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What is this T shaped thing?

bruceh

bruceh

Well Known Member
Working on updating a Garmin 200 COM with a GNC 355.
I see this T shaped device inserted on the coax cable and have no idea what it is. It is only stamped with "DO NOT REMOVE".

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I'm sure someone knows!
 
It's a notch filter to keep your comm transmit from interfering with your GPS. ACS has 'em
 
Perfect! I found what it is from ACS's web site.
Mystery solved. It is a TED 4-70 GPS Notch Filter.

Now with a different GPS/COM solution with the GNC 355, should I still keep this in the airplane? I'm curious if this is more about fixing an issue based on the current locations of the antennas (which isn't changing with the update), or just fixing the issue with the current equipment (which is going to change).
 
When transmitting on the COM-radio there is a fairly strong electric field around
the COM-antenna.
A small part of this electric field is revived by the GPS-antenna.
So if the antennas are located like before, I would use the notch filter.

Good luck
 
There is a “known problem” with at least the GTN-650. Transmit on the 650 and something else re-radiates the out of band harmonics and that is what kills the GPS signal (I have first hand knowledge on this). Perhaps other Garmin GPS navigators share this issue - I don’t know.

Here I suggest verifying the GPS antenna feed line meets the minimum required length of the install manual. If so, then you can try not using the notch filter. Watch the GPS signal page when transmitting on your 355 (and any other radio you may have). This will tell the story.

At any rate there is no real down side to keeping this bandaid fix.

Carl
 
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