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

Bob Camp kb8tq at n1k.org
Sat Feb 11 18:56:49 EST 2017


Hi

For any microwave material, the good old “toss it in a microwave” test is a quick
and dirty one. If the material heats up, it’s lossy. Yes, there are other fairly exciting 
things that can happen other than it warming a bit …. 

Bob

> On Feb 11, 2017, at 5:51 PM, MLewis <mlewis000 at rogers.com> wrote:
> 
> Interesting.
> My guess wasn't a material made for RF but a carbon added to give a decent black colour.
> 
> "It is not inconceiveable that off-spec or scrap materials from the production might end up as mousemats."  and "stealth material".
> Very interesting.
> At an airshow many years ago, these mouse pads were a promotional give-away by the Department of National Defence in Canada...
> 
> I'm now seeing some multipath signals sneak through, usually in the single digital strength but for brief moments as high as 15 dBs. Coming from elevation 5 to 10 degrees, between azimuth 300 to 330 and also azimuth 30 and 60. I'm suspecting the office tower at 135 that sticks up above the bank of buildings. I'll have to add a 1" strip up to 3" high in LOS to that building to see what that does.
> The other multipath signals remain at 0.0.
> 
> Michael
> 
> On 11/02/2017 1:22 PM, Poul-Henning Kamp wrote:
> > --------
> >
> > I can guarantee you that it is not the neoprene itself which does it.
> >
> > It could be residual ZnO, used to catalyze polymerisation of the neoprene,
> > but more likely it is metal deliberately added to the neoprene to
> > change the RF impedance of the material.
> >
> > ...
> >
> > [1] If you arrange for the imperance to ramp from open to short you
> > have a "stealth material".
> >
> 
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