[Elecraft] dBd vs dBi

[N2EY@aol.com]

In a message dated 10/20/02 7:45:00 AM Eastern Daylight Time, 
kc4kgu@ENTERZONE.NET writes:

> Can someone tell me what how these two figures would compare to each
>  other?
>  
>  3-dBd over a dipole
>  
>  3dBi freespace
>  
>  I'm trying to compare antenna specs from two different companies but, as
>  usual, they can't use the same _exact_ measurement criteria.
>  
dBi is gain compared to a hypothetical lossless nondirectional antenna 
(isotropic).
dBd is gain compared to a hypothetical lossless halfwave dipole in the most 
favored directions

A hypothetical lossless halfwave dipole in free space has about 2.1 dBi gain. 
IOW, the directionality of a dipole makes the gain in the most favored 
directions about 2.1 dB over an isotropic radiator.

So:

3 dBi is about 0.9 dBd
3 dBd is about 5.1 dBi

What are the antennas?

73 de Jim, N2EY