At W3LPL each band is essentially a multi-single operation: there are two
transceivers connected to a single amplifier for that band. The first one
to hit the footswitch (PTT) or the key locks out the other rig. That solves
the two signals on the air on the same band problem, it can't happen.
Generally, one station is running people and the other station is multiplier
picking. There is one switch for selecting the transmit antenna that will be
connected to the amplifier, but there are two switches that allow either
operator to individually select receiving antennas. Thus, if you are running
Europe and the mult station wants to work a BY multiplier, he can listen on
an antenna pointing that way without effecting the run station. When he wants
to work the BY he can grab the TX antenna switch and switch it to the right
antenna. For easy multipliers, such as the Caribbean, often we don't even
have to bother switching the TX antenna. Also, at LPL all bands above 80
have multiple yagis that allow "split" stacking, i.e pointing one at EU
and one at JA. Most, if not all, of the big multi-singles have this as well.
The key to efficient multiplier picking is the ability for the mult station to
hear through the run stations CQing. When the mult station is on another band
this is a matter of good station design to minimize inter-station interference
and obviously avoiding direct multiples of the runs station's frequency. When
the run and mult stations are on the same band (as a multi-multis like W3LPL)
it is essentially a matter of using a receive antenna for the mult station
that is far enough away from the TX antenna (either vertically or horizontally)
to keep from wiping out the front end of the mult receiver.
At LPL we find it very effective to switch the low band beverage receiving
antennas to the high band mult station receivers during the day. This lets
the mult station listen through the run station CQs amazingly close to the
run station run frequency. For all but the puny-weakest of the multipliers, this
works fine. As we continue to get whupped by N2RM, Frank will probably look at
putting some yagis up on the far tower that is currently unused, and for
a technical challenge we might play with cancellation filters.
The reason hearing through the CQs is so important is that the goal is to
not disturb the run stations rate at all. You transmit when he is listening and
listen when he is transmitting, and when it works right there are no dirty looks
between ops. From the east coast, the run station can often maintain the same
rate running Europeans listening on the beverage, so the run station can hear
responses even when the mult station is sending 599 05. The lockout switch
keeps you legal here, and prevents serious problems.
When K3NA is did 15M at LPLs last year, we used the soda can method for
control,as well - we put a soda can between us and whoever grabbed it was the
only one
who could xmit.
By the way, hearing through CQs is much more important in a CW contest, since
the exchange takes so much longer.
John Pescatore WB2EKK
PESCATORE_JT@NCSD.GTE.COM
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