Understanding how the Superhet / Superheterodyne Radio Works

The superhet or superheterodyne radio is over 100 years old - the first superhet receiver was made in 1918 and since then it has developed to become one of the most widespread types or formats of radio receiver ever.

The superhet or superheterodyne radio gains its name from the fact that it uses heterodynes above the audio radio - the word means supersonic, or above the audible range, and heterodyne, being mixed together. In other words the superhet radio concept is based around radio frequency mixers which are used to convert the frequency of an incoming radio signal to a fixed intermediate frequency.

This gives advantages in terms of filtering as fixed frequency filters are much easier to design and give much better performance. There are also advantages in terms of having the filtering at a lower frequency - particularly in the past it was possible to achieve a much better performance at lower frequencies. This is still true to some degree, but not to the same extent.

As the IF is where there is most of the gain, having a fixed frequency amplifier has a number of advantages. Also in the early days of vacuum tubes / valves, it was necessary to have a low frequency otherwise the amplifiers would burst into oscillation.

One major issue with the superhet radio is the image signal where there are two frequencies that can enter a mixer and provide an output at the intermediate frequency. The unwanted one is called the image signal and this is attenuated to a sufficient degree by adding tuning before the mixer.

[Wtfinc]

This video is a lifesaver. Literally. If I’m stranded with a broken radio…

[marconormandin]

I have been looking for someone who can explain in more details what most YouTubers are avoiding... Thank you.

[charlesmrader]

This video is quite personal to me, because of my family history. My father, Abraham L. Rader, was born in 1906, of immigrant parents, and when he was a teenager, he was interested in radio. In those days, radio for ordinary people was a crystal set, with all the problems of amplification and tuning that this video makes clear. But my father started a company to make and sell crystal radios. He also hired an engineer to try to solve some of those deficiencies. My father had no formal training in electronics, just hand-on experience. His engineer was a perfect fit, very bright but not entrepreneurial. That engineer invented the superheterodyne radio. I wish I knew his name. My dad's company sold the first superheterodyne radios to ever reach the consumer market.

Sadly, from our family point of view, Sarnoff and RCA had the necessary patents and my father, who didn't even know what a patent was, found that he had to leave his business or be sued.

He never talked to me about that part of his life, but of course my mother knew about it. When he died, I put together an obituary speech and that was when I learned about it.

[PavelLarsson]

Such an incredible and intuitive explanation! Thank you so much for making this!

[Ham]

I think I finally understand. It is easy to make very good and efficient filters for one frequency. So the super het will convert all frequencies to that one frequency to allow it to be efficiently processed.

[matambale]

This is very definitely the the correct terminology and nomenclature.

[hornsby]

Thank you for the video. Very well explained. It's a pity that the automatic Google translation often fails with technical terms.

[onemorething]

It takes 8 minutes to explain something the happens in millionths of a second. That's what is hard for me to digest!

[James_Bowie]

Very good explanation. (Sibilance reduction techniques at the mic would improve your audio)

[JohnToddTheOriginal]

Did this make radios cheaper? As in: 1 specialized tuner/het circuit, then into just a standard processing block operating at an industry standard frequency?

That would lend itself very well to mass production.

[abrahamjushua]

Why adding the ground symbol to the first boxe (RF amp.) of the block diagram ?

[marouaniAymen]

Thanks for the instructive video, I have two question:
- how the Mixer or Frequency Multiplier is implemented in terms of electronic components ?
- what will happen if the Internal Oscillator frequency is greater than the received Frequency, I mean the case where the frequency difference is negative ?

[ПашаПитецкий]

Дякую вам, це супергетеродин, підкажіть мені, хто винайшов цей приймач вперше, у мене є книга, у якій дуже добре описані дії по настроюванні цього приймача, і я теж настраював такий приймач за допомогою цієї книги

[CombFilter-vogk]

Superhet - 'Supersonic heterodyne'

[royshashibrock]

I wish folks like this author would use the correct terminology and nomenclature concerning this topic. The video shows a block diagram of a heterodyne receiver but calls it a "superhet." This is incorrect.

Heterodyning is the process of mixing two signals (usually a local oscillator and the incoming signal) to get a desired sum or difference frequency, called an intermediate frequency or IF. A receiver that uses only one mixing stage and selects one IF for demodulation is called a "heterodyne" receiver. A "superheterodyne" receiver has two or more mixing stages and consequently has the corresponding number of intermediate frequencies, the last feeding the demodulator.

Heterodyning is also used in demodulating single and double sideband signals. In this system, a type of amplitude modulation, the carrier signal is removed before broadcast. This allows for more efficient use of the transmitter's power amplifier stage. In the receiver, heterodyning is used to reinsert (or mix) the carrier signal with the incoming signal. In this case, the sum and difference signals are the demodulated audio and are called upper and lower sidebands. Usually only one is selected at a time.

[drstrangelove]

why do you find it necessary to say the zero (or nought, as you Brits do) in 0.5... just say "point five" (I never understand why people do this, the nought is redundant)