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I am using external active GPS antennas for my application. These Antennas typically have 5m cable with SMA connector that connects to the receiver, while the Antenna is mounted outside. The receiver I am using a U-Blox type module with a built-in LNA and SAW filter. However, the Antenna also includes a single (sometimes 2-stage) LNA and usually a filter as well. The Antenna is magnetic mount and placed on top of a vehicle roof (assume its metal).

In terms of what to look for in an Antenna, I have found that in general most of these Antennas have the following baseline specs:

Antenna Gain: 5dBic (zenith) Antenna VSWR: 1.5 Antenna Axial Ratio: 3dB (max) LNA Gain: 28dB LNA Noise Figure: 1.5 LNA VSWR: 2.0 Filter Insertion Loss: <3db

However, I could purchase more slightly expensive antennas, which change the specs to:

Antenna Gain: 2dBic (zenith) LNA Noise Figure: 1.0 With everything else the same.

I also have the choice of omitting the SAW filter in the antenna, and thus avoiding a potential 3db insertion loss of a filter.

In general antennas have excellent directivity.

My goal is to maximize signal to noise and maximize satellite reception.

Which Antenna would be a better choice? Would the second antenna yield better performance?

Which of these fields are more critical?

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  • \$\begingroup\$ Where will the antenna go? If its outside on your house, then about any antenna will get proper reception \$\endgroup\$ – PlasmaHH Feb 17 '17 at 15:56
  • \$\begingroup\$ On vehicle roof (metal roof). \$\endgroup\$ – Adam B Feb 17 '17 at 16:01
  • \$\begingroup\$ How severe is the interference environment? That SAW might be critical. Or not. \$\endgroup\$ – analogsystemsrf Feb 17 '17 at 16:24
  • \$\begingroup\$ Not severe. Operated in clear view (perhaps somewhat cloudy) on top vehicle in the contiguous USA. \$\endgroup\$ – Adam B Feb 17 '17 at 16:49
  • \$\begingroup\$ Lower noise figure and SAW are better. Is it worth the prize? For the use case you describe, probably not. Just be sure not to buy the cheapest far east product you can find. There are quality brands, even for the low-end magnetic-mount patch antenna market. \$\endgroup\$ – Andreas Feb 17 '17 at 17:29

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