single sideband help

Discussion in 'General Electronics Chat' started by sortofnewtoelectronics, Jan 22, 2013.

  1. sortofnewtoelectronics

    Thread Starter New Member

    Jan 22, 2013
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    hey everyone. im a student of electrical engineering. i feel grossly underprepared for the real world... probably should hang around college a bunch longer...

    anyways i dont get ssb. google gave me one link thats got lots of information and math but not enough graphics

    http://thesearemyinterests.blogspot.com/2013/01/communication-systems-ssb-1.html

    i kinda got it, but is the author right in saying its hard to see ssb in time domain? maybe the author just doesnt know.

    everyone else talks about complex envelopes and other things that hurt my brain. this link had lots of matha nd i get a little lost... is there an animation or something i can see this in time domain??

    also is there a point to doing all this math? couldnt i build and see circuits in action in real live?
     
  2. crutschow

    Expert

    Mar 14, 2008
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    A single sideband (suppressed carrier) signal is consists only of RF bursts at either the carrier frequency plus the modulation frequency (upper sideband) or at the carrier frequency minus the modulation frequency. It's difficult to identify as such in the time domain with an oscilloscope as all you see are bursts of RF. It's easier to identify in the frequency domain where a spectrum analyzer will show those frequencies as vertical lines on the display.

    The point of all that math is that the engineering world (and the complete scientific world for that matter) uses mathematics to describe the working of virtual everything. If you haven't realized that by know as a student in engineering, then you haven't been paying much attention. Nothing can be well engineered if there isn't a mathematical basis to define and characterize it's operation. You certainly can build the circuits and see SSB in operation, but without math you won't have any way to define that operation or know how well it is working. As an aside, If you can't readily handle mathematics, then engineering is not likely a good fit for your aptitudes. ;)
     
  3. sortofnewtoelectronics

    Thread Starter New Member

    Jan 22, 2013
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    thanks for your explanation... guess i didnt have to read all that blog posting stuff, but it helped... theres some good math... pro tip for others, that dude has a lot of ad links and you can sorta avoid them if you start with the SSB 2 page and the SSB 3 page which is a review

    all i have to compare with is a techie 2 years my junior who has been tinkering for 3-4 years and he can build a lot of stuff. it makes me feel like a failure because i know all this math that feels so useless. how often am i going to use vector calculus? do they even teach it to engineers other than for antenna theory? ive never seen it used practically anywhere else. and in practice i see engineers using approximations and rules of thumb anyway.

    some math i think is good, but a lot of math nonstop hurts my head. im not the only one who feels that way. all my peers feel that way too... just hope the profs know what they are talking about and that all this comes full circle.

    i heard this place is a good resorse for budding engineers so ill keep popping in :D
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    Vector calculus is a must know.
    Mathematics is the language of science and engineering. Speak it fluently or you'll be in the dark.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    It's important to understand the math behind all concepts so you will understand their basis, even if you never use it much in practice. But sometimes you will need it and, even if you don't exactly remember it, you will know how to reference it and use it as needed.

    I'm not that fond of advanced math myself, but still consider it essential to learn it. Otherwise you will just be a technician with a limited and narrow knowledge of engineering.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    I've forgotten more mathematics than most people have an opportunity to learn. Even if I don't use it every day it comes flooding back in waves every time I come across a new topic which requires some of it. Even better, a quick refresher is all it takes to be right back in the swing of things. I'm with the others in advising you that if mathematics is not your cup of tea you should seriously consider a different career path lest you wind up on the reefs of despair.

    The key to understanding SSB is that it involves the non-linear operation of multiplication on a periodic fixed frequency sine wave called the "carrier" and a "sum of sine waves" called the voice. The complicated math does not involve calculus, but rather a trigonometric identity from Algebra II.
     
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    The basic concept of transmission is to reduce the bandwidth of the signal by suppressing the carrier, and then to just transmit either the "upper" or "lower" side band.

    Basically its an AM radio with the carrier removed, the receiver has a BFO which is just an oscillator used to re-inject the carrier to make the sound understandable, without the BFO the audio would sound like "Donald Duck"

    http://www.electronics-radio.com/articles/radio/modulation/single-sideband/ssb-basics.php
     
  8. sortofnewtoelectronics

    Thread Starter New Member

    Jan 22, 2013
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    Is it really a must know? I haven't used it much since I took that course. Other than electromagnetics... I don't remember any other course that required it. Maybe if I had done some more advanced antenna design courses I might have seen it, but I just see them using MATLAB -_-
     
  9. sortofnewtoelectronics

    Thread Starter New Member

    Jan 22, 2013
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    I feel like I'm "just an engineer (in training) with a limited and narrow knowledge of engineering" mostly because I don't have the experience of building too much. I'm kind of jealous of the fact that people younger than me who didn't go to college have more practical experience and an intuition that I don't yet have...
     
  10. sortofnewtoelectronics

    Thread Starter New Member

    Jan 22, 2013
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    Never heard of a BFO until I read that link... intresting...

    But yeah, I got the frequency domain reasons for why you wanna suppress the carrier and one side band. It's the time domain representation that's like something I just remember :S

    The derivation I saw has Hilbert transforms and Fourier transforms which are hard for me but at least I follow what's going on. I don't get the complex envelope notation at all. Like what's quadrature phase? In-phase just means like... you're in phase lol...
     
  11. crutschow

    Expert

    Mar 14, 2008
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    What engineering courses have you taken that didn't require significant math? All the engineering courses I took, did. :rolleyes:
     
  12. Papabravo

    Expert

    Feb 24, 2006
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    There is optimization, modeling, simulation, filters, impedance matching and a whole host of things with a Mathematics underpinning. I wouldn't trade the Math background I got for anything related to "just building" stuff. When you consider that the life cycle of a motherboard is 18 months or less how can you feel cheated by not studying an example of how to build stuff.
     
  13. sortofnewtoelectronics

    Thread Starter New Member

    Jan 22, 2013
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    Well, you took what I said out of context. I said is vector calculus really necessary outside of an electromagnetics course and maybe simulations of antenna design in the real world?

    My point was that there are so many design "rules of thumb" in real life that are basically approximations of stuff from really complicated math and physics that I am wondering if I should put all these math courses on the backburner and spend some time building stuff...

    I picked up the ARRL Handbook. Reading through it now :)
     
    Last edited: Jan 24, 2013
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