On Sun, Oct 30, 2011 at 12:36, David Nuttall <span dir="ltr"><<a href="mailto:david@smithsgully.net">david@smithsgully.net</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
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Hi Dan,<br>
<br>
The US 900 MHz license free band goes from 902 to 928 MHz. In
Australia it's 915 to 928 MHz giving only 13 MHz bandwidth.<br></div></blockquote><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
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The RF spectrum neighbour is the Vodaphone GSM uplink allocation.
Voda will notice if you impinge on their spectrum, they will
complain to ACMA and ACMA will come and knock on your door so be
careful. Hence you'll only be able to run 5 MHz RF bandwidth (or
maybe 10 MHz if not too close to a Vodaphone mobile site) and this
may defeat the purpose.<br>
<br>
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Yep, aware of this, at least as general background - though not necessarily that they were so militant.<br><br>
<br>
</div></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div bgcolor="#FFFFFF" text="#000000">The lack of gain in your antennas is partly compensated by the
reduced path loss. There is 8.5 dB less path loss at 900 MHz
compared to 2400. 900 MHz will also be less affected by
obstructions. The 900 MHz nanos also run pretty high transmit power
at +28 dBm giving you another boost. Because you will have to run
lower RF bandwidth your energy per bit will also be higher giving a
further boost. (3 to 6 dB compared to running 20 MHz RF Bandwidth)<br>
<br>
The 915-928 band is pretty quiet in most locations around melbourne
but if you are within 100m or so of a mobile phone tower you may
suffer with receiver overload with the GSM transmitters nearby at
935 MHz.<br>
<br></div></blockquote><div><br>Thanks for the detailed info. We've been running our 2.4 link at 10MHz bandwidth some of the time, too, for the same reason - hard to tell if it really makes that much difference in practice. It seems that settings we can change are just tinkering around the edges and the random fluctuations over the course of a few hours far outweigh any effect our changes make. Denis has some interesting graphs of link rate and signal strength over time.<br>
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I suspect you may be able to get a more "stable" link but not
necessarily with big throughput.<br>
<br></div></blockquote><div><br>That's been my suspicion too.<br> <br></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div bgcolor="#FFFFFF" text="#000000">
What kind of TCP/UDP throughput do you get now?<br></div></blockquote><div><br>Varies rather wildly and unpredictably, as does the signal level. Best we've ever seen was a bit over 7Mbps, usually averages about 2-3. We're missing an order of magnitude somewhere along the way..<br>
<br>Next steps are either 900MHz, or swap my 18db Yagi for another 24 grid and try and get some more height and sturdier pole to carry the grid - hence the present question. <br></div><br></div>-- <br>Dan.<br>