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Sci.Electronics.Basics -> AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
There are 269 messages in this thread.
You are currently looking at messages 200 to 220.
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Author: Don BoweyDate: 17:27 06-07-07
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On 7/6/07 2:00 PM, in article pan.2007.07.06.21.01.00.435001@example.net,
"Rich Grise" <rich@example.net> wrote:
> On Fri, 06 Jul 2007 13:01:36 -0500, craigm wrote:
>> John Smith I wrote:
>>
>>> --this allows for almost doubling the
>>> effective range of am.
>>
>> Increased range comes from transmit bandwidth, power distribution vs
>> frequency, and receiver bandwidth. Again, what's the math that explains
>> this?
>>
>
> Say you've got a transmitter that outputs 1000 watts. So, apply a 1 MHz
> sine wave - that's CW (Continuous Wave). Now to modulate that, you have
> to add in the audio power through a modulator. This adds energy, at
> frequencies called "sidebands". These ride along with the carrier and for
> 100% modulation you also need 1000W of audio,
Small woops here....... 1000 Watts Tx carrier requires 500 watts of
modulator power for 100 % modulation, which puts 250 Watts in each sideband.
> which shows up in two
> sidebands with a total power content of 500W each. That's a total of
> 2000W; the modulator provides the additional 1000W to the xmtr's.
>
> The scope waveform would show a 1MHz sine wave that goes from 0 to 2X
> the original amplitude in step with the modulation.
>
> Now, if you could filter out the carrier, you could send the same
> amount of information the same distance with only 1000W output, which
> would all be in the sidebands. Boost this to 2000W, and you'll hear
> a 3 db increase in the audio's signal strength.
>
> Now, if you take away one of those sidebands, you only need 1000W to
> send the same amount of information, since the sidebands are simply
> mirror images of each other, you're back to 1000W again, and if you
> up that to 2KW, your audio is 6dB stronger than it would be with an AM
> signal of the same wattage, since no power is wasted on the carrier or
> extraneous sideband.
>
> NTSC TV video uses "vestigial sideband", but I don't know why - maybe
> they need more power down at the V. sync freq. or something.
>
> Cheers!
> Rich
>
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Author: Don BoweyDate: 17:35 06-07-07
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On 7/4/07 8:42 PM, in article 468c6838$0$4664$4c368faf@roadrunner.com, "Ron
Baker, Pluralitas!" <this@aint.me> wrote:
>
> "Don Bowey" <dbowey@comcast.net> wrote in message
> news:C2B16AE5.6D5BC%dbowey@comcast.net...
>> On 7/4/07 10:16 AM, in article 468bd5ad$0$16531$4c368faf@roadrunner.com,
>> "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>>
>>>
>>> "Don Bowey" <dbowey@comcast.net> wrote in message
>>> news:C2B1129D.6D573%dbowey@comcast.net...
>>>> On 7/4/07 7:52 AM, in article 468bb3c0$0$24780$4c368faf@roadrunner.com,
>>>> "Ron
>>>> Baker, Pluralitas!" <this@aint.me> wrote:
>>>
>>> <snip>
>>>
>>>>>
>>>>> cos(a) * cos(b) = 0.5 * (cos[a+b] + cos[a-b])
>>>>>
>>>>> Basically: multiplying two sine waves is
>>>>> the same as adding the (half amplitude)
>>>>> sum and difference frequencies.
>>>>
>>>> No, they aren't the same at all, they only appear to be the same
before
>>>> they are examined. The two sidebands will not have the correct phase
>>>> relationship.
>>>
>>> What do you mean? What is the "correct"
>>> relationship?
>>>
>>>>
>>>> One could, temporarily, mistake the added combination for a full
carrier
>>>> with independent sidebands, however.
>>>>
>>>>
>>>>
>>>>>
>>>>> (For sines it is
>>>>> sin(a) * sin(b) = 0.5 * (cos[a-b]-cos[a+b])
>>>>> = 0.5 * (sin[a-b+90degrees] -
sin[a+b+90degrees])
>>>>> = 0.5 * (sin[a-b+90degrees] +
sin[a+b-90degrees])
>>>>> )
>>>>>
>>>>> --
>>>>> rb
>>>>>
>>>>
>>>
>>>
>>
>> When AM is correctly accomplished (a single voiceband signal is modulated
>
> The questions I posed were not about AM. The
> subject could have been viewed as DSB but that
> wasn't the specific intent either.
You should take some time to more carefully frame your questions.
Do you understand that a DSB signal *is* AM?
Post your intention; it might help.
>
>> onto a carrier via a non-linear process), at an envelope detector the two
>> sidebands will be additive. But if you independe ntly place a carrier at
>> frequency ( c ), another carrier at ( c-1 khz) and another carrier at (c+
>> 1
>> kHz), the composite can look like an AM signal, but it is not, and only by
>> the most extreme luck will the sidebands be additive at the detector.
>> They
>> would probably cycle between additive and subtractive since they have no
>> real relationship and were not the result of amplitude modulation.
>>
>
>
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Author: Bob MyersDate: 17:37 06-07-07
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"Rich Grise" <rich@example.net> wrote in message
news:pan.2007.07.06.21.09.15.301781@example.net...
>> Sorry, John - while the ear's amplitude response IS nonlinear, it
>> does not act as a mixer. "Mixing" (multiplication) occurs when
>> a given nonlinear element (in electronics, a diode or transistor, for
>> example) is presented with two signals of different frequencies.
>> But the human ear doesn't work in that manner - there is no single
>> nonlinear element which is receiving more than one signal.
>
> Sure there is - the cochlea. (well, the whole middle ear/inner ear
> system.)
Nope - the point had to do with the inner workings of the cochlea.
You can't consider it as a single element, as the inner workings
consists of what are essentially thousands of very narrowband
individual sensors. There is no *single* nonlinear element in which
mixing of, say, the hypothetical 300 Hz and 400 Hz tones would
take place. John responded that the eardrum (typmanic membrane)
would act as such an element, but I would suggest that any mixing
which might in theory go on here is not a signifcant factor in how we
perceive such tones. The evidence for this is obvious - if presented
with, say, a pure 440 Hz "A" from a tuning fork, and the note from the
slightly flat instrument we're trying to tune (let's say 438 Hz), we DO
hear the 2 Hz "beat" that results from the interference (in the air)
between these two sounds. What we do NOT hear to any significant
degree is the 878 Hz sum that would be expected if there were much
contribution from a multiplicative ("mixing") process.
Bob M.
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Author: Bob MyersDate: 17:43 06-07-07
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"Rich Grise" <rich@example.net> wrote in message
news:pan.2007.07.06.21.01.00.435001@example.net...
