Many years ago (2003) I was running a wireless ISP. At the time Alvarion had
a new 900 MHz Part 15 band GMFSK radio that was revolutionizing our markets by
delivering 1.5 mbit through miles of trees.
Alvarion offered the standard 10 dBi panel antenna and there were no other
companies offering larger gain antenna. Luckily I was able to experiment with
the 33cm ham band antenna and found them all to be lacking. The best antenna
we found was a loop antenna, but it was very time consuming to assemble and
fragile to install. Most ham band yagi's were not broadbanded (SWR and gain)
enough to work with a 2 MHz wide FHSS signal.
I'd spoken to Wyatt from M2 and they developed a folded dipole feed sub $100
yagi with 17dBi of gain!. It was a snap to assemble as well. We ordered 50
of them and got to installing. M2 even extended us credit on a net30 account.
For a small business this was great.
Every single CPE we installed was graphed in cacti, for errors, throughput and
signal level. After we installed about 30 of the new antenna we found signals
dipping during rain, but didn't think much of it. This continued but was not
affecting the panel or loop yagi customers, so we ruled out atmospheric issues
or wet trees. The troubling thing was we'd have a -65 dBm signal (radios need
-74 or better for highest data rate, but work down to -90), and it would fade
20dB or more. I tested the SWR of the antenna during the rain thinking the
rain might be moving the resonant frequency, and it was not, still 1.2:1 over
the entire band.
Around this time I tested a theory that the antennas were still a good match
but losing the pattern when they got wet. This proved to be the problem.
Throughout this time I was in contact with Wyatt at M2 and they were doing
their own testing. Wyatt had tested a number of new designs, and had a simple
fix, using 3/8" tubing for the elements vs the 1/8" rod. This improved the
wet weather performance and fixed the issue.
Wyatt sent us replacement antennas on his dime, and never raised his voice
about any of this. It was a new design and M2 worked through the kinks with
purpose and class.
This was a serious issue for my company as we had to spend many man-days
removing the old antennas and installing the revised yagis.
I would say throughout this M2 worked hand in hand with us testing to find the
root cause of the issue and were transparent in their communications.
73's W9CR
--
Bryan Fields
727-409-1194 - Voice
727-214-2508 - Fax
http://bryanfields.net
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