Topband: Monopole Elev Pattern w.r.t. Earth Conductivity

Tom W8JI w8ji at
Wed Oct 24 17:44:20 EDT 2012

> Did you --or anyone else you are aware of-- ever A-B test a ~120' tower
> against a ~300' tower on 160?

I A-B or A-B-C tested several antennas, including a low dipole, the high 
dipole, an element from my four square, a ~318 foot  insulated tower 
vertical, and I think my tall omni vertical was about 190 feet at that time.

The tall vertical tower was definitely worse compared to shorter verticals, 
and had almost no short skip signal around Georgia. I had isolation chokes 
for lights and a base insulator, but that 300+ foot tower was so poor I 
never used it as a vertical.

By the way, to show how bad interaction is, I had to detune unused towers 
even when they were 300 feet or so apart.

If you recall W8LT and the balloon verticals, they didn't do so well with 
that antenna at 5/8th wave. I used WSPD, WOHO, and WXEZ (King Road 350 ft) 
towers also, but had no A-B tests.

Anything tall or new received good reports, if I told the other person it 
was tall or new. This is a common result, similar to the well-known G5RV 
effects. Pick an unpopular antenna like a G5RV and say you are using it in a 
test, and even if you do not actually switch antennas the G5RV will get a 
weaker report over long averages of tests. You can see a similar effect with 
guest operators and a no-change switch position. They always like the better 
antenna, even when it is the same antenna.  :-)

To avoid the G5RV effect when making A-B tests, I never said which antenna 
was actually A or B. I also would randomly change A or B around in different 
tests. Just watching reports without changing antennas at all is 

73 Tom 

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