> NTSC TV video uses "vestigial sideband", but I don't know why - maybe
> they need more power down at the V. sync freq. or something.
Nope - VSB was chosen because there simply wasn't enough room for
anything else. At the time, broadcast television was the most bandwidth-
hungry form of communications there was, at least in widespread use, and
was allocated (originally) 13 channels of 6 MHz each - a whopping 78 MHz
of spectrum allocated to a single service! (Remember, this was at a time
when
the only things living much above the VHF frequencies were such things as
radar.) You need more than 4 MHz of each channel just for the luminance
information, and that is at baseband - putting the video out as full DSB
would've meant at leadt 10 MHz-wide TV channels. But keeping the
carrier (and as a side effect, some of the lower sideband, which really
doesn't do much except force some oddities in the receiver's response
curve) kept the receiver design fairly simple.
Bob M.
>
> Cheers!
> Rich
>
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Author: Tommy TootlesDate: 22:15 06-07-07
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> Tommy Tootles wrote:
> Uh, John...respectfully, I have to wonder just who is on drugs.
>
> The original poster *ASKED* about *DSB* vs. AM
>
> YOU *ANSWERED* about *SSB*. Here is the correct answer...
>
> There are two broad types of DSB (double sideband) transmission:
>
> DSB-RC and DSB-SC, meaning BOTH sidebands are transmitted, but with
> either a (R)educed (C)arrier or a (S)urpressed (C)arrier. AM sends
> both sidebands and full carrier.
>
> Hope that answers the OP's question>
John Smith I wrote:
> Yeah, you just discovered that for all intents and purposes double
> sideband is am, and suppressed carrier is just like suppressed
> carrier am?
>
> Oh well, better late than never ...
>
> JS
What *I* discovered is -not- the point. And for all intents and
purposes, "AM" and DSB are two distinct (but certainly related) things.
Different hardware to create (balanced modulator for DSB vs high level
plate modulation for 'classic' AM), more power required for AM and
finally, back in the day, the FCC had -different- emission designators
for AM vs DSB. Now, if they were the same, why would you think the FCC
gave them -different- emission designators?
What IS the point is:
1) The original poster asked a question about "x".
2) You gave a half-assed answer to "y".
And then, you had the bare faced gall to accuse the original poster of
being on drugs!
Look at the good news--even though you gave a partially wrong answer to
a question that wasn't even asked, you at least resolved the issue of
which of the two of you is on drugs... ;-)
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Author: Roy LewallenDate: 22:25 06-07-07
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Ron Baker, Pluralitas! wrote:
>
> What is the difference between AM and DSB?
The two actually describe different properties, so a signal can be be
AM, DSB, neither, or both.
And here we run into some trouble between technical correctness and
common usage.
DSB stands for Double SideBand. Although I suppose an FM signal could be
called DSB because it has two *sets* of sidebands, and a narrowband FM
signal has only one significant pair like an AM signal, in my experience
the term DSB virtually always refers to a signal generated by amplitude
modulation.
AM is Amplitude Modulation. Straightforward amplitude modulation such as
done for AM broadcasting produces a carrier and two sidebands, or DSB
with carrier. Either the carrier or one sideband, or both, can be
suppressed. If you suppress the carrier (or don't generate it in the
first place), you get DSB with suppressed carrier, or DSB-SC. If you
suppress one sideband, you get SSB. Usually, but not always, the carrier
is also suppressed along with the one sideband, resulting in SSB-SC.
NTSC television transmission is VSB -- AM with a carrier and "vestigial"
or partially suppressed sideband and a full second sideband. Partial
suppression of the carrier is also done for some broadcast purposes.
So a commercial AM broadcast station broadcasts a signal that's both AM
and DSB. A typical amateur or military SSB transmission is AM but not
DSB. A QPSK signal is neither. And, as I mentioned, some signals like FM
could be considered DSB but not AM (although this isn't common usage).
In common amateur parlance, however,
"AM" usually means AM with two sidebands and carrier.
"DSB" usually means AM with two sidebands and suppressed carrier
"SSB" usually means AM with a single sideband and suppressed carrier
Roy Lewallen, W7EL
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Author: Ron Baker, Pluralitas!Date: 23:16 06-07-07
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"isw" <isw@witzend.com> wrote in message
news:isw-665A0A.12314506072007@newsgroups.comcast.net...
> In article <468dcc69$0$30690$4c368faf@roadrunner.com>,
> "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>
>> "isw" <isw@witzend.com> wrote in message
>> news:isw-0779A4.09400205072007@newsgroups.comcast.net...
>> > In article <468cf4d8$0$12241$4c368faf@roadrunner.com>,
>> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>> >
>> >> "isw" <isw@witzend.com> wrote in message
>> >> news:isw-A5E71F.00111305072007@newsgroups.comcast.net...
>> >> > In article <468bd109$0$31234$4c368faf@roadrunner.com>,
>> >> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>> >> >
>> >> >> "isw" <isw@witzend.com> wrote in message
>> >> >> news:isw-656111.22422003072007@newsgroups.comcast.net...
>> >> >>
>> >> >> <snip>
>> >> >>
>> >> >> >
>> >> >> > After you get done talking about modulation and
sidebands,
>> >> >> > somebody
>> >> >> > might want to take a stab at explaining why, if you tune
a
>> >> >> > receiver
>> >> >> > to
>> >> >> > the second harmonic (or any other harmonic) of a
modulated
>> >> >> > carrier
>> >> >> > (AM
>> >> >> > or FM; makes no difference), the audio comes out
sounding exactly
>> >> >> > as
>> >> >> > it
>> >> >> > does if you tune to the fundamental? That is, while the
second
>> >> >> > harmonic
>> >> >> > of the carrier is twice the frequency of the
fundamental, the
>> >> >> > sidebands
>> >> >> > of the second harmonic are *not* located at twice the
frequencies
>> >> >> > of
>> >> >> > the
>> >> >> > sidebands of the fundamental, but rather precisely as
far from
>> >> >> > the
>> >> >> > second harmonic of the carrier as they are from the
fundamental.
>> >> >> >
>> >> >> > Isaac
>> >> >>
>> >> >> Whoa. I thought you were smoking something but
>> >> >> my curiosity is piqued.
>> >> >> I tried shortwave stations and heard no harmonics.
>> >> >> But that could be blamed on propagation.
>> >> >> There is an AM station here at 1.21 MHz that is s9+20dB.
