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March 20th 04, 02:24 AM

On Sat, 20 Mar 2004 01:53:10 -0000, (Dave Platt)
wrote:

In article , John wrote:

Actually, Title 47, Part 15, specifically allows unlicensed intentional
emissions. For example, in the AM broadcast band:

#snip#

This is only an example. Most of the spectrum is available for unlicensed
operation at low power, with some frequencies having higher emission limits
than others. Therefore, intentional unlicensed emissions are allowed by US
regulations. Read Part 15.

True. However, Part 15 also states:

(b) Operation of an intentional, unintentional, or incidental
radiator is subject to the conditions that no harmful interference is
caused and that interference must be accepted that may be caused by
the operation of an authorized radio station, by another intentional
or unintentional radiator, by industrial, scientific and medical
(ISM) equipment, or by an incidental radiator.

(c) The operator of a radio frequency device shall be required to
cease operating the device upon notification by a Commission
representative that the device is causing harmful interference.
Operation shall not resume until the condition causing the harmful
interference has been corrected.

It seems to me that the "no harmful interference" clause would
put cellphone jammers outside the bounds of operation under Part 15.

As far as cellphone use on private property goes... it's certainly
within a property owner's right to declare, and enforce a "no
cellphone use" policy on that property. I cheer every time I see such
a notice.

It's also almost certainly within a property owner's right to include
some sort of perimeter/periphery shielding (passive, nonradiating
interference) to block cellphone signals from entering the property.

It's questionable, to me, whether the property owner would be able to
get away with using an active interferer, such as a jamming
transmitter. The user _might_ win in court, if it could be shown that
the jamming signal was strictly limited to the private property in
question. However, if enough of the jamming signal left the area to
[1] violate the radiated-power limits in Part 15, or [2] result in any
interference with cellphone use as little as a foot outside the
property line, the property owner would probably lose (IMO).

To keep the jamming signal strictly within the property lines, you'd
probably have to Faraday-shield the whole building... at which point
you probably wouldn't need the jamming transmitter.

If you should intentionally jam or cause a cell phone not to operate
by deliberately imposing shielding of the signals and someone with an
emergency tries to make a call, Guess who is going to get sued! And
probably win. Regardless of what federal laws are or are not violated.

73
Gary K4FMX

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