[time-nuts] GPS Antenna Voltage-Dropping
GandalfG8 at aol.com
GandalfG8 at aol.com
Thu Sep 3 07:44:26 UTC 2009
In a message dated 03/09/2009 02:05:20 GMT Daylight Time,
Brucekareen at aol.com writes:
I bought a 3.6-V Trimble Bullet GPS antenna on ePay and wish to use it
with
my T-bolt. Rather than try to internally modify the T-bolt to provide a
3.6-V antenna feed, I decided to try to build an in-line dropping adapter.
I seriesed two Si diodes inside a 100 pf tubular ceramic capacitor and
installed the shrink-wrapped assembly inside a salvaged BNC-M to BNC-F
coaxial
assembly. Unfortunately the completed assembly exhibits about a 4-to-1
VSWR when terminated in a 50 ohm load. Has anyone else tackled this
challenge?
The 3.6-V Trimble antenna has less gain than the 5-V version which makes
my planned antenna rcable run on the edge even without the high VSWR..
----------------------------
If you dont want to modify the T'bolt it would probably be easiest to
derive 3.6v from the 5v supply external to the T'bolt and feed that into the
antenna line with a blocking T.
In the long run though it might be cheaper just to cut your losses and sell
on the 3.6v version, buy a higher gain low cost 5v patch for now if you
don't already have one, and keep an eye out for a 5v bullet if that's what
you really want.
regards
Nigel
GM8PZR
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