It all happens to us at one point or another (some more than others): the dreaded dropped call. You keep talking and talking, and wait for the other end to respond, but are greeted with nothing but the sound of a dropped call. Some of us live in cell phone dead zones, so a signal booster might be your best options for regaining a bar or two of reception...
iBooster
This is specially designed for the iPhone. (but the company also makes different models for other smartphones) Very good at improving the voice and data performance; and even the signal strength in those weak areas where you may be. We like that you really will have fewer dropped calls and faster data rates. This is a type of cradle design, that includes an amplifier, battery charger and built-in antenna. You can even pair it via bluetooth for a hands free operation.
zBoost
We love the long range of 2,500 sq. ft; and that it supports multiple users at the same time. You can bring it to your home or office or even your personal workspace. It truly eliminates dead zones and is very easy to set up. The support of multiple frequencies is an added bonus. It's compatible with US carriers using the frequencies between 800 and 1900 MHz. You don't need a cradle attached to your phone to take advantage of less dropped calls.
SpotWave z1900
The Spotwave signal amplifier can improve cell phone coverage in your home or office. Using a large external antenna and an indoor repeater, it boosts signals sent by both your phone and the cell tower. We like that, within about 30 feet of the coverage unit, you'll experience clearer conversations and less dropped calls. Includes network access unit, coverage unit, 35 ft. coax cable, AC adapter and all mounting hardware you may need. Requires a minimum of 10 ft. between units. Remember, due to the frequency limitation, it doesn't support ALLTEL, Nextel, US Cellular or Verizon Wireless networks.
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If you're getting poor cell phone reception, etc change providers. Don't spend more money on these things.
I live pretty much in the center of San Francisco and ATT can't get a cell phone signal into my home. I switched to Sprint, lower my bill and get cell phone reception at home.
ATT's solution was for me to spend $250 on a cell booster.
You have choices, use them.
Do these work with both 3G and 4G networks?
Yes there are different providers available, but this isn't always an easy answer. I like the service I have but I spend time up in northern Minnesota at our cabin where there isn't the best signal. A booster is a better solution since not matter what provider I have there isn't going to be the best signal.
We use one of the portable models. My wife's commute to work is through some pretty hilly locales, and usually she passes through a couple dead zones. The car booster brings the signal from 0 or 1 bar in these places to a respectable 2/3. Don't knock it until you try it. I can't comment on how it would work say in an urban environment, but through the rural area it really does work. You need to use handsfree with it, of course because the it sits in a cradle, but for most, this is law anyway.
The indoor ones look really expensive, though, and I don't know if I could justify that expense.
We tried the Z-Boost in an LA apartment. Accommodating it's installation requirements (the receiving antenna needs to be a certain distance from the transmitter) was difficult and entailed running coax cable along the walls. I'm not sure it ever did anything to help.