[time-nuts] Improving performance of a GPS antenna...?

[Jim Lux]

On 4/4/12 5:53 AM, Michael Baker wrote:
> Hello, Time-Nutters--
>
> I saw a rather expensive GPS antenna made by one of the
> big-name GPS survey equipment mfgrs that was mounted
> on top of a 12 or 15 inch diameter disc about 3/4 inch thick.
>
> Turns out that the disc is made of some sort of RF absorbent
> foam covered by a weather-proofing coating of some sort.
>
> If one were to try to home-brew something like this, where
> would a small piece of the RF absorbent material be obtained
> without having to spend too much $$ for this experiment?
>

This material may or may not be what you want
http://www.chomerics.com/products/CHO-MUTE.htm

Parker-Chomerics *does* do samples  (probably a 10-15cm square piece 
that is mailable)

http://www.lairdtech.com/ is another supplier

http://www.masttechnologies.com/magnetic-vs-dielectric-absorber-selection/

http://www.emc-products.dk/

http://www.arc-tech.com/

http://www.aemi-inc.com/  - pyramidal absorber
http://www.ets-lindgren.com/Absorbers

If you get the blue pyramidal absorber, get the kind that has the 
waterproof coating.. not only is it more rugged, it doesn't shed as much 
of that horrible blue/black conductive dust.  (we had a roof leak in one 
of our indoor ranges at JPL a few years ago, and wound up having to buy 
all new absorber.. turns out that the fire-proofing and conductive salts 
wash out..)


Even if you have to buy the stuff, it's not all that expensive, usually. 
  Last time (5 years ago) that I bought pyramidal absorber it was 
something like $20/2x2 foot panel.  The elastomer isn't a whole lot more 
expensive: it's made in huge quantities and the raw materials are cheap. 
  The dominant cost is the packaging/shipping & handling.

the ferrite loaded elastomer is quite dense.  It reminds me of the lead 
apron they put on you when you get dental x-rays.  It's thin and floppy, 
but surprisingly heavy.

Once you get a handle on the names and kinds of stuff you might want, 
you can probably find a way to get it.  You might find it at somewhere 
like Newark or Allied.