HELP NEEDED on info needed to buy external antenna for Clear 4G USB Modem (PXU-1900)

I currently own and have been using the 'Clear 4G USB Modem (PXU-1900).' Most of the time I use it with a laptop when I'm out and receive excellent coverage wherever I am. However, I do have a backup PXU-1900 unit that I plan to hookup to my main computer which is in a basement. Here's the problem, I don't receive a signal indoors(I AM in the coverage area). I do know that I'm going to need an antenna that runs outdoors; I've ran a 15ft USB cable attached to the modem outdoors(in summer weather) through a window. My basement window is roughly 8ft below sea level and have received anywhere from 6-10 signal bars when placing the antenna outside. That was a previous fix. I do need something more permanent since I live in NYC and well...it's winter...and snowing/cold/rainy. I was originally going to put a directional antenna on the roof (which has clear line of sight and is only 30 ft give or take a few ft from the basement window) to the Clear Tower (only 0.5 miles away), but I need something with a low-profile which I can mount just outside my basement window. I was going to go with an omni instead of a directional. Any suggestions or advice would be greatly appreciated. Thanks.

Because it seems you have a very good outdoor signal this greatly expands your list of options - you need not worry about antenna gain provided that you're gain is good enough to overcome the cable losses (and for a 30ft LMR-400 cable at 2.5-2.7GHz you only lose about 2dB). Low-profile antennas are typically low gain.

Here is a kit that has the most commonly used antennas for such an application: http://www.rfwel.com/shop/4G-USB-Mod...tenna-Kit.html. By far the most popular antenna in the kit is the 18dBi panel antenna but this is quite large (15" x 15"). The 12dBi omni antenna is also a good choice and this has a length of 45" and a 1.5" diameter. The 16dBi Yagi antenna VA25-16-NF might also work.