" Since Rick correctly stated that RDF doesn't account"
RDF is everything ! The RX antenna system is the only way to improve
signal to noise ratio. All electronic device is not perfect and introduce
noise and deteriorate the signal to noise ratio, including your radio too
RDF is one way to measure directivity .
I'm a little tied up with other things like paying work, but I see this is
still going on.
RDF is directivity, I just called it that to not confuse it with gain that
is important to transmitting. I suggested it as a factor in deciding if an
antenna is **likely** to be an improvement or not because:
1.) Front gain to rear wide area ratio, based on the null width of the
entire rearward pattern, was being used. This method was rarely effective,
unless noise largely existed only in the entire rear hemisphere. It is very
unlikely to have grossly dominant noise exactly fit a rear hemisphere, and
it is impossible to have that condition in more than one direction.
2.) People were using gain as a measure, specifically with closely spaced
non-staggered Beverage antennas. If two Beverages are paralleled so close as
to not change pattern one bit and not change S/N ratio one bit, gain
increases 3 dB! Gain is a useless parameter until the receive system
internal noise affects S/N ratio.
There certainly are other things that are important, and I weigh more than
raw RDF into my selections. (Someday when I have time I may publically
document things.) Removing signal from directions where there is no noise or
where there is very little noise can make things seem better by RDF when
they are really not better, as can RFD improvements by reducing side or back
response to levels below where noise or QRM detracts from copy.
My preference with large area (not tall height) vertical arrays and Beverage
arrays is a very clean pattern with deep nulls elevated above the horizon
and maximum overall area removed from the pattern, but I always want to be
sure the next direction selected does something useful before I lose too
much from the presently selected array.
What I have and use is the result of almost 40 years of reading and
experimenting, but it only came together here because I have the room I
always needed. Most of my life I lived on small lots, and what I did then
All antennas are compromises, and RDF might be the best (far above gain or
other methods) going at the moment, but distribution of noise and QRM has to
factor in by looking at the pattern.
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