Wilson Makes iPhone Reception Possible
During CTIA, I invited Wilson Electronics to come by our San
Francisco offices so it could try to solve our ongoing
iPhone problem. Even though our office is in the heart of downtown San
Francisco, our employees can't connect to AT&T for
calls or data usage unless they stand right by the window in one or two
isolated corners of the building.
Wilson dropped off a pair of its cell phone boosters for me to test: the Sleek Cell Phone Signal Booster, which is intended to be used in conjunction with a single cell phone in an automobile; and the SignalBoost DT Desktop, which is intended for use with multiple phones in a small home or office. Since we have plenty of WiFi in our office to pump data to the iPhone, I concentrated solely on the boosters' ability to improve call coverage.
The Sleek can be purchased for $140, while the DT Desktop is available for $300. Both units promise signal boost for the 800MHz and 1,900MHz spectrum.
The Sleek comes with a 4-inch antenna with a magnetic base that is intended to be affixed to the roof of a car. Since I tested the unit indoors, I instead stuck it on a small desktop switch by the window of my office. I connected the antenna via the included coaxial cable to the Sleek Signal Booster, a combination of amplifier and cradle that is supposed to be affixed to the car's dashboard (I just sat it on my desk). To boost the signal, the iPhone must rest inside the cradle to provide a reliable connection through the Sleek's antenna.
Using an iPhone 3GS, I made a series of inbound and outbound calls first without the amplifier, and then I repeated the tests from the same location while connected via the Sleek. Unamplified, I found the iPhone 3GS failed to ring on four of five inbound calls, and failed to connect on three out of five outbound calls (and one of the successful connections failed a few seconds after I answered the call). I put the iPhone in Field Test mode for this test and found that the signal strength varied between -95 and -104 dB during the test.
When I connected the iPhone to the Sleek, the iPhone consistently reported signal strength of around -85 dB. Repeating the call tests, the iPhone 3GS successfully connected on all five inbound and all five outbound calls. According to the documentation, users should typically expect a 20 dB gain when using the Sleek, with a maximum of around 30 dB possible.
I repeated the outbound call tests, after moving the antenna about 25 feet away from the window toward the interior of the building, and experienced much less success. Without the booster, the iPhone 3GS failed to connect on all five outbound calls. While connected to the Sleek, the iPhone reported about a -10 bB boost (from -104 dB to -95 dB), but could only complete one of five outbound call attempts. Obviously, as an automotive unit, the Sleek antenna is designed to be as close to outdoors as possible.
To better serve multiple cell phones in our office, I turned to the SignalBoost DT Desktop. I surveyed all the offices on our floor using the iPhone Field Test mode, finding the best reception in our lab storage closet. I mounted the cradle antenna (the one that points to the cell tower) to the window in the closet using the included suction cups (the package also includes adhesive strips and mounting brackets). Then I ran 30 feet of included coaxial cable into the lab, where I installed the amplifier and desktop antenna (the one that points into the office, to which cell phones connect) on top of a desk.
Wilson recommends at least 20 feet of separation between the cradle antenna and the desktop antenna to avoid oscillation, but in my testbed, I found 30 feet wasn't enough as indicator lights the amplifier indicated the device was not performing up to specification. I wound up using the included cable connector and running 20 more feet of cable to solve the problem.
With the DT Desktop in place and operational, I found the unit boosted signal to my test iPhone by about 50 dB if standing within 10 feet of the desktop antenna, around 20 dB at 25 feet and no more than 10 dB gain if standing about 40 feet away with walls in between.