External GPS Antenna choices


#1

Hi,
I intend to use the inbuilt GPS receiver with an external antenna. Currently I see only one active antenna being given. Can someone point to more antenna choices (I’d like to have a 10m antenna cable)?
regards
Venkatesh


#2

At https://developer.qualcomm.com/qfile/29467/lm80-p0436-42_add_ufl_ant_and_valid_gps_on_android_app_note.pdf you can find how to add an U.FL antenna connector, so you can use an external antenna.


#3

The problem with that particular choice is that the antenna cable is very short. I’m currently not able to find an 1.8V antenna which supports around 10m cable length.


#4

Hi @Venkatash:

The Antenna shown in the application note, is only one possible choice. There are hundreds of GPS antennas out there all with different gains, directionality, connectors and cable lengths. Additionally you can have a custom antenna built. The purpose of the app note was not to show every possible solution to the problem, just a sample solution.

I am a little concerned with your desire for a 10m cable. As you would expect the signal levels from a GPS are VERY low, transmitting the signal over a long cable will further degrade the signal levels. I am reasonably certain you will need an “active” antenna to get the signal down that long a cable.

I also think you will need to use an extension cable, I haven’t seen any GPS antenna with a 10m cable (although just because I haven’t seen one doesn’t mean it doesn’t exist). Typically you see 50-100mm long cables, the U.FL connector doesn’t have the mechanical strength to reliably support longer cables. You will likely need a U.FL to SMA cable (~50mm long), then a 10m SMA to SMA cable, and then finally a GPS antenna with a SMA connector rather than the U.FL connector.

I am also curious as to what application would require a 10m cable. In general GPS is used to determine the location of something that moves, most things that move are smaller than 10m (example cell phones, watches, bicycles, atvs, etc.) The few exceptions I can think of are larger trucks and ships. Why do you need a 10m cable.

Full Disclosure: I am an employee of Qualcomm Canada, any opinions expressed in this, or any other post, may not reflect the opinions of my employer.