On 4/15/14, 8:16 PM, nuts wrote:
I don't use the surf board resin. I use
http://www.tapplastics.com/product/fiberglass/polyester_resins/tap_marine_vinyl_ester_resin/34
I don't have specifics on what Tap sells, but vinyl ester resins have a
dielectic coeficient around 4 and dissipation of at least 0.00x. The
resin is actually better than the S-2 glass.I suppose I can ask who
makes their resin, but I don't know if anyone at a store has that
answer.
ah, but this is "time nuts" and we obsess about the 14th decimal point<grin>
It kind of depends on what you're looking for. For instance, I don't
recall what the big radome over the fancy Leica multiband artichoke
antennas is like. I think it's just plastic (some UV inhibited
plastic), but it might have glass or nomex in it.
The one over the actual elements (inside the choke ring) is some fairly
exotic filled plastic in a carefully designed shape to keep the phase
center in the same place regardless of incidence angle.
1mm phase center shift is 0.005 wavelength (about 2 degrees) of carrier
phase. Over a 8 hour pass (4.3E13 cycles) that's in the 1 part in 1E15
range.
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