>> >> >> Tuned to 2.42 MHz. Nothing. Generally the lowest
>> >> >> harmonics should be strongest. Then I remembered
>> >> >> that many types of non-linearity favor odd harmonics.
>> >> >> Tuned to 3.63 MHz. Holy harmonics, batman.
>> >> >> There it was and the modulation was not multiplied!
>> >> >> Voices sounded normal pitch. When music was
>> >> >> played the pitch was the same on the original and
>> >> >> the harmonic.
>> >> >>
>> >> >> One clue is that the effect comes and goes rather
>> >> >> abruptly. It seems to switch in and out rather
>> >> >> than fade in an out. Maybe the coming and going
>> >> >> is from switching the audio material source?
>> >> >>
>> >> >> This is strange. If a signal is multiplied then the
sidebands
>> >> >> should be multiplied too.
>> >> >> Maybe the carrier generator is generating a
>> >> >> harmonic and the harmonic is also being modulated
>> >> >> with the normal audio in the modulator.
>> >> >> But then that signal would have to make it through
>> >> >> the power amp and the antenna. Possible, but
>> >> >> why would it come and go?
>> >> >> Strange.
>> >> >
>> >> > Hint: Modulation is a "rate effect".
>> >> >
>> >> > Isaac
>> >>
>> >> Please elaborate. I am so eager to hear the
>> >> explanation.
>> >
>> > The sidebands only show up because there is a rate of change of the
>> > carrier -- amplitude or frequency/phase, depending; they aren't
>> > separate, stand-alone signals. Since the rate of change of the
>> > amplitude
>> > of the second harmonic is identical to that of the fundamental, the
>> > sidebands show up the same distance away, not twice as distant.
>> >
>> > Isaac
>>
>> That doesn't explain why the effect would come and go.
>
> I don't understand what effect you're referring to here.
When I was tuned to the 3rd harmonic sometimes
I would hear it and sometimes not.
It would come and go rather abruptly. It didn't seem
to be gradual fading.
>
>> But once again you have surprised me.
>> Your explanation of the non-multiplied sidebands,
>> while qualitative and incomplete, is sound.
>
> I'm a physicist/engineer, and have been for a long time. I have always
The you understand Fourier transforms and convolution.
> maintained that if the only way one can understand physical phenomena is
> by solving the differential equations that describe them, then one does
> not understand the phenomena at all. If you can express a thing in
> words, such that a person with little mathematical ability can
> understand what's going on, *then* you have a good grasp of it.
I too am a fan of the intuitive approach.
But I find that theory is often irreplacable.
>
>> It looks to me that the tripple frequency sidebands
>> are there but the basic sidebands dominate.
>> Especially at lower modulation indexes.
>
> I don't understand what you are saying here either. And in my
> experience, the term "modulation index" is more likely to show up in a
> discussion of FM or PM than AM; are you using it interchangeably with
> "modulation percentage"?
http://en.wikipedia.org/wiki/Amplitude_modulation#Modulation_index
>
> Isaac
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Author: iswDate: 23:21 06-07-07
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In article <C2B3FA99.6DC3F%dbowey@comcast.net>,
Don Bowey <dbowey@comcast.net> wrote:
> On 7/6/07 12:15 PM, in article
> isw-C7349C.12150506072007@newsgroups.comcast.net, "isw"
<isw@witzend.com>
> wrote:
>
> > In article <C2B3C3A0.6DC14%dbowey@comcast.net>,
> > Don Bowey <dbowey@comcast.net> wrote:
> >
> >> On 7/6/07 9:36 AM, in article
> >> isw-F124E8.09362406072007@newsgroups.comcast.net, "isw"
<isw@witzend.com>
> >> wrote:
> >>
> >>> In article <C2B399E5.6DB60%dbowey@comcast.net>,
> >>> Don Bowey <dbowey@comcast.net> wrote:
> >>>
> >>>> On 7/5/07 10:27 PM, in article
468dd266$0$20597$4c368faf@roadrunner.com,
> >>>> "Ron Baker, Pluralitas!" <this@aint.me> wrote:
> >>>>
> >>>>>
> >>>>> "Don Bowey" <dbowey@comcast.net> wrote in
message
> >>>>> news:C2B25726.6D728%dbowey@comcast.net...
> >>>>>> On 7/5/07 12:00 AM, in article
> >>>>>> 468c96c3$0$16567$4c368faf@roadrunner.com,
> >>>>>> "Ron Baker, Pluralitas!" <this@aint.me>
wrote:
> >>>>>>
> >>>>>>>
> >>>>>>> "Don Bowey" <dbowey@comcast.net> wrote
in message
> >>>>>>> news:C2B1DFAF.6D6BD%dbowey@comcast.net...
> >>>>>>>> On 7/4/07 8:42 PM, in article
> >>>>>>>> 468c6838$0$4664$4c368faf@roadrunner.com,
> >>>>>>>> "Ron
> >>>>>>>> Baker, Pluralitas!" <this@aint.me>
wrote:
> >>>>>>>>
> >>>>>>>>>
> >>>>>>>>> "Don Bowey"
<dbowey@comcast.net> wrote in message
> >>>>>>>>> news:C2B16AE5.6D5BC%dbowey@comcast.net...
> >>>>>>>>>> On 7/4/07 10:16 AM, in article
> >>>>>>>>>> 468bd5ad$0$16531$4c368faf@roadrunner.com,
> >>>>>>>>>> "Ron Baker, Pluralitas!"
<this@aint.me> wrote:
> >>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> "Don Bowey"
<dbowey@comcast.net> wrote in message
> >>>>>>>>>>>
news:C2B1129D.6D573%dbowey@comcast.net...
> >>>>>>>>>>>> On 7/4/07 7:52 AM, in article
> >>>>>>>>>>>>
468bb3c0$0$24780$4c368faf@roadrunner.com,
> >>>>>>>>>>>> "Ron
> >>>>>>>>>>>> Baker, Pluralitas!"
<this@aint.me> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>> <snip>
> >>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> cos(a) * cos(b) = 0.5 *
(cos[a+b] + cos[a-b])
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Basically: multiplying two
sine waves is
> >>>>>>>>>>>>> the same as adding the (half
amplitude)
> >>>>>>>>>>>>> sum and difference
frequencies.
> >>>>>>>>>>>>
> >>>>>>>>>>>> No, they aren't the same at all,
they only appear to be the
> >>>>>>>>>>>> same
> >>>>>>>>>>>> before
> >>>>>>>>>>>> they are examined. The two
sidebands will not have the correct
> >>>>>>>>>>>> phase
> >>>>>>>>>>>> relationship.
