The issue of data rate has less to do with the transmission media than with
other factors.
Twisted pair started to become more dominant because it could be routed as
a star network rather than point to point. The coaxial cable would run in
a line starting at one end of the network and would go from system to
system. You could design a star architecture, but it was more complicated.
A single break in the line, missing terminator, misapplied terminator or
faulty network card would cause the entire network to go down. Twisted
pair used with a hub was more fault tolerant. A problem on one computer
would be isolated by the hub and would not affect the rest of the network.
As more money was poured into twisted pair development, hubs were replaced
by switches. Now, the switches look at the addresses of packets. Each
packet is only sent across the part of the network that has the system with
the specified IP address. This can reduce some of the overhead required
for each network adapter. On a coax network, each adapter receives every
message and must parse it to determine if the adapter needs to read or
ignore the packet.
Further, the star architecture using hubs and switches makes it much easier
to keep older and slower hardware on the same network. It is easy to make
a 10/100BaseT hub or switch. You can connect old 10 Mbit/sec hardware
easily to a fast network. However, all network adapters on the same length
of coax must operate at the same speed.
I expect others will have better information and I might be incorrect on
some of what I have said. I am no expert in networks or hardware. My
experience is primarily from my previous employment at a small company
where I helped set up the network. We went from coax to twisted pair when
our network hit about 20 nodes. Because twisted pair was easier to route
through walls and over ceilings, our network overhead costs went down. The
network reliability certainly went up. With the coax network, somebody
would move their computer and dislodged the connection. The whole network
would go down and we would spend far too much time trying to find the
fault.
Ted Eckert
American Power Conversion Corporation
The items contained in this e-mail reflect the personal opinions of the
writer and are only provided for the assistance of the reader. The writer
is not speaking in an official capacity for APC nor representing APC's
official position on any matter.
Ken Javor
<ken.javor@emccom
pliance.com> To
Sent by: <[email protected]>
[email protected] cc
Subject
08/30/2006 09:41 Re: Chamber transition panels
PM
That sounds like an excellent suggestion to me. It does raise one
unrelated
question in my mind, because I know little about Ethernet. This is just
for
my own understanding, it doesn't bear on the original post. Why is it you
can get 100 MHz on "phone-line" type Ethernet cable, but only 10 MHz when
on
coax? Seems like it ought to be just the reverse.
> From: [email protected]
> Date: Wed, 30 Aug 2006 20:23:52 -0500
> To: [email protected]
> Cc: [email protected]
> Subject: Re: Chamber transition panels
>
> Hello Gary,
>
> May I suggest going to older Ethernet hardware? There are 10BaseT to
> 10Base2 Ethernet adapters. You may have to look in a computer resale
shop
> to find this older hardware. This will get you to the older 50 ohm
coaxial
> Ethernet connection. You should have no trouble getting the coax through
> the wall. You will be limited to 10 megabits/second, but that may be
> sufficient.
>
> Ted Eckert
> American Power Conversion Corporation
>
> The items contained in this e-mail reflect the personal opinions of the
> writer and are only provided for the assistance of the reader. The writer
> is not speaking in an official capacity for APC nor representing APC's
> official position on any matter.
>
>
>
> "McInturff Gary"
> <GMcInturff@spray
> cool.com> To
> Sent by: <[email protected]>
> [email protected] cc
>
> Subject
> 08/30/2006 01:52 Chamber transition panels
> PM
>
>
>
>
>
>
>
>
>
> Dumb question maybe
> I have to get a UTP Ethernet connection out of a
semi-anechoic
> chamber. There no anti-chamber so any unfiltered cable routing opening is
a
> major leak because of the opening and the induced noise on the cable
> itself. Since Ethernet signals don¹t like to be filtered. I¹m considering
> two options neither of them make me real happy.
> 1) Find, if one exists, some sort of metallic RJ-45 bulkhead
> transition connectors and mount that into the transition panel. I¹ve
> seen the plastic versions for inter-connecting Ethernet cables, but
> the were neither metallic nor bulkhead mounted.
> 2) Make an air dielectric waveguide out of foot or so 1Ž2 inch metal
> pipe and attach that to the transition panel and route the cable
> through the ³wave guide² The opening itself even at 1Ž2 is larger than
> 18 GHz upper test frequency, but the width of the wave guide buys me
> some attenuation and I don¹t expect to see much in the way of
> ambient up that high anyway.
>
> I don¹t have an option of putting the test gear into the chamber with the
> EUT. The test gear would be a worse problem.
> I don¹t think this is completely brain dead but don¹t see any easier
> solution, but this doesn¹t address any induced ambient noise on the
cable.
> Your thoughts?
> Thanks
> Gary
>
>
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