Bill:
I think the use of lasers results from the FCC
regulations in the US which specifically say that all
frequencies above 275 GHz are allocated to amateurs
(as I understand it). So the ARRL more-or-less has to
include ALL of that in the rules (since it IS an
amateur band) if they are to be consistent with the
goal of trying to encourage activity on all bands
above 50 MHz.
As one who has made some of those laser contest QSOs
over a few feet, I can assure you that a combination
of shorter distance tests and calculations indicated
the gear used is capable of more than one kilometer,
although it has yet to be attempted with that gear.
The tests involve making a shorter distance QSO with
the transmit beam spread out by a lens, which reduces
the received signal strength by the ratio of the solid
angles subtended by the beam in the spread and
unspread cases. Knowing that the the received signal
power is inversely proportional to the square of the
distance one can then calculate the distance that can
be covered with the same signal strength if the
spreading lens is removed. This ignores lens and
atmospheric losses, but they are normally quite low,
and can be estimated if a more rigorous calculation is
desired.
Perhaps the real issue is how practical it is to
actually work 1 km in a contest, since the aiming of
laser gear can take a VERY long time when significant
distance is involved. But you could say the same
thing about many of the higher frequency bands to some
degree. The new 241 GHz world dx record QSO made
during the January VHF Sweepstakes took 5 hours ! But
I don't think anyone would consider that this QSO
would not count for contest points because it took too
long.
So there has to be some cutoff where we stop worrying
about the nitty-gritty of the rules and concentrate on
what is needed to stir up activity and technical
achievement. Of course no two people will agree on
where that point is !
In the meantime, to ease my conscience a bit, I have
been working towards laser gear which is capable of
making the 1 km for real with minimum setup and search
time, by using lasers with the beamwidth spread out
with a lens to many times that of the laser alone.
I've made a one-way contact of 1.4 km at night which
took about 30 minutes (with the help of VE3ZXK), so
there is a way to go yet. And nobody else local is
working in that direction yet. But if laser QSOs were
not permitted in contests I am sure I wouldn't be
working on it....and would lose out on some
interesting and educational experimentation.
73,
Steve VE3SMA
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