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Juan,<br>
There are other frequencies available for low bandwidth digital
communication, the main problem is finding sources for the hardware
to use these frequencies. A lot of them are for use only with serial
(rs-232) style signals.<br>
When I was at CERI we had to deal with multiple users in this band.
there are 2 solutions that you might want to try before you abandon
those frequencies.<br>
1st, you might try using more directional antennas. small parabolic
dishes (2-3ft provide a narrow beam width for your signal. Not only
does this concentrate the energy you are radiating, it also
minimizes off azimuth received energy as well. Inside of Memphis we
resorted to a 6ft dish at the Memphis end of the link for just this
reason! Unfortunately these types of antennas cost about 2K and
require a substantial mount so they aren't blown around too much.<br>
2nd,<br>
You might try changing the polarity of your radiation from vertical
to horizontal or vise versa. Sometimes a slight repositioning of the
antenna can also help a great deal. <br>
Don't be tempted to use the small omni type antennas as they are the
worst possible solution to the problem. Small yagis are better but
still have quite a few side lobes with significant gain in them.
Flat panel antennas are better, but the parabolic dishes are the
best when it comes to eliminating interference.<br>
<br>
You may want to look at the pattern of the interference. One thing
this band suffers from is interference from microwave ovens. because
the operation of this type of device produces a large amount of
noise adjacent to the actual band used by the telemetry equipment it
may be possible to filter this out using cavity type filters. All rf
spectrum is crowded today and you have to use best practice not only
for antennas but feedlines, connectors and all the parts of the
system.<br>
Hope this helps.<br>
<br>
On 2/3/2011 6:00 AM, <a class="moz-txt-link-abbreviated" href="mailto:anss-netops-request@geohazards.usgs.gov">anss-netops-request@geohazards.usgs.gov</a> wrote:
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Today's Topics:
1. 2.4GHZ problems (Juan B Lugo Toro)
----------------------------------------------------------------------
Message: 1
Date: Wed, 2 Feb 2011 09:56:16 -0400
From: Juan B Lugo Toro <a class="moz-txt-link-rfc2396E" href="mailto:juanb.lugo@upr.edu"><juanb.lugo@upr.edu></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:anss-netops@geohazards.usgs.gov">anss-netops@geohazards.usgs.gov</a>
Subject: [ANSS-netops] 2.4GHZ problems
Message-ID:
<a class="moz-txt-link-rfc2396E" href="mailto:AANLkTinu0TJ2v7RQEo86QE4BctWT8mHX4TCJ5d6EAk+S@mail.gmail.com"><AANLkTinu0TJ2v7RQEo86QE4BctWT8mHX4TCJ5d6EAk+S@mail.gmail.com></a>
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Hi
We, at PRSN has been using the 2.4ghz radios but some weeks ago we started
having problems in some sites. I understand that because it is an open
frequency it is too busy. I was thinking to move to 5.0ghz but it will be a
matter of time to start having problems. I will appreciate any suggestion. I
am thinking on a private frequency but I will like to know first if there is
already a government frequency available on that range like the VHF and UHF
bands that we can use.
Thanks in advance
Juan Lugo
</pre>
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