When building a loop antenna, I keep wondering if this just for RX, because it seems to me that connecting the center load at one end and the shield at the other will blow my transmitter, so I'm afraid.

This is a wise question! The name of the game with antennas is not resistance but impedance. Technically they represent the same thing with one big caveat. Resistance is constant, impedance changes with frequency, So, keep your power low when testing a loop antenna for transmitting and you should be fine, unless the specs state receiving antenna. In my experience, I've used more than a few receiving loops successfully for several hundred-mile connections utilizing an antenna tuner and low power (QRP) output. As I've stated before, experimentation is what it's all about. Keep notes on what you do so you can repeat it, explain it to others and even build upon it!