> >>>>>>>>>>>
> >>>>>>>>>>> What do you mean? What is the
"correct"
> >>>>>>>>>>> relationship?
> >>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>> One could, temporarily, mistake
the added combination for a full
> >>>>>>>>>>>> carrier
> >>>>>>>>>>>> with independent sidebands,
however.
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> (For sines it is
> >>>>>>>>>>>>> sin(a) * sin(b) = 0.5 *
(cos[a-b]-cos[a+b])
> >>>>>>>>>>>>> = 0.5 *
(sin[a-b+90degrees] -
> >>>>>>>>>>>>> sin[a+b+90degrees])
> >>>>>>>>>>>>> = 0.5 *
(sin[a-b+90degrees] +
> >>>>>>>>>>>>> sin[a+b-90degrees])
> >>>>>>>>>>>>> )
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> --
> >>>>>>>>>>>>> rb
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> When AM is correctly accomplished (a
single voiceband signal is
> >>>>>>>>>> modulated
> >>>>>>>>>
> >>>>>>>>> The questions I posed were not about AM. The
> >>>>>>>>> subject could have been viewed as DSB but that
> >>>>>>>>> wasn't the specific intent either.
> >>>>>>>>
> >>>>>>>> What was the subject of your question?
> >>>>>>>
> >>>>>>> Copying from my original post:
> >>>>>>>
> >>>>>>> Suppose you have a 1 MHz sine wave whose amplitude
> >>>>>>> is multiplied by a 0.1 MHz sine wave.
> >>>>>>> What would it look like on an oscilloscope?
> >>>>>>> What would it look like on a spectrum analyzer?
> >>>>>>>
> >>>>>>> Then suppose you have a 1.1 MHz sine wave added
> >>>>>>> to a 0.9 MHz sine wave.
> >>>>>>> What would that look like on an oscilloscope?
> >>>>>>> What would that look like on a spectrum analyzer?
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>> So the first (1) is an AM question and the second (2) is a
non-AM
> >>>>>> question......
> >>>>>
> >>>>> What is the difference between AM and DSB?
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>> AM is a process. DSB (double sideband), with carrier, is it's
most
> >>>> simple
> >>>> result. DSB without carrier (suppressed carrier dsb) requires
using, at
> >>>> least, a balanced mixer as the AM multiplier.
> >>>
> >>> And requires, for proper reception, that a carrier be recreated at the
> >>> receiver which has not only the amplitude of the original,
> >>
> >> There is no need at all to match the carrier amplitude of the original
> >> signal. You can use an excessively high carrier injection amplitude with
> >> no
> >> detrimental affect, but if the injected carrier is too little, the
> >> demodulated signal will be over modulated and sound distorted.
> >>
> >>> but also its exact phase.
> >>
> >> Exact, not required. The closer the better, however.
> >
> > Well, OK, the phase must at least bear a constant relationship to the
> > one that created the signal. If you inject a carrier that has a
> > quadrature relationship to the one that created the DSB signal, the
> > output will be PM (phase modulation). In between zero and 90 degrees,
> > the output is a combination of the two. If the injected carrier is not
> > at precisely the proper frequency, the phase will roll around and the
> > output will be unintelligible.
>
> Not unintelligible.... Donald Duckish.
I think you are confusing *single* sideband, for which that is correct,
and *double* sideband (which we were discussing), for which it is not
true.
> On a more practical side, however, most receiver filters for ssb will
> essentially remove one sideband if there are two, and can attenuate a
> carrier so the local product detector can do it's job resulting in improved
> receiving conditions. But this is more advanced than the Ops questions.
Doing it that way will work, but it's not "fair", because you are not
actually demodulating a DSB signal (which was the subject of the
discussion).
Isaac
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Author: iswDate: 23:26 06-07-07
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In article <138tudplgcuuq26@corp.supernews.com>,
Roy Lewallen <w7el@eznec.com> wrote:
> Ron Baker, Pluralitas! wrote:
> >
> > What is the difference between AM and DSB?
>
> The two actually describe different properties, so a signal can be be
> AM, DSB, neither, or both.
>
> And here we run into some trouble between technical correctness and
> common usage.
>
> DSB stands for Double SideBand. Although I suppose an FM signal could be
> called DSB because it has two *sets* of sidebands
Um, actually, it has a lot more than that. A carrier FM modulated by a
single sine wave has an infinite number of sidebands. If the modulating
signal is more complex, then things get really complicated.
Isaac
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Author: Ron Baker, Pluralitas!Date: 23:43 06-07-07
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"Tommy Tootles" <tommy@toot.com> wrote in message
news:cHCji.20841$RX.6448@newssvr11.news.prodigy.net...
>
>> Tommy Tootles wrote:
>
>> Uh, John...respectfully, I have to wonder just who is on drugs.
>>
>> The original poster *ASKED* about *DSB* vs. AM
>>
>> YOU *ANSWERED* about *SSB*. Here is the correct answer...
>>
>> There are two broad types of DSB (double sideband) transmission:
>>
>> DSB-RC and DSB-SC, meaning BOTH sidebands are transmitted, but with
>> either a (R)educed (C)arrier or a (S)urpressed (C)arrier. AM sends
>> both sidebands and full carrier.
>>
>> Hope that answers the OP's question>
>
> John Smith I wrote:
>
>> Yeah, you just discovered that for all intents and purposes double
>> sideband is am, and suppressed carrier is just like suppressed
>> carrier am?
>>
>> Oh well, better late than never ...
>>
>> JS
>
> What *I* discovered is -not- the point. And for all intents and purposes,
> "AM" and DSB are two distinct (but certainly related) things. Different
> hardware to create (balanced modulator for DSB vs high level plate
> modulation for 'classic' AM), more power required for AM and finally, back
> in the day, the FCC had -different- emission designators for AM vs DSB.
> Now, if they were the same, why would you think the FCC gave
> them -different- emission designators?
You make good, relevant points there.
>
> What IS the point is:
>
> 1) The original poster asked a question about "x".
>
> 2) You gave a half-assed answer to "y".
>
> And then, you had the bare faced gall to accuse the original poster of
> being on drugs!
>
> Look at the good news--even though you gave a partially wrong answer to a
> question that wasn't even asked, you at least resolved the issue of which
> of the two of you is on drugs... ;-)
>
I would agree with the above also, but don't
wish to be provocative. ;)
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Author: John Smith IDate: 00:09 07-07-07
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Tommy Tootles wrote:
> [chit]
Hmmm, why be a half-assed-idiot when you can be a full fledged one? I
see your point ...
Point is, DSB IS AM, you can receive it on any am receiver, get a life,
get off drugs and certainly get off the news groups, you are ill suited
to be here ...
