[Elecraft] dBd vs dBi

Mon Oct 21 00:31:00 2002

You need to be a little careful of the Force 12 numbers.  What they mean
is that they have taken into account the effect of ground reflections. 
Notice the phrase  "compared to a full sized dipole at same height".  It
is not a free space measurement, like the SteppIR.  While the Force 12
number may be more realistic by measuring in a real world environment,
it does make it difficult to compare antennas.

Good Luck with your comparison.
Logan, KZ6O

[email protected] wrote:
> 
> OK.  My brain is fairly fried right now.  I've managed to get my get
> "end of summer" cold in record time this year and am in a cold-medicine
> fog right now so, here are the two antennas I'm comparing:
> 
> Antenna                         Gain            F/B
> -------------------------------------------------------------
> SteppIR 3-element Yagi          8.8dBi          20-50dB
>                                 Average in
>                                 freespace
> 
> Force 12 XR-5                   4.2-4.6dBd      14-20dB
>                                 compared to
>                                 full-sized
>                                 dipole at
>                                 same height
> 
>                 Force 12 XR-5           SteppIR 2-element Yagi
> --------------------------------------------------------------
> Boom Length     18'                     16'
> Turning Radius  20.2'                   19.7'
> Longest Element 36.5'                   36'
> Freq Coverage   20, 17, 15, 12, 10      20-6 continious
> Windload        8.5 sq ft               6.1 sq ft
> Survival        100 Mph                 100 Mph
> Weight          57 lbs                  42 lbs
> Power           > 5KW                   2KW
> Elements        10 (2 per band)         3
> 
> If I understand correctly, the SteppIR wins here but, I'm not positive.
> I realize that we're comparing a 3-el (per band) Yagi vs a 2-el per
> band.  I am just trying to compare the SteppIR against an antenna that a
> friend has so I can decide what to put up.  The "gadget lover" in me is
> leaning towards the SteppIR but, I don't want to give up performance for
> gadget appeal.
> 
> 73 de John - KC4KGU
> K2/100 #2490
> 
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