[EMAIL PROTECTED] wrote:
> One thing I've never been able to explain to people is: Why do the
> big Celwave, Sinclair, etc. "StationMaster" type antennas have only
> 5.2 dB gain? Actually, the 2-meter range ones are listed as typically
> having only 4.8 dB gain, after putting the longer, lower-frequency
> elements in the 22' long or so radome.
>
> The typical 5/8 wave mobile antennas have "3 dB gain", some of the
> "ham-grade" antennas claim 7-8 (and even 10 dB gain). I occasionally
> get asked, why do you use one of those expensive, low-gain Sinclair,
> Celwave, etc. antennas instead of Hustlers, Diamonds, etc that have
> so much more gain? Even the big Scala OG-4 2-Meter antennas are 4 dB
> gain, if I remember correctly.
>
> I've always been at a loss to explain, but having tried some of these
> amateur antennas, I see quite a performance difference (for the
> better, of course) when I go back to using the "real"
> commercial-grade antennas.
>
> I'm sure there must be something simple that I'm overlooking.
>
> LJ
Remember that dB gain is a relative term, not absolute. Normally, mobile
antenna gain is referenced to a quarter-wave whip on a metallic roof for
a ground plane, where base antennas are referenced to a dipole, which is
different. I forgett the exact number, but a diploe is something like
1dB above a 1/4-wave GP.
A lot of amateur-grade antennas are referenced either to a 1/4-wave, or
worse yet, an isotropic source, which is a theoretical point-source
antenna. A dipole is about 2.1dB over an isotropic, I think.
--
Jim Barbour
WD8CHL
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