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Could someone include a reference for the stuff (ahem) on brain behavior? At best it isn't well written (not clear which wave phenomenon in the brain is being referred to, e.g. the electrical pulses? If so, what is with the comment on low frequency as it relates to the ear?) At worst, it seems like unsupported pseudoscience. Thanks —The preceding unsigned comment was added by Al Biglan ( talk • contribs) 18:17, 3 June 2005 (UTC)
One ref is "Auditory beats in the Brain", Gerald Oster, Scientific American Oct 1973. See also http://gnaural.sourceforge.net which discusses a program for experimenting with brain beats; the page notes that "snake oil salesmen" have made claims about brain beats. It is not an area of any important research and is basically a curiosity; it should not be at the beginning of the talk section on "Heterodyne" except as a coincidence. 76.105.16.80 ( talk) 22:09, 3 May 2011 (UTC)
This article has to de: links, that legal? Thanx 69.142.2.68 00:22, 19 September 2005 (UTC)
My fellow wikipedians - I've added sections to this article (as it is in quite a mess!) however I still think it could use some more reorganization. An image or two wouldn't hurt either. Maybe also more uses for electronic heterodynes?
This article says that the beat frequency is equal to the difference of the the frequencies divided by 2. Nearly every other source says it is merely the difference (f1 - f2). Does someone want to set this straight?
As someone who works on how the brain processes sound, I found this section pretty unbelievable, and hence added a "Disputed" tag. For example, you would not hear a mix of 100 Hz and 102 Hz as "101 Hz", because your brain effectively performs a Fourier transform on the sound you hear. Now, it is true that you could not properly distinguish the tones; they would probably just sound slightly out-of-tune.
While the article gets it right that epilepsy can be temporarily induced by a periodic stimulus (which is one of the things my research group works on), virtually the entire rest of the article is based on pseudoscience or misunderstandings.
I vote that the whole section be axed.
And yes, the beat frequency is . (This was a question on an exam I was marking last semester!)
My experience with audio and using an oscilloscope leads me to these conclusions on heterodyning. Any one with a waveform generator and oscilloscope can do the experiments and prove it to themselves.
When 2 audio (or r.f.) signals are added together, the higher frequency "rides" on top of the lower frequency. The peak to peak amplitude of the higher frequency does not change, however it's amplitude in reference to 0v. rises and falls at the frequency of the lower signals frequency. A speaker would produce this rising and falling at the frequency of the lower frequency signal. A frequency spectrum analyzer will show only the 2 original signals. There is no mysterious beat frequency...only the rising and falling of the higher frequency at the lower frequency's rate. .........I assume that when 2 independently created audio signal come into the ear, the results are the same. What the brain does with them I do not know.
If signals are mixed nonlinearly 4 signals result: The 2 original and the sum and difference of those originals. The trignometric product of 2 sine waves verifies this...hence nonlinear mixing is often referred to as the "multipling" the 2 original sine wave signals together. To produce this multiplication effect with 2 original sine waves, the higher frequency is usually modulated with the lower frequency. This process, done electronically, involves changing the peak to peak amplitude of the higher frequency at the lower frequency rate. The peak to peak amplitude of the higher frequecy is never higher then the original peak to peak value, but it varies at the rate of the lower frequency. An oscilliscope very clearly shows this waveform, and a spectrum analyzer will show 4 frequencies present in the waveform.
I do not know how this nonlinear mixing takes place in nature, but if it does then 4 distinct signals should result. GregFiore 19:08, 16 August 2006 (UTC) Greg Fiore
Mr GregFiore, dunno if you are still reading this 7 years later, but you have gained totally the wrong impression in your first comment. But rather than simply name calling, why don't I give you an example. Consider a twin-engined aircraft, with the engines not quite in sync. You will hear - and no doubt have heard, many times - the resultant beat. It is very easily audible.
