[Elecraft] dBd vs dBi

[k6se@juno.com]

John, KC4KGU wrote:

"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."
==========
The term "dBd" means dB gain compared to a dipole.

The term "dBi" means dB gain compared to an isotropic radiator.

A dipole has 2.14 dB gain over an isotropic radiator, so a dipole has
2.14 dBi gain and an isotropic radiator has -2.14 dBd gain.

IMO, the most meaningful and honest term would be "dBi".  All antenna
manufacturers should adopt this as the "standard".

To be honest, any gain specs given should be the gain in free space
because when antenna specs are given over real ground (rather than free
space), the amount of  gain realized can vary widely depending on the
soil conductivity in the locale that the gain was tested at.

Gain over real ground will always be greater than gain in free space.

Be skeptical of any manufacturer's gain claims they give in their specs. 
Unscrupulous claims of antenna gain is why ARRL will not publish gain
figures in QST ads.

Some claims are honest, while many are not.

73, de Earl, K6SE