Herb's experience below echoes mine at my house here in GA and at BC
stations in the Midwest. Others besides Herb have reported the same.
----- Original Message -----
From: "Herb Schoenbohm" <herbs@vitelcom.net>
To: <topband@contesting.com>
Sent: Wednesday, October 24, 2012 6:58 PM
Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
I used or tried to use a 308 foot self supporting base insulated Blau-Knox
in the late 70's and early 80's (Picture on QRZ.com) and although I could
not do A-B tests I found it horrible and that was over a 2 degree buried
260 foot radial ground system for 970Khz right next to the ocean. I found
better use for it by using it to run a rope up to the top and hung 1/2 wave
slopers down to the sea, and that was much better for RX reports on 160
from Europe. I really expected better results but was amazed at the
difference over many years of testing. I would drop the sloper(s) to the
ground when trying to use the 308 foot free standing tower...which the
books said would be an optimal low angle radiator. The slopers and even a
full sized corner fed delta loop were always much better.
Herb, KV4FZ
On 10/24/2012 5:44 PM, Tom W8JI wrote:
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 interesting.
73 Tom
_______________________________________________
Topband reflector - topband@contesting.com
_______________________________________________
Topband reflector - topband@contesting.com
_______________________________________________
Topband reflector - topband@contesting.com
|