Notch Filters?

[4kilo]

The installation manual for my GNC 300XL calls for a notch filter in the com antenna line.

Have people found this neccessary? Where could I find one? (Googling the Garmin suggested part number only hits Garmin GPS installation manuals)

Pat

[az_gila]

Originally Posted by 4kilo

The installation manual for my GNC 300XL calls for a notch filter in the com antenna line.

Have people found this neccessary? Where could I find one? (Googling the Garmin suggested part number only hits Garmin GPS installation manuals)

Pat

I got one from my local avionics shop.... about $40 IIRC

In my case, I upgraded an Apollo Loran to a slide-in replacement GX-55.

The installation instruction gave a set of Comm frequencies to transmit on... if any of these frequencies caused a loss of GPS signal, the installation needed to be tweaked. I had a comm. antenna too close (since moved) and a notch filter in that co-ax solved the problem.

Since it's a "plug-in" device, it's somewhat easy to add later as long as you can get to the coax. behind the panel. In my case I had a straight coupler in line, so I just replaced it with the notch filter.

Do your installation instructions give you the specific comm. frequencies to test?

gil in Tucson

[Mel]

It's been a while ago and I may be mistaken, but I'm pretty sure that one was included with my GNC-250XL.

[ptrotter]

When I ordered my GNC300XL from Stark, I asked about the notch filter. He said he didn't think it was really necessary. He said he would throw one in with it, but I think it came with the unit anyway.

[4kilo]

Mel,

You were right again. There is a gizmo in the GNC 300XL materials which must be a notch filter. I didn't recognize it as such because it was labled something else in German.

Thanks all,

Pat

[az_gila]

Originally Posted by 4kilo

Mel,

You were right again. There is a gizmo in the GNC 300XL materials which must be a notch filter. I didn't recognize it as such because it was labled something else in German.

Thanks all,

Pat

It should look like a BNC "T" connector, with the long leg not having a connector on it...

gil in Tucson

[4kilo]

Gil,

That describes it exactly.

Thanks again,

Pat

[az_gila]

Pat... glad you found it...

Just to be clear, the notch filter goes in line with the Comm. antenna cable. You might need 2 filters if you have 2 comms. Put in in line first with the comm. that has it's antenna closest to the GPS antenna.

Some details here...

http://www.avionics.com/Avionics%20O...20Interference

It's usually not needed in you label your GPS "VFR USE ONLY"....

gil in Tucson