JS
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Author: Ron Baker, Pluralitas!Date: 00:23 07-07-07
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"isw" <isw@witzend.com> wrote in message
news:isw-67F596.12192706072007@newsgroups.comcast.net...
> In article <468dcf2b$0$16588$4c368faf@roadrunner.com>,
> "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>
>> "isw" <isw@witzend.com> wrote in message
>> news:isw-15D472.09430705072007@newsgroups.comcast.net...
>> > In article <468cf7f7$0$16602$4c368faf@roadrunner.com>,
>> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>> >
>> >> "isw" <isw@witzend.com> wrote in message
>> >> news:isw-FB6C92.00093805072007@newsgroups.comcast.net...
>> >> > In article <468bdadd$0$20558$4c368faf@roadrunner.com>,
>> >> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>> >>
>> >> <snip>
>> >>
>> >> >> >>
>> >> >> >> While it might not be obvious, the two cases I
>> >> >> >> described are basically identical. And this
>> >> >> >> situation occurs in real life, i.e. in radio
signals,
>> >> >> >> oceanography, and guitar tuning.
>> >> >> >
>> >> >> > The beat you hear during guitar tuning is not
modulation; there
>> >> >> > is
>> >> >> > no
>> >> >> > non-linear process involved (i.e. no multiplication).
>> >> >> >
>> >> >> > Isaac
>> >> >>
>> >> >> In short, the human auditory system is not linear.
>> >> >> It has a finite resolution bandwidth. It can't resolve
>> >> >> two tones separted by a few Hertz as two separate tones.
>> >> >> (But if they are separted by 100 Hz they can easily
>> >> >> be separated without hearing a beat.)
>> >> >
>> >> > Two tones 100 Hz apart may or may not be perceived separately;
>> >> > depends
>> >> > on a lot of other factors. MP3 encoding, for example, depends on
the
>> >> > ear's (very predictable) inability to discern tones
"nearby" to
>> >> > other,
>> >> > louder ones.
>> >>
>> >> I'll remember that the next time I'm tuning
>> >> an MP3 guitar.
>> >>
>> >> >
>> >> >> The same affect can be seen on a spectrum analyzer.
>> >> >> Give it two frequencies separated by 1 Hz. Set the
>> >> >> resolution bandwidth to 10 Hz. You'll see the peak
>> >> >> rise and fall at 1 Hz.
>> >> >
>> >> > Yup. And the spectrum analyzer is (hopefully) a very linear
system,
>> >> > producing no intermodulation of its own.
>> >> >
>> >> > Isaac
>> >>
>> >> What does a spectrum analyzer use to arive at
>> >> amplitude values? An envelope detector?
>> >> Is that linear?
>> >
>> > I'm sure there's more than one way to do it, but I feel certain that
>> > any
>>
>> Which of them is linear?
>
> A well-designed filter running into a bolometer would be. You can make
> the filter narrow enough to respond to only one frequency component at
Any real spectrum analyzer has a lower limit
to its resolution bandwidth, does it not?
The resolution bandwidth of the human ear is non-zero
and not really adjustable, is it not?
> the time, and a bolometer just turns the signal power into heat; nothing
> nonlinear there...
Really?
You said you are a physicist/engineer.
What does "linear" mean?
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Author: Don BoweyDate: 00:35 07-07-07
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On 7/6/07 8:21 PM, in article
isw-C85095.20210406072007@newsgroups.comcast.net, "isw"
<isw@witzend.com>
wrote:
> In article <C2B3FA99.6DC3F%dbowey@comcast.net>,
> Don Bowey <dbowey@comcast.net> wrote:
>
>> On 7/6/07 12:15 PM, in article
>> isw-C7349C.12150506072007@newsgroups.comcast.net, "isw"
<isw@witzend.com>
>> wrote:
>>
>>> In article <C2B3C3A0.6DC14%dbowey@comcast.net>,
>>> Don Bowey <dbowey@comcast.net> wrote:
>>>
>>>> On 7/6/07 9:36 AM, in article
>>>> isw-F124E8.09362406072007@newsgroups.comcast.net, "isw"
<isw@witzend.com>
>>>> wrote:
>>>>
>>>>> In article <C2B399E5.6DB60%dbowey@comcast.net>,
>>>>> Don Bowey <dbowey@comcast.net> wrote:
>>>>>
>>>>>> On 7/5/07 10:27 PM, in article
468dd266$0$20597$4c368faf@roadrunner.com,
>>>>>> "Ron Baker, Pluralitas!" <this@aint.me>
wrote:
>>>>>>
>>>>>>>
>>>>>>> "Don Bowey" <dbowey@comcast.net> wrote in
message
>>>>>>> news:C2B25726.6D728%dbowey@comcast.net...
>>>>>>>> On 7/5/07 12:00 AM, in article
>>>>>>>> 468c96c3$0$16567$4c368faf@roadrunner.com,
>>>>>>>> "Ron Baker, Pluralitas!"
<this@aint.me> wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> "Don Bowey" <dbowey@comcast.net>
wrote in message
>>>>>>>>> news:C2B1DFAF.6D6BD%dbowey@comcast.net...
>>>>>>>>>> On 7/4/07 8:42 PM, in article
>>>>>>>>>> 468c6838$0$4664$4c368faf@roadrunner.com,
>>>>>>>>>> "Ron
>>>>>>>>>> Baker, Pluralitas!"
<this@aint.me> wrote:
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> "Don Bowey"
<dbowey@comcast.net> wrote in message
>>>>>>>>>>> news:C2B16AE5.6D5BC%dbowey@comcast.net...
>>>>>>>>>>>> On 7/4/07 10:16 AM, in article
>>>>>>>>>>>>
468bd5ad$0$16531$4c368faf@roadrunner.com,
>>>>>>>>>>>> "Ron Baker, Pluralitas!"
<this@aint.me> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> "Don Bowey"
<dbowey@comcast.net> wrote in message
>>>>>>>>>>>>>
news:C2B1129D.6D573%dbowey@comcast.net...
>>>>>>>>>>>>>> On 7/4/07 7:52 AM, in article
>>>>>>>>>>>>>>
468bb3c0$0$24780$4c368faf@roadrunner.com,
>>>>>>>>>>>>>> "Ron
>>>>>>>>>>>>>> Baker, Pluralitas!"
