Topband: Non-resonant receive antennas

[Tom W8JI]

>" Since Rick correctly stated that RDF doesn't account"
>
>
> Jim
>
> 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 
was ideal.

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.

73 Tom