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<TITLE>RE: [MLB-WIRELESS] Client side access</TITLE>
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<P><FONT SIZE=2>Damnit!!! I had that idea quite sometime ago about using a long USB cable and a USB adapter instead of using a long antenna cable!!!!</FONT></P>
<P><FONT SIZE=2>grrr, I knew I should have posted it to the list.</FONT>
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<P><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2> -----Original Message-----</FONT>
<BR><FONT SIZE=2>From: Richard Talbot [<A HREF="mailto:richardt@frontline.com.au">mailto:richardt@frontline.com.au</A>]</FONT>
<BR><FONT SIZE=2>Sent: Monday, 21 January 2002 15:45</FONT>
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<P><FONT SIZE=2>Ok, some more testing was done on the weekend, this time with hardware suitable for user (leaf) nodes.</FONT>
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<P><FONT SIZE=2>We have noted several issues with the present method of, buying a Lucent card, pigtail and 10-15m LMR-400 including:</FONT>
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<P><FONT SIZE=2>Most users have desktops, necessitating a $120 investment on a PCI -> PCMCIA adaptor. </FONT>
<BR><FONT 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>
<BR><FONT 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></P>
<P><FONT 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>
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<P><FONT 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 infrastructurem ode.</FONT></P>
<P><FONT 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></P>
<P><FONT 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. T esting 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 toos habby 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></P>
<P><FONT 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 seconda ntenna 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 quitei nexpensive. The whole lot can be mounted in a waterproof box very close to the antenna feed point.</FONT></P>
<P><FONT 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 theo riginal signal levels. With some more accurate positioning and a fewm ods, 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></P>
<P><FONT 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 www.ht.com.au . 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></P>
<P><FONT SIZE=2>The only remaining problem was that of ourP C. 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 www.ht.com.au has some USB dual port cards for $29 and they work with Linux. Much better than the $120 PCI -> PCMCIA converters.</FONT></P>
<P><FONT SIZE=2>The testing continues and I'll keep you all posted.</FONT>
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<P><FONT SIZE=2>Cheers</FONT>
<BR><FONT SIZE=2>Richard</FONT>
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