You need manufacturer data, for instance, are you talking about TV-grade coax or satellite/cable coax (usually double-shielded)?

Degredation of speed is due to noise and capacitance. Channel capacity (speed) is given...
CC = W Log₂(1 + P/N) where W = bandwidth, P = power and N = noise

Capacitance increases with length and thus reduces potential bandwidth, but by how much will depend on the detailed cable spec. But, additionally, you need to consider the spectrum of the transmitter for instance a high-power low-bandwidth transmitter may not suffer from increased capacitance as much as a low-power high-bandwith system.

As for twisted pairs, the principles are much the same but noise (and cross-talk) are bigger issues.

You may find the data you require in electronics catalogs such as RS (Radio Spares) but such data can be too detailed and complex unless you work in the field.

Kaled.

I work in the field but I need the data in a form someone who isnt will understand.

Its not satellite tv cable (double shielded as you mentioned) its just normal cable tv cables.

Obviously I cannot get the exact specs on that but a comparison of the two (with a generic coaxial cable type) would do the job just as well.

Simply, co-axial suffers greater loss than twisted pair, which in turn suffers greater loss than open pair. However, the adverse is true of interference, that is co-axial cable suffers less from interference than twisted pair and so on.

In a digital ebvironment, you may find that intereference is more of an issue than attenuation, causing data errors which then cause packets to be resent, slowing down the process more than a weak signal resulting in a lower operating speed.

With so many variables, such as the environment in which the installation is situated and cable lengths, I'd say try both and see which works in practice, theory is fine for the classroom, but fails to take into account 'chaos' or real life.

Matt

Do you know anywhere I would be able to get some data in a tabular format with attenuation and interference rates over different differences?

I could do it manually but it would take ages to lay the cable out and test it.!

Did you try the cable manufacturer's web site?

Attenuation should be a slam-dunk. "Speed loss" is something you are unlikely to get from the manufacturer's site. It would depend on the modulation technique used and even the specific equipment used at the endpoints.

If you know the kind of equipment being used to modulate/demodulate, you might get data from the equipment manufacturer's website, or some general guidelines or aggregate data from some industry association website.

Indeed... I was hoping someone had already done a study on it so I didnt have to... Back to the drawing board I guess...!