Nothing seen here but it looks from checking later with Markus and Jim's
messages as though I may have been monitoring the wrong frequencies. The
problem here with only a 5 Hz or so window (30sec slow) is that the starting
frequencies need to be known and declared to at least a few parts in 10^8.
According to my discussions with Vaino OH2LX some years back in the case of
the use of a BC station the effect would only be heard on a fairly narrow
angle (20 to 30 degrees from memory) on the opposite side of the BC station
to the source. This suggests that the active area is a sort of halo around
the BC station. It probably will not be directly overhead the BC station as
the radiated power will be a minimum "off the end" of the vertical tower.
Audible ICM seems to require driving stations with a power in the 1MW
region. Our detection methods are much more sensitive so we should be able
to dig down below that with single "tone" and DSP methods. The question is
"how does the ionosphere react to lower powers.....will it still produce
intermod." One problem could be that if the intermod is created in the
F-layer (as with 14MHz signal) the resulting LF product may nor be able to
penetrate the lower layers again and may in fact "bounce off" out into
space. From that point of view the MF frequencies might be a more productive
area to test.
I also believe that I have heard ICM (Ionospheric Cross Mod.) most when
there has been a geomagnetic storm and lots of absorption. Vaino says there
is no confirmation of this in any professional literature and my
observations are sporadic and undocumented, but it sounds possible that the
"hot" electrons in the D-layer after a storm could produce the effect. If
this is the case we may have to wait another 4 or 5 years to confirm it.
Cheers de Alan G3NYK
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