The noise you hear "floating across the bands" - MIGHT- be one
or more ionospheric sounders. These are transmitters that send
high-power signals ... usually straight up ... into the ionosphere.
They usually sweep upward from frequencies below the BC band
into the higher HF regions and can be heard as their signals pass
through your receiver's bandpass. One long-running system is
located on the grounds of the NBS in Boulder, CO.
There are many, many ... hundreds .... of these systems located
around the world and most are on the air 24/7. Some play an role
in how SWBC, governments, the military and other users of the HF
spectrum choose what frequencies to use at a given time of day.
Others are pure research operations. One, at Weber State in northern
Utah caused much consternation on 75M several years, until a SLC
ham tracked it down and knocked on the door, so to speak. The
operator had never heard of ham radio or knew anything about
frequency assignments.
Most of the operators of these systems have little knowledge ... or
care about ... the HF spectrum beyond their own particular project.
Most systems today are digital and very advanced. They spurt a
short burst of data and then hop off to another frequency within
their sounding range. A burst from one of these systems ... if you
happen to hear it ... can be best verbalized as "brack, brack, brack,"
for perhaps two or three seconds.
Touch-lamps are another source of "strange" noise ... often in the
80/75M region.
Googe; "Ionospheric Sounder" for more info ....
If you hear noise from the sun, it is a broad-band rushing noise ...
white noise ... that may rise and fall slowly. I used to work at the
University of Colorado's radio astronomy installation in the mountains
west of Boulder, where we operated the western hemisphere's largest
solar interfermeter, with antennas a mile apart.
73! Ken Kopp - K0PP
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