[time-nuts] Building a DC Block Thingy....

John Ackermann N8UR jra at febo.com
Fri Jul 27 17:44:29 EDT 2007

SAIDJACK at aol.com said the following on 07/27/2007 05:00 PM:

> I have one of these Tucker HP 8-ports GPS antenna amps/splitters too,  and 
> they are configured to only accept an external power supply, but can be  easily 
> modified:
> All you need to do is add a small inductor (say 33nH, 200mA) in the  
> footprint that's reserved for it on the PCB. There is a location connecting the  Port 
> 1 center pin to the power input jack, and the 0805 component is simply  
> missing from the PCB.

I thought about it and decided not to do that because I didn't want my
whole stack of receivers to be depending on Port 1 being connected.
With the external power, I still have a point of failure, but
accidentally turning off a GPS without remembering the consequences
isn't an issue.

> With this simple modification GPS Port 1 can supply power to both  the 
> antenna and the splitter/amplifier.
> At the same time it would be advisable to add a GDT (Gas Discharge Tube) or  
> TVS against lightning proximity strikes.
> This can be done by adding another small inductor (33nH, 3Amps or better  
> rating!) to the GPS antenna port, then connect that through the GDS/TVS to  
> ground.

That's a good idea that I hadn't thought of...


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