November 10, 2006
In keeping with my goal of making the Bearhawk as streamlined as possible, I want to mount the GPS antenna inside and let it look up through the fabric. I know that GPS antennas look through fiberglass and paint as if it were thin air so i wondered if the same was true for fabric.
I asked the question on several of the airplane building lists that I belong to including the AeroElectric list. Some folks said that it will have little or no effect on the signal reception so go for it. Others were of the opinion that the UV reflecting Silver PolySpray would block the signal making the GPS useless.
To that end, I devised a very unscientific experiment. I build a square frame out of 1" x 2" wood and covered it with fabric. I heat shrunk the fabric, then put on several coats of Poly Brush letting them dry between coats. I then brushed on 3 heavy cross coats of poly spray letting it dry between coats. When finished, I could hold the box up to the sun and not see any light coming through.
I then moved my Jeep Cherokee out into a clearing where I had a nice unobstructed
view of the sky. Here is the
I started by taking a control reading without the fabric box covering the
GPS antenna. Here is the Satellite Status page on my Lowrance 2000C
GPS without the box covering the
I then turned off the GPS and unplugged it. I covered the GPS Antenna
with the fabric box and restarted the GPS. Here is the Satellite Status
page on my Lowrance 2000C with the Fabric Box covering the GPS
As you can see, the reception changed very little if any. Some of the satellites near the horizon were slightly degraded but not enough to hardly notice.
I have not run this test on an overcast day yet but I will the next time we have one. I'll post the results here when I get them.
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