A quality shortwave receiver will often be able to make up for an antenna's shortcomings (pun intended ). However, the good news is that there are ways to install a shortwave antenna that will offer acceptable performance over the entire shortwave spectrum. Therefore, all else being equal, stations above and below in frequency will be fainter. The amount of RF energy captured by your antenna will rapidly diminish as you move away from its resonant frequency. Referring back to the tuning fork analogy, a shortwave antenna will perform best at the frequency for which it is cut for. The bad news is that such an antenna does not exist! Why? Ideally, you would like your shortwave antenna to be equally effective at all shortwave frequencies. When propagation conditions are poor, not enough RF energy reaches your antenna and you will hear nothing but atmospheric noise - with perhaps some stray electromagnetic interference mixed in. A reminder: at least fair to good propagation conditions must exist for enough RF energy to travel from the broadcasting station to your antenna. When you tune your shortwave receiver to receive Radio Marti's programs on the 25-meter band its circuitry is designed to eliminate RF it receives from the antenna above and below 11.93 MHz - to only let you hear Radio Marti. Of course your antenna is exposed to the RF energy of other radio frequencies that reach it! But, as it is cut for 11.93 MHz, the RF energy (at that frequency) reaching your receiver will be considerably stronger than all the other radio frequencies to which your antenna is exposed. Its vibrations would be strongest at 11.93 MHz. It would vibrate in response to the radio frequency (RF) energy it captures from Radio Marti. If you had an outdoor half-wave dipole antenna, cut to vibrate at that exact frequency, it would be 39 feet 2 3/4 inches long (11.957 meters long). That radio station broadcasts in Spanish from Miami, Florida. For example, the Radio Marti shortwave broadcasting station's antenna will vibrate at a frequency of 11.930 MHz (11,930,000 times per second). Two shortwave antennas that are cut to vibrate at the same frequency will behave like the two tuning forks in my example. Note that the " receiver" fork will only vibrate faintly because much of the sound wave energy will have been lost over the distance separating the two forks. The other fork will immediately begin to vibrate in response to the sound waves that have hit it after having travelled across the room from the first tuning fork.
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