This is a proven performer and they are cheap surplus on Ebay.
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L-Com SP97177 800/900 MHz 6 dBi Omnidirectional Antenna like HGV-906U w/Hardware | eBay
(1) L-Com SP97177 800/900 MHz 6 dBi Omnidirectional Antenna with Mounting Hardware. Model: SP97177. 800/900 MHz. This antenna is like HGV-906U but has a Female-N connector and would require an N-Male to N-Male adapter (L-Com AXA-NMNM) to work identically.
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