Pete these are BCI images from our AM
broadcast stations spaced 10 kHz in NA,
making carrier images at each 10.00 kHz.
This is why we often remind DX stations to
avoid 1810.00, 20.00, 30.00 etc if they are
trying to be heard in NA.
Similarly, in Europe their BC stations
are spaced 9 kHz, so the images appear
at 1818.00, 27.00, 36.00, etc. So we should
avoid those exact frequencies when trying
to work Europe. A 100 Hz shift to either side
usually works fine.
Of course harmonics from a single BC
station will land on 10.00 kHz frequencies, but
you would normally hear modulation with
those. For example, there has been one
from "Radio 93" (HI8?) on 1820.00 our mornings
recently and its modulation has been covering
XU7ACY who has been using 20.4.
EU: stay away from exact 10.00 multiples.
NA: Stay away from exact 9.00 multiples.
73, Bill W4ZV
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