ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
220/230/240V 60Hz Systems
by gfretwell. 09/16/18 12:37 PM
Acronis Backup 2017
by gfretwell. 09/16/18 12:46 AM
Inspection camera help
by Bill Addiss. 09/15/18 11:32 AM
Tingle off the water spigot
by Trumpy. 09/15/18 03:24 AM
Lighting Load questions
by HotLine1. 09/14/18 07:04 PM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
0 registered members (), 12 guests, and 16 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Bandwidth #127761
11/26/01 04:07 PM
11/26/01 04:07 PM
F
Frank Cinker  Offline OP
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
What is a "simple" definition of bandwidth? Is this term only used with fiber optic cable?

Tools for Electricians:
Re: Bandwidth #127762
11/26/01 04:49 PM
11/26/01 04:49 PM
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
http://www.auburn.edu/helpdesk/glossary/bandwidth.html

Bandwidth - Bandwidth (the width of a band of electromagnetic frequencies) is ordinarily means how fast data flows on a given transmission path. Specifically, it is the width of the range of frequencies that an electronic signal occupies on a given transmission medium. Any digital or analog signal has a bandwidth. Bandwidth is measured in Megabits per second.

[This message has been edited by Joe Tedesco (edited 11-28-2001).]


Joe Tedesco, NEC Consultant
Re: Bandwidth #127763
11/26/01 05:33 PM
11/26/01 05:33 PM
F
Frank Cinker  Offline OP
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
Thank you Joe.

Re: Bandwidth #127764
11/26/01 05:43 PM
11/26/01 05:43 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
That reference mentions a general definition that bandwidth is the range of spectrum taken by a signal, but otherwise it seems to be looking at it solely from the point of view of digital signal transmission.

I'm not too happy with the "bandwidth is measured in megabits per second" either. The latter is the rate at which data is transferred, and although everything else being equal a higher data rate requires a greater bandwidth, there are other variables in the equation.

In its purest form, bandwidth is the measure of the difference between the lowest and the highest frequencies employed to transmit the signal, be it analog or digital, and is measured in Hertz (or kHz, MHz, etc).

The term was in use long before fiber-optic cable was invented, and can refer to a signal sent down a twisted pair of wires, a coaxial cable, a microwave waveguide, or broadcast through the air.

For example, the signal sent down a regular phone line is normally limited to a range of about 300 to 3400Hz, a bandwidth of some 3.1kHz, while a good hi-fi system might have a bandwidth of 20kHz or more.

For comparison, an AM broadcast radio signal has a bandwith of 9 or 10kHz, an FM radio signal 200kHz, and a TV signal (U.S. system) about 6MHz.

Re: Bandwidth #127765
11/26/01 06:31 PM
11/26/01 06:31 PM
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
Paul,

Very good explanations!!!

I also felt the reference was making more of an emphasis on Digital packets, rather than explaining an Analog envelope [which as you know is rather complex as compared to a packet].

The reference from Joe is just what Frank needs to use for FDDI LAN tech, so it's probably better on that angle to keep within the Digital / Binary spectrum as opposed to an explanation of complex Analog envelopes.

Once again - just my $0.02 [Linked Image] [Linked Image] [Linked Image]

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Bandwidth #127766
11/26/01 07:44 PM
11/26/01 07:44 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Scott,

I guess almost everything these days is now angled toward digital signals, as this definition clearly illustrates.

I won't even start the argument about whether to measure bandwidth at -3dB, -10dB, etc. [Linked Image]

For anyone still pondering this, just consider that today's 56.6kbps dial-up modems operate over the same 3kHz telephone bandwidth as did the 300 bps modems of yester-year.

Which brings to mind another related point to remember: Despite what some advertisement may say, bits-per-second and baud rate are NOT the same thing.

Re: Bandwidth #127767
11/27/01 10:24 AM
11/27/01 10:24 AM
F
Frank Cinker  Offline OP
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
Scott,

The information Joe provided was exactly what I needed. Beyond that, it's well over my head. I do have one more question. In general, doesn't fiber optic cable provide the greatest bandwidth? That is to say compared to Category 5 UTP cable etc.

Re: Bandwidth #127768
11/27/01 11:51 AM
11/27/01 11:51 AM
E
ElectricAL  Offline
Member
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
Frank,

You're right. In the most basic sense, light on a fiber optic strand has a greater (much greater) bandwidth than voltage and current on a unshielded twisted pair (UTP) of CAT5e or "CAT6" copper conductors.

How much greater is roughly indicated the cycles per second of the light verses the maximum cycles per second of the wire. On Wire, electrical frequency can go up to 200 to 300 million cycles per second before being distorted beyond recognition by the wire's total impedance. Light's frequency is roughly a MILLION times greater than the frequency of the electricity in common UTP.

The way that information is changed into a signal in the electricity or light is in different stages of development, UTP vs. fiber, as is the hardware that modulates the electricity or light, so the million-fold difference above may be less or greater depending on the individual schemes compared. But basically, fiber is a fat pipe for information compared with UTP.

Al


Al Hildenbrand
Re: Bandwidth #127769
11/27/01 02:10 PM
11/27/01 02:10 PM
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,901
NY, USA
Good question Frank!

I'm a bit 'stuck' on fathoming this word "Bandwidth" as it is used. As Paul described it I can understand how it is a measurement of the range of frequencies employed in the transmission of a signal.

What I am having a problem with though is how it relates to the transmission speed. It seems to me that the word "Bandwidth" should not be measured in Mps. Or that they are not necessarily that directly related.

Al,

I understand your analogy that "basically, fiber is a fat pipe for information compared with UTP." I find it interestingly ironic that the "fastest" Fiber is actually the thinnest.

Bill

Re: Bandwidth #127770
11/27/01 10:14 PM
11/27/01 10:14 PM
E
ElectricAL  Offline
Member
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
Bill,

I, too, stand in awe at the information flow that a little hair of glass is capable of.

Speaking to transmission speed. . .when information is crunched by electronics into a binary stream of "on" and "off" and the binary stream is compressed by an exotic algorithm into a shorter, simpler binary stream, there is additional bandwidth gained over the basic analog bandwidth. The better the compression algorithm, the faster a fixed block of info will travel over a connection of fixed analog bandwidth. The actual signal on the wire or fiber is traveling at near light speed, but that is not the speed in consideration. Rather, it is how long it takes to disassemble a piece of info into a binary code, manipulate the code into a minimum of actual bits to be sent down the pipe, sending down the pipe, reversing the manipulation recreating the original binary code (with error detection and correction) and, finally, recreating the info.

So, there are at least two "bandwidths", the analog and the digital, that together work to develop a "transmission speed". Various noise will create errors that slow down the overall transmission by causing retransmission.

Sounds like a transporter. Beam me up Scotty. [Linked Image]


Al Hildenbrand
Page 1 of 2 1 2

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
mersadrad
mersadrad
Montreal, Quebec, Canada
Posts: 28
Joined: March 2011
Show All Member Profiles 
Top Posters(30 Days)
Admin 13
Trumpy 11
sparky 11
Popular Topics(Views)
249,262 Are you busy
187,190 Re: Forum
176,545 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.024s Queries: 15 (0.003s) Memory: 1.0278 MB (Peak: 1.2051 MB) Zlib enabled. Server Time: 2018-09-18 17:28:33 UTC