On Sun, 11 Apr 2004 13:31:22 -0500, Cecil Moore
wrote:

Dave VanHorn wrote:
Absolutely. Whenever I see a gain number that dosen't reference something,
I assume they mean dBi, rather than dBd.

Looks like some antenna retailers reference dBdl. :-)
(dl stands for dummy load)

Actually it appears as if some manufacturers only measure the
directivity and express it in dB :-), completely ignoring the
efficiency, which is often quite low in "exotic" antenna designs.

An exotic antenna design with directivity 10 (10 dB) and 10 %
efficiency will have a 0 dB gain and will produce the same effective
radiation power (ERP) as an omnidirectional (directivity 1 or 0 dB)
antenna with 100 % efficiency when using the same transmitter power.

Paul OH3LWR