What Mike said. Read the install instructions.
Specifically for antennas, any rod or whip antenna is 'vertically polarized'. This means it is designed to transmit (ELT antennas ONLY transmit) from a vertical position, either pointed straight up or straight down. If you could look down at the tip of the antenna the signal would look like the circular ripple created when you drop a pebble into water. it's a concentric circle that starts at the antenna and grows out from there. If you move the antenna to another position, such as sideways, the antenna still sends the signal out the same way. So, in that position the signal pattern is also sideways, so now it looks more like a figure eight, when viewed from above.
Also, metal dampens/deflects the signal so don't place an antenna inside a fuselage with a metal frame and/or metallic coatings (silver dope). Just don't do it.
All antennas need a ground plane. This is a metal surface that the antenna fits in the center of. On a fabric aircraft, I like to use a piece of stainless window screen glued to the inside surface of the fabric, at the mounting location. Fit the antenna through the fabric, through the center of the ground plane material, and secure with a fabricated bracket, to the fuselage tubing. Traditionally ELT antennas have been mounted on the battery box access cover on Cubs. As they are going away, I like to mount them just forward of the vertical stab. Like it was stated above, if the aircraft flips over, there should be some protection for the antenna.
If you ever hear 'good enough' used to describe the installation of safety equipment, it's wrong.
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