The SteppIR 3L Yagi has a 16 ft boom.
This corresponds to 0.46 WL on 10M,
0.34 WL on 15M,
0.23 WL on 20M.
The W2PV Yagi Design Book shows
gain and F/B curves for 3L Yagi's with
boom lengths from 0.1 to 1.0+? WL
and parasitic element tunings offset
by 2,3,4,5,6,7 percent.
Bottom Line: Boom lengths around 0.25 WL
(and odd multiples) exhibit HIGH F/B ratios
but lower gain (-1 dB), Boom Lengths around
0.5 WL exhibit LOW F/B ratios and high gain,
and boom lengths around 0.35 WL are a good
compromise between gain and F/B.
The SteppIR can be optimized for each band
given it's FIXED boomlength, but remember that
for full optimization ALL parameters (including
Boomlength) must be varied. This is NOT the
case with the SteppIR antenna. On 20M, it's
F/B can be made to be near optimum. On 15M,
it can achieve good gain and intermediate F/B,
on 10M it can achieve good gain but LOW F/B
as originally stated.
Tom N4KG
On Fri, 13 Sep 2002 K7LXC@aol.com writes:
> In a message dated 9/13/02 11:07:48 AM Pacific Daylight Time,
> stevek@jmr.com
> writes:
>
> > You might consider how important F/B is to you...the TH11 is
> excellent on
> > all bands; the StepIR is good on 20m and degrades on the higher
> bands..
>
> I think it's the other way around. The StepIR is an optimized 3L
> beam AT
> ALL FREQUENCIES.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site:
> http://www.mscomputer.com
> Call 888-333-9041 to place your order, mention you saw this ad and
> take an additional 5 percent off
> any weather station price.
> _______________________________________________
> Towertalk mailing list
> Towertalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:
http://dl.www.juno.com/get/web/.
|