but for reasons of cost did not become successful until the 1930s. Before the second world war other, simpler receiver technologies ...

Varactor (or “varicap”) diodes are used primarily in radio-frequency (RF) circuits to provide a capacitance that can be varied by changing the applied voltage. These types of diodes often are used for ...

The author is a consultant in Carterton, New Zealand. This follows up his December article “Tuned Bandpass Filter Is Solution to Backup STL.” Many years ago, the active whip antenna and the active ...

A pair of advanced circuit verification tools, Analog FastSPICE and RF FastSPICE, offer full-SPICE accuracy at 5X to 10X the performance of other tools, while requiring no block tuning, according to ...