I would have a look at the www.AESHAM.com web site and use one of the Hustler G-6-440 antennas. With the Hustler antennas make sure you use some clear silicone caulk around the fiberglass radome where it meets the plastic cap on top and at the cap over the base.
The other site would be http://www.comtelcoantennas.com/ http://www.comtelcoantennas.com/PDF%20Datasheets/BS450XL6.pdf I have used a few of these Comtelco antennas and had great service. I work for one of the wireless carriers and we use Comtelco antennas for our Microcells. Paul R. Dumdie Jr. "73" W9DWP/R IRLP-NODE-4455 443.025/2A 145.270/1B/1Z/NAC-293 ARC-Radio-8 KCARES HERD546 EX WB9QWZ WQGG738 AAR5CU/T www.riflesandradios.com
