[CUWiN-Dev] Rugged Node Construction DOCO:

[Quantum Scientific]

Very thorough.

A few suggestions:

On Saturday 29 January 2005 12:18, Sascha Meinrath wrote:
>        We recommend the NEMA-4x enclosures sold by Metrix Communications for use with Soekris 4526 boards.

Have a look at:
http://socalfreenet.org/node/view/267

... it's actually a (secret, shhh) product of:
http://www.alcoa.com/afl_tele/en/product.asp?cat_id=74&prod_id=222

Also there's:
http://www.demarctech.com/products/reliawave-ode/reliawave-rw-ode-8585.html
... but it's way too expensive.  I use Stalin J-boxen myself (~$40), which come in white.  Most boxes come in gray;  light, light gray is the best match for the sky.


>        You must build your antennas for the band that you are using-2.4GHz (802.11b/g) or 5.8GHz (802.11a). Use an
>        N connector for the connection between the cable and the antenna. The N connector is most appropriate for
>        the high frequency signals used by 802.11x.

Actually 'a' is 5.2GHz.  5.8GHz is also unlicensed, and is officially the only freq you're supposed to point-to-point on, but range is not good for allowed powers.  Who cares about the FCC anyway, pffft...  :j

*All* N connectors can handle up to 11GHz, and all are ostensibly watertight.  But the ones with a solid ring (not split) can handle up to 18GHz.


>        Mesh nodes will typically use omni-directional antennas. This is recommended for most cases.
>        Omni-directional antennas transmit and receive equally in any direction towards the horizon. This allows
>        the formation of arbitrary meshes without having to aim antennas (or re-aim after a high wind). It also
>        means that there may be "wasted" radio energy that causes interference for nearby nodes.

One concern I have is one radio.  Because all radios must operate half-duplex...  Node 1 transmits a packet to Node 2;  then Node 1 must shut up while Node 2 passes that packet on to Node 3 (as all are on the same freq).  In practice this means a 50% drop in bandwidth for *each hop*.  The solution is two or more radios, but of course this greatly adds to costs.  See MeshDynamics' website for an in-depth analysis.

 
>        We recommend the HyperLink Technologies HGV-2409U 2.4GHz 8dbi omnidirectional antenna for most generic mesh
>        applications. This antenna features a flared base which makes it less susceptible to windshear than similar
>        antennas from other manufacturers.

I think Hyperlink has gotten difficult to deal with;  maybe they have too many customers.  I suggest the Superpass:
http://www.superpass.com/SPDG16O.html    ($44)

... or 10 degree downtilt:
http://www.superpass.com/SPDG6O-D10.html    ($74.50)
if clients are below the node.

 
>        Microwave signals are extremely dependent on line of site. The higher you can place your antenna,the more
>        likely it is that you will achieve line of site between your nodes.
>
>        Generally, you can use an antenna mast on a rooftop to acheieve height. If you live in a tall building you
>        may be able to simply place the node in a window. Ideally, you will be able to place your node on a radio
>        tower. 

I recommend 35' above the ground.  If mounted too high or too low, neighboring nodes may be above or below the pattern, especially if close.

Some mention should be made of what power level to use.  This is a complex subject which would need to be discussed.  In summary, it would be best if the meshing software could control the radio's power, either manually or dynamically.


>        There are several ways to mount an antenna mast on a rooftop. For flat roofs, you can use an excellent
>        non-destructive flat roof mounting platform that is held in place by cinderblocks. There are also special
>        mounts for gables and chimneys, as well as tripod mounts. Any hardware designed for television antenna
>        mounting will suffice for a mesh node antenna.

Tripod:
http://www.radioshack.com/product.asp?MSCSProfile=745D84CBF04D14A48AA6FF9C89D722C0BA68C1B04FE384678A5285FCD6E056B17AF21627FDABE316B90B3C038D68EBD6B7F9F3BD1712EAA9951ACB2590A05C6517EFE46941FEFDD1985D4EFD6321F5E70B4DE9B6C1D45512DCD9FB3DBCACB947D7076BC4B63499596306E58DCCE63EABBB65646AE016C354FF5FACB7431DDA458E70AD5A313B21E2&cookie%5Ftest=1&catalog%5Fname=CTLG&category%5Fname=CTLG%5F003%5F001%5F003%5F004&product%5Fid=15%2D517

Big stuff:
http://www.valmont.com/asp/communication/specialty_structures/asp/components_catalog.asp?url=2

 
>        We recommend the Radio Shack ratchet style Chimney Mount (cat no 15-839) and any 5 foot antenna mast
>        typically sold for television antennas.

Channelmaster makes excellent powder-coated masts which are inexpensive (Fry's).


>        Lightning can travel down either of the 2 conductors in the antenna cable and, due to the design of the
>        antenna, they can't both be directly connected to ground. To protect this signal from lightning you will
>        need to install an inline gas-discharge lightning arrestor and connect that to ground.

I would note that gas-discharge fails after a few strikes, and needs to be replaced.  A quarter-wave stub is ideal in all respects, but I haven't found any for less than $106 (Radiall), despite their simple construction.  Maybe China is making one.


>    Outdoor CAT-5 Cable and PoE Injector
> 
>        The cable travelling from the node into the user's house is a CAT-5 ethernet cable, which also carries the
>        node's power. Although it is more expensive than standard ethernet cable, it is important to get special
>        outdoor CAT-5 cable. The outdoor cable's jacket will not break down in UV light and is filled with a
>        waterproof gel that prevents condensation-related corrosion of the conductors.

I suggest using solid-wire only, for higher current capacity, and note that the RJ45 connectors come in solid and stranded flavors as well.  I also suggest Cat5e for higher datarates;  If 802.11g is used, one should absolutely use Cat5e, not Cat5.  Cat5e is twisted-pair, so that any EMI/EMP is induced in both wires at the same time.  Damage to electronics comes when one wire becomes significantly different from the other in amplitude.  Finally, *shielded* outdoor is highly desirable, although probably asking too much.

The POE should use *two* conductors each for voltage and ground, not one, for best current capacity.  There are 4 unused conductors in Cat5e ethernet.

Hope this helps.  

Man, I wish I had a platform to run this on, but I absolutely need NoCatSplash functionality.  Right now I'm investigating upgrading the Locustworld platform to Debian Sarge, although I have serious doubts about AODV.  If I were sure I could add NoCatSplash in a reasonable time (never done it before), and if we were sure of a final platform, I'd start work now adding it.

Best,

Carl Cook