I'll use English as we have company;
Generally speaking, we use two types of antennas on aircraft; Omni directional and directional. As their names indicate, omni antennas are designed to receive or transmit from any clock position. Com antennas are of the omni type. With the antenna properly installed, you can listen from or talk to a station regardless of the direction of the signal with respect to the aircraft. Directional type antennas either transmit or receive a signal in one direction. Unless you are using special mission equipment, we only use direction receiving antennas on aircraft. Nav antennas and ADF antennas are examples of this. When a signal is received, the receiving unit is able to 'see' the direction from the aircraft to that signals source.
ELT antennas are omni directional, transmitting antennas. We need to have a signal radiated in all clock positions to increase the odds of someone (now days a satellite) receiving that signal. They are also of the quarter wave design. At our level, this means that the antenna length is one quarter of the wavelength of the signal it's designed to work with. Not important to us, but what IS important is that quarter wave antennas require a ground plane to operate properly, so keep that in mind when installing. While it would be awesome to find an antenna that transmitted in a full sphere they don't exist in the aircraft world. Each kind of antenna has strong points and weak points. For us, using rod type antennas, they will transmit the strongest signal when the receiving antenna is oriented the same way as the transmitting antenna. I.e., They antenna at ATC is straight up and if ours is too, then we can communicate well. Have a buddy with a Bonanza with the com antenna in the wing tip? He still has to turn the aircraft 90º to the tower to talk at a distance. This is because the Bonanza's antenna is horizontal to the vertical antenna in the tower.
To visualize the signal put a donut (or a bagel if you prefer) on a rod antenna. That is what the signal looks like as it is transmitted. Just an every growing donut. (See the attached pic, the rod antenna would be along the Y axis) If you have another rod antenna, oriented vertically, the 'donut' will eventually cross that one and allow the radio to hear the signal. Now take the donut with the antenna in it's hole, and lay it on it's side. The signal still has the 'growing donut' shape, but now it's on it's side. The receiving antenna will have no trouble IF it is perpendicular from the transmitting antenna. But if the receiving antenna is off the tip or the base of the transmitting antenna, there will be almost no signal to be received.
No, we can't foresee all outcomes of a crash and therefore the final position of the ELT, but the antenna's installed position is designed to give the best chance of survival, to remain operational, after the crash.
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