[MLB-WIRELESS] Waterproof casing advice...

[Dan Flett]

> Good idea... I didn't think of that. How would the little minitar omni
> hold up against the weather?  Should I put it in heatshrink? Is it OK
> for the aerial to point down, reducing the chance of water getting in,
> or does it need to point up?

The Minitar omni is about 2dB gain - that means it radiates pretty well
in almost every direction except straight up and straight down.  You'd
be pretty safe to use it upside down I think.  Glue heatshrink will do a
pretty good job of keeping the water out - it's not really watertight
and I imagine water would get in and corrode the radiating elements
inside the plastic.  You're probably better off pointing it straight up
if you're going to put glue heatshrink on it though - I don't know if
the heatshrink is RF transparent and you would benefit from the slight
amount of extra height the antenna would have by being on top.

It'd be easy to test if the heatshrink was RF transparent - just put an
unshrunk sleeve over the antenna and check with netstumbler if your
received signal drops.

> 
> > If you extend the aluminium plate past the box so as it sits behind
the
> > antenna it will act as a reflector and give you a bit of
directionality
> and
> > an extra 3 dB of antenna gain.  Ideally the antenna should be about
3-4
> cm
> > away from a plane reflector.
> 
> Another good hint... should this stuff go up on the wiki? I can write
up
> this stuff after I do it if people think it's worthwhile.

Definitely!  Put all the stuff you can possibly find and think of in the
wiki! :)
 
> > BTW it is easy to mod a Minitar for POE, just cut the two tracks
that
> run to
> > the terminating resistors for the unused cat-5 pairs.  Then run a
wire
> at
> > the back of the Ethernet connector from each of the unused pairs to
the
> > power inlet connector.  Make sure you get the polarity right!
> 
> I think I'd rather modify a cable than modify the minitar :-)
> 
> If someone plugs a modified minitar straight into a 10/100 switch and
> the power plug-pack, they will feed 12V into the switch... not good
:-(

It might be a good idea to use diodes to connect the Ethernet connector
to the power inlet instead of plain wire.  Then the power can't go the
wrong way.  I have however found (from experience :) ) that most 10/100
ethernet gear leaves the unused pairs disconnected internally.  So in
most cases the power on those pairs doesn't damage anything if plugged
directly into a non-POE device.  Much better to be safe than sorry
though!

Dan

To unsubscribe: send mail to majordomo at wireless.org.au
with "unsubscribe melbwireless" in the body of the message