GPS issue related to GPS antenna selector ?

Philippe Guillebert phyce at
Sun Jul 13 18:58:27 CEST 2008


Thanks to , I 
ran into the following (and quite scary) thread :

So I was wondering, maybe the poor GPS performance issue many FR seem to 
have, especially on the internal antenna, is related to the GPS antenna 
MUX (the part responsible for the switch between internal antenna, and 
external antenna if you hook one up) selecting the external antenna, 
even when there isn't one ?

The randomness of this issue could be explained because driving the mux 
with levels like 26% Vdd is kind of "grey zone" and can result in some 
devices working as expected and some selecting the ext. antenna without 
one and then having bad reception.

I see one way to test this theory, by driving the select signal VCONT to 
0V (Werner Almesberger talks about shorting R7616) and see if this 
improve reception on the internal antenna.

This is pure speculation, I didn't test anything and perhaps that's just 
plain stupid but I'd love to hear from someone that focused on this 
issue back in April.


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