[time-nuts] 5V GPS antenna on 3.3V device?

[Christian Vogel]

On Tue, 10 Apr 2012 05:29:20 +0200, <lstoskopf at cox.net> wrote:
> How's the best way to run an older 5V antenna with the new 3.3V GPS  
> engines?  Bias T?

Assuming you want to open up and modify your GPS:

In many GPS devices you'll find the biasing circuit easily just next
to the antenna connector, built with discrete components.

Sometimes you'll have to look in the datasheet of the GPS module,
there will be a (often well accessible) pin to feed the bias voltage.

Typical circuit:

Antenna
o------+-----||---(GPS-Input-Amp)
        |
        |
        +---uuuu----/\/\/\----(Vcc)
            RF       I-limit
            Choke    Resistor


Just lift up the I-limit resistor and feed in the suitable bias voltage
to the RF choke.