[TowerTalk] lp V stepIR
jimlux at earthlink.net
Sat Jan 23 13:14:47 PST 2010
Steve, W3AHL wrote:
> Your model of the 8-element LPDA was apparently done from a formula
> and wasn't optimized at all. Although I do agree that 6 & 8 element
> logs are sub-optimum. But an optimized design for a 9 element 14-30
> Mhz LPDA on a 20' boom will average closer to 6.5 dBi with 17 dB F/B,
> except at 20m, where it drops to 5.7 dBi & 11.3 F/B in free space.
> Add a 10m director and you can get 7+ gain with 30 dB F/B on 10M
> (with a 4' boom extension).
Is that gain in free space, or over some assumed ground at some assumed
> And stacking an LPDA does have unique issues. Anything that disturbs
> the current phasing in the active-element region will distort the
> pattern more than with a standard yagi design.
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