Gain loosely refers to 'better than' .
If you have an antenna with 2.5 dbd gain then it has 2.5 db gain of a
'dipole' (the last 'd' in dbd). (good).
"Unity" is another way of saying 'one'.
"Unity gain" means its no better than whatever you're comparing it to - and
no worse.
Unity gain is good if the antenna has other redeeming attributes (like
being smaller or less noticeable).
Unity gain is not good if you're expecting it to outperform the antenna
you're comparing it to.

The term 'Unity Gain' is not 'reserved' for any particular type of antenna.

"Dan Richardson @arrl.net" ChangeThisToCallSign wrote in message
...
From time to time an antenna manufactures will state that an antenna
has "unity gain". It is my understanding that this term is used for
describing antennas used in mobile applications and is referenced to
the gain of a quarter-wave whip.

Does anyone know of any instances where this term is used otherwise?


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