Old_Wombat (
talk) 07:49, 10 June 2013 (UTC)
I think missing here is the acknowledgment that mixing can occur through any non-linear device/function. So we're not generalizing enough to say that there are x number of frequencies generated, frequency y is here, frequency z is here, etc. The implication in most of these examples, I think, is that a quadratic is used, but this is only a commonly used approximation for some mixers, notably diode mixers. I think it would be more appropriate to indicate that the harmonics that are generated are determined by the function that governs the device's behavior, and that generally at least a difference term is produced. To some degree the method of mixing is also important to the harmonic production. Bolometric mixers, for instance, act like capacitive envelope detectors and inherently filter out higher harmonics. I know it's a fine point because it's only briefly discussed in the first paragraph, but the topic seems to be causing confusion in the discussion.-- Jschultz 01:42, 23 October 2006 (UTC)
I'm making a tweak in the example in the header that cites a 3000 Hz and a 3001 Hz frequency to produce an "audible beat frequency of 1 hertz" (emphasis added) and changing it to a 3000Hz/3100Hz/100Hz example because 1Hz is not audible to humans (see Human_hearing#Localization_of_sound_by_humans:_a_brain_circuit).
If anyone disagrees, please discuss.
-- KNHaw 22:56, 20 December 2006 (UTC)
The definition is not consistent with "beating", which is the article's favorite example. If beating is truly an example of heterodyning, then the definition is wrong. For example: 1) The definition says "...in a nonlinear device". However, beating is a linear phenomenon that occurs in linear devices and mediums (it's just addition!). The definition should be expanded to include linear phenomenon also... if beating is to be included. 2) "...the generation of new frequencies..." - beating doesn't really create new frequencies. A spectrum of the beating signal would actually show the original two frequencies unchanged. The beating frequency wouldn't show up anywhere. By contrast, multiplication actually creates REAL signals at the sum and difference frequencies. Instead of saying "new frequencies" maybe "new frequencies (real or apparent)" 3) "mixing of two frequencies". Using the word "mixing" would be ok in general usage, but in this field it has a technical meaning which would exclude beating (for example, see wikipedia for "Frequency Mixer"). I suggest using a word that doesn't have the same technical association for example: "combining" instead of "mixing". It's great to use the word mixing elsewhere in the article as an example, but not in the definition where it excludes other types of heterodyning. Catapultsam 22:59, 14 April 2007 (UTC)
Speaking of definitions, I didn't see this discussed already, but if we're talking about mixers and audio in one direction, saying that what a radio engineer calls a mixer, an audio engineer calls a ring modulator, I wonder if we ought to talk about it in the other direction as well, and say that the audio device called a "mixer" is an X to radio engineers. Adder? I don't know what to call it. Obviously not really directly related to heterodynes, but probably helpful to the inexperienced reader when an article is discussing both radio and audio, and using the word "mixer." When I first started working with radio, this tripped me up.
I *believe* I once read a mathematical derivation of how heterodyning works in a book by Donald Wehner.. it may have been the 2nd Ed. of "High Resolution Radar", but my point is that heterodyning made ALL THE SENSE IN THE WORLD to me at the time I read that derivation. When I read this Wiki article, heterodyning seems very vague and mysterious. Perhaps a mathematical treatment could illuminate things... I recall it being a very simple derivation. —Preceding unsigned comment added by 69.183.146.246 ( talk) 04:38, 7 February 2008 (UTC)
Recall that the product of two complex numbers is a complex number whose argument is the sum of their arguments, and whose magnitude is the product of their magnitudes. Therefore, if f(t) = A cis(ut) and g(t) = B cis(vt), f(t)*g(t) = A*B cis (ut + vt) = A*B cis ((u + v)t). The frequency of a sinusoid is the coefficient on t inside it (or that coefficient over 2*pi, depending on your convention), so we multiplied a sinusoid with frequency u by one with frequency v, and got one with frequency u+v. I'm eliding some complexity, here, specifically aliasing and phase, but I hope that gives you some intuition for what's going on.
Please see the section on Frequency Counter, and Prescaler. —Preceding unsigned comment added by 70.177.16.209 ( talk) 17:05, 3 June 2008 (UTC)
I disagree with the unilateral name change of this article. I think "heterodyne" is the much more recognisable term than the verb form. A quick google seems to indicate it is not just me: ghits for "heterodyne" = 14.6 million, for "heterodyning" = 60,800. I propose to move it back to heterodyne. SpinningSpark 19:52, 5 October 2008 (UTC)
It may be clearear if it is shown the graphics with the original sine waveform and the mixed ones, or a screenshot of an osciloscope...
As a matter of fact, this article contains very little jargon. Perhaps this was not the case when the notation was added, but as it stands today, there is no further need of jargon removal/definitions.
