Letter: Cell Phone Jammers vs. Blockers

Hi Hugh,

I just wanted to pass along a quick clarification for readers to a posted review by Scot two weeks ago.

After Scot’s great review of the MobileSec cell phone blockers, there has been discussion about cell phone blockers vs. jammers. I wanted to make a few points regarding jammers vs. blockers and the pros and cons of each.

Jammers, like the Duke (used by the Army), spam the airwaves to prevent detonations via cell phone or other devices. The reason to use them is “area denial”- blocking all the phones around. The tradeoff:

  1. The price is high,
  2. Jammers can be triangulated and warn the enemy you are there,
  3. Jammers need a lot of power, and
  4. Jammer usage is illegal in most U.S. jurisdictions.

Functional blocker bags don’t have these issues; they mask your RF signal emissions, but most blockers aren’t functional. The reviews online show people writing “X or Y” blocker “drains the battery.” Phones die faster only if they receive enough signal through a blocker that they keep searching for signal. In other words, the blocker is not working. An iPhone 4S in a weak bag, where some reception was possible, drained 50% in two hours. An isolated iPhone 4S, in a functioning bag, drained only 20% over almost a day. Weak blockers are worse than no blockers at all, in many cases. For phones with non-removable batteries, like the iPhones, weak blockers overuse your batteries so you have to replace the phone faster than you would otherwise. – J.H.

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