blocking cellular and WIFI signals?

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jerry - 13 Oct 2004 14:02 GMT

I would be very grateful if anyone in the group could let me know if
there are products other than c-guard that are commercially available
in your country.

And does anyone know in what countries (such as France and Japan)these
devices are allowed to be used?

My specific interest is schools but I'm collecting general info on a
range of places at this time and would appreciate any links.

I hope to classify locations along the dimensions of soft...hard and
shielded...unshielded and record what I expect will be a gradual
deployment of technology to restrict access.

I have selected the concept of shielding as it seems the users of
products such as c-guard are deploying in order to protect something
that they may consider essential.

Many thanks for any help.

Jerry Hewitt
PhD Student
Institute of Education
University of London

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michael turner - 13 Oct 2004 14:14 GMT

> I would be very grateful if anyone in the group could let me know if
> there are products other than c-guard that are commercially available
[quoted text clipped - 15 lines]
>
> Many thanks for any help.

For sale in the UK:
http://www.globalgadgetuk.com/mgb1.htm

However:
----
Cell phone jamming equipment is illegal to use in the UK as it violates
sections 1 & 13 of the 1949 telegraphy act, we are therefore unable to
supply cell phone jammers to any UK customer who does not hold a valid
licence issued by the UK Office of Communications (Ofcom). Please note
that no exceptions can be made on this policy.
----

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Michael Turner

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zvxr.gheare1963@grfpb.arg

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John Phillips - 13 Oct 2004 21:02 GMT

> I would be very grateful if anyone in the group could let me know if
> there are products other than c-guard that are commercially available
> in your country.

Illegal in Australia.

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Jer - 14 Oct 2004 00:30 GMT

> I would be very grateful if anyone in the group could let me know if
> there are products other than c-guard that are commercially available
[quoted text clipped - 20 lines]
> Institute of Education
> University of London

Cell jamming systems are likely illegal in most countries, so acquiring
the equipment may be a stuffer. OTOH, few people I'm familiar with
actually care about the law, so they do it anyway while daring someone
to grow a pair and come find them. So far, nobody has.

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Jer - 14 Oct 2004 00:31 GMT

Oh, I forgot to comment about WiFi, which is no man's land so you can do
whatever you want with that.

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matt weber - 14 Oct 2004 04:18 GMT

>> I would be very grateful if anyone in the group could let me know if
>> there are products other than c-guard that are commercially available
[quoted text clipped - 23 lines]
>Oh, I forgot to comment about WiFi, which is no man's land so you can do
>whatever you want with that.

Yes and no. Devices that are designed to produce interference are
almost always illegal, but it is possible to use legitimate wireless
devices (spread spectrum 2.4Ghz phones are very good at this) that
effectively disrupt Wi-Fi. Wi-Fi is in shared spectrum, however the
mechanics of sharing are the responsiblity of the users, not the
equipment... For example at one USA airport, the Wi-Fi hotspot took
out the cordless bar code readers the airline was using to scan
baggage.

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Clueless2 - 16 Oct 2004 00:55 GMT

>>Oh, I forgot to comment about WiFi, which is no man's land so you can do
>>whatever you want with that.
[quoted text clipped - 5 lines]
> mechanics of sharing are the responsiblity of the users, not the
> equipment...

I don't think spread spectrum 2.4GHz phones are legal in Europe.

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jerry - 14 Oct 2004 10:35 GMT

Thanks for that info. I had no idea about Australia. And will look
into the WIFI difference too. Jerry.

PS...Theres some media talk about this issue at

http://www.bbc.co.uk/radio4/arts/frontrow/index.shtml

Piece starts 16:30 mins into the program.

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Trey - 15 Oct 2004 22:01 GMT

Brass mesh works nicely, Mount it to the 2x4 studs before you put up the
drywall. Make sure to put a metalic film tinting on all the glass for best
sealing of the facility.

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michael turner - 15 Oct 2004 23:55 GMT

>> I would be very grateful if anyone in the group could let me know if
>> there are products other than c-guard that are commercially available
[quoted text clipped - 24 lines]
> drywall. Make sure to put a metalic film tinting on all the glass for best
> sealing of the facility.

The floor and ceiling would have to be screened as well.

...and don't forget, a faraday-cage installation must be earthed.

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Michael Turner

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gopi - 16 Oct 2004 13:19 GMT

> > Brass mesh works nicely, Mount it to the 2x4 studs before you put up the
> > drywall. Make sure to put a metalic film tinting on all the glass for best
> > sealing of the facility.

I had an office with metallic windows at one point. It was absolutely
horrible in terms of RF; my ham radio coverage was horrible. It was a
new office

> The floor and ceiling would have to be screened as well.
>
> ...and don't forget, a faraday-cage installation must be earthed.

Are you sure about that? I'm fairly confident that the basic physics
of a faraday cage don't require grounding at all.

"...the whole being mounted on four glass feet, 5.5 inches long, to
insulate it."
-Michael Faraday, describing the very first Faraday Cage he built.
http://www.rfsafe.com/research/rf_radiation/shielding_rf_hazards/faraday_cage.htm

This being said, I'm not sure if a _poor_ faraday cage is improved by
grounding or not...

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matt weber - 17 Oct 2004 04:43 GMT

>> > Brass mesh works nicely, Mount it to the 2x4 studs before you put up the
>> > drywall. Make sure to put a metalic film tinting on all the glass for best
[quoted text clipped - 10 lines]
>Are you sure about that? I'm fairly confident that the basic physics
>of a faraday cage don't require grounding at all.

It is theoretically possible for a faraday cage to become a tuned
cavity, in which case it would re-radiate quite effecitvely. If you
ground it, it won't re-radiate.

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Jer - 16 Oct 2004 00:36 GMT

> Brass mesh works nicely, Mount it to the 2x4 studs before you put up the
> drywall. Make sure to put a metalic film tinting on all the glass for best
> sealing of the facility.

A Faraday screen works well for enclosed areas, but a cell jammer works
nicely for beach areas and other open venues. Thankfully.

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Trey - 16 Oct 2004 02:20 GMT

>> Brass mesh works nicely, Mount it to the 2x4 studs before you put up
>> the drywall. Make sure to put a metalic film tinting on all the
>> glass for best sealing of the facility.
>
> A Faraday screen works well for enclosed areas, but a cell jammer
> works nicely for beach areas and other open venues. Thankfully.

A Cell phone jammer/blocker can become a Safety issue though. Not only from
the stand point of no one being able to call emergency personnel, but also
in the effect of having a high concentration of irate users that can not
"connect" and will soon turn violent on eachother while suffering from "low
signal syndrome"

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