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James Knott
Guest
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 Posted:
Sun Feb 20, 2005 12:04 am Post subject:
Re: Anything faster I can run on Thinnet? |
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J. Clarke wrote:
| Quote: | In principle you could with suitable fittings use the Thinnet cable to
carry the wifi signal. I've never heard of it being tried but it would be
an interesting experiment.
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RG-58 is very lossy at WiFi frequencies. |
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James Knott
Guest
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| Posted:
Sun Feb 20, 2005 12:12 am Post subject:
Re: Anything faster I can run on Thinnet? |
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Gerard Bok wrote:
| Quote: | No. You would not.
Your thinnet cable is designed for 10 MHz operation and is
practically useless above say 100 MHz.
Wifi operates at 2400 MHz. So go figure :-)
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RG-58 cables, which is what's used for ethernet, is usable at much higher
frequencies than 100 MHz. However, it becomes very lossy at higher
frequencies, so that it's only suitable for short distances. According to
my catalog, at 900 MHz, the loss is about 22 dB at 100 feet or almost 66 dB
at 100 metres. For rough estimates, 20 dB = 99% loss and 60dB = 99.9999%
loss. The figures will be much higher for 2.4 GHz. At WiFi frequencies,
you'd only use RG-58 for short patch cords. |
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James Knott
Guest
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| Posted:
Sun Feb 20, 2005 12:17 am Post subject:
Re: Anything faster I can run on Thinnet? |
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William P.N. Smith wrote:
| Quote: | Belden 9907, for instance, has 14.8dB loss per 100 feet at 1GHz...
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However, it's not likely to have been used for ethernet.
BTW, Belden 9311 would be a bit better and use the same hardware as RG-58. |
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James Knott
Guest
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| Posted:
Sun Feb 20, 2005 12:22 am Post subject:
Re: Anything faster I can run on Thinnet? |
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William P.N. Smith wrote:
| Quote: | "sphealey" <sphealey@worldnet.att.net> wrote:
faster than 10 Mb that I can run over Thinnet cable?
I'd get a couple of WiFi devices and see if I could couple them to the
cable. Depending on their specs and the cable length you might want
to add some attenuators, but it might work to just get coax
adapters...
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You might want to read some of the other posts, to find out that attenuators
are the last thing you need. WiFi over coax will not likely work as far as
WiFi through the air. |
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Gerard Bok
Guest
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| Posted:
Sun Feb 20, 2005 12:32 am Post subject:
Re: Anything faster I can run on Thinnet? |
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On Sat, 19 Feb 2005 11:36:04 -0500, "J. Clarke"
<jclarke@nospam.invalid> wrote:
| Quote: | sphealey wrote:
Trying to patch a bad situation for a few months until we can get a
fiber contractor into our semi-rural mfg facility. Is there
anything
faster than 10 Mb that I can run over Thinnet cable?
Can you go wireless? You didn't say what the distance was, or if
there
were obstructions that would make this impossible.
Good thought, but I truely doubt wireless would work in that
facility/environment.
In principle you could with suitable fittings use the Thinnet cable to
carry the wifi signal.
No. You would not.
Your thinnet cable is designed for 10 MHz operation and is
practically useless above say 100 MHz.
Wifi operates at 2400 MHz. So go figure :-)
Thinnet cable is typically RG-58 coax, which is an RF cable _rated_ for
over a GHz and capable of carrying a good deal more than that with
reasonable attenuation.
I am talking about the stuff that typically came out of the box
labeled 'thinnet cable'. Typical specs:
RG58 c/u
capacity 93.5 pf/m
attenuation at 100 MHz 174 dB/km (= 278 dB per mile)
In my opinion you cannot even characterize this stuff at 2.4 GHz
as its behavour is no longer that of a 'coaxial cable'.
I would imagine that you could even get better performance if you
just connect a single wire; either the core or the shield.
I fail to see your point. Belden Thinnet cable, purpose made, is rated for
16 dB/100 feet at 1 GHz.
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Wich would be some 30 dB per 100 feet at 3 GHz, I guess ?
A stretch of 10Base-2 is limited to 600 feet so...
| Quote: | Their RG58 is rated 14-22 depending on which particular variety.
