[time-nuts] GPS antenna in silicon/RTV encapsulation

[Chris Albertson]

Radom for a GPS antenna.  I used this for a while...

Place your patch type antenna on a small round black of plastic foam
packing material.  Make a slit for the antenna cable so that the little
antann lays flat on the disk of foam and the cable comes up from the
bottom.   Now find a suitable glass jar.  Maybe you have finish some
pickles or whatever.  Clean the jar and turn it upside down then force the
jar over the disk of foam.

If you like to mount it to a pole or mast, cut a one inch hole in the jar
lid turn the lid upside down and screw it to the a wood pole (2x4)  The jar
with thread onto the lid.

Eventually the lib will rust and the flat bottom jar might not work in your
location but is is completely weather proof for zero cost.  I eventually
bought a real timing GPS antenna and paced it on e 1" galvanized pipe mast.
   BTW I looked at some expensive GPS antenna  mounting hardware intended
to connect an antenna to a pipe and found it was functionally identical to
a pipe flange.    An inverted jar lid glued to a pipe flange would make a
great radome, and then you lead the cable down the pipe.  Spray paint it
all white and it would even look good.


On Tue, Apr 15, 2014 at 1:53 AM, nuts <nuts at lazygranch.com> wrote:

> I'd be inclined to look at radome construction.
> > http://www.mpdigest.com/issue/articles/2008/may/mfg/default.asp
> The E-3 AWACS is mostly S-2 glass, but they need the strength. For a
> radome sitting outside, you might be able to do better.
>
> The advantage to S-2 glass is you can buy it easily, especially if you
> have a Tap Plastics handy. It works well with the Marine Resin they
> sell, so you know it will last a long time outdoors.
>
> You need to cure the resin in a vacuum, though not a particularly good
> vacuum. There are probably guides on the internet, but here is the
> basic scheme to make a fiberglass composite structure.
>
> Make a form of the final product.
>
> Cover the form in mylar. Tap Plastics sells the mylar too. The resin
> won't stick to the mylar.
>
> Cut the cloth to cover the form. Where you overlap, leave at least an
> inch. You need both the S-2 glass and the thin fiberglass mat. The mat
> is a very loose weave that can hold more resin than the glass.
>
> The basic construction is a sandwich of cloth, mat, then cloth. You can
> add more layers, but you always want mat between the cloth, and cloth
> on the outside.
>
> You will need more mylar to cover the last layer of cloth. This is to
> keep the air out. It helps to have this cut ahead of time because the
> resin will be hardening as you work.
>
> Mix the resin with hardener.
>
> Brush the mylar on the form with resin. The resin on the form is needed
> to hold the cloth onto it.
>
> Place the cloth on the form. Brush on resin.
>
> Cover with mat. Brush on more resin.
>
> Cover with the final layer. Apply more resin.
>
> Apply the mylar. Use masking tape to keep it attached.
>
> Wait two days.
>
> Note that the form has to be "destructible", that is you need to pull
> it away from the radome. Generally you use cardboard.
>
> An alternative scheme, though I don't suggest it for a radome, is to
> use a foam core. You can bush directly onto the form. You need to at
> least a layer of mat then cloth on both sides of the form. Apply the
> mylar and wait two days. The form is part of the final structure, so
> there is nothing to remove.
>
> Generally for antennas in radome, all you do is have a "weep" hole at
> the bottom the antenna to allow air exchange.
>
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-- 

Chris Albertson
Redondo Beach, California