My name is Thaddeus. I’m an FAE with Taoglas. Just wanted to chime in with some commentary on how to get the best LTE performance out of the MangOH Red platform.
FXUB66 is going to be a better choice for poor signal propagation conditions. To Andy’s point, larger antennas tend to have better performance. There is a point of diminishing returns, but the advice is true up to about half a wavelength of the lowest frequency you are using.
As for performance metrics, generally for LTE applications, the metric you care most about is efficiency. Peak gain is a good thing if you have line of sight to the base station and have a very directional antenna, but for your application this is not so much the case. Using a highly efficient omnidirectional antenna will ensure that you have relatively high gain in nearly every direction.
For LTE, there are some antenna efficiency targets that the cellular carriers recommend to aid connectivity in edge conditions like yours. Generally, you’ll want to target >35% at 700MHz, and >50% at 1700/1900MHz. This ensures the WP7603 that talk back to the base station reliably to initiate requests. Adhered to plastic, FXUB66 can get better than 60% efficiency at both bands.
If you are using the CAT-4 version of 7603, definitely grab a second FXUB66 so you can take advantage of the channel gain and diversity MIMO provides. Be sure that they are separated by several inches to get maximum throughput. Even if you are only using CAT-1 though (with the 7603-1), using a second antenna can help increase downlink throughput.
Also, and this is true for all ground plane independent LTE antennas, make sure you provide at least 20mm clearance from metals to get best efficiency and omnidirecitonality.
P.S.: Per Varanith’s comment, TG.30 is also a great LTE antenna. Rock solid performance and very flexible from an integration standpoint.