Dear Hugh, LF Group,
At 22:57 19/01/2003 +0000, you wrote:
I notice the sounds and patterning on the screen are only there during the
hours of darkness, does that prove that it is the ionosphere and not the
radio ?
Does the ionosphere cause non-linear mixing of higher frequencies or just LF
?
I believe it's called the Luxembourg effect because it was first observed
on MF signals from Radio Luxembourg in the 20s or 30s. I don't know much
about the field, but any frequency that is absorbed by the ionosphere will
cause "heating", which modulates it's reflecting properties. There are
number of research facilities which transmit megawatts of HF straight up
in order to investigate ionospheric physics - searching the web under
"ionospheric heater", "HAARP" or "EISCAT" will give you lots of hits,
including the conspiracy theorists, who of course will tell you what the
real purpose of these experiments is!
The fact that the noises disappear during daytime, also that any amount of
preselector filtering does not remove them, is quite convincing that these
signals originate outside the receiver.
Have you tried out your buffer circuit - or is it just a "circuit idea" I
wonder ?
Yes, it is a real circuit - I have not tried it with the notch filter, but
I did test it as a high impedance antenna preamp, as well as the bench
measurements I mentioned - it seems to do the job quite well, and since
there are 4 medium wave broadcast stations within 1km of my QTH, it
demonstrates the linearity must be OK!
Cheers, Jim Moritz
73 de M0BMU
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