<this@aint.me> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> <snip>
>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> cos(a) * cos(b) = 0.5 *
(cos[a+b] + cos[a-b])
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Basically: multiplying two
sine waves is
>>>>>>>>>>>>>>> the same as adding the
(half amplitude)
>>>>>>>>>>>>>>> sum and difference
frequencies.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> No, they aren't the same at
all, they only appear to be the
>>>>>>>>>>>>>> same
>>>>>>>>>>>>>> before
>>>>>>>>>>>>>> they are examined. The two
sidebands will not have the correct
>>>>>>>>>>>>>> phase
>>>>>>>>>>>>>> relationship.
>>>>>>>>>>>>>
>>>>>>>>>>>>> What do you mean? What is the
"correct"
>>>>>>>>>>>>> relationship?
>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> One could, temporarily, mistake
the added combination for a full
>>>>>>>>>>>>>> carrier
>>>>>>>>>>>>>> with independent sidebands,
however.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> (For sines it is
>>>>>>>>>>>>>>> sin(a) * sin(b) = 0.5 *
(cos[a-b]-cos[a+b])
>>>>>>>>>>>>>>> = 0.5 *
(sin[a-b+90degrees] -
>>>>>>>>>>>>>>> sin[a+b+90degrees])
>>>>>>>>>>>>>>> = 0.5 *
(sin[a-b+90degrees] +
>>>>>>>>>>>>>>> sin[a+b-90degrees])
>>>>>>>>>>>>>>> )
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> --
>>>>>>>>>>>>>>> rb
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> When AM is correctly accomplished (a
single voiceband signal is
>>>>>>>>>>>> modulated
>>>>>>>>>>>
>>>>>>>>>>> The questions I posed were not about AM.
The
>>>>>>>>>>> subject could have been viewed as DSB but
that
>>>>>>>>>>> wasn't the specific intent either.
>>>>>>>>>>
>>>>>>>>>> What was the subject of your question?
>>>>>>>>>
>>>>>>>>> Copying from my original post:
>>>>>>>>>
>>>>>>>>> Suppose you have a 1 MHz sine wave whose amplitude
>>>>>>>>> is multiplied by a 0.1 MHz sine wave.
>>>>>>>>> What would it look like on an oscilloscope?
>>>>>>>>> What would it look like on a spectrum analyzer?
>>>>>>>>>
>>>>>>>>> Then suppose you have a 1.1 MHz sine wave added
>>>>>>>>> to a 0.9 MHz sine wave.
>>>>>>>>> What would that look like on an oscilloscope?
>>>>>>>>> What would that look like on a spectrum analyzer?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> So the first (1) is an AM question and the second (2)
is a non-AM
>>>>>>>> question......
>>>>>>>
>>>>>>> What is the difference between AM and DSB?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> AM is a process. DSB (double sideband), with carrier, is it's
most
>>>>>> simple
>>>>>> result. DSB without carrier (suppressed carrier dsb) requires
using, at
>>>>>> least, a balanced mixer as the AM multiplier.
>>>>>
>>>>> And requires, for proper reception, that a carrier be recreated at
the
>>>>> receiver which has not only the amplitude of the original,
>>>>
>>>> There is no need at all to match the carrier amplitude of the original
>>>> signal. You can use an excessively high carrier injection amplitude
with
>>>> no
>>>> detrimental affect, but if the injected carrier is too little, the
>>>> demodulated signal will be over modulated and sound distorted.
>>>>
>>>>> but also its exact phase.
>>>>
>>>> Exact, not required. The closer the better, however.
>>>
>>> Well, OK, the phase must at least bear a constant relationship to the
>>> one that created the signal. If you inject a carrier that has a
>>> quadrature relationship to the one that created the DSB signal, the
>>> output will be PM (phase modulation). In between zero and 90 degrees,
>>> the output is a combination of the two. If the injected carrier is not
>>> at precisely the proper frequency, the phase will roll around and the
>>> output will be unintelligible.
>>
>> Not unintelligible.... Donald Duckish.
>
> I think you are confusing *single* sideband, for which that is correct,
> and *double* sideband (which we were discussing), for which it is not
> true.
What do you propose the term be for the output of a slightly de-tuned
demodulator of a DSB sans carrier, signal?
>
>> On a more practical side, however, most receiver filters for ssb will
>> essentially remove one sideband if there are two, and can attenuate a
>> carrier so the local product detector can do it's job resulting in improved
>> receiving conditions. But this is more advanced than the Ops questions.
>
> Doing it that way will work, but it's not "fair", because you are not
> actually demodulating a DSB signal (which was the subject of the
> discussion).
I don't believe the OP stated whether the DSB signal was with or without
carrier. If without carrier, demodulation is certainly called for. If with
carrier, it hardly merits discussion.
>
> Isaac
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Author: Don BoweyDate: 00:55 07-07-07
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On 7/6/07 7:15 PM, in article
cHCji.20841$RX.6448@newssvr11.news.prodigy.net, "Tommy Tootles"
<tommy@toot.com> wrote:
>
>> Tommy Tootles wrote:
>
>> Uh, John...respectfully, I have to wonder just who is on drugs.
>>
>> The original poster *ASKED* about *DSB* vs. AM
>>
>> YOU *ANSWERED* about *SSB*. Here is the correct answer...
>>
>> There are two broad types of DSB (double sideband) transmission:
>>
>> DSB-RC and DSB-SC, meaning BOTH sidebands are transmitted, but with
>> either a (R)educed (C)arrier or a (S)urpressed (C)arrier. AM sends
>> both sidebands and full carrier.
>>
>> Hope that answers the OP's question>
>
> John Smith I wrote:
>
>> Yeah, you just discovered that for all intents and purposes double
>> sideband is am, and suppressed carrier is just like suppressed
>> carrier am?
>>
>> Oh well, better late than never ...
>>
>> JS
>
> What *I* discovered is -not- the point. And for all intents and
> purposes, "AM" and DSB are two distinct (but certainly related) things
> Different hardware to create (balanced modulator for DSB vs high level
> plate modulation for 'classic' AM), more power required for AM and
> finally, back in the day, the FCC had -different- emission designators
> for AM vs DSB. Now, if they were the same, why would you think the FCC
> gave them -different- emission designators?
You are confusing FCC use codes and technical processes. Do you believe the
FCC Designator of "J" for ssbsc says HOW to do it. Not for an instant.
>
> What IS the point is:
>
> 1) The original poster asked a question about "x".
>
> 2) You gave a half-assed answer to "y".
>
> And then, you had the bare faced gall to accuse the original poster of
> being on drugs!
>
> Look at the good news--even though you gave a partially wrong answer to
> a question that wasn't even asked, you at least resolved the issue of
> which of the two of you is on drugs... ;-)
>
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Author: Roy LewallenDate: 01:47 07-07-07
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isw wrote:
> In article <138tudplgcuuq26@corp.supernews.com>,
> Roy Lewallen <w7el@eznec.com> wrote:
>>. . .
