Gain-HPBW relation of uniformly illuminated circular dish antennas
Joachim Köppen DF3GJ Kiel, Jul 2018

Some brief explanations

The green curve is an approximative relation from Kraus: gain = 41000/(HPBW_h * HPBW_v) which uses the HPBWs (in degrees) in horizontal and vertical direction to estimate the solid angle ΩA of the antenna's main lobe. Kraus (Antennas for all Applications, 3rd ed., 1997) writes: "... formulas like [this] ... are useful in the context that if we know that an antenna has a 1° pencil beam and small minor lobes, its gain is approximately 41 000 or 46 dB, give or take a decibel or two, but not that the result is accurate to 1/10 of a decibel or better."

The red curve is a more accurate formula which is also consistent with the HPBW-diameter relation HPBW = 58.95701° λ/Deff for evenly illuminated circular dishes.

The mouse position shows HPBW (half power beam width), BWFN (beam width between first nulls), and the gain in dBi.
Mouse position

| Java Applets Index | JavaScript Index | my HomePage |