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[aprssig] Re: APRS In A Car

KC2MMi kc2mmi at verizon.net
Tue Jan 24 17:53:05 UTC 2006


Ron-
 Since the laptop was being powered by an inverter, it *probably* was isolated
from the vehicle ground, and the "ground" level on your serial cable might not
have matched the ground supplied directly to the GPS from its own power cable.
So, ground loop, and somehow enough power to heat the cable to a dangerous
level.

Interesting question since the serial cable needs a "ground" and just putting
fuses in it won't help restrict the current flow, so you're left with either no
signal ground, or a fire. Hmmmm. I think you'd need to run some tests with
changing the power supply to the computer, or moving the GPS to an isolated
battery, and keeping a multimeter inline on the serial cable to make sure you
don't have that handling "heater power" any more.





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