[time-nuts] Galvanic decoupling of GPS antenna

Yuri Ostry yuri at ostry.ru
Thu Jun 17 00:34:43 UTC 2010


Thursday, June 17, 2010, 2:44:43, Didier Juges wrote:

D> It is not clear to me why the antenna should be isolated from the
D> receiver, I would prefer to keep the antenna and receiver on the
D> same return, and isolate that assembly from the rest of the world.

D> It is much easier to provide isolation on the supply, RS-232 and
D> 10MHz (if you use it) than on the antenna, in my opinion, at least
D> as much as it is less likely to have a negative performance impact,
D> and you can do it with off-the-shelf parts.

Too long story to explain it now. I have very limited power available
on those what named "outside world" here. Just enough to "feed" some
low-power active GPS antenna (I can allocate approx 15 ma @ 3.6V).
In addition, whole design is battery powered, so it will be
difficult to allow extra 30-40 ma for DC-DC converter module
quiescent current. ;)

From my first look it was a good idea to isolate antenna (and maybe
even consider passive antenna if tests will show that there is enough
gain) and make a full use of low-power features of that tiny uBlox

Best regards,
 Yuri                          mailto:yuri at ostry.ru

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