Talk:Superheterodyne receiver

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What are the disadvantages of this type of receiver?[edit]

It does not have any significant disadvantages and that is why it is so popular but one could cite i) its relative complexity and larger component count (typically one needs three transistors for a superhet up to the aduio amplifier stages, and only one for a super-regenerative receiver ii) susceptibility to image frequencies (the receiver will pick up another signal separated from the intended input signal by twice the IF frequency and lying on the other side of the local oscillator frequency. This problem can largely be eliminated by using a tuned front end to suit the desired band of frequencies iii) a superhet can be sensitive to adjacent channel interference and other forms of interference. Use of a double-tuned superhet (eg radio control receivers) helps to reduce the superhet's noise susceptibility

Also mention that the local oscillator signal is a source of spurious emissions and can sometimes be detected a long way from the receiver. The practical consequence of this can be seen by anyone who's ever experienced a radar detector detector at work. The mixer stage can sometimes be overloaded by strong out-of-band signals which can produce interference. These disadvantages should be written up for the article. --Wtshymanski 14:39, 17 November 2005 (UTC)

Subheterodyne mixing[edit]

A good example can be found at
In particular the 11th paragraph of the DETAILED DESCRIPTION section.

The desired output signal is at 10.74 MHz (see 9th paragraph).

The 11th paragraph describes two techniques: "... using a lowpass FIR digital filter and a 10.84 MHz oscillator to carry out a superheterodyne ... rather than the bandpass FIR digital filter and the 10.64 MHz oscillator to carry out the subheterodyne...".

I'd never seen this "subhetrodyne" term before yesterday on the Wikipedia and I've read a *lot* about receivers in the last 30+ years. Since the term is *not* standard in the industry (for example, its not in IEEE 100), I think it's a neologism and should not be propagated here. It's also wrong, since the "super" means "supersonic", i.e., above audible, intermediate frequency, and does not describe the relationship of the local oscillator to the incoming signal. The cited patent pages do not use what I believe to be is standard vocabulary. --Wtshymanski 14:35, 17 November 2005 (UTC)

Bob K 00:31, 17 November 2005 (UTC)

Would everyone please sign your comments with four tildes i.e. ~~~~ DV8 2XL 22:47, 16 November 2005 (UTC)

Double tuned[edit]

  • Superheterodyne receivers usually contain double tuned circuits (sets of two loosely coupled circuits) as filters in IF receiver - this is because such a filter has almost flat band instead a peak - filtering a signal through many "peak" filters would severely distort it. Seems these tuned circuits are not even mentioned on English Wikipedia, and I am not sure what is their preferred name - is it the "double tuned circuits", or another one?
  • There were many different AM IF frequencies used after II World War: in Poland there is 465 kHz standard, in GDR most receivers has 468 kHz, but there were also 440 kHz (Beethoven) and 473 kHz (Undine EAW 7695E) - from engineer's handbook (Poradnik radio- i teleelektryka, PWT Warszawa 1959, Poland) where 42 receivers are briefly described ... which countries used the 455 kHz said here?
  • Except image frequency receiving, I recall two other problems these receivers have: larger noise (because mixer both produced own noise due to "sampling", and it catched noise at image frequency produced in RF amplifier), and tuning both input RF filter and oscillator circuit in a way that their frequencies keep constant difference (there was e.g. three-point tuning - for three RF-s of a band the RF filter and oscillator were tuned correctly, for any other RF there was some mismatch). And design of such a receiver requires a lot of work - it is not a receiver an amateur can build in a day or two, unless he has detailed information how to tune it correctly; it is suitable to design such a receiver for mass-production, when high cost of design has little effect on price.
  • In "Overview" (near end): "The oscillator also shifts..." - I think the mixer shifts, not the oscilator.

JerzyTarasiuk 19:14, 10 November 2007 (UTC)

As far as I know, the real inventor of the superhet was Lucien Levy, french ingenieur diplomed from the Ecole Supérieure de Physique et Chimie de Paris. The very first patent concerning the superhet has been issued in August 1917, one year before E.H. Armstrong's work (patent number 493660). This patent was completed one year after (describing not only the principle, but the schematic of a superhet receiver) the first of october 1918, patent n°506297. —Preceding unsigned comment added by (talk) 09:13, 18 December 2007 (UTC)

With regards requestphoto[edit]

Are these images of any use to the article?

