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

[Poul-Henning Kamp]

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In message <589F4A79.3050800 at rogers.com>, MLewis writes:

>Late yesterday I placed old neoprene rubber mouse pads, rubber side 
>outwards, up the metal blinds between the blinds and the antenna.

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.

Polymers with varying metal content offer a handy range of
electromagnetic impedances between "short" and "open"[1], and it
is used a fair bit in various niche markets.

See for instance the first document here;

	http://www.eccosorb.com/resource-white-papers.htm

It is not inconceiveable that off-spec or scrap materials from
the production might end up as mousemats.

Here is an interesting article about other things you can do with
such materials:

	https://archive.org/details/bstj27-1-58

Poul-Henning


[1] If you arrange for the imperance to ramp from open to short you
have a "stealth material".

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