Copper cable distance limit

[jorgon]

I've been studying the current options available when cabling my house to permit a desktop computer to be operated from another room.

In order to keep down the bulk of the workstation I don't want to network, but instead I want direct connections to the computer with whatever devices I need to use at the time. This will also permit me to use the computer directly in the same way as if it were in close proximity.

The solution to the keyboard, video and mouse is easy - use a KVM extender over Cat5 cabling.

I've run up against a problem however, with peripherals such as CD, DVD, printer and webcam. I could choose USB 2.0 or better still, Firewire IEEE-1394b. However I have read that the distance limit is 15 feet with copper which will not be long enough for my house. I could use optical but I don't want the additional overheads.

What I do not understand is this. If it is possible to achieve Gigabit ethernet transmission rates using copper and Cat5 cabling over distances longer than 15 feet, why is IEEE-1394b and USB 2.0 limited to 15 feet? Is this something to do with the power supplied by the cable? If so, if the remote devices are self powered would the signal pass over a longer distance?

Thanks
Jeremy Gordon

 

[jeffbouldin]

The signal from one device to the other will only travel that far, that is all those standards will allow. It wont matter if you have all the power in the world at the receiving end if the signal is too degraded to be used.

I know Black Box makes a device that converts RS-232(50 foot maximum) to RS-485(4000 foot maximum) then back. So maybe they make one for USB.

If they do, you may find it more cost effective to purchase an inexpensive computer, run Cat5e between the two do a simple peer to peer network.

Why not just move the computer?

 

[jorgon]

Thanks for your reply jeffbouldin

I shall look at the Black Box devices.

I am intrigued by this restriction of 15 feet and I suspect that in reality the signal will travel much further than this. Has anyone tried USB or copper IEEE 1394b over longer distances without repeaters?

Is the problem that the actual transmission is not on a radio carrier like Gigabit ethernet? If so, then maybe someone ought to establish a new standard.

Or is it something to do with the power supplied by the cable? If so, if the remote devices are self powered would the signal pass over a longer distance?

>Why not just move the computer?
Well this is the whole point really. I want to use a powerful upgradeable desktop rather than a laptop and my wife does not want such a large machine visible. So I need to find a way to operate the computer remotely using the minimum number of components - flat screen monitor, keyboard + mouse only, but also with a CD/DVD connection when I want it. Jeremy Gordon

 

[jeffbouldin]

Get an external CD that connects thru your serial port then get a RS232 to RS-485 converter for the computer end, and a RS-485 to RS-232 converter for your device end. You'll only need a 22 gauge 2 pair twisted shielded wire between the two.

 

[RFKennard]

Have you looked into Black Box's "Extended-Distance/Quiet (ED/Q) Cables" (

http://catalog.blackbox.com/BlackBox/Templates/blackbox/mainscreen.asp)?

 

[daronwilson]

I had a similar problem at one point in my life. My solution was a bit different, but it worked.

I got a new wife. Now we have the whole house networked and 5 computers accessable. Simple, easy, and it is more than what I wanted.

Just my two bits.

Daron It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[leko]

I don't have a solution to your problem, however you may find the following useful.
A standard Cat5 ethernet cable system utilises pins 4&5 & pins 3&6 for data transmission and recieving on a RJ45 connector. Pins 1&2 & 7&8 are not used. They are allowed for in the standard so that commercial data cabling systems can be linked to customers telephone systems which may or maynot utilise these pins as either power sources for telephone hand sets or power sinks depending on the system type.
The same applies for Cat5e.
A Commercial data cabling systems then has the flexibility to connect either PCs or Phone to an outlet.
The max. length for Cat5 & Cat5e cabling is 90m.
However I have successfully connected network pc's on Cat5e cabling upto 130m.
The cable is designed such that each of the pairs is twisted at a different pitch, this reduces xtalk (crosstalk) betweeen pairs. Cat5e scanners conduct multiple tests to ensure cable operation over multiple frequencies and are used to test the cable at the time of installation.
Gigabit transmission rates can be achieved over Cat5e cable but only by using all 4 pairs (250Mb per pair).

In general the lower the digital transmission rate the further you are able to transmission data.
USB 1.1 is rated at 12Mbps & USB2.0 is rated at 480Mbps.
If you are handy with a soldering iron you could make yourself a cable for your cdrom etc. by increseaing the conductor size of your IDE IDC cable between PC and Drive.
Being a 40Pin cable is a problem because it may be hard to find a 20pr twisted pair cable with pairs twisted at different pitchs to eliminate xtalk.
I suggest a 20pr twisted pair individually and overall shielded cable with the shields earthed at one end only to prevent earth loops. You may be able to find this through electrical wholesalers.

Good luck

 

[jorgon]

leko

Thanks very much for this idea. Yes, I see that one of the problems with longer cables is crosstalk and using twisted pairs will help with this. I was not aware that Cat5e had varied pitch - this is interesting and useful information. The other problem which occurred to me was signal strength over long stretches, but this seems less likely to be a problem.

I suspect that a CR-ROM drive would not use all 40 pins. Just looking at an externally connected CD-ROM drive I have handy I can see it uses a 15-pin socket, and it may not use all these.

I am pretty handy with a soldering iron, so certainly I shall investigate this idea further.

