What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?

Terminated loop antennas, such as the pennant, flag, and K9AY loop, are specialized receive antennas widely used on the lower frequency bands. Unlike simple resonant loops, they feature a termination resistor strategically placed in the loop circuit. This terminating resistor introduces traveling-wave behavior into the loop, absorbing energy from signals arriving from the rear. This cancellation creates a cardioid (heart-shaped) radiation pattern, featuring a single, distinct null in the reverse direction. This cardioid pattern is highly prized by low-band operators because it provides excellent front-to-back directivity, which is crucial for rejecting noise and interfering stations arriving from unwanted directions.