High frequency communication (High Frequency, HF) has a frequency
range between 3 MHz to 30 MHz. In this research, the used HF frequency is
27.125 MHz for the transmitting mode and 26.670 for the to receiving mode.
Trainer for high frequency communication is still very rare in the market, so in
this research will be make a high frequency communication systems trainer .
The frequency generation at the transmitter and the receiver carried by a
quartz crystal, the frequency of oscillator will be mixed with the audio
information signal by a mixer section that will produce a modulated signal
Amplitude Modulation, AM, this signal will be strengthened first before it is fed to
the final amplifier. At the receiver, the AM modulated signal will be amplified by
the radio frequency amplifier section, then be mixed with a local oscillator to
generate intermediate frequency signal (intermediate frequency, IF), this signal
will be given to the next section to take the signal information. This information
signal will be amplified by the amplifier section henceforth be given to the loud
The results of the research show that the signal input to the audio
amplifier section has a maximum limit of 40 mVp-p, if greater than this
amplitude, the signal generated will be distortion, the frequency generated by the
transmitter part is 27,1275 MHz which have little deviation of 27.125 MHz, and
also for the receiver amounted 26,6720 MHz which has little deviation of 26.670
MHz. The test signal / information signal used is a sinusoidal signal with a
frequency of 4500 Hz and a maximum amplitude of 40 mVp-p. The final results
show that the test signal has been successfully sent by means of high frequency
communication systems trainer.
Keywords : High frequency communication, Quartz crystal, Amplitude