Topband: Power Coupling in the USA

[Steve Ireland]

At 08:34 AM 4/05/2002 -0400, you wrote:

W4ZV said:
>> Colorado.  The vertical would typically be >10 dB stronger than the
>> dipole on the same Pacific paths up until sunrise and then the dipole
>> would take over.  These effects were due primarily due to takeoff
>> angle differences IMHO.
>
W8JI:

>I second that. I see similar effects here, and hundreds of AB tests 
>by VK3ZL between his dipole and short vertical have showed similar 
>results.

VK6VZ replied:

Tom didn't mention the many contacts he has had with me/VK6HD.  I listen to
Tom working into VK several times each week and call him from time to time.
 At this end, my inverted vee dipole at 90' is almost always slightly
better on rx (and transmit) than my Marconi-T with a 66' vertical section
and 30 x 66' radials - whether close to his sunrise or not.

The ground conductivity and thus far field reflection is much better in VK3
than here in VK6, where the ground is either sand (the coastal plan, where
most people in WA live) or gravel/rock (where I live).

W8JI said:
>Like Bill, I'd hate to see DX stations assume they can look at a map 
>and get by with a low dipole! Overall, the best signals from long 
>distances seem to come from verticals, no matter what direction they 
>are.

VK6VZ replied:

Forgive me for stating the obvious, but both W8JI and W4ZV live in the
northern hemisphere, at relatively high latitudes.  In my experience, at a
low geomagnetic latitude, on poor ground, an efficient vertical antenna
system can be a pretty useless DX antenna - the equivalent of a low dipole
at the latitudes that W8JI and W4ZV - and most of the people who use this
reflector - live at.

This conclusion is based on thirty-plus years of operation on 160m from the
northern AND southern hemispheres - on clay soil at a high latitude from
the former and on rock/gravel/sand at a low latitude from the latter.
Frankly, I am sick of the results of those like myself who actually
live/operate from low latitudes on poorly conductive soil seeming being
dismissed by some who have often never operated from here and who put a
northern hemisphere 'vertical' spin on everything - even when physicists
like Bob NM7M explain that things work differently at low latitudes. 

The majority of DXpeditions who go to similar latitudes to VK6 and use
vertical antennas place their stations by the sea - thus getting rid of the
far field losses that occur for those of us who live well away from the sea
or on rock/gravel, enabling the vertical polarisation from their antennas
to be effective.

The other thing to note is that those DXexpeditions who equip themselves
with the great Battle Creek Special - an inverted-L antenna - get as much
radiation above 45 degrees as they get below it.  The BCS gets a lot of
credit as a low angle radiator, but it is also a good high angle antenna on
160m, with appreciable horizontal polarised radiation.

On a final note, I have 185 countries worked on 160m - all but two of them
worked using horizontally polarised dipole antennas.  What is more, the
first 150 were worked with ones less than 50 feet/15 metres high.  This
ain't bragging - it is fact.  Vertically polarised antenna have accounted
for 0.01 per cent of the VK6VZ 160m DXCC count - despite the fact that 90
per cent of my antenna building effort/time on 160 has gone into verticals...

I'd hate to see DXpeditions coming to low latitudes and assuming they can
get by with a short vertical - without actually trying a
high-as-possible-but-relatively-low dipole, which unless they are close to
the sea could well be better than the former.

Vy 73,

Steve, VK6VZ






   

 While it is certainly possible to have a really poor vertical 
>(especially if it is near other structures or has a poor ground 
>system) it is nearly impossible to get a useful DX wave angle on 160 
>from a low dipole. Wave angle is an important consideration.73, Tom 
>W8JI
>W8JI@contesting.com 
>
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