How Simple Can A Superhet Be

October 30, 2025 by Jenny List 20 Comments

If you cultivate an interest in building radios it’s likely that you’ll at some point make a simple receiver. Perhaps a regenerative receiver, or maybe a direct conversion design, it’ll take a couple of transistors or maybe some simple building-block analogue ICs. More complex designs for analogue radios require far more devices; if you’re embarking on a superhetrodyne receiver in which an oscillator and mixer are used to generate an intermediate frequency then you know it’ll be a hefty project. [VK3YE] is here to explode that assumption, with a working AM broadcast band superhet that uses only two transistors.

The circuit diagram of the radio — It doesn’t get much simpler than this.

A modern portable radio will almost certainly use an all-in-one SDR-based chip, but in the golden age of the transistor radio the first stage of the receiver would be a single transistor that was simultaneously RF amplifier, oscillator, and mixer. The circuit in the video below does this , with a ferrite rod, the familiar red-cored oscillator coil, and a yellow-cored IF transformer filtering out the 455 kHz mixer product between oscillator and signal.

There would normally follow at least one more transistor amplifying the 455 kHz signal, but instead the next device is both a detector and an audio amplifier. Back in the day that would have been a germanium point contact diode, but now the transistor has a pair of 1N4148s in its biasing. We’re guessing this applies a DC bias to counteract the relatively high forward voltage of a silicon diode, but we could be wrong.

We like this radio for its unexpected simplicity and clever design, but also because he’s built it spiderweb-style. We never expected to see a superhet this simple, and even if you have no desire to build a radio we hope you’ll appreciate the ingenuity of using simple transistors to the max.

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Arduino Becomes Superhet With A Little Help From Friends

October 10, 2021 by Al Williams 8 Comments

A radio receiver is always a fun project. [Jayakody2000lk] decided that his new superheterodyne design would use an Arduino and it looks like it came out very nicely. The system has four boards. An off-the-shelf Arduino, a Si5351 clock generator board (also off-the-shelf), and two custom boards that contain the IF amplifier and mixer.

The receiver started out in 2015 without the Arduino, and there’s a link in the post to that original design. Using the Si5351 and the Arduino replaces the original local oscillator and there have been other improvements, as well. You can see a video about the receiver below.

Tuning is by a rotary encoder and the current software lets you tune from about 4.75 MHz to a little over 15.8 MHz. Of course, you could change to any frequency the Si5351 can handle as long as the mixer and other components can handle it. The IF frequency is the usual 455 kHz.

If you decide to build this yourself, the design files are on GitHub. Overall a very nice and neat design. We are always amazed how little radio architecture has changed since Edwin Armstrong’s day. Of course, we have better components, even if they aren’t meant for radio purposes.

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Superheterodyne Radios Explained

January 2, 2019 by Al Williams 17 Comments

The general public thinks there is one thing called a radio. Sure, they know there are radios that pick up different channels, but other than that, one radio is pretty much like the other. But if you are involved in electronics, you probably know there are lots of ways a radio can work internally. A crystal set is very different from an FM stereo, and that’s different still from a communications receiver. We’d say there are several common architectures for receivers and one of the most common is the superheterodyne. But what does that mean exactly? [Technology Connection] has a casual explanation video that discusses how a superhet works and why it is important. You can see the video, below.

Engineering has always been about building on abstractions. This is especially true now when you can get an IC or module that does most of what you want it to do. But even without those, you would hardly start an electronics project by mining copper wire, refining it, and drawing your own wire. You probably don’t make many of your own resistors and capacitors, neither do you start your design at the fundamental electronic equations. But there’s one abstraction we often forget about: architecture. If you are designing a receiver, you probably don’t try to solve the problem of radio reception; instead you pick an architecture that is proven and design to that.

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Simple Superheterodyne SW Receiver Harks Back Almost 100 Years

March 8, 2015 by Anool Mahidharia 13 Comments

Early radio receivers worked on a principle called Tuned Radio frequency (TRF), patented in 1916. They weren’t very easy to use, requiring each stage to be tuned to the same frequency (until ganged capacitors made that a bit easy). The Superheterodyne design, devised in 1918, was superior, but more expensive at that time. Cost considerations led adoption of the Superhet design to lag behind TRF until almost 1930. Since then, until quite recently, the Superhet design has been at the heart of a majority of commercial radio receivers. Direct Conversion Receivers were devised around 1930, but required elaborate phase locked loops which restricted their use in commercial receivers. The point of all this background is that the Superhet design has served very well for more than 90 years, but will soon be rendered redundant once Software defined Radio (SDR) becomes ubiquitous. Which is why this study of the simple Superheterodyne shortwave receiver deserves closer study.

[Dilshan] built this two transistor and two IF transformer based superheterodyne radio designed to receive 13m to 41m bands. The whole build is assembled on a breadboard, making it easy to teach others to experiment. [Dilshan] offers very useful insights into antenna, rod coil and IF transformer parameters. To dive in to Radio architecture, check this post on Amateur Radio. And if you would like to get a closer look at Antique Radios, check this post on Restoring Antique Radios.