Hi JC
In my experience, here in the southern hemisphere and relatively close to
the equator, I wish that "Vertical TX antenna is the only way to work DX on
topband!"
Unfortunately vertical antennas mostly don't work here well where I am in
south-western WA - there is too much ground loss in the far field and poor
geomagnetic latitude for them.
When I lived in the UK and was G3ZZD (1971 to 1989) , I used verticals,
inverted-Ls and inverted-tees over elevated radials exclusively for low-band
DXing. It was very disappointing to find that when I moved into the Perth
Hills in 1995 and got back on 160m that verticals didn't work like they did
at my previous QTHs in the UK.
Mystified by this situation, I contacted Dr Nick Hall-Patch, a radio/physics
scientist at a university in British Columbia, who explained the wonders of
geomagnetic lat/long to me - and pointed out at my geomagnetic lat/long a
(mainly) vertical polarised antenna might only break even with a (mainly)
horizontal antenna, even if the ground conductivity was good.
Mike VK6HD, who was my mentor on 160m, had learnt about the favouring of our
location for predominantly horizontal polarisation many years before - and,
after trying a raft of inverted-Ls and various ways of shunt-loading his
tower, settled on using a flat-top dipole or inverted vee dipole as high in
the air as he could get it. Independently, Phil VK6GX (formerly VK6ABL) went
a similar journey to Mike and also settled an identical philosophy for 160m
antennas.
As outlined in my tribute on Mike's QRZ.com page, when Mike moved to his
final QTH, near Albany, on several hectares besides the Kalgan River
estuary, he finally thought he had found a location where a vertical would
work. Over about 18 months, he laid down a full-size broadcast ground screen
of 120 quarter wave radials and put up an inverted-L with an 80 feet
vertical section over it. He compared this very carefully against an
inverted vee dipole at 90', which was detuned/shorted when the vertical was
in use.
Mike then embarked on 18 months of testing - and much to his disappointment
discovered that the inverted-L was mostly up to two 'S' points down on the
inverted vee dipole. The only times the vertical was better was
occasionally over one and half hours before sunrise - and similarly it could
sometimes be better over one a half hours after sunset.
The good news is once in a blue moon the vertical would work better than the
dipole on long distance DX - and enabled Mike to work P4 (Aruba) and HC.
Almost entirely the rest of Mike's 260+ countries on 160m were worked on
flat-top or inverted vee dipoles.
After another year or so, Mike quietly took the inverted-L down - and
concentrated instead on improving his 160m reception through the use of
Beverage antennas.
For many years, Mike and I were treated by several knowledgeable 160m DXers
as being either incompetent or deluded about a simple horizontal cloud
warmer being better than a vertical in south-western WA. I used to get
angry about it, but Mike (who was older and wiser) would just laugh and say
let those in the rest of the world have their own beliefs about what
actually happens where we live.
If the books in English on 160m antennas and operating had been written in
VK6, rather than in high latitude USA and Europe, they would say very
different things about verticals, along the lines of: "Don't torture
yourself." ;-) Note also that verticals seem to work just fine in the rest
of Australia on 160m, but not in relatively coastal south-western VK6
Practically for me, verticals of all kinds are occasionally useful at this
QTH in working middle distances around 1,000 to 5,000 km, such as in the
western Pacific. Later this year, I'll carry out the switching arrangements
so I can use my 160m doublet as a top-loaded vertical, but I'm not expecting
much in the way of good results, except at these distances (in which I've
already just about worked all the countries there is ;-)).
By the way, I have a ground screen of over 30 x 30m radials and a K2AV
counterpoise over them - for all the good they (don't) do me. If I was back
in Kent as G3ZZD they would do very well for me.
Vy 73
Steve, VK6VZ (also G3ZZD and VY2LF)
-----Original Message-----
From: n4is@n4is.com
Sent: Saturday, November 17, 2018 8:38 PM
To: 'Steve Ireland' ; donovanf@starpower.net ; 'Topband reflector'
Cc: 'Dave Olean'
Subject: RE: Topband: Vertical and horizontal polarized antennas in the same
space (was Propagation improves from VK6 into Europe)
Hi Steve.
You are 100 % right, the V works like a top hat for a vertical TX antenna.
I it simple to detune any vertical TX antenna. Vertical TX antenna is the
only way to work DX on topband!
You may ask about the inverted V or low dipole, they are not 100%
horizontal, actually they are 50% horizontal on the broadside and 50%
vertical along the wire.
Ground reflects horizontal signals -1, it means 180 degree out of phase, and
the reflected signal cancels the arriving signal, The Arriving signal is
maximum only near 1 1/2 wave high above ground 750ft!!!.
The vertical reflected signal has +1 and add to the arriving signal
producing gain, ground gain.
Detuning a TX antenna is like a LC circuit, you need high impedance between
the antenna and the ground. The UNIPOLE or cage antenna works very well to
detune grounded towers up to 30 db, and it is easy to feed with 200 ohms,
becoming a very large broadband antenna. Isolated towers or inverted V is
the same, they need high isolation from ground.
I sed the same configuration for over 20 years, the open line works very
well 80 - 10m.
Regards
JC
M4IS
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