This is far too conservative, and a far too limited approach. I can
offer several examples.
At home, I have two 3-el 20M Yagis spaced about 130 ft, and regularly
use two K3s to drive two 1,500W amps. If I aim those two Yagis so that
their driven elements are approximately colinear with each other, I can
operate CW on the same band within 60 kHz of each other and not know the
other is there! I first experienced this about four years ago with the
original K3.
Successful multi-transmitter operations require both very good radios
and very good SYSTEMS ENGINEERING. I regularly operate from W6GJB's
contesting trailer on county expeditions for CQP and 7QP. From the
trailer, we regularly run two stations, each equipped with a K3,
P3/SVGA, KPA500, KAT500, and W3NQN bandpass filter sets. We mostly work
CW, and usually have the two stations on adjacent harmonically related
bands. The 80M and 40M antennas each have double stubs inline to
suppress amplifier harmonics, and there is a serious common mode choke
on each antenna at its feedpoint. Antennas for all three bands are
within about five feet of each other on a 46 ft pneumatic mast. The K3s
have the new synth boards installed. There are photos of the trailer at
k9yc.com/7QP.pdf Since these photos were taken in May 2016, Glen
(W6GJB) has rigged the tri-bander to be at the top of the mast above the
40M dipole.
For CQP, we run at least one SSB station in addition to the two CW
stations, and we regularly operate CW and SSB on the same band. This
does, of course, require good separation of antennas, and, when
possible, colinear alignment. Operating from the same site for several
years with colinear alignment of the antennas, we found that 200 ft was
sufficient running tribanders on 20, 15, and 10, and 300-400 ft was
enough on 40 and 80 with dipoles. The SSB station(s) have the same
equipment as the CW stations.
As to failures at 3C0L -- the generator regulation failures could easily
fry power supplies, which could include frying their regulators, which
could fry the K3s. But the failures could also have been the result of
poor system engineering, or operator errors, or both. Every human being
I've ever run into screws up now and then, especially when we are tired.
As the examples cited above clearly show, there is far more to a
DXpedition or contest than hooking up a bunch of radios to a bunch of
antennas! The most successful of these operations have team members who
are good operators and are worker bees, and at least some who are good
engineers. I've seen drawings for the setups for DXpeditions that
demonstrated careful planning and great engineering. The 2008 VP6DX
expedition is a great example. It used some of the very first K3s to
come off the production line, and the systems engineering was
spectacularly good. Be sure to look at the site map and click on it to
blow it up to see the antenna layout.
http://ducie2008.dl1mgb.com/index.php
This pdf describes the receive antennas for the low bands.
http://ncjweb.com/bonus-content/200807NCJVP6DXreceiveantenna1.pdf
73, Jim K9YC
On 10/27/2017 11:33 AM, Ron D'Eau Claire wrote:
Successful multi-transmitter operation begins with a rational antenna layout
considering the power levels involved. IMX, we've always used at least one
wavelength between transmitters running 100 watts or so (250 feet on 80, 120
feet on 40, and so on) and we orient the antennas to minimize coupling.
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