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GPS Antenna voltage and current requirements

by n8ur

I am working on a current limiter circuit for a GPS antenna bias tee, and wanted to measure the minimum voltage required by particularly modern 3.3V antennas.  I did a very simple measurement of a bunch of antennas I had laying around, and these are the results.

I put a little stub on the output port of a network analyzer, and connected the GPS antenna to the input port and set it a foot or so from the output.  DC power was fed to the antenna via the VNA’s internal bias tee.  The analyzer swept 1 to 2 GHz and the signal strength seemed reasonable and I didn’t detect any signs of gain compression due to overmuch signal.   In each case, I started at 0V and increased until the amplitude of the signal on the analyzer peaked and flattened off, then noted the voltage and current (and sometimes some other interesting info).  Current was usually measured at the minimum voltage, but sometimes at the nominal (e.g. 5.0 where 4.7 is minimum).  There was no attempt to accurately measure gain, filter bandwidth, etc. — this was simply to check DC power requirements.

You can see three main generations of antenna: the oldest that want at least 9 volts, a big mid-range designed for 5 volts, and the newest that use 3.3V.


Generic mag mount
“hockey puck”
6.523~3dB down @ 5V
Motorola ANT1A0797
mag mount
Unknown “bullet”
timing antenna
4.235Sharp filter peak
Symmetricom 58532A
timing antenna
3.818Very sharp filter peak
u-blox ANN-MB-00-00
dual-freq mag mount
dual-freq survey
Ashtech ASH11661
dual-freq survey
2.654A pretty modern antenna
Trimble Zephyr
dual-freq survey
4.33V96Very high gain

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