Ready for this - Does chicken wire block Wi-Fi signals?

[Mike Outmesguine]

I'm being asked some questions about the effect of chicken wire in old houses. Does it block the wifi signal?

We know that old houses are hard on wireless, vs. new drywall-style houses. But I always felt it was more the plaster and wood density and water-content of the walls than the chicken wire in the walls absorbing and/or reflecting the signal.

My half-baked notes on the matter..............

Most of the problems I've seen with old houses seems more likely due to the plaster and sheer density of the building material than specifically chicken wire. For the wire to be a strong reflector, and so to block the Wi-Fi signal, it will need to be a specific length between the gaps in the wire mesh. For example, a parabolic grid antenna spaces the wires about 15 mm apart for optimal reflection of the 2.4 GHz Wi-Fi signal. I think chicken wire is made with larger gaps than that, so the signal will mostly pass right through it. My feeling is that the water content in the plaster and wood in the wall is blocking the signal. But I haven't done, or seen any tests of this theory as compared to modern drywall.

As I understand it, the wire mesh would need to be in certain fractions of the wavelength to make a good reflector. It's not so much that the wave can't "fit" through the mesh as the mesh material actually absorbing and/or reflecting the signal - where each component of the mesh acts as individual antennas.

So, I think the mesh would need to be 1 full wavelength, or 3/4 or 1/2 or 1/4 wavelength to be quite good at blocking the signal. Which would mean the mesh would interfere best at around 4.8, 3.6, 2.4, and 1.2 inches (for Wi-Fi Channels 1-11). Anything in between those would not be as effective at blocking the signal.


What do you SOCALWUGgies think about it?

-Mike




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Mike Outmesguine

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[Mike Burgess]

It all depends on the "mesh"

Old plaster mesh was expanded metal, about 80% solid. No Wi-fi thru that.

Then came plasterboard, just sheet rock with thumb sized holes in it for the plaster to oze thru. No metal except edges and corners.

Stucco wrap has varied mesh, sometimes 1" chicken wire, which is pretty porous to wi-fi. I'd guess anything smaller than 1" chicken wire would have a bad effect, along with real plaster (concrete) over substrate (metal or plasterboard or wood lath) Stucco (concrete about 1.5 - 2" thick) can't be good for the signal either.
Then there are the plywood sheer walls (earthquake resistance) which is 10-20% moisture to suck up your signal.

And the neighbors leaky microwave oven gasket.....

( side note, my question last week about antenna vendor, resulted in my purchase fo a 19db panel antenna, which gave me a +2 mile range from the ranch to open AP's in town. )

Mike B.

--- On Tue, 10/13/09, Mike Outmesguine <m...@transstellar.com> wrote:

[John McDermon]

We've observed similar behavior out here in New Mexico. In one high-
end home with copper window screens, ironically we had to reposition
the interior base stations to transmit through the walls, since the
signal wasn't getting out the windows. Fortunately this adobe home
didn't have much, if any , mesh in the walls.

Cheers,
--John
Founding Board Member
La Canada Wireless Association

Those who do not understand Unix are condemned to reinvent it, poorly.
Usenet signature, November 1987
—Henry Spencer

[Pete]

The higher the frequency, the less chicken wire will block, as the wavelength and energy
level of the signal will go through the holes of the mesh, where the wire is not.

At 04:52 PM 10/13/2009, you wrote:
>As I understand it, the wire mesh would need to be in certain fractions of the wavelength to make a good reflector.

Well, not so much fractions, as any mesh whose hole diameter is small enough will
reflect 100% of the signal, or well over 90%. However, the mesh needs to be
well grounded, not a floating ground, otherwise it does reradiate.

It's too complex to give you full details here. My last 2 years in college
were spent learning EMF and charged particles moving through such.
Since then I have learned how to Tempest shield to milspec, and better.

>It's not so much that the wave can't "fit" through the mesh

Actually, there is a strong component of that, if the mesh is "large" compared to the wavelength.

>as the mesh material actually absorbing and/or reflecting the signal - where each component of the mesh acts as individual antennas.

Correct. The incident EM wave creates eddy currents, which do reradiate,
an equal amount of EM as impacted the wire. Energy is conserved.
The only time this does not happen, is when those eddy currents
are "ground" to earth, 100% grounded, and then the wire mesh
fully absorbs the signal, and reflects little, providing shielding.
Of note is these eddy currents reradiate to both sides of the mesh.
Thus, half is reflected, while half is transmitted.

But, like I first wrote, some EM waves go through the center of the mesh,
and create no eddy currents, so the full incident power is transmitted
through the mesh.

There are both processes going on. It's complex.

>So, I think the mesh would need to be 1 full wavelength, or 3/4 or 1/2 or 1/4 wavelength to be quite good at blocking the signal. Which would mean the mesh would interfere best at around 4.8, 3.6, 2.4, and 1.2 inches (for Wi-Fi Channels 1-11). Anything in between those would not be as effective at blocking the signal.

Anything under 1 wavelength is going to start blocking, until the signal is fully blocked.
It is a asymptotically decreasing signal strength, having nothing to do with fractions
of wavelength.

[Batey, Everett II NAVSEA]

Are we considering LATH_Wire or Chicken wire and if latter, what is the
dimension of the hex?

--
R / Everett
Cell & Days: (805) 616-2471

> -----Original Message-----
> From: soca...@googlegroups.com
> [mailto:soca...@googlegroups.com] On Behalf Of Mike Outmesguine
> Sent: Tuesday, October 13, 2009 16:52
> To: SOCA...@googlegroups.com
> Subject: [SOCALWUG] Ready for this - Does chicken wire block
> Wi-Fi signals?
>

[Tom Tcimpidis]

Lath used for plaster, particularly in older houses, has a denser "weave"
than chicken wire and is an excellent reflector at WiFi frequencies.
On a friend's 1920s house, I measured a pitch of about 18mm.

Tom K6TGT

-----Original Message-----
From: soca...@googlegroups.com [mailto:soca...@googlegroups.com] On Behalf
Of Batey, Everett II NAVSEA
Sent: Wednesday, October 14, 2009 9:16 AM
To: soca...@googlegroups.com
Subject: [SOCALWUG] Re: Ready for this - Does chicken wire block Wi-Fi
signals?