Operating a modern shortwave receiver IV

 
travel radios
portable receivers
communication receivers
oldie - receivers
"boatanchors"
military equipment
 
shortwave reception
 
operation
dial indicators
reception modes
signal processing
 
bandwidth
passband tuning
notch filter
AGC / RF-Gain
preselection
 
receiver list
receiver manuals
 
links
varia / copyright
about / contact

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.
11 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.
12 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.
13 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.