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Some browsing revealed that over 50 dB per 100 feet at 3GHz is
not an uncommon figure for commercial grade RG 58 C/U thinnet
cable. (Which actually surprises me. I didn't expect any testing
to be done on this cable in the GHz region. As I wouldn't even
expect it to be '50 ohms' at this type of frequencies.)
| Quote: | 1671A, a purpose-made microwave cable rated to 20 GHz,
has 19.4, 1672A, a purpose-made high-frequency video cable, has 26.
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Great! But the original poster doesn't have either 'purpose-made
microwave cable' or 'purpose-made high-frequency video cable''.
He has a cable rated as 'thinnet cable' preinstalled.
| Quote: | Now you can "imagine" anything you want to but in the real world cables with
that performance have been carrying signals in those frequency ranges for
decades.
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Sure. I don't claim that you cannot run 2.4 GHz over any coax
cable. (Although it is not always easy).
I just stated that it is very unlikely that OP can effectively
run a 2.4 GHz link over coax that is thinnet rated.
--
Kind regards,
Gerard Bok |
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James Knott
Guest
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| Posted:
Sun Feb 20, 2005 1:41 am Post subject:
Re: Anything faster I can run on Thinnet? |
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Gerard Bok wrote:
| Quote: | Some browsing revealed that over 50 dB per 100 feet at 3GHz is
not an uncommon figure for commercial grade RG 58 C/U thinnet
cable. (Which actually surprises me. I didn't expect any testing
to be done on this cable in the GHz region. As I wouldn't even
expect it to be '50 ohms' at this type of frequencies.)
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A length of coax can greatly improve the performance of a dummy load, used
in testing UHF or microwave transmitters. |
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Guest
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| Posted:
Sun Feb 20, 2005 1:53 am Post subject:
Re: Anything faster I can run on Thinnet? |
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James Knott <james.knott@rogers.com> wrote:
| Quote: | William P.N. Smith wrote:
Belden 9907, for instance, has 14.8dB loss per 100 feet at 1GHz...
However, it's not likely to have been used for ethernet.
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My mistake then, I went to the Belden site and typed "thinnet" into
their search tool. |
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Guest
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| Posted:
Sun Feb 20, 2005 1:57 am Post subject:
Re: Anything faster I can run on Thinnet? |
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James Knott <james.knott@rogers.com> wrote:
| Quote: | William P.N. Smith wrote:
I'd get a couple of WiFi devices and see if I could couple them to the
cable. Depending on their specs and the cable length you might want
to add some attenuators, but it might work to just get coax
adapters...
You might want to read some of the other posts, to find out that attenuators
are the last thing you need. WiFi over coax will not likely work as far as
WiFi through the air.
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What, no attenuators for the OP's 10 feet of cable? Hunh, I'd at
least have kept an open mind, but maybe that's just me. |
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Guest
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| Posted:
Sun Feb 20, 2005 1:58 am Post subject:
Re: Anything faster I can run on Thinnet? |
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"sphealey" <sphealey@worldnet.att.net> wrote:
| Quote: | faster than 10 Mb that I can run over Thinnet cable?
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Bail us out here, and tell us how long the existing cable is! 8*)
[I kinda like the idea of using the cable _shield_ as an antenna!] |
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sphealey
Guest
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| Posted:
Sun Feb 20, 2005 3:39 am Post subject:
Re: Anything faster I can run on Thinnet? |
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William wrote:
| Quote: | "sphealey" <sphealey@worldnet.att.net> wrote:
faster than 10 Mb that I can run over Thinnet cable?
Bail us out here, and tell us how long the existing cable is! 8*)
[I kinda like the idea of using the cable _shield_ as an antenna!]
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Sorry dudes - I had to go back and look at my own original post as I
thought I had included that information. Which I had not ;-(
Length is over 100m - about 125 I think. Longer than 10' for sure.
sPh |
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Robert Redelmeier
Guest
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| Posted:
Sun Feb 20, 2005 5:41 am Post subject:
Re: Anything faster I can run on Thinnet? |
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Gerard Bok <bok118@zonnet.nl> wrote:
| Quote: | What I am saying is, that for Wifi frequencies a Pringle
can probably outperforms any thinnet cable :-)
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An interesting statement.
