Well, you are all right.
There is several different things to factor for coax.

First, The size (RG-59, RG-6, RG-11) which is for residential houses has a certain bandwidth
for each.
RG-59 = 5 megabit <<Which is not preferred for broadband>>
RG-6 = True 10 megabit <<Which IS preferred for broadband by majority of ISP's>>
RG-11 = 10 to 20 megabit <<Which is very high quality coax, usually used for
apartments, duplexes, and etc>>

Second is the Spectrum that the broandband is ran:
There is different ratios to accuire by:
What MHz your upstream is coming in on
What MHz you downstream is going out on

Most all ISP's usually use for their upstream somewhere between 80Mhz to 1Ghz or higher (usually ranging within 6Mhz worth of bandwidth) On the downstream side anywhere from 5Mhz to 200Mhz with a 6Mhz range.
<<At my company, we use 98Mhz for our downstream and 32 Mhz for our upstream
using a Cisco uBR7114>>

Third is the distance and how far it has to go before it hits a HFC plant amplifier until it's reaches the Headend. Here is a link to look at http://www.radio-ware.com/products/t...o/coaxloss.htm

There is several more factors to look at when determining bandwidth with coax but
I would be here all day talking about it. Something to look at if you are having problems
with bandwidth with coax is to talk to your ISP and tell them to check your dB levels, check for C/N (Carrier Over Noise), Check for leaks (such as bad connectors or cracks in the coax), Or to see if there is too many splitters in the coax line.

Hope this helps

Caine