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Scramble This!
Ask Chris · October 12, 2000

Q: In your last column you made a reference to a 800 MHz jammer that could be built for around $100 in parts. Any idea where I could get a schematic for such a device?

-- Jim Klein

A: The scrambler was an afterthought to my commentary about annoying cell phone users. Although I consulted with an expert before publishing it, I didn't have the schematics for a call-blocking device, nor would it be practical to release them in this forum. But read on - I think I can help.

First, I should warn you that the device you want to build is illegal. Allow me to quote from a recent Federal Communications Commission memo regarding scramblers:

"There are no provisions in the FCC's rules that permit the operation of any device intended to interfere with cellular communications. Further, Section 333 of the Communications Act, 47 USC 333, prohibits any person from willfully or maliciously interfering with the radio communications of any station licensed or authorized under the Communications Act or operated by the U.S. Government.

"Based on the above, the operation of transmitters designed to jam cellular communications is a violation of 47 USC 301, 302(b), and 333. The manufacture, importation, sale or offer for sale, including advertising, of such transmitters is a violation of 47 USC 302(b). Parties in violations of these provisions may be subject to the penalties contained within 47 USC 501-510. Fines for a first offense can range as high as $ 11,000 for each violation or imprisonment for up to one year. The equipment can also be seized and forfeited to the U.S. Government."

Still with me? OK, if those chatty cell phone callers are so annoying that you're willing to risk an $11,000 fine and imprisonment, then don't let me stop you. Here's how you would theoretically build a scrambler. (And for all of you legal folks out there, let me state for the record that I am in no way encouraging this.)

The scrambler recipe comes to us courtesy of a reader who, for obvious reasons, will remain anonymous:

"Get a 74HC04 hex inverter from Radio Shack, a bit of 22 gauge wire, 2 AA batteries, a battery holder, and a small switch," he writes.

"On a hex inverter, there are 6 identical circuits. You make two identical circuits, each with three inverters. (Let's call each set A, B and C.) Output of A goes to the input of B. Output of B goes to the input of C. Output of C goes to the input of A."

"Leave the wires between pins a few inches long (they are your antennas). Repeat for the other set of inverters. Connect the negative lead (black) of the battery holder to the GND pin on the chip. Hook the positive lead of the battery holder to the switch, and the other side of the switch to the Vcc of the chip. Install batteries - turn on," he adds.

Got that? OK, what you do with this is up to you …

Personally, I think it's much easier to move - or ask the talkative passenger to pipe down. No sense building something illegal in your basement just because you're ticked off at another traveler.

Christopher Elliott is a travel commentator and author of A Bridge to Nowhere: A Year in the Florida Keys. All e-mailed questions may be edited, condensed or republished at the site's discretion. Ask Chris appears weekly on this site.