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

[Steve Ireland]

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 at n4is.com
Sent: Saturday, November 17, 2018 8:38 PM
To: 'Steve Ireland' ; donovanf at 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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