RDF is the key point to improve signal noise, not gain. Vertical or low
dipole has very or none directivity, so low RDF or directivity does not
improve signal noise.
In general, this is the case, but it is not always true.
Since I started using RDF, let me explain what it really is.
RDF is really just directivity. I used RDF so people would stop using gain,
because gain has little value for receiving. For example, if I place two
Beverages side-by-side 1/4 wave apart there is almost no pattern change.
Gain increases 3 dB, but certainly not receiving ability!!!
As long as the noise is evenly distributed in all directions, or if dominate
noise would be randomly distributed in all directions at different times,
RDF works great as a guideline.
If dominant noise comes from the SAME direction and polarization as the
desired signal, nothing will help. Anything that nulls the noise also nulls
the signal.
If dominant noise comes from a null direction, the difference between gain
in the desired signal direction to null of the noise will set the
performance. For example, with a thunderstorm off the rear, F/R is most
important.
If noise is unevenly distributed, then it becomes very complex.
Most people out in a rural area are probably in a situation where whatever
QRM or noise bothers them, comes from random, differing, directions. Some
people in congested areas have significant noise from one direction, and
they need a deeper null in that specific direction. Going for exceptionally
high F/R is meaningless unless there is somewhat-consistent strong QRM from
the rear.
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Topband reflector - topband@contesting.com
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