A 5-tubes superhet receiver made in Japan about 1955.
Two section variable capacitor, used in superhet receiver

If so please cut and paste to article page. Traveler100 (talk) 06:05, 24 August 2008 (UTC)

Edited History Section[edit]

Would whoever recently pasted large lumps of technical explanation into the text please stop doing that. The History section does not need to go into such extreme detail; you're simply making it harder to follow. There are places for that further down. Ultramince (talk) 02:20, 26 February 2009 (UTC)

455 kHz for medium-wave AM broadcast receivers[edit]

This was a standard frequency long before ceramic resonators were common - for example, the RCA "Radiotron Designer's Handbook 3rd Edition" says frequencies in the range 450-460 kHz were common, and that edition is from 1942. --Wtshymanski (talk) 17:40, 1 September 2009 (UTC)

Why super ??[edit]

Why superheterodyne receiver called super........... —Preceding unsigned comment added by (talk) 12:40, 7 November 2009 (UTC)

'Cause it's super. More seriously, because the heterodyne (beat) frequency is above (super) the audible range. Unlike an earlier version of the detection technique, where the heterodyning oscillator is on the same frequency as the input and beats it down directly to audio. This works, but has drawbacks too numerous to describe here. Hmm, does this need to be more explicitly described ? --Wtshymanski (talk) 22:17, 20 November 2009 (UTC)

That explanation is commonly given, and is completely wrong! Superheterodyne is a contraction of "Supersonic Heterodyne". Before WWII "Supersonic" meant "having a frequency beyond the range of Human hearing", so a Supersonic Heterodyne simply meant one where the characteristic whistle was too high in frequency for a person to hear. However since WWII the term "supersonic" has come to mean: "something that travels faster than sound" (such as a Supersonic Aircraft). The original meaning of "supersonic" has now been generally replaced by the term "Ultrasonic". — Preceding unsigned comment added by Elekas (talkcontribs) 02:16, 1 March 2012 (UTC)

When is intermediate frequency higher than carrier?[edit]

Ultramince recently added language to the introduction indicating that intermediate frequency can be lower or higher than the carrier. I've simplified the language but I'd like to see a reference showing where this technique is used. I've added a citation request tag to the one sentence in the article that mentions this. --Kvng (talk) 15:03, 20 November 2009 (UTC)

Check out the ARRL handbook or, gosh, just about anything that talks about superhets. It's a stone-standard technique. A scanner (radio) will often up-convert, because if you have a wide-band RF front end it contributes little to image rejection - by converting to a higher IF than the input, images are placed so far out that the IF filters can handle it. Often done in general-coverage shortwave radios, for example the DX 440 I have uses a first IF around 55 MHz, then converts down again before demodulation. AM broadcast recievers get away with down converting to 455 kHz because that's still fairly high compared to the input signal, and there's always a tuned circuit ahead of the converter stage. --Wtshymanski (talk) 22:12, 20 November 2009 (UTC)
My problem is that higher IFs are mentioned very briefly in the article with no elaboration as to why this technique would be useful. I now appreciate that a receiver covering a wide frequency range (e.g. a scanner) must have a wide-band front end and therefore has a problem rejecting input that would land on top of a lower IF. I'd be happy to edit the article to include this information. Are there any other cases where a higher IF is useful? Also I don't have a copy of the AARL handbook so can't pull up citation. --Kvng (talk) 16:45, 22 November 2009 (UTC)
I don't have specialist literature on design of receivers at hand, either, and the principle is so general it only gets mentioned in passing in the more general references I've got. The 1991 ARRL handbook discusses IF choice around page 12-26, and says that a 455 kHz If isn't very useful above about 7 MHZ because of the image problem. "Solid state design for the radio amateur", another ARRL book, also describes IF choice and the different approaches used in hf ham gear from the 40's to the '70s. The CRC Press "Electrical Engineering Handbook" edited by R. C. Dorf just blithely says a superheterodyne converts up or down to an IF and then skips off into the bushes, not describing why you'd go either way. I think it's sufficent for encyclopedia purposes to mention that the if may be below...or above...the signal frequency, and refer to the textbooks for the gory details of why you would pick different ifs. A quick spelunk through my confused files has not turned up my DX 440 manual yet, which is a digital tuning general coverage SW radio. It's not unique in up-converting. --Wtshymanski (talk) 17:26, 22 November 2009 (UTC)
Finding my scanned manuals, for interest, the Radio Shack DX 440 (also Sangean 803) has a first IF of 55.845 MHz and tunes 150 kHz to 30 MHZ, the Radio Shack PRO 2006 scanner has a first IF around 610 MHZ, (tuning from 25 MHZ to about 1300 MHZ in several bands) and the Radio Shack PRO-2050 has a first IF of around 380 MHZ ( again, tuning several VHF and UHF bands). --Wtshymanski (talk) 04:31, 23 November 2009 (UTC)

Proposed merge of Intermediate Frequency[edit]

