2-wire bandwidth

[brownianmotion]

Hello,

Is there a rough rule-of-thumb way to say how much bandwidth I can send down 2 wires of say, 30 gauge or 32 gauge? Where do I begin to do piece together something like this? How can I take length into account - so if I need to send this data from one end of the field to the other, say 1000-3000ft, how much does my bw drop by as a function of feet? I'm open to using higher voltages. (Needless to say, silly restrictions are keeping me away from using a regular cable or fiber or wireless.)

M

 

[itsmoked]

brownianmotion .. nice handle!

You have mentioned a bunch of things that make a responder try to see the mind of a, ummm.. giant squid.

What is the bandwidth of 2 wires? Answer it depends.
30 and 32 gauge wire is absurd for any field use whatsoever.

What regulation can possibly prevent you from using "regular cable"?!?!

You are asking philosophical-theoretical-metaphysical questions in a forum that specializes in concrete, useful, real life applications and solutions.

I would suggest you speak about:
What devices are at each end.
What "silly restrictions".
What style of protocol you are entertaining.
What kind of data you need to transport.
Whether or not bidirectional information is needed or if one way can be made to work.
What power sources will be used at each end.

We can help you but only if you help too.

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[VEBill]

Have a look at the existing state-of-the-art.

DSL (and all its variants) can send several Mbps down a twisted pair at distance of several miles. The newer variants do better than the older variants. At closer distances (like 3000 ft) you could probably exceed 10 Mbps.

If you want to really push the limits of practicality, you could use the wire as a guided wave G-wire and send a low power microwave signal along the wire (assumes it is suspended, not buried). Once you have a microwave link, then you could probably get WAN bandwidths. This technology probably sets the limit for what could be done with simple wires, but it isn't really practical for most applications.

Also, you might want to look at:

http://www.blackbox.com

 

[VEBill]

For example:

http://www.blackbox.com/Catalog/Detail.aspx?cid=381,1452,1464&mid=3921

"Operate across any 2-wire unconditioned 24 AWG cable—even phone cables! Support speeds up to 16.67 Mbps."

 

[MacGyverS2000]

3,000 feet, 10Mbps.... on 32 Gauge?! ;-)

Dan
Owner

http://www.Hi-TecDesigns.com

 

[IRstuff]

telephone wire goes down to 26G

TTFN

 

[brownianmotion]

Point taken

Maybe this is a silly reason....but I'm trying to pull a prank on some guys from my college and thus, the smaller my wires and cheaper the whole setup, the better it'll turn out. On the victim side, Im going to have a big oldfashioned clunky strain gauge that's currently in his bed springs. it's being amplified and pumped through an a-to-d and the data is just being sent over said wires over to me in a safe location. I'll dig around and look for the right (ie free) AtoD to sample it but Im concerned that if I send at too high a rate it'll get all garbled up (I only care about 8 bit accuracy). Then, on my side, I'll just take that bitstream and look for a pattern and some poor slob will get woken up to the sweet sweet smell of 20 gallons of dr pepper. However, Id like to actually learn something interesting while I do this and apparently they dont teach us jack in engineeirng, hense Im here. Even if you can just say 'hey go read this' thats probably good for me and I can take it from there. To fully answer your questions, I dont really know what protocol, but once I rummage around and find an AtoD (and possible a few buffer/driver chips thereafter) I'll know. I only need one direction of data and the wires will probably need to be twisted to be better concealed. Does that help any?

Thanks again.

 

[DanEE]

One of the key parameters for long distance two wire transmission is the level of longitudual balance maintained by the driver, receiver circuits and the cable itself..

http://www.trendcomms.com/multimedi...pper/Theme/Chapter2/Longitudinal Balance.html

------------------------------------------

In God we trust. All others state the facts and cite references.

 

[Noway2]

If you are REAALLY interested in the physics of siganl propegation, you can read Dr. Howard Johnsons High Speed Signal Propegation book. It deals very heavilly with skin depth and the other electromagnetic properties governing signal propegation in a transmission medium.

 

[VEBill]

The latest DSL variant is (apparently) vDSL and is good for as much as 52Mbps downlink and 12Mbps uplink. Not sure about the max distance.

 

[2dye4]

would it be safe to assume the "pattern" you are searching
for would be somewhere in the 0.2-2 hz range ???!!

If so sampling 10/sec would be adequate.
this is really low speed. good old RS232 would work.

Or just amplify at the source and filter at the destination.

Make a circuit to detect ac on what should be dc if
all parties are behaving.

 

[lighterup]

Things have really gone high tech since we smeared a thin layer of Limburger cheese on the inside of our suite-mate's light fixture. It was a perfect, passive prank and we got to rib them for about a week about their smelly socks until the smell started permeating our room also. Took a week of leaving the windows open in freezing weather to get the smell out, even after we told them about the cheese.;-)
Good to see after all these years that kids are still kids.