Talk:Heterodyne

message: This article has to de: links, that legal? Thanx 69.142.2.68 00:22, 19 September 2005 (UTC)
thread_title:  Heyyy!! 

message: 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?
:There's a difference between the beat frequency and the difference frequency. If you create sin(100Hz)*cos(2Hz), you will hear four beats of 100Hz per second, and not 2. The reason is that cos flips between +1 and negative 1, but the amplitude of the signal you are hearing is really the absolute value of it, thus the beating of amplitude is really |cos(2Hz)|, which has a wavelength of 4Hz (but is not shaped like a cosine). - Rainwarrior 17:52, 16 August 2006 (UTC)
thread_title:  formula contradicts other sources 

message: 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 f_1-f_2.  (This was a question on an exam I was marking last semester!)
:I very much disagree with: "your brain effectively performs a Fourier transform on the sound you hear". There is much, much more going on than a Fourier decomposition in the brain. If you work with computer sound recognition (you may, you didn't say exactly), you should know just how inadequate Fourier analysis is on its own for that purpose. Now, I don't know what this bit about "brain wave frequencies" is all about, perhaps it should be removed, but binaural beats are a well known and easily demonstratable process. I would agree that the language is inaccurate, though. The heterodyning principle is that the signal produced by mixing 100Hz and 102Hz is equivalent to the amplitude modulation of 101Hz with 1Hz (percieved as a 2Hz beating). It is not so much that the brain will percieve one or the other, but that the perception of it is ambiguous between the two, mostly (but not entirely) resolved by which parts of the signal lie in the audible range. - Rainwarrior 17:04, 16 August 2006 (UTC)
replies: text: Also, binaural beating is generally a quieter effect than the beating of a mixed signal. So, 100 in one hear with 102 in the other ear is going to have a stronger perception as an unmixed signal than as as the 101Hz * 1Hz idea. Quickly doing the experiment on myself, I would say that I hear a tone that is wavering in pitch (up and down) with slight amplitude changes, rather than two distinct pitches. If actually mixed, I definiftely hear is as 101Hz with a 1Hz amplitude modulation. But, if I take two tones that are more distinct, and gradually slide them into 100 and 102Hz, they are felt as more distinct (in the binaural test), but in the mixed test the distinction seems to be lost at some point. - Rainwarrior 17:49, 16 August 2006 (UTC)
thread_title:  Brain wave stuff <math>\ne</math> good 

message: 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)
replies: text: I'm not sure what you're calling nonlinear mixing... but because of the trig identity you've discussed, the amplitude modulation (nonlinear mixing?) of two sine waves is indistinguishable from the addition (linear mixing?) of two corresponding sine waves. If doing amplitude modulation, it doesn't matter which is the "modulator" and which is the "carrier", because the result either way is identical. Whether or not you get 4 frequencies in your analysis usually depends on whether the outer two tones are withing the detectable range (frequently they are not), though  the two original "additive" tones usuall come up stronger, and the two heterodyned frequencies may have additional harmonics. - Rainwarrior 03:55, 17 August 2006 (UTC)
thread_title:  An Oscilloscope and spectrum analyzer show it all. 

message: 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)
thread_title:  Heterodyne Harmonics 

message: 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)
thread_title:  Modifying Example in Header 

message: 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)
thread_title:  Need different definition 

message: 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)
replies: text: The "Mathematical principle" section has a derivation using ordinary trig functions.   Your complex exponentials is an interesting alternative approach, though. --ChetvornoTALK 19:57, 15 September 2020 (UTC)
thread_title:  Mathematical Treatment/Derivation? 

message: 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)
thread_title:  Important reference 

message: 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)
replies: text: Agree.--79.74.165.39 (talk) 19:11, 10 October 2008 (UTC)
thread_title:  Name change 

message: 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...
:I agree that a signal diagram would be useful. I think it is most illustrative to show what's happening in the frequency domain. Time-domain representation is not particularly insightful. --Kvng (talk) 14:29, 14 September 2009 (UTC)
thread_title:  It may be clearer with graphics 

message: 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)
replies: text: As the only two comments here show no need for the Jargon tag, I am removing it.  -tonsofpcs (Talk) 01:00, 9 August 2009 (UTC)
thread_title:  Jargon?  What jargon? 

