[Elecraft] diversity receive what bands

[Jim Brown]

On 11/9/2013 10:42 AM, ve6dc wrote:
> I am new to the idea of diversity receive and wonder if this is mainly used
> on the lower bands, 160, 80 and 40 meters or all amateur radio bands.

It's most useful when there is QSB, or when signals are arriving at 
different vertical angles or when there is selective fading. Much QSB is 
the result of multiple copies of signals that arrive by slightly 
different paths, and are thus a bit out of time (and phase) by virtue of 
slightly different travel times.  The result is heard as "picket 
fencing" with short VHF/UHF wavelengths, very slow QSB with the 200X 
longer wavelengths on 160M.  When the two arrivals are nearly equal and 
close to 180 out of phase, they cancel, often by as much as 20 dB, and 
when in phase, add by as much as 6 dB.

With diversity RX, the concept for this sort of fading is to have 
antennas separated by some significant fraction of a wavelength, so that 
when the arrivals are cancelling at one, there will be addition (or at 
least less cancellation) at the other.  For the other situation of high 
angle vs low angle paths, using a vertical antenna that favors low 
angles and another antenna (Beverage or low horizontal dipole) that 
favors high angles.

An excellent place to study these the propagation concepts is the ON4UN 
Low Band DXing book. The fading caused by cancellation of multiple 
arrivals is not widely understood by hams on the HF bands and 160M, but 
it is VERY well understood by many audio professionals working in live 
sound.

73, Jim K9YC