Thanks again Jeremy Gordon

 

[leko]

Check this link for cdrom info.

http://webhome.idirect.com/~cati/cd.html#support

Chances are your external drive maybe connected via your parrallel port - I don't know. If so, you are working with an RS232 connection and will only need a a standard cable.
I would still suggest shielding though, and at least 24AWG cable to minimize signal lose.
Instrumentation cable is often sourced by conductor size,
and is displayed as
"cross sectional area" - (# strands/diameter per strand)
eg. 24AWG = 0.23mm2 7/0.20
Calcutlation = 7*(3.1415*(0.20/2)2)
I suggest you use a B31 20AWG 16/0.20 PLC flexible cable or equivalent as found at this link

http://www.brandrex.com.au/download/brexrexon.pdf

 

[daronwilson]

A standard Cat5 ethernet cable system utilises pins 4&5 & pins 3&6 for data transmission and recieving on a RJ45 connector. Pins 1&2 & 7&8 are not used. They are allowed for in the standard so that commercial data cabling systems can be linked to customers telephone systems which may or maynot utilise these pins as either power sources for telephone hand sets or power sinks depending on the system type.


Actually, 10/100 ethernet uses pins 1,2,3 and 6. The center two pins (4 and 5) are not used, this is because those two pins would be the ones in use for a digital phone connection or a single line phone connection on an 8 pin modular jack. Early on I think this was the design so that equipment would not be damaged by 48 volt phone battery on that pair or worse 90 volt ring voltage. However, in practice today it is rare that the ethernet Cat5 5e 6 cable is shared with any other service (except for power over ethernet (POE) which provides low voltage power for devices at the other end on unsued (7,8) pins).


It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[jorgon]

Thanks for all your information and ideas. After much thought about this, and some experimentation, in the end I settled for a software solution - using Remote Desktop in XP Professional. This now comes with a small prog to load on the client machine.
I now have a powerful desktop in the loft, which my wife is aware of, but tolerates completely because its out of the way. I have cabled part of the house using CAT-6 cabling and sockets (hoping to upgrade to Gigabit in the end). I connect to the powerful desktop from my old laptop using Remote Desktop, and have ensured that all the necessary files and peripherals are "shared". Internet access is through the loft, taking advantage of the XP Pro firewall which really does work effectively.
The response of the powerful machine is very fast in itself, the only delay being screen refresh which is not instantaneous for a whole screen (you can adjust things to make this as quick as possible). However it is sufficient for normal use. Windows cleverly only updates that part of the screen which has changed, which makes things quicker and scrolling using the normal scroll bars seems to be handled locally, which also speeds things up.
Now I'm looking for a PCMCIA Gigabit ethernet connection which should make it all 10x quicker. I don't think anyone makes these yet.
Even at 100MHz, I am very pleased with how things have turned out.
There is a slight problem with hibernation. I have set the loft computer to hibernate (includes power-off) but can't get it to do so if it is set to hibernate beyond 20 minutes of inaction. This seems to be because something in the machine is taking some action (Task scheduler or something like that) so the machine thinks there was some action. I'm well on the way to sorting this one out though.

Jeremy Gordon

 

[jpm121]

My suspicion is that you aren't going to see a huge improvement going from 100bT to 1000bT.

Remote desktop isn't a terribly bandwidth-intensive application. I've run it over 768kbps DSL connections (public internet) and it does just fine. A 10bT LAN would surpass this by a factor of 10, and you're surpassing it by a factor of 100.

Not trying to talk you out of anything (you seem a stubborn type anyhow!); just wanted to offer some objective thoughts on managing your expectations.

 

[EdPorts]

I agree with JPM. I've used a lot of windows terminal applications, including VNC and Microsoft's terminal services. I've used them over a Cable 1.5MB/128K upload connection and it's worked fine. The upload for the computer you're connecting to is the real issue. If I can get away with 128k, you should be fine with anything close to that.

 

[jamesch]

Jorgon, No one has mentioned this option. For us network admins that work in server rooms all day, we also use KVM switches that control severs servers/computers to one Monitor/keyboard/mouse, and you can switch between them. Your servers/computers can sit several feet away, ours is 25 feet away. These servers/computers all connect through special cables too and from at different lengths. They also have other options as well. Instead of using the special cables, they have KVM boxes that use Cat5, and up cables, and you are only restricted by the cable length. Although this isn't too cheap, but then again you didn't mention the price you are willing to spend. This option will allow you to have a computer per say 150 feet away and only have the switch box/monitor/keyboard/mouse, in the bed room, next to your wife's laptop. You have only one central location where your hub and all computers are located.

 

[jorgon]

jamesch

Well I did think of using KVM over Cat-5 cable, would it be any faster than the Remote Desktop solution?
My current solution actually connects to the laptop, which is good, because the monitor, keyboard, mouse are all integrated in a neat package, instead of having separate monitor with power cable/supply, keyboard, mouse which you would need with KVM. The remote machine can also access and use the local CD and floppy disk drives down the same line.

I sorted the hibernate problem by the way - in fact it wasn't a problem, the latest XP versions only let the task manager work once per session if it restarts the hibernate clock, so it just means that hibernate is sometimes slower to occur than usual.

Jeremy Gordon

 

[jamesch]

It's possible, that a KVM switch is faster, the devices inside the KVM use different technology than a NIC card, so it could be faster or it could be slower. You could go to

http://www.raritan.com

we use there products and havent had any problems. the cable distance is 1000 feet between switches. One major benifit using this is that it frees up you wifes laptop, so you dont have her on your ass for using her computer when she wants to use it at the same time. you might want to make a list of pro's and con's, and see what's bets for your needs.