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überarbeitet am 17.10.2007
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From the example of the short wave receiver NRD-535, I try to inform You
how to operate a contemporary shortwave communication receiver with it's most important
control elements and functions.
Note that not all receivers are equipped with all features mentioned,
the simpler receivers with fewer options and knobs are easier to operate.
Before starting with reception experiments, the receiver must be powered by
mains or batteries, in addition a HF signal must be supplied by means of a suitable
antenna.
In some receivers, You only have to pull out the telescopic antenna,
the professional receivers usually require an outdoor aerial,
for the first attempts, some meters of isolated wire connected to the clamps
long wire antenna should do the job well.
| 1 |
The Power switch or Mains Switch will switch
the receiver on or off, a third position activates the timer. |
| 2 |
In semiprofessional and professional receivers, the volume control
is often marked with AF-Gain (audio frequency). |
| 2a |
With the RF-Gain(radio frequency) knob,
You can adjust the high frequency amplification- Particularly when using long wire
antennas which high signal voltages, there is the possibility of overloading
the "front end" / input stage of the receiver, which can cause massive distortion.
In case of "ghost stations" appearing as unwanted signals in the presence of
very strong signals from nearby transmitters, You can reduce the signal to
a lower level, that is not harmful to the front end anymore: reduce the RF-Gain
control or activate the attenuator knob for this purpose.
Caution: in normal operation, the RF-Gain control must always be turned to the
maximum setting, if the RF-gain is turned down inadvertently, You may be surprised
not to hear anything coming out of the speaker. Sometimes, the
signal-strength meter will go up to middle or maximum position when You have reduced
the RF-gain.
Caution: in some receivers, when activating the RF-Gain, the AGC / automatic gain control
is switched off, You have to control the RF amplification carefully by hand to avoid
distortions caused by strong signals. |
| 3 |
The frequency can be selected with the main tuning knob,
in many receivers, the tuning increment and thus the tuning speed can be
switched. The maximal acceptable tuning step for AM reception is 1 kHz,
0.1 kHz kHz are even better. For SSB reception the tuning steps should be
no bigger then 40 - 50 Hz to avoid heterodyne tones and "Mickey mouse" like
sounding speech. Some communication receivers provide 1 Hz tuning steps.
The rotary tuning knob should have a certain weight for flywheel effect,
tuning should be possible without mechanical backlash.
Some receivers have a brake to adjust the resistance of the tuning knob,
in others, a too light tuning button can be improved by glueing small lead balls
in the interior of the knob to give it a certain weight and tuning feeling.
Few commercial receivers only provide up/down tuning buttons, some rare
models use decadic switches to set the reception frequency. |
| 4 |
With the decimal / number keys,
You can type in directly a desired reception frequency, pushing the "Enter"
button will bring You immediately to the desired frequency. Some receivers,
for example some Lowe sets or the AOR 7030 use a remote control for
direct frequency input. |
At least, a noise should be audible from the loudspeaker, now.
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