HSMM and balloons

[Robert E. Seastrom]

Louis Mamakos <louie at transsys.com> writes:

> Not if you're using 802.11 Wi-Fi radios at 2.4GHz. 
>
> http://en.wikipedia.org/wiki/Hidden_node_problem

Hidden node doesn't mean it won't work; it just won't work well.  When
people suggest playing with mesh networks for moving any non-trivial
amount of data, I go with the assumption that they already discarded
the notion that they will work "well" long ago.  Remember that 1200
baud packet suffers from the hidden node problem too, yet somehow it
manages to "work".

I think the number for pure-Aloha mode throughput is 18.4% of
available channel bandwidth.

On a related note, I buy helium periodically (in 60 cubic foot "owner
tanks" - $78.87 each for the fill last time I picked one up).  Helium
is in short supply and expensive like whoa these days, to the extent
that grocery stores are not handing out free balloons to kids anymore.

Had a conversation with the guys at Arcet a while back.  One can get
(4 9s pure grade which is the cheapest stuff they've got) hydrogen for
a fraction of the cost (4x volume tank for same price plus rental;
they don't do owner tanks for H2), but for some reason they're weird
about selling hydrogen to the general public.  Maybe someone read up
on the H-Bomb and didn't realize they're selling the wrong isotope or
that you need a little nuke to light it off.  But I digress.  Kind of
ironic considering that they sell acetylene which is some fairly nasty
stuff to all sorts of dodgy characters with no questions asked.

So, if AMRAD gets at all interested in doing balloon stuff let me know
and I'll see what I can do about filling out the paperwork and talking
to anyone who calls from ATF and wants to know what's going down.  I
even have a place to store the tanks where I don't think they
represent a hazard to anyone.

-r

> On Oct 20, 2012, at 4:47 PM, Martin <dcmk1mr2 at gmail.com> wrote:
>
>> There was talk over tacos today of using a balloon to get a mesh
>> router to some altitude.
>> 
>> Federal and local regulations apply to  balloon operations.  There is
>> FAR 101 that limits moored balloon operations to an altitude of 500 ft
>> with many restrictions.  A FAA NOTAM issued in 2009 forbids moored
>> balloon operations within the DC FRZ.  I believe these restrictions
>> can be violated with a waiver from the FAA and coordination with local
>> ATC.  A local business routinely gets waivers to fly a large balloon
>> in the area for photographic purposes (http://www.airphotoslive.com/).
>> 
>> Chloroprene rubber balloons are used for advertising and such. They
>> will outlast a plain latex balloon and should last several days if
>> needed.  They go for about $30.  A WRT54GL runs for about four hours
>> on a set of eight "AA" NiCads.  A WRT54GL weighs about 14 oz and the
>> batteries weigh about 8 oz.  That takes a 5' balloon and about 40
>> cu-ft of He.
>> 
>> It sounds like a fun experiment in the right setting.
>> 
>> Martin
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