message: 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)
replies: text: Ugh.  I just noticed there is also Radio frequency downconverter which seems to mirror upconverter. Dsmouse (talk) 06:16, 17 September 2009 (UTC)

text: I agree with the proposal. I'm not sure the diagrams in the Downconverter article are useful for the Heterodyne article. It looks like there's a technical misunderstanding there (see Talk:Downconverter) --Kvng (talk) 14:26, 14 September 2009 (UTC)

text: Are you in favor of merging the Downconverter article? --Kvng (talk) 17:03, 15 September 2009 (UTC)
replies: text: Weakly In favor of both mergers. --ChetvornoTALK 09:23, 18 October 2009 (UTC)

text: I think there is a place for these articles.  Firstly, it is helpful to readers who want a clear description of what these devices are all about without the in-depth technical descriptions of the heterodyne process.  Secondly, heterodyning is not the only method of achieving a frequency shift - although, admittedly, it is ubiquitous.  Technical errors in the existing articles are a non-reason for merging, editing is the answer to that.  I do, however, think that the upconverter and downconverter articles could usefully be merged with each other. SpinningSpark 09:45, 4 April 2010 (UTC)

text: Agree; there is next to no content in the upconverter and downconverter articles, and the reader would therefore be better served by being redirected to the Applications section on this article.  If the merge into this article does not reach consensus, then I think there's no question that at the very least, the two stub articles should be merged into one.  Oli Filth(talk|contribs) 14:47, 4 April 2010 (UTC)

text: Merged. Cutting and pasting from one article to another then inverting a few words doesn't really make the encyclopedia stronger. --Wtshymanski (talk) 20:46, 25 August 2010 (UTC)
thread_title:  Merger proposal  

message: 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.
Fig. 6.  Unique Alternating Current Generator for Exciting Tesla's Early “Beat” Receptor.  Actuated by Comprest Air or Steam Which Vibrates a Special Diafram-Coil.
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)
replies: text: For there to be any case for "heterodyne technique was first used by Tesla around 1896" or "Heterodyning was invented by Tesla" you would have to show where the above author says "Tesla's ""Beat" Receptor" anticipated the Fessenden's radiotelegraphic heterodyne receiver" and then show some version of that statement many more times from other reliable sources that are mainstream, i.e. easily found here or here. Again it is pretty cut and dry per Wikipedia policy. Fountains of Bryn Mawr (talk) 02:16, 22 May 2011 (UTC)
replies: text:  Peterson created an article for this device, Beat receptor, inadequately sourced as usual, which makes the same WP:REDFLAG claims.  I don't know what should be done with this article, whether it should be rewritten or merged, would appreciate some input.  I put my criticisms on the Talk page. --ChetvornoTALK 20:24, 4 October 2017 (UTC)
replies: text: Hard to find any sources on it that postdate Calvin Coolidge, I found one (calls it a "beat receiver" or "oscillating detector"). A pre-Taft source attributes it to Fessenden. I do not see any sources that attribute it to Tesla. I would say, if this is not a Beat frequency oscillator, then crop the article back to available RS. Fountains of Bryn Mawr (talk) 21:26, 4 October 2017 (UTC)
thread_title:  "Dr. Nikola Tesla and His Achievements" (excerpt)

message: 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)
thread_title:  Picture worth a thousand words? 

message: 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 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)
thread_title:  Tesla wp:redflag 

message: 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)
replies: text: Agree; there is absolutely no need for that article. --ChetvornoTALK 11:51, 11 February 2017 (UTC)
thread_title:  Merger proposal: Heterodyne detection  

message: 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 131.22.200.58 (talk) 21:10, 19 December 2018 (UTC)
replies: text: There is a saying from a famous scientist: Any noun can be verbed.  Can we also say that any verb can be nouned?  Gah4 (talk) 08:10, 24 August 2019 (UTC)
replies: text: There were three, one of which is the plural of superheterodyne (receivers). I removed one, is it already was followed by frequency. Now they aren't throughout, but only one.  Maybe one isn't too many. Gah4 (talk) 19:45, 16 September 2019 (UTC)
thread_title:  "Heterodynes" vs "Heterodyne Frequency" 

message: 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)
replies: text: I wouldn't call the standard method of transmitting Morse AM; it is OOK. (Compare WWVB's ASK.) There's FCC terminology such as A1 (Morse) and A3 (voice). Morse can be sent as a tone modulating an AM or FM carrier, but such usage does not have the benefit of concentrating the transmitter power into a narrow band. Glrx (talk) 20:50, 23 August 2019 (UTC)
replies: text: on-off keying claims to be a form of Amplitude-shift_keying which claims to be a form of amplitude modulation. Using transitivity, then, OOK is a form of AM.  The OOK article mentions minimizing bandwidth, which I believe means making sure that the transitions aren't too fast.  If one just keys the carrier (besides the safety problems at high power), one will get sharp transients and large bandwidth. I think that makes it more like AM, with a band-limited modulation signal. Gah4 (talk) 07:20, 24 August 2019 (UTC)
thread_title:  AM