What about antenna design applications, do they give you a choice or one or the
other as a standard?
Bob AD5VJ
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Roger (K8RI)
> Sent: Tuesday, November 03, 2009 7:36 PM
> To: Tower Talk
> Subject: Re: [TowerTalk] Fwd: Dbi vs DBd
>
> Nearly all of my engineering textbooks used dbi, but in the
> end, it makes not a bit of difference whether you use dbi or
> dbd in the practical world *IF* you know which is bing used
> AND you stick with the same units.
>
> db is a *ratio* whether it's db, dbi, or dbd. Some have a
> problem when the reference is different, but as long as the
> person reading or doing knows the difference it doesn't
> matter which reference is used.
>
> The dipole reference is often preferred, but the signal from
> any specific dipole is affected by both height and nearby
> objects. Long haul even terrain well outside the "near field"
> has an effect. Comparing to a dipole in the real world is
> more or less accurate when both are at the same height and
> location. Mathematical comparisons are something else and
> there either reference works and is accurate. Note that with
> a beam the front to back and front to side are plain db,
> rather than dbi or dbd as they are referenced back to the
> strength of the main lobe.
>
> So, for me, I don't care whether they use db, dbi, or dbd as
> long as I KNOW WHICH is bing used. Once you know the
> shortcuts and rule of thumb, db problems become simple enough
> to work in your head.
>
> 73
>
> Roger (K8RI)
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