Digital Antenna's PowerMax signal booster

We've all had this experience. You are in an office or a house, and your mobile phone just doesn't work. No signal. Suddenly, you're not so well connected anymore. But what can you do, right?

Well, if happen to be the owner of said house or office, now there is something you can do. The new PowerMax DA4000 from Digital Antenna Inc is a mobile phone signal booster/repeater for the North American market. It supports the 800/850 and 1900Mhz network bands used in North America, and it works with any carrier except Nextel. It doesn't matter if you are using GSM, and the guy in the next office cube is using CDMA, the PowerMax can help.

The PowerMax DA4000 kit includes the amplifier unit, both internal and external antennas, a 30' coax cable, and a couple of power adapters. By making use of one of the 12 volt power adapters, you can use the PowerMax system on your boat or RV as easily as you can use it in your home or office. Since I don't happen to own a boat or RV, I tested the unit at my home, and the home of my sister. Both of us live in areas with relatively poor 1900Mhz T-Mobile signals. My sister's house also has a basement, in which the signal is almost nonexistent. These locations provided a decent test area for the product.

The system works like this. The large exterior antenna can pick up weaker signals than a typical mobile phone can. Plus, the fact that it is outside means that the signal doesn't have to penetrate the walls of the building. This antenna is attached by a shielded cable to the amplifier, which processes both signal bands, and retransmits with more strength to the interior antenna. This is where your phone presumably is. But the process works both ways. Signals sent from your mobile phone are then picked up by the internal antenna, amplified, and retransmitted with greater strength by the exterior antenna, where they will hopefully be picked up by the local transmission tower.

The DA4000's amplifier is protocol independent, meaning it doesn't actually look at what is being transmitted. It has no concept of GSM vs. CDMA vs. TDMA. It just knows when it sees a signal in the correct band, amplifies it, and sends it along. Some technical idiosyncrasies of the Motorola iDen network used by Nextel are the reason that system does not work with the DA4000. Digital Antenna Inc. plans to have a Nextel module available soon, though.

When setting up the DA4000 system, you need to be aware of a few things and follow a few rules. For one, both the large black external antenna and the small white interior antenna need to be oriented vertically. This is important. Also, they need to be as far away as possible from each other, and realistically need to have an exterior wall between them. When the antennas are too close to each other, the amplifier will reduce power so as to prevent a feedback loop where the system would end up amplifying its own signal over and over again. The higher the external antenna is located, the more likely it will find an unimpeded signal to relay, too. So experimentation with antenna location, both internal and external, is important. For this reason, you will probably need more than the included 30' of coax cable. But for our tests, we used only what was provided in the kit.