This past weekend I did some experimentation with Don,
W4OC, (A very knowledgeable broadcast engineer) with elevated and ground
mounted radials on my 160m shunt fed tower. W4OC's QTH is roughly 20 miles
away and signals are groundwave and consistently the same signal strengths
the many times we have gotten on on 160 at this time.This was between 9AM
and 10 AM. There were no indications of propagation changes observed. With
24 insulated radials laying on the ground Don observed a reference signal
and I observed likewise. I connected 3 elevated 130 foot long radials at a
height of 8 feet. The reference signal increased 2 db. I disconnected and
re-connected the elevated radials many times and he observed identical
results. I did not see any change in receive signal.
The next thing done was to totally disconnect the 24
ground mounted radials and leave the 3 elevated radials connected. The
signal was still the original reference signal plus 2 db. I next
disconnected the 3 elevated radials. This left the shunt fed tower with no
radials connected whatsoever. The results were the same readings as the
original reference level. In other words, it appears that my 24 radials were
not doing much if anything at all for the shunt fed tower. We repeated many
steps over again and still had the same results.
Now I was really curious. I quickly added another 7
elevated radials to the original 3. This time Don was seeing a 3 db increase
above the original reference level. This was repeated with the same results.
After I let Don go I added another 6 radials for a total of 16 elevated
radials. At no time did I ever see a difference in receive signal level. The
next morning at 9AM we tried the same experiment. Granted, this is a
different day but I was still seeing the same receive reference level on my
end. Don was still seeing a 3-4 db increase over the original reference
level. This has proven to me for the umpteenth time that 7-10 elevated
radials are better than 24 radials of insulated radials laying on the
ground. I have seen this many times with my 75m vertical system. This seems
to concur once again with written reports. I am very pleased that I was able
to increase my transmit efficiency 100 percent with such a minor change
here. Now if we'd only get some decent conditions to get a few signal
reports! 73, Ken , N4UK
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|