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

[SAIDJACK at aol.com]

In a message dated 7/27/2007 13:10:12 Pacific Daylight Time, jra at febo.com  
writes:

>I  actually did just that on one of the HP 8 port splitters that was on  
>eBay a few months ago.  It was configured for external DC but  simply 
>passed the input voltage through untouched.  A 78L05  regulator on a 
>piece of perfboard mounted fairly easily inside the  case and allows me 
>to drive the splitter from my 13.8 volt  bus.



Hi John,
 
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.
 
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.
 
I do not see any impact on sattelite SNR C/No with these two mods on my  
system.
 
bye,
Said



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