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?