[time-nuts] Failure mode in GPS receivers

David Smith dwsmith at bigpond.net.au
Sun Dec 17 18:25:49 EST 2006


I've owned a Trak Systems 8821 for over a year, and had a problem with 
the antenna side.  Yours may be different.

My unit is designed to work with a powered antenna, and it feeds 12V up 
the coax to power it.  Apparently this is the "standard" voltage for TNC 
antenna connections - the smaller MCX etc. are 5V standard.

In my ignorance, I initially connected one of the regular "mouse" type 
antennas to it that requires 5V.  The antenna worked OK for months, and 
I only discovered the error when I was fitting another more permanent 
antenna.  Strangely, the "mouse" no longer works on 5V, but seems to get 
by on 12V.

Because most powered antennas these days seem to be 5V, I modded the 
Trak with a 78L05 in the antenna power circuit to match.

So, what you could have done is fried the port on your splitter with the 
12V?  Just a guess.

David Smith.

P.S. Have you got any software for yours?  I've got a User Manual PDF 
for mine if that helps.

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