Topband:

[John Kaufmann]

Tom Rauch wrote: 

> Another thing is when we look into an area of
> good propagation, noise is enhanced from that direction also. The same
> mechanisms that enhance noise propagation enhance signals, so we had better
> consider beamwidth (which RDF does).


>From a New England DX contesting perspective, the big source of DX QSO's on the low bands is Europe.  When the band is open to Europe, you run them and the majority of stations that come back are extremely weak.  When the band is open this also means the dominant noise is from the direction of Europe.  Each additional dB or two that can be gained in RDF opens up another layer of very weak Europeans that can be worked.  


> Eznec and other programs do patterns at "infinite" distance
> and do not show true response along the earth. They have no groundwave. If
> your modeling program does not have an input for distance, you can be sure
> it ignores groundwave. 

The "standard" version of EZNEC does not do ground wave calculations.  However, EZNEC-PRO (the more expensive version) does have this option and when you enable it, you can see that antennas do have ground-wave response at essentially zero elevation angle (towards the horizon).  It's also interesting to observe that the ground wave patterns of even simple antennas like dipoles or delta loops do not always look like the far field patterns.  The reason is that these antennas actually transmit a vertically polarized component of radiation.  Because vertical polarization propagates much better than horizontal over ground-wave distances, the ground wave patterns of these antennas exhibit what appears to be distortion from the enhanced vertical component.  You can get significant off-axis ground-wave response from dipoles or delta loops which doesn't show up in a far-field plot.  This can significantly influence how local vertically-polarized noise is rejected.

73, John W1FV