Topband: Vertical antennas aren't always best for DX everywhere - the facts

[Mike Waters]

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 and include a link to this thread.

I stand corrected. Thank you, gentlemen! :-)

73, Mike
www.w0btu.com

On Mon, Nov 26, 2018, 12:56 AM Steve Ireland <vk6vz at 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.
> ...