[time-nuts] GPS from a window seat

Brian Kirby kilodelta4foxmike at gmail.com
Thu Oct 1 23:57:50 UTC 2009

In order to fake out some Garmin units, when using them via splitters on 
a external antenna, we put 220 ohm resistors from the center of the coax 
to the sheild.  The splitters we used were capacitive coupled and this 
work fine for the Garmins.

The Garmin units needed to see some sort of DC load, is you wanted to 
use the external antenna ports.  If you did not pull any current, the 
unit stayed on its internal antenna.

Brian KD4FM

Magnus Danielson wrote:
> Jim,
> Jim Palfreyman wrote:
>> I've done this with two separate GPS units. One was a basic unit with
>> no maps - more designed for bushwalking, boating and other direct
>> navigation. It worked really well.
> Mmm. Bushwalking is one of your local specialities I gather...
>> Just recently (a few days ago) flying to Perth I used my car-designed
>> Navman. It locked easily and I chuckled as it rapidly swept across
>> roads and intersection on the ground at 777 km/hr telling me "Go to
>> nearest road".
> That must have been one jumpy ride... 777 km/hr offroad.
> Once again I have been forced to invent a DC fake load to handle the 
> case where the current sensing of the GPS receiver is set higher than 
> the hooked in GPS antenna consumes. The shot-from-the-hip solution 
> involves a T-connector, a 10 uH SMD coil and a 470 Ohm SMD resistor. 
> Not ideal in any sense, but hopefull pulls enought (additional 10 mA) 
> while not mocking too much with the signal. A similar approach has 
> worked before.
> Cheers,
> Magnus
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