Topband: Power Coupling in the USA

[Tom Rauch]

> 1. Vertical antennas are usually better DX antennas than
> (higher-the-better) dipoles at high latitudes (over 35 degrees),
> especially over good conductive ground. Dipoles (the
> higher-the-better) are usually better DX antennas than verticals at
> low latitudes (under 35 degrees), especially over poor conductive
> ground.

Like Bill and others, I think there is FAR too much going on to make 
definitive statements that at a certain latitude things "just switch" 
and one antenna is generally better than another. there are far too 
many variables.
 
I'm at N33,04,27 degrees, and my vertical generally works noticeably 
better in ANY direction than a dipole at any height **unless at the 
peak**. As far as I can tell, that was true even when I had a dipole 
broadside NE and SW as well as on broadside E-W dipole tests.   

For example this morning at 1000Z (off-peak) VK3ZL (west path) 
reported my vertical one S-unit better than my 300 foot high dipole. 
The low dipole was unreadable, so it was at least 15dB weaker.

In an average of hundreds of tests, the vertical and dipole at 300 
feet are about even at peaks and the vertical is generally better off 
peak. The low dipole is always well down at distances over 200 miles, 
unless we are having a geomagnetic storm.

Just now at sunrise peak, the high dipole was ~10dB better than the 
vertical. The low dipole was ~5dB worse than the vertical. 

VK3ZL at S 37,42,10 was 3dB louder on a 40-foot vertical than a 
dipole at about 100 feet at sunrise, and was unreadable on his high 
dipole off-peak at 1000Z. 
 
> This is not simply anecdotal, but is based on the physics of
> geomagnetic latititude, power coupling, rather than just my own
> observation. 

This is not meant to be argumentative, but exactly how was that 
theory verified? It seems strange such sharp directional peaks are 
predicted. Patterns that sharp are difficult to obtain in antenna 
arrays, I would expect less through alignment of random ions.

How critical is that null to polarization tilt? Very few cases would 
occur where polarization was almost perfectly horizontal, even with a 
horizontal antenna.

> I'd also add a fourth and fifth point.
> 
> 4.  Wherever if you live, if you can, either have an antenna that has
> substantial vertical and horizontal polarisation (such as an half-up
> half-out inverted-L), can be switched from one to the other, or have
> two antennas, one for each polarisation  - and make sure you switch
> regularly between them. 

A half-up half-out Inverted L does not have half-and-half 
polarization Steve. That is a myth, just like the claim an Inverted V 
dipole has mixed polarizations.

Mixed polarizations, which really can only be obtained through 
special antenna planning like 90-degree phased single-point radiators 
or similar circular polarization systems, are actually undesirable 
for ionospheric paths because they increase multipath fading. 
Thankfully virtually all antennas only radiate one polarization at 
each angle!!73, Tom W8JI
W8JI@contesting.com