[time-nuts] Galvanic decoupling of GPS antenna

GandalfG8 at aol.com GandalfG8 at aol.com
Wed Jun 16 21:33:12 UTC 2010

In a message dated 16/06/2010 22:11:28 GMT Daylight Time, yuri at ostry.ru  

I'm  trying to put gps (for a coarse timing sync and RTC
auto-setting) to a  small controller that must be completely
galvanically decoupled from  outside world. Antenna power must be
supplied from separate power source  (ground potential of isolated part
of circuit can slowly float up to +/-  250 volts referenced to ground
of antenna power supply).

First  thinked about using some choke to inject power, then DC-blocking
capacitor  around 20-30 pf and then smt 1:1 wideband transformer, but
looks like  Mini-Circuits don't make standard models for frequencies
over 1200 MHz,  their search engine give me some part numbers that looks
like special order  ones, and cannot be found in their catalog.

Is there any chances to get  decent performance if I'll simply split
stripline (both ground and signal  traces) by dc-blocking caps? Idea
looks not very good to me, of course, I  suspect that i'll get all
sorts of interference right to GPS LNA  input...

Maybe there is some well proven solution with easily  obtainable parts?

Is there any reason why the GPS module itself can't be part of the outside  
world ?
All you'd need to do then would be to isolate the lower frequency  data 
lines between that and your "controller" which should be a lot  easier.

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