Leaky Coax

Any solutions?

All I can find is Radiax cable, which seems expensive, and looks
like it's geared towards cellular communications instead of 802.11.

I'm looking at installing WiFi in a hotel with long hallways. An
access point in the center with an antenna at each end of the
hallway doesn't make it to the center due to all of the concrete.
Would leaky coax, or another solution do the trick?

Smowk

smowk <(E-Mail Removed)> wrote:
>Any solutions?

Unfortunately, at those frequencies, any coax is too lossy to be
useful.

>I'm looking at installing WiFi in a hotel with long hallways. An
>access point in the center with an antenna at each end of the
>hallway doesn't make it to the center due to all of the concrete.

I can't parse that, can you try again? How about multiple APs?

On Thu, 09 Feb 2006 21:11:29 -0600, smowk <(E-Mail Removed)> wrote:

>Any solutions?

Solutions are liquids. I don't think liquids will work.

>All I can find is Radiax cable, which seems expensive, and looks
>like it's geared towards cellular communications instead of 802.11.

This has been covered somewhat in the past. See:
| http://groups.google.com/group/alt.i...c86eba275378c2

Mitsubishi-cable URL has changed to:
http://www.mitsubishi-cable.co.jp/pr...ari/leaky.html

>I'm looking at installing WiFi in a hotel with long hallways. An
>access point in the center with an antenna at each end of the
>hallway doesn't make it to the center due to all of the concrete.
>Would leaky coax, or another solution do the trick?
>
>Smowk

Are you trying to cover the hallways or the rooms? RF doesn't turn
corners (through doorways) very easily.

I only have some experience with bench testing leaky coax. If the
coax is suffiently low loss to be useful, it will be big, fat, and
expensive. Smaller diameter cables might work for short runs, but
forget it past about 50ft.

How long are the hallways (in feet or meters)?

Methinks if you can run coax, you can also run CAT5 and use multiple
access points. I suspect the 2nd access point will be much cheaper
than the coax past about 100ft of cable.

Also, if you have a long thin hallway, shooting down the hallway with
a directional (panel) antenna will work. However, if you expect to
make the right angle turn through a doorway, it won't work.

Another way that might work is to use directional couplers or "taps"
along a low loss cable. This is similar to some CATV installations. I
don't know of any cheap directional couplers or -10dB taps for 2.4GHz.
One could be built from just a circuit board, 2 chip resistors, and
three connectors, but I couldn't find any with Google.





--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

William P.N. Smith <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> smowk <(E-Mail Removed)> wrote:
>>Any solutions?
>
> Unfortunately, at those frequencies, any coax is too lossy to
> be useful.
>
>>I'm looking at installing WiFi in a hotel with long hallways.
>>An access point in the center with an antenna at each end of
>>the hallway doesn't make it to the center due to all of the
>>concrete.
>
> I can't parse that, can you try again? How about multiple APs?

im trying to cover all of the rooms on the floor by an access
point in the center of the hallway, and an antenna on each end.
the first few rooms from the end of the hallway get the signal
fine, but it looks like i'll need another antenna in the center.

as you mentioned, looks like ill need more access points...oh well

smowk

smowk wrote:
> Any solutions?
>
> All I can find is Radiax cable, which seems expensive, and looks
> like it's geared towards cellular communications instead of 802.11.
>
> I'm looking at installing WiFi in a hotel with long hallways. An
> access point in the center with an antenna at each end of the
> hallway doesn't make it to the center due to all of the concrete.
> Would leaky coax, or another solution do the trick?

Coax is always Leaky, Drippy, Sneezy and Coughy. Do your networking
with Cat5 or better. Does away with that crap.

smowk wrote:
> Any solutions?
>
> All I can find is Radiax cable, which seems expensive, and looks
> like it's geared towards cellular communications instead of 802.11.
>
> I'm looking at installing WiFi in a hotel with long hallways. An
> access point in the center with an antenna at each end of the
> hallway doesn't make it to the center due to all of the concrete.
> Would leaky coax, or another solution do the trick?
>
> Smowk
Hi,
What is leaky coax? Holes on the cable or nicked cable?
It'll raise SWR on the transmission line ans causes signal loss.
(going up as heat)

Tony Hwang <(E-Mail Removed)> hath wroth:

>What is leaky coax? Holes on the cable or nicked cable?
>It'll raise SWR on the transmission line ans causes signal loss.
>(going up as heat)

It's coax with either pieces ground off at regualar intervals, or
slots die cut into the aluminum shielding. I couldn't find a decent
picture. This is as close as I could get with the RCT series:
http://www.andrew.com/products/trans...x/default.aspx
http://www.andrew.com/search/BN_661.aspx
Times also makes something called Flexrad-600-DB and Flexrad-600-PVC,
but I couldn't find any data sheets (in English) on the stuff.

