On Sat, 13 Dec 2003, Ev Tupis (W2EV) wrote:
> o Antenna: number of elements
> o RF Output: PEP output
>
> Multiply (number of elements in your antenna) X (RF Output, PEP)=ERP factor
>
> Antenna elements x RF output ERP-factor
> --------------------------------- -------
> Halo & 160-watt amp = 160
> 4-element beam & 25 watts = 100
> 9-element beam & 160-watts = 1,440
> 4-halo's & 300-watt amp = 1,200
> 13-element beam & 160-watt amp = 2,080
> 2x13 element beam & 160-watt amp = 4,160
> 18-element beam & 300-watt amp = 5,400
> 4x9 element beams & 600-watt amp = 21,600
>
It is the length of the boom, rather than the number of elements, that
determines the gain of the antenna. For example, I have designs I've run
on Yagi Optimizer for 6, 7, 8, 10 and 12 element beams on 144 MHz all with
the same boom length. The patterns are all different but the optimum
gain is about the same.
But when you are running QRP-portable and have to put the elements onto
the beam as you set it up, the fewer the better. Especially in January
VHF SS when it's during an ice storm! :)
73, Zack W9SZ
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