[TowerTalk] M2 antenna problem and how M2 fixed it

[Jim Thomson]

Date: Tue, 14 Apr 2015 12:55:08 -0400
From: Bryan Fields <Bryan at bryanfields.net>
To: "towertalk at contesting.com" <towertalk at contesting.com>
Subject: [TowerTalk] M2 antenna problem and how M2 fixed it

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.

73's W9CR

##  OK, Ill bite. Why does 3/8” tubing have zero issues in the rain /wet
vs  1/8” rod ????     You are on 900 mhz.   Does this  rain problem 
with 1/8” rods happen on higher and lower freqs ???   Isnt there a
ham band around 800 mhz ?    What about 432 mhz and also 144 mhz ..or 1296 mhz ?  

##  has anybody tried dousing eles with a layer of clear acrylic plastic ? 

Jim   VE7RF