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rmhou(at)yahoo.com
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 Posted: Wed Jan 02, 2008 2:38 pm Post subject: GPS antenna tripping breaker |
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I run into a possible antenna related problem when testing my Northstar M3 GPS.
First, let me describe my set up. My M3 is wired to MD40 CDI, Narco AR850, and an USB RS-485 converter to a PC. During my test, I connected a Trimble GPS antenna (P/N 16248-20) via an SMA-to-BNC adapter. I used the Trimble antenna because that was what I have on hand although I knew it is not an approved antenna for M3.
My M3 did acquire GPS signals OK, and outputed GPS position to my PC. However, after few minutes, my ship power 3A breaker tripped. I felt the power wire and the breaker, and they are HOT. I re-wired my setup to a seprate 12V battery via a 5A fuse, and it again tripped the fuse. And the M3 felt very hot like a light bulb.
I then tried a 10A fuse & it managed to run for 15 min without tripping the fuse. I know I should have measue the amp but did not because I don't have a amp meter that will handle the current.
I let the M3 cooled then use new 3A fuses for the rest of my test. I found the M3 would run for more than 30 min without tripping the 3A fuse and not getting hot when the antenna was disconnected.
I intend to buy an M3 compatible antenna for my install, but I want to confirm that the Trimble antenna, and not the M3, was the cause of hight current draw. Any idea of how can I confirm that short of sending my M3 to an avionice shop for a yellow tag?
Thanks in advance.
Robin Hou
Be a better friend, newshound, and [quote][b]
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hdwysong(at)gmail.com
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| Posted: Thu Jan 03, 2008 3:56 pm Post subject: GPS antenna tripping breaker |
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| Quote: | I intend to buy an M3 compatible antenna for my install, but I want to confirm
that the Trimble antenna, and not the M3, was the cause of hight current draw.
Any idea of how can I confirm that short of sending my M3 to an avionice shop
for a yellow tag?
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Warm wires/fuses come before smoke/fire. Stop while your M3 is still
alive, Robin. 
The problem is likely w/ the antenna since you can run the unit on the
bench with the antenna disconnected without blowing fuses and popping
breakers. The installation manual is rather adamant about using one
of the approved antennas (AN120, AN135, AN155) for reasons you've
discovered.
1. Put the Trimble antenna away.
2. Measure the voltage on the antenna cable coming from the M3
between the center conductor and the outer connector and make sure you
see 5V.
3. Order a COMANT CI 405-200 (AN120 equivalent) and be done with it.
NOTE --- If you see 12V on the antenna cable your M3 is configured for
use with an AN155. You can change an internal M3 jumper for 5V or buy
an AN155.
Regardless, don't do any more testing with the Trimble antenna.
D
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