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'[OT] 20 meter USB cable?'
2003\02\02@115954 by Marcelo Puhl

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Hi,

Is it possible to make a 20 meter long USB cable? Will it work?

Thanks.
Mark

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2003\02\02@122307 by Josh Koffman

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I believe for something that long you'd need an "active" cable, one that
amplifies the signal (for lack of a better explanation). You can buy
long ones, but I don't know how long they get, and I don't know anything
about building one yourself.

Josh
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Marcelo Puhl wrote:
> Is it possible to make a 20 meter long USB cable? Will it work?

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2003\02\02@122314 by Tal

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Mark

you can't connect strait trough cable .
you need an active cable that can give you 4.8m each... you can connect up
to four cables to achieve 24m.
about 20us$ each cable.

Tal


{Original Message removed}

2003\02\02@202522 by Bob Ammerman

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The USB spec limits you to 5 meters.

To create a longer cable you have to place a hub every five meters.

So, to go 20 meters you'd need three intermediate hubs.

It is possible that cables longer than 5 meters would work, but they would
be out of spec.

There is a limit (5?) on the number of hubs between the computer and the
peripheral.

Bob Ammerman
RAm Systems

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2003\02\02@203558 by rad0

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I have used a 25 foot usb cable with no problems, that's foot.

But over this, the computer coughs when you plug in the cable.

UNLESS, you use an  Active Extension Cable, which
lets you daisy-chain your USB devices up to 80 feet in most applications.

I have used these things and they worked for me. I only went to 32 feet
though.

FWIW



{Original Message removed}

2003\02\02@214750 by Marcelo Puhl

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Thanks for the info.

Is there a way to DIY such a cable?

Mark

On 2 Feb 2003 at 19:35, rad0 wrote:

{Quote hidden}

> {Original Message removed}

2003\02\03@023654 by Kyrre Aalerud

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I've used one like that with a usb quickcam.
Total length was 15 meter extension + 5 meter camera-cable.
Total was 20.  It works.

   KreAture


{Original Message removed}

2003\02\03@084246 by John Ferrell

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How did you make up the out of spec cable?
Is it as simple as cutting a shorter cable & splicing?

It would be very handy to extend the distance on an inexpensive usb video
camera in a motor home to cover side & rear blind spots. The computer is
already in place for navigation.

John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
Dixie Competition Products
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"



{Original Message removed}

2003\02\03@084249 by John Ferrell

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John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
Dixie Competition Products
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"



{Original Message removed}

2003\02\03@182934 by Andrew Warren

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Marcelo Puhl <spam_OUTPICLISTTakeThisOuTspammitvma.mit.edu> wrote:

> Is there a way to DIY [an active USB extension] cable?

   Not easily, no.  The active extension cables actually
   incorporate single-port USB hub chips; they're not just
   electrical amplifiers.  This means, by the way, that active
   cables with full-speed-only (12 Mbps) hub chips will limit the
   communication between a high-speed (480 Mbps) host and a
   high-speed (480 Mbps) device to only 12 Mbps... So if you buy one
   of those active cables, make sure it's fast enough for your
   needs.

   The 5-meter maximum USB cable length was chosen to allow
   reflections from the far end of the cable to settle between
   bits; if a longer cable is used, reflections won't be damped as
   well, and the line voltage could rise high enough to cause
   physical damage to the drivers.

   The 5-hub limit on serially-connected hubs is a consequence of
   the USB spec for maximum turnaround delay between an outgoing
   packet and the incoming response.  That spec allows for 70 ns of
   propagation delay through each cable/hub combination, and 30 ns
   through each cable alone; the sum of the propagation delays
   through 5 hubs and 6 cables (and back), plus the delay allowed in
   the device itself, beats the full-speed timeout spec by less
   than half a nanosecond.  Adding even a few inches of cable to a
   full-length serial string of USB cables and hubs would violate
   that spec.

   There ARE very long-range USB links available, but they're more
   complicated than what we're discussing here; they consist of two
   USB chips -- one that looks like a device (peripheral) and one
   that looks like a host -- connected by ethernet or whatever.

   -Andy

=== Andrew Warren -- .....aiwKILLspamspam@spam@cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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2003\02\03@191049 by Marcelo Puhl

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On 3 Feb 2003 at 15:34, Andrew Warren wrote:

>     There ARE very long-range USB links available, but they're more
>     complicated than what we're discussing here; they consist of two
>     USB chips -- one that looks like a device (peripheral) and one
>     that looks like a host -- connected by ethernet or whatever.
>
>     -Andy
>

Thanks for your very enlightening reply!

Are these USB-Ethernet links available?

Mark

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2003\02\03@193548 by Andrew Warren

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Marcelo Puhl <PICLISTspamKILLspammitvma.mit.edu> wrote:

> >     There ARE very long-range USB links available, but they're more
> >     complicated than what we're discussing here; they consist of two
> >     USB chips -- one that looks like a device (peripheral) and one
> >     that looks like a host -- connected by ethernet or whatever.
>
> Are these USB-Ethernet links available?

   Yes; for an example (no endorsement implied) see Icron's
   "Ranger" series of USB extenders at:

       http://www.icron.com

   -Andy

=== Andrew Warren -- .....aiwKILLspamspam.....cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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2003\02\03@224322 by William Chops Westfield

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   > Is there a way to DIY [an active USB extension] cable?

   Not easily, no.  The active extension cables actually
   incorporate single-port USB hub chips; they're not just
   electrical amplifiers.

Well, that implies to me that a DIY active extension cable can be made using
several regular USB cables and cheap USB hubs...  Given that a cheap cable
is about $3, and a cheap hub is about $10, and both are commodity items,
this kludge might be both cheaper and less expensive than a "rare specialty
item" like an active USB extension cable :-)

BillW

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