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I'd like to test GPS Antenna performance, but I don't have access to any expensive RF equipment. What is the best way to evaluate GPS antenna performance by using only standard NMEA sentence type data? The Sirf and U-blox based receivers I am using allows me to enable almost any standard NMEA sentence.

One crude way of testing an antenna is seeing if it actually gets a lock -- however, that's the most basic test. I'd like to evaluate further.

Some ideas that I have:

  1. Measuring number of satellites it can lock to
  2. Looking at all the signal strengths of all satellites
  3. Adding up all signal strengths of all satellites that it can lock to.
  4. Look at the HDOP and VDOP values -- however, perhaps this is not helpful or meaningful as this only depends on the geometry of the locked satellites.
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  • \$\begingroup\$ What are your performance metrics - what would qualify as Good and Better for you? Where will it be mounted? What is the GPS information used for? Are you comparing good and great, or average and poor antennas - are you looking to weed out complete disasters or to get the absolute best from a selection of available antennas? \$\endgroup\$ – tomnexus Feb 25 '17 at 20:21
  • \$\begingroup\$ @tomnexus, all antennas are active, magnetic mount antennas placed on top of a roof of a vehicle. All are typically using a 25mm patch, with a builtin LNA, and 3-5m cable length hooked up to a receiver inside a vehicle. I am comparing good and great Antennas and I am trying to find the absolute best from a selection of available antennas. Antennas range from $5 / each to $100 / each. \$\endgroup\$ – Adam B Feb 26 '17 at 2:14
  • \$\begingroup\$ Adding reference I just found: digikey.ca/en/pdf/t/tallysman-wireless/gnss-antenna-performance \$\endgroup\$ – Adam B Feb 26 '17 at 5:18
  • \$\begingroup\$ Also this: digikey.ca/en/pdf/t/tallysman-wireless/antennas-gps-gnss \$\endgroup\$ – Adam B Feb 26 '17 at 5:20
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None of your approaches are better than the simple "how well does my GPS receiver work for my application" test.

GPS antennas are actually combined antennas and amplifiers. So you'd not only have to take the property of the actual antenna (gain/directivity, efficiency) into consideration, but also (partly conflicting) properties of the amplifier (gain, noise figure, iiip3,...). That all makes testing the device actually application specific:

If you're using it in an urban environment, you might not want the amplifier to be too sensitive, because sensitive amps are usually faster at being driven into nonlinearity by interference, and there's a lot there.

On the other hand, you'd of course want to amplify even the weakest signal if you're traveling in a dense, wet mountain forest where satellite signals are heavily attenuated.

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