How many dB of loss are there in closely coupled transmitting
& receiving antennae ? 100 dB in antenna efficiency? Add to
that the inverse-square losses of ~400ft of air (52db?)
-- Robert |
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Guest
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| Posted:
Sun Feb 20, 2005 5:50 am Post subject:
Re: Anything faster I can run on Thinnet? |
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"sphealey" <sphealey@worldnet.att.net> wrote:
| Quote: | Length is over 100m - about 125 I think.
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Ah, in that case the wireless thing probably wouldn't work for you.
What kind of cable do you have installed? |
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Walter Roberson
Guest
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| Posted:
Sun Feb 20, 2005 6:17 am Post subject:
Re: Anything faster I can run on Thinnet? |
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In article <N0RRd.14838$D34.4118@newssvr12.news.prodigy.com>,
Robert Redelmeier <redelm@ev1.net.invalid> wrote:
:Gerard Bok <bok118@zonnet.nl> wrote:
:> What I am saying is, that for Wifi frequencies a Pringle
:> can probably outperforms any thinnet cable :-)
:An interesting statement.
:How many dB of loss are there in closely coupled transmitting
:& receiving antennae ? 100 dB in antenna efficiency? Add to
:that the inverse-square losses of ~400ft of air (52db?)
http://www.signull.com/fsc.php
and choose a consumer access point specification such as +15 dBm
transmission and -80 dBm sensitivity. The result is 0.1 miles
which is greater than the 0.08 miles which is 400'.
Thus, with a plain inexpensive AP of no great quality, using
only the standard omnidirectional diversity antenna, one can
go the necessary distance.
That's with omnidirectional. If one using a Pringles can antenna,
then the EIRP is much more focused and one can go considerably further.
How much further? Well, under contest conditions in Utah, up to 0.8
miles using jury-rigged antennae.
http://www.wired.com/news/culture/0,1284,64440,00.html
--
100% of all human deaths occur within 100 miles of Earth. |
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Robert Redelmeier
Guest
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| Posted:
Sun Feb 20, 2005 6:45 am Post subject:
Re: Anything faster I can run on Thinnet? |
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Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:
| Quote: | http://www.signull.com/fsc.php
and choose a consumer access point specification such as
+15 dBm transmission and -80 dBm sensitivity. The result is
0.1 miles which is greater than the 0.08 miles which is 400'.
Thus, with a plain inexpensive AP of no great quality,
using only the standard omnidirectional diversity antenna,
one can go the necessary distance.
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I don't doubt that. What I wonder is if direct coupling
antennae feeds with coax has lower attenuation. All
sort of different numbers are floating around for
coax attenuation at 2.4 GHz.
It would be relatively interesting that a fairly decent
direct-coupled copper line has higher losses than
indirect EMF over the air.
-- Robert |
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Gerard Bok
Guest
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| Posted:
Sun Feb 20, 2005 5:16 pm Post subject:
Re: Anything faster I can run on Thinnet? |
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On Sun, 20 Feb 2005 01:45:36 GMT, Robert Redelmeier
<redelm@ev1.net.invalid> wrote:
| Quote: | Thus, with a plain inexpensive AP of no great quality,
using only the standard omnidirectional diversity antenna,
one can go the necessary distance.
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Provided you have clear line of sight :-)
| Quote: | I don't doubt that. What I wonder is if direct coupling
antennae feeds with coax has lower attenuation.
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I think the first question would be: what happens if you attempt
to feed 2.4 GHz into commercial thinnet coax.
Are you actually feeding signal into a transmission line or are
you chooking your source by connecting some weird object, mainly
a huge lumb capacitor to it ?
| Quote: | It would be relatively interesting that a fairly decent
direct-coupled copper line has higher losses than
indirect EMF over the air.
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There is no direct EMF over the air.
Either you couple your output directly into a proper antenna or
you feed it into a 50 ohms transmission line :-)
Note: output data for your wifi device is only valid if it is
terminated as in one of the above situations :-)
--
Kind regards,
Gerard Bok |
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