Andrew also uses air dielectric Heliax, with the corrogated copper
outside shield, and just grinds holes into the shielding. It's called
RLX series. This worked well, but is a nightmare to handle as any
bending would cause the cable to buckle.

As for VSWR, think about it for a moment. If the forward signal is
mostly lost to radiation, then there is no RF left inside the coax to
be reflected. Therefore, without a reflected signal, there's no VSWR.
The coupled mode Radiax is actually a transmission line transformer
that matches the 50 ohm coax impedance, to the 377 ohm free space
impedance. In other words, it's an antenna.

There's quite a bit on Radiax in the Andrew catalog. Start here:
http://www.andrew.com/products/trans...x/default.aspx
and select "Catalog 38" for links.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 11 Feb 2006, in the Usenet newsgroup alt.internet.wireless, in article
<(E-Mail Removed)>, Jeff Liebermann wrote:

>As for VSWR, think about it for a moment. If the forward signal is
>mostly lost to radiation, then there is no RF left inside the coax to
>be reflected. Therefore, without a reflected signal, there's no VSWR.
>The coupled mode Radiax is actually a transmission line transformer
>that matches the 50 ohm coax impedance, to the 377 ohm free space
>impedance. In other words, it's an antenna.

Many moons ago, I was playing with some test gear in a screen room. I
took a ten meter piece of RG-58A/U at 11.8 GHz. More signal was leaking
out of the single braid coax than was making it to the far end. The
insertion loss was over 1.0 dB per foot, and the stuff leaking out the
side was only down about 25 dB. Changing it to RG-55/U brought the
loss down a bit, but improved the shielding to almost 40 dB.

Old guy

Jeff Liebermann wrote:

> Tony Hwang <(E-Mail Removed)> hath wroth:
>
>
>>What is leaky coax? Holes on the cable or nicked cable?
>>It'll raise SWR on the transmission line ans causes signal loss.
>>(going up as heat)
>
>
> It's coax with either pieces ground off at regualar intervals, or
> slots die cut into the aluminum shielding. I couldn't find a decent
> picture. This is as close as I could get with the RCT series:
> http://www.andrew.com/products/trans...x/default.aspx
> http://www.andrew.com/search/BN_661.aspx
> Times also makes something called Flexrad-600-DB and Flexrad-600-PVC,
> but I couldn't find any data sheets (in English) on the stuff.
>
> Andrew also uses air dielectric Heliax, with the corrogated copper
> outside shield, and just grinds holes into the shielding. It's called
> RLX series. This worked well, but is a nightmare to handle as any
> bending would cause the cable to buckle.
>
> As for VSWR, think about it for a moment. If the forward signal is
> mostly lost to radiation, then there is no RF left inside the coax to
> be reflected. Therefore, without a reflected signal, there's no VSWR.
> The coupled mode Radiax is actually a transmission line transformer
> that matches the 50 ohm coax impedance, to the 377 ohm free space
> impedance. In other words, it's an antenna.
>
> There's quite a bit on Radiax in the Andrew catalog. Start here:
> http://www.andrew.com/products/trans...x/default.aspx
> and select "Catalog 38" for links.
>
Hmmm,
Aha, talking about stub kind of things on transmission line.
If Z matching is not maintained there will be always higher than
desirable SWR.
Tony

Moe Trin wrote:

> On Sat, 11 Feb 2006, in the Usenet newsgroup alt.internet.wireless, in article
> <(E-Mail Removed)>, Jeff Liebermann wrote:
>
>
>>As for VSWR, think about it for a moment. If the forward signal is
>>mostly lost to radiation, then there is no RF left inside the coax to
>>be reflected. Therefore, without a reflected signal, there's no VSWR.
>>The coupled mode Radiax is actually a transmission line transformer
>>that matches the 50 ohm coax impedance, to the 377 ohm free space
>>impedance. In other words, it's an antenna.
>
>
> Many moons ago, I was playing with some test gear in a screen room. I
> took a ten meter piece of RG-58A/U at 11.8 GHz. More signal was leaking
> out of the single braid coax than was making it to the far end. The
> insertion loss was over 1.0 dB per foot, and the stuff leaking out the
> side was only down about 25 dB. Changing it to RG-55/U brought the
> loss down a bit, but improved the shielding to almost 40 dB.
>
> Old guy
Hi,
Did not measure the SWR there? Standing wave is bad thing.
Tony