Again it is the basic physics of a transmission line
A copper wire pair will be quite lossy as frequencies (ie bitrates)
increase. In radio antenna work, you wouldnt use an open wire
transmission line above HF (ie 30MHz say approx 20 MBit/s) because of
loss and radiation of the signal over a distance of 50-100m. This is in
open air, well insulated, with no adjacent conductors. In a CAT5
network, a twisted pair will work again over a distance of several
hundred metres.
Try putting several hundred pairs together in an underground cable (are
they shielded?) over a distance of 3km and you get problems of loss and
crosstalk from adjacent pairs, which increase dramatically with
frequency. Signal to noise is inversely related to frequency/bitrate and
distance. Wire pairs will always be limited in their ability to deliver
high speed data, regardless of the fancy gear hung on the end. OK,
technology is advancing all the time, but I dont think it has been able
to overcome these basic problems.
Add the software overhead of protocols such as TCP you get a further penalty
I would be interested to see any real world results that show a 24MBit/s
rate over a wire network at a distance of 3km, in the presence of
multiple other signals on the same network.
R
Ken Harvey wrote:
Peter Machell wrote:
Ken, how do you get an reply out of a politician the next day?
You zap them every time their public utterances are stupid and ill
informed (which takes a lot of E-mails) and sometimes you get a response!
I suspect Senator Coonan got a flood of E-mails over her latest gaffe
and her staff composed an form response in an attempt to placate the
noisy hoi polloi.
You will note that her response, typically full of government
platitudes, didn't address my specific concern that the speed of ADSL
II plus rapidly falls off as the distance from the exchange increases.
For example, while the iiNet ADSL II plus has a theoretical
(advertised) speed of (24,000 KBits down / 1000 KBits up) in practice
I get a download speed of around 3000 KBits/sec and an upload speed of
about 650 KBits/sec) speed test from http://www.tcpiq.com/
I trust that those who have posted on this matter have also cc'd to
[EMAIL PROTECTED]
[EMAIL PROTECTED]
Cheers
Ken
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