There is a template on Intermediate frequency proposing a merge here. I am not so sure this is a good idea, I suggest that the proposer states the case for merger here before anything is done. Also it is normal in proposed mergers to put a template on the proposed target article as well with a link to the same discussion. SpinningSpark 18:18, 29 November 2009 (UTC)

I oppose this merger. Frequency upconversion and downconversion using intermediate frequencies is a common technique in communications engineering, widely used in many devices besides superheterodyne receivers, such as radio transmitters, modems, cable television systems, radio repeaters, microwave radio relays, satellite transponders, fiber optic communication systems, cell phones and cellular base stations, telemetry systems, and microwave test equipment. --ChetvornoTALK 19:39, 29 November 2009 (UTC)
This does not look like a good idea to me either. The Hetrodyne article would be a better merge destination candidate but I don't support that. I do support some other heterodyne merge proposals --Kvng (talk) 17:51, 30 November 2009 (UTC)
Oppose = the article is about a receiver, not just a circuit module component.Francis E Williams (talk) 16:55, 17 January 2011 (UTC)

Duplication of content[edit]

The article contains the same informaion in many of its sections, it needs to be restructured slightly and some sections rewritten to clarify what is being said.Francis E Williams (talk) 15:19, 17 January 2011 (UTC)

You'll find the Wikipedia chief editor's Telex and FAX numbers on the home page; using either of these media, you can request the forms to make an editorial change to the article. Please allow 4 to 8 weeks for the submittal to be considered at the next editorial committee meeting. Rememmber, all manuscript submissions must be typed double-spaced, pica font, with a new fresh ribbon on 20 lb paper, on only one side. Please enclose a self-addressed stamped envelope with your submission in case it is rejected by the editorial committee and you want your manuscript back. --Wtshymanski (talk) 15:35, 17 January 2011 (UTC)
Thank you for the information. I have since received a suitable responce via UPS and have uploaded the approved content accordingly. My submission was approved on the basis that it did not remove any content, but was simply re-ordered it into a logical more readable sequence.Francis E Williams (talk) 16:52, 17 January 2011 (UTC)
The joke "They must be in a hurry; they Fedex'd you a FAX machine" is meaningless to today's Twitterati. And 07 57506 was the compnay Telex number, a generation ago when dinosaurs ruled the Earth. --Wtshymanski (talk) 17:26, 17 January 2011 (UTC)
The invention of the 3D printer has been a Godsend here in my village.Francis E Williams (talk) 17:33, 17 January 2011 (UTC)

Which characteristic is amplified in "IF Amplifier" stage?[edit]

Which characteristic is amplified in "IF Amplifier" stage? — Preceding unsigned comment added by (talk) 06:05, 2 July 2011 (UTC)

Wikisc84 (talk) 14:59, 28 November 2012 (UTC)
The IF amplifier has two primary goals.
First, it amplifies the weak signal coming out of the mixer. It is often difficult to obtain gain at RF frequencies; translating the RF frequency to a lower frequency IF eases the problem of obtaining gain. In addition, some stability issues are easier to meet.
Second, the IF amplifier provides selectivity. At a lower IF frequency, a bandpass filter has a lower Q for the same signal bandwidth.
Glrx (talk) 04:56, 11 December 2012 (UTC)

Local oscillator radiation to detect receivers[edit]

I don't know if the BBC uses LO radiation, but Britain knew coded instructions were being sent to spies, so it tried to find those listening by searching for oscillator radiation (in the 1950s?). The reported search was unsuccessful, but that does not mean it wasn't later refined. I think it was in a book about Britain's anti-spy efforts. The book included a bizarre scheme where plaintext was recovered from the teletype transients that leaked across the coding equipment. I don't recall the author or the title.

In California many years ago, a common carrier hired amateur photographers to take pictures of dish antennas that were capturing forbidden content. A van confirmed that the receiver was active.

Glrx (talk) 22:48, 2 August 2012 (UTC)

I worked on systems that successfully detected radio receivers via their LO radiation. As part of the research we investigated "TV Detector Vans" and found the idea that they caught non-licence-holders by detecting LO leakage to be a complete myth.
Wikisc84 (talk) 14:55, 28 November 2012 (UTC)
I could easily believe detector vans would have trouble with today's TV sets, and I could believe detector vans would have problems with old VHF tuners. I expect those receivers would use RF amplifiers. However, old UHF tuners were just diode mixers and could have significant LO leakage. Glrx (talk) 05:04, 11 December 2012 (UTC)

TRF/Neutrodyne was easier to use than superhet?[edit]

In the History section, paragraphs about why superhet didn't catch on immediately in the consumer market claim that one reason was that the superhet required greater technical skill than tuned receivers. How can it be easier to use, when you have to separately tune multiple stages to the station frequency? That text needs to expand about what it is that made early superhet receivers hard to use. Because, clearly, later superhet receivers are such that anyone can use them without technical skill: just turn a knob until you hear a station. Did the early superhet units require the user to tune two or more circuits? Like the local oscillator and a filter for the incoming signal? (talk) 05:26, 3 February 2013 (UTC)

