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<DIV><FONT face=Arial size=2>Ok, some more testing was done on the weekend, this
time with hardware suitable for user (leaf) nodes.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>We have noted several issues with the present
method of, buying a Lucent card, pigtail and 10-15m LMR-400
including:</FONT></DIV>
<DIV> </DIV>
<UL>
<LI><FONT face=Arial size=2>Most users have desktops, necessitating a $120
investment on a PCI -> PCMCIA adaptor.</FONT></LI>
<LI><FONT face=Arial size=2>LMR-400 is not cheap and there is an appreciable
investment involved to buy it (around $120-$140 for a 10m cable)</FONT></LI>
<LI><FONT face=Arial size=2>Pigtail cables are very lossy and expensive to
boot. The Lucent connector alone is rated with a SWR of 1.56:1 at 2.4
Ghz, to say nothing of feedline losses and poor construction
techniques.</FONT></LI></UL>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>In short, Losses between the card and the antenna
are high, as are the costs involved in setting the whole thing
up.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>In our particular application there are bigger
problems. We are planning to mount the Galaxy antenna on the roof,
about 6-8 m up a TV antenna mast. Common sense would kind of dictate that
we are not going to run a 15-18m length of LMR-400 to the office
downstairs. The smartest thing to do would be to put an AP or a computer
in the roof and run ethernet the rest of the way. In order to do this we
are also going to need 10 m of feed line. The AP is also not to good as it
is expensive and requires our neighbours to have a card in infrastructure
mode.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>We wanted to try another method. The
plan was to use a USB based card (in this case
the Dlink DWL-120). These are cheap, easily modified and
allow us to run a simple USB cable up the mast. The unit is smaller than a
AP and cheaper.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Our first job was to test the performance of the
card as both of us had heard they didn't go as well as a PCMCIA unit.
Testing on a celeron 400 running win 2k and 64 mb ram, showed us
downloading a 20Mb file from a local ftp server at 470k/sec. Not too
shabby at all, so this was obviously worth the trouble to test. There may
be an issue with USB being a bit slower than PCMCIA, but will everyone really be
running at 11Mb?</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>So far so good, the next question is, can we get
into it? This turned out to be fairly simple. The board is setup for
easy access to the antenna terminals. We also found that the second
antenna is easily disabled and connected to an external antenna. This has
some serious possibilities. We could run two antennas in diversity
mode. Due to the negligible amount of additional coax, this is quite
inexpensive. The whole lot can be mounted in a waterproof box very close
to the antenna feed point.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Having some surplus Galaxy's about we had an
interesting idea. What if we put the card in front of a grid in about the
same place as the dipole sits in the feedhorn? Some experimentation came
up with a fairly predictable result. Approximately 13db gain on the
original signal levels. With some more accurate positioning and a few
mods, I am sure this could be better. So with some work we might not even
need to open the box and take to it with soldering iron.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Now the cabling.... It seems you can only run 5m of
USB cable between two devices. That's a real shame because we were so
close. However, we found a 5m active USB cable advertised at <A
href="http://www.ht.com.au">www.ht.com.au</A> . Seems you can use this
with a simple 5m cable to do 10m. You can use 4-5 of these things if you
really want to get 20-25m of USB. We have seen prices elsewhere as low as
$30 / 5m cable. So it works out about $6 per meter in cable. Less
than LMR-400 and definitely less than the LMR-400 and the connectors for each
end. The USB cables are definitely easier for the amateur to setup
too.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>The only remaining problem was that of our
PC. We have some old 486's and some low end Pa's that we want to use in
the roof at each end. Unfortunately no USB ports. Nevermind <A
href="http://www.ht.com.au">www.ht.com.au</A> has some USB dual port cards for
$29 and they work with Linux. Much better than the $120 PCI -> PCMCIA
converters.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>The testing continues and I'll keep you all
posted.</FONT></DIV>
<DIV><FONT face=Arial size=2><BR>Cheers<BR>Richard</FONT></DIV>
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