>> DSB stands for Double SideBand. Although I suppose an FM signal could be
>> called DSB because it has two *sets* of sidebands
>
> Um, actually, it has a lot more than that. A carrier FM modulated by a
> single sine wave has an infinite number of sidebands. If the modulating
> signal is more complex, then things get really complicated.
Sometimes it's difficult to communicate. A "set" can consist of more
than one. In the case of FM, each set includes an infinite number,
although only a limited number contain a significant amount of energy.
The remainder can be ignored without any substantial degradation of
received signal quality. This is true regardless of the complexity of
the modulating signal.
Roy Lewallen, W7EL
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Author: Tommy TootlesDate: 10:08 07-07-07
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John 'Half-way' Smith I wrote:
> Point is, DSB IS AM, you can receive it on any am receiver,
Well, another of your half-assed answers. You can receive *DSB-RC* on
any AM receiver because the carrier, although reduced, allows reception
via a simple envelope detector. On the other hand, DSB-SC requires a
product detector, a coherent detector or a Costas Loop, detectors NOT
available on "any" AM receiver. So, yet another "half-an-answer" on
your
part.
> get off drugs and certainly get off the news groups, you are ill suited
> to be here ...
A person asks about "a", *you* give them an answer to "b", then
accuse
-them- of being on drugs and say -they- are ill-suited to be here. May I
suggest that you look in the mirror if you are concerned about
suitability...
Your thought processes and (lack of) logic seem quite odd. Odd enough to
question who the drug user might be.
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Author: Tommy TootlesDate: 10:10 07-07-07
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Tommy Tootles wrote:
>> What *I* discovered is -not- the point. And for all intents and
>> purposes, "AM" and DSB are two distinct (but certainly related)
things
> > Different hardware to create (balanced modulator for DSB vs high level
>> plate modulation for 'classic' AM), more power required for AM and
>> finally, back in the day, the FCC had -different- emission designators
>> for AM vs DSB. Now, if they were the same, why would you think the FCC
>> gave them -different- emission designators?
Don Bowey wrote:
> You are confusing FCC use codes and technical processes. Do you believe the
> FCC Designator of "J" for ssbsc says HOW to do it. Not for an instant.
Don,
I believe you are misinterpreting or misunderstanding what I wrote--and
my apologies if I wasn't clear enough in my statement above. Let me
clarify...
I was NOT confusing FCC use codes and technical processes. I made two
separate, *stand-alone* statements:
Statement 1 (re: technical processes)--low level balanced modulator
vs.high level plate modulation. A true statement.
Statement 2 (re: FCC emission designators)-- that the FCC had different
emission designators for AM, DSB-SC and DSB-RC *BACK IN THE DAY*. A true
statement.
By "back in the day", I was referring to the late 50s and early 60s when
sideband (of all varieties) was just coming in to usage in the ham radio
world. Everything was so new that SSB hadn't yet emerged as the mode of
choice. Some rigs back then were capable of both SSB and the two flavors
of DSB. The FCC (AT THAT TIME--"back in the day") had designators for
all of the above. The FCC emission designators have changed at least
once (and maybe more) since those days.
In any event, they were meant to be two stand-alone statements, with
-no- implication intended that the designator tells how to do it. So,
either you need to read more carefully, I need to write more carefully
or all of the above... :-)
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Author: iswDate: 13:29 07-07-07
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In article <C2B4663F.6E4EC%dbowey@comcast.net>,
Don Bowey <dbowey@comcast.net> wrote:
--bunch of stuff trimmed off--
> >>> Well, OK, the phase must at least bear a constant relationship to the
> >>> one that created the signal. If you inject a carrier that has a
> >>> quadrature relationship to the one that created the DSB signal, the
> >>> output will be PM (phase modulation). In between zero and 90 degrees,
> >>> the output is a combination of the two. If the injected carrier is not
> >>> at precisely the proper frequency, the phase will roll around and the
> >>> output will be unintelligible.
> >>
> >> Not unintelligible.... Donald Duckish.
> >
> > I think you are confusing *single* sideband, for which that is correct,
> > and *double* sideband (which we were discussing), for which it is not
> > true.
>
> What do you propose the term be for the output of a slightly de-tuned
> demodulator of a DSB sans carrier, signal?
I'm not sure it has a name. The output is constantly swishing around
between AM and PM, at a rate determined by the frequency error of the
reinjected carrier. Most detectors will have a problem with it.
Isaac
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Author: iswDate: 13:43 07-07-07
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In article <468f14f2$0$16528$4c368faf@roadrunner.com>,
"Ron Baker, Pluralitas!" <this@aint.me> wrote:
> "isw" <isw@witzend.com> wrote in message
> news:isw-67F596.12192706072007@newsgroups.comcast.net...
> > In article <468dcf2b$0$16588$4c368faf@roadrunner.com>,
> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
> >
> >> "isw" <isw@witzend.com> wrote in message
> >> news:isw-15D472.09430705072007@newsgroups.comcast.net...
> >> > In article <468cf7f7$0$16602$4c368faf@roadrunner.com>,
> >> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
> >> >
> >> >> "isw" <isw@witzend.com> wrote in message
> >> >> news:isw-FB6C92.00093805072007@newsgroups.comcast.net...
> >> >> > In article <468bdadd$0$20558$4c368faf@roadrunner.com>,
> >> >> > "Ron Baker, Pluralitas!" <this@aint.me>
wrote:
> >> >>
> >> >> <snip>
> >> >>
> >> >> >> >>
> >> >> >> >> While it might not be obvious, the two cases I
> >> >> >> >> described are basically identical. And this
> >> >> >> >> situation occurs in real life, i.e. in radio
signals,
> >> >> >> >> oceanography, and guitar tuning.
> >> >> >> >
> >> >> >> > The beat you hear during guitar tuning is not
modulation; there
> >> >> >> > is
> >> >> >> > no
> >> >> >> > non-linear process involved (i.e. no
multiplication).
> >> >> >> >
> >> >> >> > Isaac
> >> >> >>
> >> >> >> In short, the human auditory system is not linear.
> >> >> >> It has a finite resolution bandwidth. It can't resolve
> >> >> >> two tones separted by a few Hertz as two separate tones.
> >> >> >> (But if they are separted by 100 Hz they can easily
> >> >> >> be separated without hearing a beat.)
