Which is generally true for 160- and 80-meter receiving antennas?
Atmospheric noise is so high that directivity is much more important than losses✓Respuesta correcta
They must be erected at least 1/2 wavelength above the ground to attain good directivity
Low loss coax transmission line is essential for good performance
All these choices are correct
Explicación
On 160 and 80 meters, atmospheric and man-made noise arriving through the antenna is far stronger than the receiver's own noise, so a receiving antenna can afford substantial loss without harming the signal-to-noise ratio. What does help is directivity, since rejecting noise from unwanted directions is the only way to improve that ratio.