überarbeitet am 26.9.2007
Radio reception on shortwave has characteristic difficulties due to very
often low transmitter power or signal strength, propagation disturbances and
interference from signals from stations on adjacent channels or even on the same frequency.
Most modern communication receivers have technical possibilities to improve
the signal. With sophisticated technical tricks, You can get most information out of
a hardly unreadable signal and make it intelligible. A very poor signal suffering from
heave interference will although never give pleasant music quality.
||With the passband - tuning
knob, You shift the part of the signal, that will pass through the gate of a
narrow IF filter, as if You would slide a small window so You can see the most
interesting bit out of a landscape.|
In case of an interfering signal 3 kHz above the desired stations carrier,
You can move the gate of the IF filter using the passband tuning / PBT control
a bit further down and the ennoying
interference hiss will disappear.
||With the notch filter,
you can selective suppress one interfering heterodyne frequency. In some receivers,
the notch filter acts on the high frequency side
on the intermediate frequency, in others in the audible frequencies.|
After switching on, turn the Notch filter control very carefully until an
annoying interfering beat note will disappear. In the AOR 7030, You find
an automatic notch filter that will automatically detect the interfering
sugnal and will successfully suppress it in most cases.
||The noise blanker
eliminates very short pulse noise such as ignition noise from cars or impulses
of over-the-horizont - radar systems working in the shortwave frequency range
(known as "Russian Woodpecker"). It is not effective against broad band
noise from poertable computer's power supplies or energy saving lamp bulbs.|