Propagation - Shortwave Bands - AOR The New Classic AR3030 Operating Manual

AR3030 operating manual
Typical usable coverage starts from about 25 MHz and extends continuously to
500 MHz 1300 MHz or even 2000 MHz. The coverage peaks and dips
throughout it's range as the elements interact to provide the widest possible
coverage. Due to their necessary construction discone aerials are a little prone
to "wind noise" due to vibration and possible damage in severe gales.
Earth systems
The AR3030 power supply has no EARTH connection to the mains plug.
However a separate earth point is provided on the rear panel of the AR3030 for
connection to a water pipe, central heating radiator or external earth rod. If
fitting a separate external earth rod, consider the implications carefully if your
mains supply uses Protective Multiple Earth (PME) system. If in doubt consult
an experienced electrician.
Connecting an external earth wire may greatly reduce the local noise
encountered when listening on the shortwave bands. It is very important to
provide a good earth should you use an aerial tuning unit.
A short length of thick gauge earth wire may be connected to a nearby central
heating radiator or water pipe but never use a gas pipe for earthing. Ideally a
separate earth rod should be used but the length between the receiver and rod
becomes restrictive, if too long the earth system may well "pick up" noise rather
than remove it.
If a long run of earth wire is necessary, it may be worth considering a
"screened earth system". This simply comprises a coaxial cable (such as
URM43, URM76 for short runs or URM67 or RG213 for longer runs) shorted
inner to outer at the earth rod end with only the centre core connected to the
AR3030 earth point, the outer braid being cut back and insulated.
This provides a screen for potential incoming interference and passes any
noise down the cable away from the receiver and toward the earth rod.

(11) Propagation - shortwave bands

Unlike VHF and UHF transmissions which generally propagate only on a
localised basis (to the horizon plus a small amount), shortwave transmissions
may travel for many thousands of kilometres. Depending upon the frequency in
use, time of day, season of the year and sun spot activity, transmissions may
propagate completely around the World.
Radio signals are electromagnetic waves very similar to light beams. As such
they do not readily follow the curvature of the Earth but attempt to travel out into
space.
The ionosphere
Luckily the frequency spectrum of shortwave is often reflected back down to
Earth by the upper layer of the Earth's atmosphere called the ionosphere.
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