Primary beam
= Primary beam
{title2=$A(l,m)$}
The primary beam is the individual <antenna> pair's directional sensitivity envelope in the <complex visibility> equation. For identical, identically pointed elements it is the individual element's power pattern. Its angular width sets the useful field of view; the much longer <interferometric baselines> set finer measured scales. The <primary beam> and the <dirty beam> describe different responses.