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I have a 5V active GPS antenna, and want to try using it on a device with a 3.3V bias provided. Obviously, operating at an over-voltage can damage or destroy the LNA. But what happens when the voltage is too low? Will it work with reduced gain, or will it cause some weird state and distort the signal? Is there a risk of damage of components?

I do not know the specifications of my antenna nor my device that provides the 3.3V bias voltage.

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    $\begingroup$ It's unlikely that any damage would occur with undervoltage. In fact, it may work just fine; many modern antennas are designed to work at either voltage. There's no reason not to just give it a try. $\endgroup$ – Dave Tweed N3AOA Nov 14 '16 at 12:52
  • $\begingroup$ Just in case anyone comes across this, I did end up just trying my antenna (an old Garmin boat antenna) out, and it did work pretty well. I don't have any hard numbers to report, but I did receive a signal and picked up many satellites when the antenna was in a good position. $\endgroup$ – Paul Dec 28 '16 at 15:55
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It's hard to say whether your active antenna would work properly if provided with 3.3 VDC instead of 5 VDC. I doubt that any damage would be done, but I'm not the engineer that designed the antenna. You might consider adding a boost regulator (and the other parts it requires) to your circuit, which could convert 3.3 VDC to 5 VDC. Here's such a part, selected more-or-less at random from the astonishing variety of boost regulators on offer.

Your LNA may work fine with 3.3 VDC, so you might as well just try it as-is first. A boost regulator has an inherently-noisy switching power supply inside, which might raise the noise level at the frequencies used by the GPS satellites, as @AndrejaKo points out, so there is some risk that a boost regulator would impair your circuit. However, the switching power supply internal to the boost regulator uses many of the external parts that the boost regulator requires; this gives the engineer an opportunity to reduce the noise level on the band of interest by tweaking the component values, if the noise proves to be a problem.

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  • $\begingroup$ A boost regulator can very easily increase the noise floor in some bands. Depending on the regultor, this may or may not be an issue. $\endgroup$ – AndrejaKo Nov 16 '16 at 13:12

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