While many of the terms used in the article are unfamiliar to the unwashed masses, they are fairly ordinary words, often used for varied purposes having nothing to do with radio, or electronics. We aren't expected to dumb down articles on technical subjects to the point where functional illiterates can read them, are we? If one hasn't the vocabulary to understand this article, this article will remain undecipherable, whether definitions/explanations are given, or not. Eudaemonic Plague ( talk) 21:01, 20 July 2009 (UTC)
Upconverting and downconverting currently have two separate pages, but both are really just the application of the heterodyne process. I believe they should be merged into a new section of this article. Dsmouse ( talk) 05:47, 14 September 2009 (UTC)
I would say keep it separate, the upconverter should have a bit more on the real world application and be expanded. rather than merged. Graeme Bartlett ( talk) 21:36, 14 September 2009 (UTC)
Thanks for taking care of that. -- Kvng ( talk) 21:50, 25 August 2010 (UTC)
I recently added this sentence to the introduction: "It [heterodyning] is used for moving signals carrying information from one frequency to another, and for modulation and demodulation." This was reverted with the comment: "rewrite changes meaning. hetrodyne does not directly modulate or demodulate." I think this is erroneous. Although the term "heterodyne" is not often used to describe modulation, heterodyning (mixing two frequencies to generate new frequencies) is the process behind AM and several other types of modulation. In AM modulation, two frequencies, the carrier and the modulation frequency, are mixed in a nonlinear mixer, resulting in sum and difference frequencies (the sidebands). It's just a matter of terminology whether it's called modulation or heterodyning. I think the sentence should be put back. -- Chetvorno TALK 07:01, 22 December 2010 (UTC)
144px|thumb|right|Instrument to receive radio waves of 1896-1899 structure.
One of the simplest devices I used in my experiments between my laboratory on South Fifth Avenue and the Gerlach Hotel, and other places in and outside the city, was an instrument constructed in 1896 with a magnet which sometimes was so designed as to give me a very intense magnetic field up to 20,000 lines per square centimeter. In this I placed a conductor, a wire or a coil, and then I would get a note which I amplified and intensified in many ways. From the characteristics of the audible note, I would immediately judge the quality of my apparatus.
When I speak of an audible note, I mean a note audible in a telephone as produced by the diaphragm of a telephone, or by a vibrating wire within the range of audibility.
[The figure] shows the general arrangement of the apparatus. Two condensers are the boxes at each end, and in the center a coil, or two coils, according to necessity, with which I produced a strong magnetic field and in it a wire. These condensers and the wire form a circuit which I tune. The condensers are of comparatively large capacity because my conductor is so short. I usually would transform the current in the receiving circuit and make as close a connection as possible and then tune the circuit to the vibrations. I would also mechanically tune the wire, according to the frequency, to the same note or to a fundamental.
This machine was suitable for transportation. I could put it under my arm with a couple of batteries. I had relays, which were very big, in which I produced (for stationary work) a very intense magnetic field so as to affect the conductor by the feeblest current. Furthermore, I used these relays particularly in connection with beats. When the frequencies were very high, I combined two frequencies very nearly alike. That gave me a low beat. One of the frequencies I sometimes produced at the receiving station, and at other times at both the receiving and transmitting stations. This always gave me the means of producing an audible note. I used machines of this character from 1892, but this specific instrument in my laboratory on Houston Street.
This instrument comprising a magnet and chord or coil in the magnetic field -- I mean a wire or coil in the magnetic field. . . . It was very convenient for producing audible effects because, if I used other forms of a receiver, I had a reading which was not at once translatable. If I listened to a note, I could immediately tell the quality of the transmission. For instance, I would tune a circuit in my laboratory, take it out to another building, and I would receive the signals; and from the quality of the signals I would see how I was progressing.
Counsel
In the experiments that you have spoken of with the instrument of which the picture is shown, what were the distances between the transmitting and receiving stations?
Tesla
The distance at that time, and I think the greatest distance at which I ever received signals from the Houston Street laboratory, was from the Houston laboratory to West Point. That is, I think, a distance of about 30 miles. This was prior to 1897 when Lord Kelvin came to my laboratory. In 1898 I made certain demonstrations before the Examiner-in-Chief of the Patent Office, Mr. Seeley, and it was upon showing him the practicability of the transmission that patents were granted to me. . . .
144px|thumb|right|Ways of receiving practiced in 1898-1900.
