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14
More than you might think.
A good hailstorm will bounce
and scatter radio signals.
Even rain clouds can
affect signals.
More unusual forms of propagation include
scatter from meteor showers, and
bouncing signals off the moon. Very high
gain antennas are usually needed to
reliably pick up the weak return signals.
DSP has improved
amateur radio
performance in recent
years. It makes it
much easier to isolate
the signal you want to
listen to and eliminate
QRM (interference).
Bill, what was the other way
you said could help us hear
signals more clearly –
changes in the atmosphere.
It could have
been favourable
atmospheric
conditions.
What does the
atmosphere have to do
with radio signals?
Very High
Frequencies
144 MHz
and above
But the biggest way the
atmosphere affects radio signals
isn’t by weather but by the different
properties of the ionised layers in
the sky.
There are several different layers in
the ionosphere 70 to 400 km high.
Radio signals usually travel in
straight lines. Very High Frequency
(VHF) signals usually travel directly
into space but lower frequencies
can be bent back to earth by the
ionosphere. There is also a ground
wave close to the earth’s surface.
Micro-chips are now so
powerful they can replace
many processing parts of a
radio. Software upgrades
can later be downloaded.
Higher frequencies “bend” differently to low frequencies
Range covered
in one hop
at 7 MHz
Range covered
in one hop
at 14 MHz
Ground Wave
Ground Wave