Avionics: GPS antenna shelf.

Many folks put their GPS antennas on the glareshield.  I think that's a great location, however I wanted mine to be hidden (other than the one for the GTN-650), so like many others, I wanted it under the cowl.  For that I had to create a shelf.

The SkyRadar DX, GRT AHRS and TruTrak ADI 2, each have a GPS antenna.  However, one is magnetic, one uses adhesive and the last one uses screws.  So I replaced them all with Linx Technologies antennas (MCX and SMA types).  These antennas are tiny, mount with screws and have the proper specs for the purposes intended.

I secured some scrap 1/8" thick aluminum left over from when my first panel revision was cut, match drilled a 3/4x3/4" angle into it, then match drilled antenna mounting holes.

Then I match drilled holes into the firewall, above the VA-168 Sender Mount, attaching nutplates to the firewall so that the shelf can be easily removed if necessary.  The shelf was primed and the antennas were attached with 4-40 screws.  This picture brings to mind the "array factor" of an antenna array's radiation pattern.

Here is where the shelf shall sit when in operation.

If it turns out that they sit too far below the cowl (so that the line-of-sight angle subtended aft is too shallow), I can flip the mount around and install the antennas on the other side to get them higher up.