Topband: Power Coupling in the USA

[Tom Rauch]

> 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.

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.

At sunrise, it **sometimes** doesn't matter very much what antenna I 
pick. A low dipole at 70 feet, a high dipole at 300 feet, or a 200 
foot vertical are all somewhat similar in strength. The same is true 
into Japan from here. 

Averaged over many hundreds of reports, the dipole and vertical are 
about the same. The low dipole is almost always just a few dB behind 
either the high dipole or 200 foot vertical.

During full dark, or on days when there is no strong peak, the 
vertical beats the high dipole by a few dB. The low dipole becomes an 
absolute dog, and is sometimes 15 dB weaker than the high dipole.

On receiving, the results are generally identical. Whatever antenna 
transmits best hears the best (keep in mind none of my antennas are 
limited by local noise sources).    
 
>         Remember also that total signal strength is a combination of
> many factors including takeoff angle, quality of near and far field
> ground conductivity, power coupling, etc.

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. 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