[Elecraft] Band Conditions

[Ron D'Eau Claire]

Karl wrote:

    If you just turn on your radio right now you may hear nothing but 
noise. As you say if you tune around for and hour you might hear 
something. But if your looking for a friend across country your not 
likely to hear him now. In a year or two it will get much better.

---------------------

Of course you have to consider the general propagation that is pretty
independent of the sunspots. 40 meters and longer wavelengths are "local"
bands in the daytime, thanks to lower atmospheric ionization caused by solar
radiation. 

I think this last cycle was my fifth sunspot maxima on the HF bands. My
first was the mega-cycle on the 1950's when I frequently chatted with South
American Hams on 10 meter AM phone running perhaps one or two watts into a
mobile whip on my way home from school in the afternoons in Southern
California. That cycle has never been repeated - yet. 

Of course, what's different during the sunspot minimum is that the MUF runs
much lower than during the maxima. Instead of reaching 50 or 60 MHz at times
during a maxima, the MUF might not get above 15 or 20 MHz many days during
the minima; sometimes it won't reach 10 MHz. On the other hand, geomagnetic
storms are much less frequent, so "black out" periods are pretty rare during
the minima. Of course, atmospheric QRN is lower on the higher bands, so when
the MUF is high, the problem of band QRN is much reduced. That's a major
reason why so much spectacular DX on wavelengths shorter than about 20
meters turns up during the maxima: a signal that's Q5 on 15 meters might be
buried deep in the QRN on 40 or 80. 

Another point is that propagation is more stable now. When sunspots are more
active, things change more quickly. Openings open and close much more
quickly. Now the bands change much more slowly and are predictable. If you
have a weekly sked with a buddy on a given band and time of day, you'll find
the signals much more consistent week in and week out now. Of course, if
you're trying to link up over a path that requires exceptional skip
conditions, you may be out of luck until things get more chaotic again with
the rise of the next cycle.  

But that's only the propagation that has been identified well enough to
study and predict. There are other modes that appear that still confound the
scientists to identify, much less predict, and which definitely do not show
up in the computer models. 

For example, I have experience with Marine CW communications in the 600
meter band (400-500 kHz). Some years ago a ship in the middle of the Pacific
heard an SOS on 500 kHz in the middle of the night. Sparky woke the Captain
and they immediately headed for the signal using the radio direction finder
all ships  carried then. After several hours of chasing the signal and not
being able to find anything, they finally got the whole story. The signal
was real. It was a lifeboat radio with survivors aboard, but it was in the
middle of the Mediterranean Sea halfway around the world and in daylight!
There was no way a 500 kHz signal running a few watts into a miniscule
antenna should have been heard more than a few miles in daylight or perhaps
some dozens of miles at night, but there is was, rattling the automatic
alarms half a world away. 

Also, the sunspot upswing tends to happen faster than the downswing. That
is, it won't be long before hints of future chaotic propagation heralding
the rise of the next cycle start appearing more often. So enjoy this period.
It can be as interesting as the peaks, in its own way.

Ron AC7AC