NTIA Releases Cell Jamming Report

The National Telecommunications and Information Administration has a released a report detailing the results of tests conducted at its Boulder, Colo., lab in December on mobile phone signal jamming equipment. The tests were done as some members of Congress and others push to permit jammers to be allowed to be used in prisons.

The testing, which was done mainly in a radio-anechoic chamber, involved a jammer supplied by CellAntenna Corp. that used both the 800 megahertz cellular and 1900 MHz PCS bands. The equipment operated at a power level of up to 100 watts, and emissions were measured in bands from 100 MHz to 6 gigahertz.

"If jamming were to be performed across the full width of the targeted bands, improved RF output filtering might be needed to reduce the device's out-of-band (OOB) emission levels in the adjacent bands," the report said. "An alternative approach to reducing OOB emissions in the adjacent bands would be to reduce the device's in-band chirp width while using less-effective RF output filtering."

"The device's unwanted emissions are better contained within the cellular and PCS bands when the chirp range is limited to a 2 MHz band segment vs. a full band," the report added. "The diplexer did improve the OOB roll-off in the spectrum immediately adjacent to the jammed bands, although measurable emissions did occur in those bands even with the diplexer installed. Beyond the OOB region of the adjacent bands, and with the exception of one emission near 3000 MHz, installation of the diplexer reduced unwanted spectrum emissions to levels that were below the 100 dB [decibels] dynamic range of the measurement system across the range of 100 MHz to 6 GHz."

The report did not address (1) whether CellAntenna's product was effective at jamming signals, (2) OOB levels for "alternative jammer designs," and (3) "[t]he aggregate radiation level from a jammer installation."

Howard Melamed, CellAntenna's president and chief executive officer, told TRDaily that he was pleased with how his equipment, a high-power device normally used for military purposes, performed.

"What you see from the report is that the unit performed great, but needs to be placed within an engineered solution," he said. "At all times we made sure to point out to the NTIA that the solution to cell phones in prisons is not about a specific product but, rather, an engineered solution. Some of the points they made agreed with us directly. Better filtering ( which we do) reduces the chance of out of band emissions."

He said the same equipment, "configured by our engineers with our own specially designed filters," was used for an NTIA-run test last week at a federal prison in Cumberland, Md. Mr. Melamed called the prison demonstration "an overwhelming success."

"We are proud to have participated in this experiment with the NTIA," he added. "The testing of the equipment has given the NTIA valuable information that they did not have before and now can no doubt supply the right advice to both the Federal Bureau of Prisons and Congress, so that jamming of cell phones can be deployed to keep us safe from criminals behind bars."- Paul Kirby, paul.kirby@wolterskluwer.com