[time-nuts] Neoprene rubber drops GPS multipath signals to zero

[MLewis]

My TW4722 GNSS active antenna is on a 100 mm stainless ground-plane, 
placed on 2" of wood on a window sill behind two panes of glass, between 
metal blinds and the glass, almost touching the glass. Feeds a NEO-M8T.

Late yesterday I placed old neoprene rubber mouse pads, rubber side 
outwards, up the metal blinds between the blinds and the antenna.
All signal levels dropped, many around 3 to 5 dBs, a few as much as 15 
dBs. Seemed to equally affect LOS and multipath signals.

After running the night with that to see the affect, I stripped the 
neoprene rubber off another mouse pad and placed the resulting neoprene 
rubber pad under the antenna's 100 mm stainless circular ground-plane 
(left resting on the pad), with the front of the pad folded upwards 
extending an arbitrary 2" up the glass window pane. Pad is 8.75" wide.

Multipath signals reflecting from the bank of buildings opposite the 
window were as high as 24 dBs. After placing the neoprene rubber pad 
under the ground-plane and up the glass, they dropped down to zero.
Zero.
0.0
(screen shot from LH attached)
(Skyview is somewhat less than azimuth ~60 degrees to ~240 degrees. 
Everything outside of that is multipath.)

Mouse pads were the earlier thin bottom-textured pads of denser neoprene 
rubber, not the later thick smooth air-foamed pads (which I've not tried).

Hope this info can help someone as much as it's helped me.

Michael

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