Tuesday, June 17, 2008

Homemade GPS Antenna

I needed a very small, lightweight passive GPS antenna for an ET-301 USGlobalSat GPS module, but didn't have anything to use on-hand. I started some research to make one but information on this topic is very limited... so I figured a good option would be to make my own. As far as passive antennas go, there doesn't look to be very much too them. I looked at lots of pictures of antennas online and reverse engineered them as best as I could. The result was an antenna made out of a thin piece of metal that is 24mm x24mm located 2mm over a 30mm x 30mm ground plane.

Now i'm not an RF engineer, and basic antenna math fails me on this antenna design (1/4 wavelength at a gps frequency on the L1 band of ~1.5Ghz would be 50mm) which is much larger than the antenna I designed mine after... but upon power up I had GPS lock.

So it works... which really shows how sensitive modern GPS receivers are. This is really amazing since this module is sitting inside, on my bench, located about 6 feet away from the nearest window... and I made the antenna by copying antenna designs I found online. The NMEA $GPGGA string shows that there are only 4 satellites in view (which is expected since I am indoors) so I am really looking forward to testing it outside.

At some point I hope to find a good resource for GPS antenna designs to really make a proper antenna the right way, but for now it works... and I am still impressed by the sensitivity of this receiver.


  1. I assume you powered up your receiver without the antenna to ensure it didn't receive a signal. :-)

    Antenna technology is a black art. Nothing about it makes any sense to me. Congrats

  2. Yes, absolutely no lock without the antenna. :)

    And haha, I totally agree about how antenna design is a black art... almost magic.

  3. my gps modul couldn't lock any sattellites. and i want to try your antenna. what kind of metal did you used?