There is no such things as "best antenna".
When I lived in Arizona, I had on a hill-top a doublet with 300 foot arms at
100 foot height (effectively more because of the hill-top). I used it both
as a doublet and as a vertical T (with the two wires of the ladder line
shorted). It had about 40 radials of various lengths, between 100 and 150
feet. Almost always the doublet was better.
Now I live in FL, on an island, and my vertical is on the edge of the
salt-water. It is only 45 foot tall with two top loading wires. It gets out
very well and I have no interest in trying a dipole.
A lot depends on the location. I believe that it mostly has to do with the
ground, but there are other factors that are harder to figure.
I used to operate mobile/portable from the Australian outback (mostly
central and western Queensland). The ground there is generally very poor
(low conductivity). I had a a 20 foot vertical fed via a tuner and an
inverted V doublet. I would stop every night, camp, throw on the ground a
few "radials" and the doublet over a tree.I operated, mostly on 80 and 40
meters. Different locations, with pretty much the same looking ground (dry
dirt) gave very different results on the two antennas. Sometimes the doublet
was better, sometimes the vertical, often both were either bad or good at
the same time. Most of the time I could not pin-point the reason. Hill-top
locations were not always the best. Near creeks or swamps, even from a
valley, generally I got better results. But some of the best locations were
totally unremarkable. I did this for more than 15 years, often visiting the
same sites. There was a consistency: the good sites were good year after
year and the bad ones stayed bad.
Go figure...
73,
George
On Mon, 26 Nov 2018 15:19:58 -0600
Mike Waters <mikewate@gmail.com> wrote:
This has been an eye-opening discussion for me! I have always preached the
'gospel' of vertical-is-usually-best based on W8JI, ON4UN, and *many* other
long-time Topbanders. Someday I'll have to revise
www.w0btu.com/160_meters.html <http://www.w0btu.com/160_meters.html> and
include a link to this thread.
I stand corrected. Thank you, gentlemen! :-)
73, Mike
www.w0btu.com <http://www.w0btu.com>
On Mon, Nov 26, 2018, 12:56 AM Steve Ireland <vk6vz@arach.net.au> wrote:
Hi Frank (and Rick)
Somewhere I have a map of the lines of geomagnetic latitude superimposed
on a Mercator projection of the world, but I can’t find it right now.
Unlike the ruler-straight lines of conventional latitude, geomagnetic
latitude lines wander across the world like a collection of snake tracks.
As a result of how geomagnetic latitude snakes across the globe, a
comparison can’t be directly made between similar geomagnetic latitudes in
the northern and southern hemispheres – where Tom W8JI lives is probably
very different to me in terms of the closeness of his geomagnetic latitude
to the electron gyro-frequency. As Carl K9LA points out, the geomagnetic
latitude relates to polarization and involves the ordinary and
extraordinary waves that propagate through the ionosphere, and how 160m is
affected by being close to the electron gyro-frequency.
About 10 to 15 years ago, Carl, Nick Hall-Patch VE7DXR and Bob NM7M (SK)
(also a physicist like Carl, as I’m sure you recall) helped Mike VK6HD (SK)
and I to understand why our horizontal cloud-warmers outperformed efficient
vertical antenna systems in SW WA.
You are quite correct, the Fresnel zone where I live (the mostly far field
region where ground gain is developed) has very poor conductivity. And, to
repeat your point as this is not as widely known as it should be, poor
Fresnel Zone conductivity has very little impact on the performance of
horizontally polarized antennas, while having a major impact on vertically
polarised ones.
While the Fresnel (far field) zone of my location, is basically rock
(granite and ‘coffee rock’), Mike’s final location beside the Kalgan
estuary appeared to have much better Fresnel zone conductivity, with less
rock than me and, in around half the compass directions, salt water.
However, his inverted-L with an 80’ vertical section over 120 buried
quarter-wave radials at Kalgan performed only marginally better than our
previous attempts at vertical antenna systems did.
On this basis, I came to the conclusion that the dominant problem was
likely to be the geomagnetic latitude issue, rather than poor conductivity
in the Fresnel zone – which it certainly is also an issue here.
To investigate this further, I sought out the opportunity to operate
directly by the sea here with a good vertical antenna. After much
paperwork, I managed to get permission to operation from the Cape Leeuwin
lighthouse, which is 40m-plus high and on a narrow finger of land
surrounded by sea for over 300 degrees.
In a Stew Perry TBDC in the early 2000s, with the assistance of my friend
Phil VK6PH, we put up a full-sized quarter-wave wire vertical on the most
seaward side of the lighthouse, less than 60 metres from the sea. This was
fed against a quarter wave counterpoise and the feeder decoupled with a
large ferrite choke to stop common mode effects. On the other side of the
lighthouse was an inverted vee half-wave dipole. Both antennas were
supported from the lighthouse balcony (at about 40m!) and detuned when not
in use. An Yaesu FT-1000MP was used, running less than 100W
Unfortunately conditions were poor during our evening time into North
America, but at about three hours before sunrise the 160m band opened into
Europe. Right from this point, the vertical was slightly down on the
inverted vee by a few dB, but I would always call on the vertical first and
then switch onto the inverted vee if I got no response.
All the way until
just after sunrise, the inverted vee outperformed the vertical, mostly
raising the stations who did not hear us on the vertical.
The only time this situation was reversed was when 160m started to go out
as the sun started to rise and I had by then switched over to just calling
stations on the inverted vee.
After about five minutes of this, the Europeans I could still hear were
not coming back to me anymore. Out of curiosity, I switched to the
vertical – and found I could still raise a few of them.
I recall vividly
the last QSO with a CT1 using the vertical about 20 minutes after sunrise,
exchanging 559 reports.
The crazy thing is that the vertical appeared to be doing exactly what a
dipole is known for doing on 160m in the northern hemisphere in some cases
– extending the sunrise opening. However, this was the only time the
vertical outperformed the inverted vee.
As far as I know, Mike VK6HD never experienced this phenomenon when he was
comparing his inverted-L quarter wave antenna against his inverted vee
dipole. However, my vertical antenna was directly adjacent to the sea,
surrounded by sea, which may have helped.
The final event was highly interesting, but did not sway me into repeating
the experiment the following year when I also operated from the lighthouse
in the Stew Perry TBDC.
The fact was the inverted vee had been responsible for 80 to 90 per cent
of my QSOs - can’t remember exactly how many – while the vertical had only
accounted for three or four.
Mike VK6HD, Phil VK6GX and I are not the only ones to have experienced the
“verticals aren’t always best for DX” situation here. About five to ten
years ago, I understand a group of German DXers came here and operated in
the CQ WW CW (I think).
The group operated from the the Northern Corridor superstation
VK6ANC/VK6NC, using a quarter wave vertical on 160m. After disappointing
results, one of the ops (Mar DL3DXX, I think) recalled Mike, Phil and I
used inverted vees at 90 to 110’ and suspended a inverted vee dipole as
high as they could and changed over to using this. My understanding is then
they found they could work a much larger amount of DX stations on 160m.
...
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