[TowerTalk] lp V stepIR

[Scott McClements]

So you are lengthening the boom length to 20 feet. I thought the
discussion was comparing a Tennadyne T8 to a 3 element Steppir. Does
the Tennadyne T8 use a parasitic director for 10 meters?  Sure, if we
just allows things to get "just a little bit longer" we can start to
get better performance from the LPDA. But the 3 element SteppIR  is
sitting on a 16 foot boom.   I wouldn't argue a T10 or T12 is closer
to the performance of the 3 element SteppIR, but that wasn't what was
originally stated.

-Scott, WU2X



On Sat, Jan 23, 2010 at 3:26 PM, Steve, W3AHL <w3ahl at att.net> 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).
>
> 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.
>
> Steve, W3AHL