[Elecraft] K3 Diversity Rocks!

[Dick Green WC1M]

Does it ever!

My best Diversity setup is on 40m: a Cal-Av 2D-40A (full-size 2-el
horizontal phased array with excellent gain and F/B) at 110' and a full-size
4-square vertical array with 60 ground radials per element.

While effective for receive (highly directional and quiet), the 4-square
can't hold a candle to the Cal-Av on either receive or transmit (that was
also true when the beam was a 40-2CD at 50'!) When conditions are good, the
Cal-Av is significantly louder on receive than the 4-square. I've seen
differences ranging from 5-20 dB. The DC-grounded design make the Cal-Av an
unusually quiet horizontally-polarized antenna, but under some
circumstances, such as very heavy rain or snow static, the 4-square can be
quieter. There's absolutely no comparison on transmit: the beam is always
superior. Before trying Diversity, I only used the 4-square when noise on
the beam was really bad, or more often to work stations off the back of the
Cal-AV, which has about 20 dB F/B. I was skeptical about how much it would
help to use the antennas in Diversity, and wasn't at all prepared for how
effective the combination would be. It's made a huge difference in my
contest production on 40m. I'm consistently running at higher rates on 40m
than ever before, with fewer mistakes and fewer fills.

As others have pointed out, Diversity is terrific for dealing with QSB. In
the vast majority of cases, when a signal fades on one antenna I can still
hear it on the other antenna. I've also found Diversity to be effective
during static crashes -- the signal coming from one antenna will get wiped
out, but I'll still hear it on the other (not 100% of the time, but often.)
Diversity is also a great help for sorting out stations in big pileups. My
2-el is pretty loud to EU, so I can generate deep pileups. When stations of
about the same signal strength are on top of each other, it's pretty-much
impossible to separate them. But often the two signals will arrive
differently on the two oppositely-polarized antennas, and that small
difference can be just enough for me to pull out one of the calls or at
least a few letters. Finally, when I'm running EU and a weak US station
calls me off the back of the beam, I can flip the 4-square to SW and hear
the station without compromising my signal to EU (I can also continue to
transmit on the beam while switching the 4-square back and forth, something
I couldn't do when I used to parallel the antennas.)

I haven't tried Diversity on 160m and 80m all that much. I have a dual 580'
NE/SW beverage (more like NNE/SSW), but my transmit antennas are modest: an
80m delta loop at 70' and a trapped 160m/80m inverted vee at 90'. I can't
generate big pileups where Diversity would help me sort out calls. Also, I
rarely run on 160m and the rate is considerably lower on 80m than on 40m.
Consequently, I'm usually S&Ping another band on the second radio, which
eliminates use of that ear for Diversity. Another reason for avoiding
Diversity is that the transmit antennas usually pick up a lot of noise.
Under poor conditions noise from the transmit antennas in one ear becomes
distracting and it's best to listen on the beverage only. Under less noisy
conditions, I think Diversity could be helpful for combating QSB and QRN, as
well as hearing weak stations off the back of the beverage. I'll have to
experiment with that some more.

73, Dick WC1M