Topband: power coupling from C5

[Carl K9LA]

I took a look at the pattern of a vertical at C5 with respect to 
coupling into the ionosphere, and I agree with W4ZV that C5 is very 
similar to D4. I also agree with NM7M's assessment that North America is 
not in the direction where the coupling loss is highest.

This coupling loss is just another loss that goes into the equation (not 
that we really have an equation) that determines how strong a signal 
will be in going from Point A to Point B. For the C5 to East Coast path, 
it's 6000 to 7000km and it's essentially all over water.

Thus the coupling loss may not be a big factor on a path this short, 
even in the direction of highest coupling loss (toward the Caribbean). 
But on a longer path, where every dB really counts, I have no doubt that 
coupling loss takes its toll and is very important. And yes, most of its 
impact is to a narrow range of azimuthal angles. On the other hand, if 
those angles are toward a target area, then it becomes very important.

Along these lines, W4ZV made a good point about all the other factors. 
In addition to all the normal variables in propagation on our higher 
frequencies, 160m also has the Earth's magnetic field and 
weather-related effects tied to its propagation characteristics. I think 
it can be very difficult to separate out all these variables to say that 
X is what caused Y. All we can do is try to understand all of this and 
apply it to make our chance of success as high as possible - whatever 
the scenario is.

Carl K9LA