[This] illustrates a device which has already been discussed. I have used it very frequently. This is also a drawing of the period of 1898 to 1900 and illustrates a way of producing audible notes by reaction of the received impulses upon a magnetic field. Here is a transmitter, diagrammatically represented, with an arrangement for varying the intensity of the waves emitted, and on the receiver side I have, as you see, a grounded antenna. [The] secondary [has a conductor under tension in] a very powerful magnetic field, and [the reaction of] this conductor, traversed by the received currents in the field, causes the conductor to emit audible notes.
I had several magnets of various forms, like this, and employed a cord in the field, which, when the current traversed it, vibrated and established a contact. Or, I used a small coil like this one here through which the current was passed, and which by its vibrations produced the signal, an audible note, or anything else I desired.
Counsel
Where was that patent drawing published?
Tesla
That drawing was not published. It is exactly the same thing as the other, but in my writings, which I have before commented upon, I had already shown the reaction of the high frequency and low frequency currents on magnetic fields, and had specified the frequencies within which one has to keep in order to receive efficiently audible notes.
Counsel
This drawing, however, was actually made about when?
Tesla
From 1899 to 1900. The date of these drawings we can easily locate from the bills I have received.
Counsel
And the devices shown here, were they ever used by you?
Tesla
I used them, of course, frequently. That is, in fact, one of the best forms, but as far as the principle of the employment of the magnet is concerned, it is not novel. The only novel thing was that I used my own discovery, which I had made known in my writings before. I was the first to use high frequency currents reacting on a magnetic field and producing audible notes through the reaction. I employed here only what I described in my lectures. It was a logical application of the principles which I then set forth.
144px|thumb|right|AC Generator/Local Oscillator.
[This] oscillator was one of high frequency for isochronous work, and I used it in many ways. The machine, you see, comprised a magnetic frame. The energizing coil, which is removed, produced a strong magnetic field in this region. I calculated the dimensions of the field to make it as intense as possible. There was a powerful tongue of steel which carried a conductor at the extreme end. When it was vibrated, it generated oscillations in the wire. The tongue was so rigid that a special arrangement was provided for giving it a blow; then it would start, and the air pressure would keep it going. The vibrating mechanical system would fall into synchronism with the electrical, and I would get isochronous currents from it. That was a machine of high frequency that emitted a note about like a mosquito. It was something like 4,000 or 5,000. It gave a pitch nearly that of my alternator of the type which I have described.
Of course this device was not intended for a big output, but simply to give me, when operating in connection with receiving circuits, isochronous currents. The excursions of the tongue were so small that one could not see it oscillate, but when the finger was pressed against it the vibration was felt. . . .
Regards,
GPeterson (
talk) 23:57, 16 May 2011 (UTC)
By Samuel D. Cohen
The Electrical Experimenter, February, 1917
PERHAPS the ever-broadening field of invention has never known a genius more successful in developing far-reaching and original inventions than Dr. Nikola Tesla, whose name is known in every corner of the globe for his scientific achievements. . . .
Dr. Tesla's most important work at the end of the nineteenth century was his original system of transmission of energy by wireless. In 1900 Tesla obtained his two fundamental patents on the transmission of true wireless energy covering both methods and apparatus and involving the use of four tuned circuits. He also obtained a number of other patents at the same time, describing many other improvements. Among these may be mentioned his application of refrigeration and the oscillatory systems with which he obtained remarkable results in his well equipt laboratory on Houston Street, New York City.
In 1901 and 1902 several patents were granted to him describing a number of improvements, among which two have assumed great importance in the radio art; one of these is known under the name of the “tone wheel” and the other the “tikker.” Others are making claim to these inventions, but Tesla was far ahead of any of them.
Fig. 5. The First “Beat” Receptor for Radio-Telegraphy Invented by Tesla, Which Foreshadowed the “Heterodyne.”
At a little later date Tesla secured two patents on what he termed the principle of individualization, involving the use of more than one oscillation for the operation of the receiver. This property is now known under the commercial name of beat receptors. In long protracted interference proceedings carried on in 1903, however, Tesla has been accorded full and undisputed priority over Fessenden and other claimants. His first beat receiver is shown in Fig. 5, which consisted of a steel band stretched above a powerful electro-magnet excited by a high frequency current, causing the steel band to vibrate at an enormous rate. A small sensitive electro-magnet is placed in proximity to the band, in which is produced an alternating e.m.f., and this is acted upon by the received wave.