OK, I understand everything.
  • Tuned radio frequency receivers put the incoming signal through numerous stages which tried to amplify the band around the station frequency and suppress other frequencies. The purified result is then subject to detection to extract the signal. The problem with this is that three or more stages need to be tuned to change a station.
  • Superhet essentially replaced a whole section of the TRF with fixed-frequency circuits. However, it did not entirely eliminate the tuning of multiple stages. Superhet still requires the RF and LO stages to be tuned in step. Yet this appears simpler than the operation of a TRF: tuning at most two things in step is easier than three or more. See here: "However, because of the number of tuned stages in a superheterodyne, a simpler method was desired. In 1932, a team of British scientists experimented with a method to surpass the superheterodyne. This new type receiver, called the homodyne and later renamed to synchrodyne, first consisted of a local oscillator, a mixer, and an audio amplifier. "
  • The new method was to use heterodyning to go directly from the carrier frequency to baseband, skipping the intermediate frequency: Synchrodine (direct-conversion receiver).
  • Superheterodyne reigned for a few decades because Synchrodyne required a complex phase-locked-loop circuit which didn't become economic until integrated circuits came along. The reason it needs a PLL is because direct conversion does not use a rectifier based envelope detector to extract the amplitude-modulated signal. Therefore a very accurate tuning is required in the local oscillator which dynamically tracks the frequency of the station.
It might be something worth incorporating into the History section. (talk) 19:43, 3 February 2013 (UTC)

Separate/combined mixer/oscillator.[edit]

Yes, conceptually the local oscillator and mixer are two separate things, but every practical Am broadcast band receiver that I have ever worked on, or even just seen a circuit diagram for, had the one transistor being a combination mixer oscillator. (talk) 07:40, 10 June 2013 (UTC)

Wax potting[edit]

While I don't doubt that a little security might have been a consideration, a larger one is illustrated by, illustration. Wax potting prevents corrosion in wet and salt environments. The wax melts out quite easily, and is useless to prevent commercial espionage. Anmccaff (talk) 17:22, 22 February 2016 (UTC)

Frequency spectrum diagram[edit]

How a superheterodyne works. The incoming radio signal (RF) from the antenna consists of a carrier frequency (dark blue) with sidebands (light blue) on either side containing the modulation. Mixing this with the local oscillator signal (LO), creates a heterodyne intermediate frequency (IF) at the difference between these frequencies. This is bandpass filtered in the IF amplifier, and the demodulator extracts the modulation (M). Because the Image frequency when mixed with the LO also creates a signal at the IF, the RF image rejection filter on the input of the receiver filters out any radio signal at the image frequency.

@Glrx: what is your objection to the diagram? --ChetvornoTALK 20:29, 31 October 2016 (UTC)

It's too busy and confusing. I've inserted the diagram and caption as they were in the article. It's a figure where one must already understand what is going on in order to appreciate it; I don't think it is clear to one who is learning. The diagram plots multiple signals (baseband, IF, LO, RF) on the same axis; that's confusing. You know how the signals are used, so you can separate them out in your mind. That's not the case with someone who does not know what is going on. Is the LO received along with the image and RF? LO and RF convolve to produce a result, but they are not present in the same signal. Why is the image a dashed CW frequency more reminiscent of the LO and not looking like another, undesired, station? Is the image another oscillator? The figure has multiple operations described without separating them. Consider plotting separate signals that are tied to the signals in the block diagram. In addition, the figure implies a specialized source (DSB) in a general situation; what about CW, SSB, and FM? The figure focuses on the artifact issue (image rejection) while ignoring primary asset of high selectivity. The heterodyne didn't leave any work for the IF filter (only one station needs to be filtered). Glrx (talk) 21:55, 31 October 2016 (UTC)

Inventor - What About Schottky?[edit]

Reading [1] it seems that Walter Schottky should be mentioned as well, any thoughts on this? Or has this been discussed earlier? Cyberroach (talk) 24 June 2017 (UTC) — Preceding unsigned comment added by (talk)


Article text in the EL section[edit]

Not sure why a large amount of martial was added to the EL section, seems way beyond MOS. If its sub-material from the same site, link only the site (WP:ELPOINTS #4). If its a mass of martial on an alternative view to correct a "poorly sourced and skewed" history section, well, the EL section is not the place where you do that (WP:ELPOV). If this is material from reliable sources then it should be added to the "History", not the EL section. Fountains of Bryn Mawr (talk) 22:56, 4 July 2017 (UTC)