> >> >> >
> >> >> > Two tones 100 Hz apart may or may not be perceived
separately;
> >> >> > depends
> >> >> > on a lot of other factors. MP3 encoding, for example,
depends on the
> >> >> > ear's (very predictable) inability to discern tones
"nearby" to
> >> >> > other,
> >> >> > louder ones.
> >> >>
> >> >> I'll remember that the next time I'm tuning
> >> >> an MP3 guitar.
> >> >>
> >> >> >
> >> >> >> The same affect can be seen on a spectrum analyzer.
> >> >> >> Give it two frequencies separated by 1 Hz. Set the
> >> >> >> resolution bandwidth to 10 Hz. You'll see the peak
> >> >> >> rise and fall at 1 Hz.
> >> >> >
> >> >> > Yup. And the spectrum analyzer is (hopefully) a very linear
system,
> >> >> > producing no intermodulation of its own.
> >> >> >
> >> >> > Isaac
> >> >>
> >> >> What does a spectrum analyzer use to arive at
> >> >> amplitude values? An envelope detector?
> >> >> Is that linear?
> >> >
> >> > I'm sure there's more than one way to do it, but I feel certain that
> >> > any
> >>
> >> Which of them is linear?
> >
> > A well-designed filter running into a bolometer would be. You can make
> > the filter narrow enough to respond to only one frequency component at
>
> Any real spectrum analyzer has a lower limit
> to its resolution bandwidth, does it not?
> The resolution bandwidth of the human ear is non-zero
> and not really adjustable, is it not?
>
> > the time, and a bolometer just turns the signal power into heat; nothing
> > nonlinear there...
>
> Really?
> You said you are a physicist/engineer.
> What does "linear" mean?
Let's not get too far off the subject here. We were discussing whether
the "tuning beat" that you use to tune a musical instrument involved a
nonlinear process (ie. "modulation"). I said that it does not, and that
it could be detected by instrumentation which was proveably linear (i.e.
not "perfectly" linear, because that's not required, but certainly
linear enough to discount the requirement for "modulation").
That's all.
Isaac
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Author: Ron Baker, Pluralitas!Date: 15:23 07-07-07
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"isw" <isw@witzend.com> wrote in message
news:isw-BAF518.10432307072007@newsgroups.comcast.net...
> In article <468f14f2$0$16528$4c368faf@roadrunner.com>,
> "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>
>> "isw" <isw@witzend.com> wrote in message
>> news:isw-67F596.12192706072007@newsgroups.comcast.net...
>> > In article <468dcf2b$0$16588$4c368faf@roadrunner.com>,
>> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>> >
>> >> "isw" <isw@witzend.com> wrote in message
>> >> news:isw-15D472.09430705072007@newsgroups.comcast.net...
>> >> > In article <468cf7f7$0$16602$4c368faf@roadrunner.com>,
>> >> > "Ron Baker, Pluralitas!" <this@aint.me> wrote:
>> >> >
>> >> >> "isw" <isw@witzend.com> wrote in message
>> >> >> news:isw-FB6C92.00093805072007@newsgroups.comcast.net...
>> >> >> > In article
<468bdadd$0$20558$4c368faf@roadrunner.com>,
>> >> >> > "Ron Baker, Pluralitas!"
<this@aint.me> wrote:
>> >> >>
>> >> >> <snip>
>> >> >>
>> >> >> >> >>
>> >> >> >> >> While it might not be obvious, the two
cases I
>> >> >> >> >> described are basically identical. And
this
>> >> >> >> >> situation occurs in real life, i.e. in
radio signals,
>> >> >> >> >> oceanography, and guitar tuning.
>> >> >> >> >
>> >> >> >> > The beat you hear during guitar tuning is not
modulation;
>> >> >> >> > there
>> >> >> >> > is
>> >> >> >> > no
>> >> >> >> > non-linear process involved (i.e. no
multiplication).
>> >> >> >> >
>> >> >> >> > Isaac
>> >> >> >>
>> >> >> >> In short, the human auditory system is not linear.
>> >> >> >> It has a finite resolution bandwidth. It can't
resolve
>> >> >> >> two tones separted by a few Hertz as two separate
tones.
>> >> >> >> (But if they are separted by 100 Hz they can easily
>> >> >> >> be separated without hearing a beat.)
>> >> >> >
>> >> >> > Two tones 100 Hz apart may or may not be perceived
separately;
>> >> >> > depends
>> >> >> > on a lot of other factors. MP3 encoding, for example,
depends on
>> >> >> > the
>> >> >> > ear's (very predictable) inability to discern tones
"nearby" to
>> >> >> > other,
>> >> >> > louder ones.
>> >> >>
>> >> >> I'll remember that the next time I'm tuning
>> >> >> an MP3 guitar.
>> >> >>
>> >> >> >
>> >> >> >> The same affect can be seen on a spectrum analyzer.
>> >> >> >> Give it two frequencies separated by 1 Hz. Set the
>> >> >> >> resolution bandwidth to 10 Hz. You'll see the peak
>> >> >> >> rise and fall at 1 Hz.
>> >> >> >
>> >> >> > Yup. And the spectrum analyzer is (hopefully) a very
linear
>> >> >> > system,
>> >> >> > producing no intermodulation of its own.
>> >> >> >
>> >> >> > Isaac
>> >> >>
>> >> >> What does a spectrum analyzer use to arive at
>> >> >> amplitude values? An envelope detector?
>> >> >> Is that linear?
>> >> >
>> >> > I'm sure there's more than one way to do it, but I feel certain
that
>> >> > any
>> >>
>> >> Which of them is linear?
>> >
>> > A well-designed filter running into a bolometer would be. You can make
>> > the filter narrow enough to respond to only one frequency component at
>>
>> Any real spectrum analyzer has a lower limit
>> to its resolution bandwidth, does it not?
>> The resolution bandwidth of the human ear is non-zero
>> and not really adjustable, is it not?
>>
>> > the time, and a bolometer just turns the signal power into heat;
>> > nothing
>> > nonlinear there...
>>
>> Really?
>> You said you are a physicist/engineer.
>> What does "linear" mean?
>
> Let's not get too far off the subject here. We were discussing whether
> the "tuning beat" that you use to tune a musical instrument involved a
> nonlinear process (ie. "modulation").
Then linearity is at the core of the matter.
What does "linear" (or "nonlinear") mean to you?
> I said that it does not, and that
> it could be detected by instrumentation which was proveably linear (i.e.
> not "perfectly" linear, because that's not required, but certainly
> linear enough to discount the requirement for "modulation").
No nonlinearity is necessary in order to hear
a beat?
Where does the beat come from?
>
> That's all.
>
> Isaac
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