Directional antennas are typically better if you can orient the antenna to one direction that has significantly better signal reception than other directions. Omni-directional is better if you have equally strong signals from several directions and cannot tell that any one direction is better than another.
You could use an amplifier kit such as:
http://www.rfwel.com/shop/Amplifiers...x-weboost.html which has everything you would need or you could find other amplifiers from here:
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You rely on your cellular connection every day to connect with family and friends, to access emails and make important calls. Connect 4G-X can significantly improve your coverage when and where you need it. It will amplify a cellular signal throughout a large area and on all cellular-connected devices, including tablets and laptops. Designed to meet your specific needs, Connect 4G-X features dynamic, self adjusting gain controls that automatically customize the gain level on each frequency band as conditions require.
Features:
Installs in minutes
Boosts signal for all U.S. & Canadian cell carriers
Friendly, U.S.-based customer support
All components needed for installation in one package
FCC & Industry Canada Certified
Wireless operation
Works on all generations of CDMA, GSM, LTE, AWS
850 MHz, 1900MHZ, AT&T 700 MHz 4G Networks
Supports multiple phones, data cards simultaneously
Attractive, sleek design
Automatic overload/oscillation protection
Benefits:
Improved indoor cellular voice and data signal
Reliable cell signal and more consistent data speeds
Faster data downloads
Up to 2 hours additional talk time in weak-signal areas
What's Included:
470004 Connect 4G-X 5-band Cell Phone Amplifier/ Repeater
311135 Inside Wall Panel Antenna
314411 Outside Directional Antenna
859948 Power Supply
952360 60' Black 400 Ultra Low Loss Cable (50 ohm)
952375 75' Black 400 Ultra Low Loss Cable (50 ohm)
471104 Installation Manual/ Instructions