The apparatus is timed by adjusting the periodicity of the band until the received wave is made audible. The large electromagnet was usually excited by means of an alternating current generator, and this is illustrated in Fig. 6. Like all Tesla inventions, the construction of this oscillator is very unique, consisting of two chambers in the center of which is placed a vibrating membrane. This is inclosed in a magnetic field, consisting of a powerful coil encircling the device as seen and which was excited by a direct current. The membrane was caused to vibrate by passing interrupted, comprest air thru the two chambers by the inlet pipes as indicated. In the process of vibration, an E.M.F. is produced in a coil secured to the vibrating disc.
The above analysis of Tesla's work concludes that Tesla's ""Beat" Receptor" anticipated the Fessenden's radiotelegraphic heterodyne receiver.
GPeterson ( talk) 18:48, 21 May 2011 (UTC)
I wrote a simple BASIC program to graphically show this principle. I could easily grab some screen captures of various frequency pairs (eg, two very similar frequencies, two very different frequencies, different amplitude ratios, etc) and put them here. Would that be worthwhile? Old_Wombat ( talk) 07:46, 10 June 2013 (UTC)
I object to the recent change made to the sentence in the introduction about the relation of "beats" to heterodynes. The previous sentence
was changed to
The original sentence is more accurate. As Glrx pointed out, beats and heterodynes are related (note the original sentence didn't say they were the same phenomenon); they are duals of each other. They both come from the same trigonometric identity, the prosthaphaeresis identity. The "heterodyne equation is
By changing variables and adding and subtracting, you get from this the "beat" equation
More importantly, however, the word "beat" is often used for heterodyne, for example in the beat frequency oscillator, which actually uses heterodyning, not beating. Both techniques combine two frequencies to produce sum and difference frequencies. The sentence in question is in the introduction, where it will be read by readers who are not experts in the field. To them, the objections that AmarChandra made to the original sentence on Glrx's talk page, that the power in the sum and difference frequencies in the case of beats can be unequal, is simply not important. I think not only should the original accurate sentence be restored to the introduction, but the article needs a section on the relation of beating to heterodyning. -- Chetvorno TALK 00:01, 7 September 2013 (UTC)
I have removed this paragraph because I do not see this claim in any mainstream sources. It is a "surprising or apparently important claim not covered by multiple mainstream sources" and a "claim that is contradicted by the prevailing view within the relevant community," i.e. two points of WP:REDFLAG. The Leland I Anderson source does not mention Heterodyne [6] and the Samuel D. Cohen source is almost 100 years old and offers no detail for the claim (only appearing in a caption) "The First “Beat” Receptor for Radio-Telegraphy Invented by Tesla, Which Foreshadowed the “Heterodyne.”". We are way short of the "multiple high-quality sources" required at WP:REDFLAG. Fountains of Bryn Mawr ( talk) 00:01, 8 October 2014 (UTC)
I propose that the short article Heterodyne detection be merged into this one. That content all seems relevant here (if it isn't here already). Layzeeboi ( talk) 08:45, 11 February 2017 (UTC)
The Tenerife airport disaster article links to this page in the context of two simultaneous radio broadcasts heterodyning into illegibility. Can someone more knowledgeable than me maybe add a section or subsection discussing this phenomenon? Ninjalectual ( talk) 02:13, 19 December 2018 (UTC)
This article uses the term "heterodynes" throughout in place of "heterodyne frequency". Heterodyne, and all its forms, are either an adjective or a verb. There is no recognized noun form of the word that I can find from any dictionary source in print or online. As we all know, words matter. The proper syntax for the two new frequencies created by mixing two original frequencies in a non-linear device is "Heterodyne Frequencys". In the words of Steven Crowder, "Change my Mind". — Preceding [[Wikipedia:Signatures| 131.22.200.58 ( talk) 21:10, 19 December 2018 (UTC)]] comment added by 131.22.200.56 ( talk) 16:22, 19 December 2018 (UTC)
The article says: CW Morse code signals are not amplitude modulated. It seems to me that they are amplitude modulated, with the amplitudes being either zero or full power. The exact sound depends on the shape of the on-off and off-on transitions. But yes, spark gaps generate a wide spectrum of frequencies, including audio frequencies, and CW transmitters mostly don't do that. Gah4 ( talk) 05:09, 5 August 2019 (UTC)