[TowerTalk] Help in planning a new QTH

[Michael Tope]

Steve,

For the "optimized" yagi's in the ARRL antenna book what
were the optimization criteria? There is a tradespace between
forward gain, pattern and VSWR bandwidth, and F/B. With
a  SteppIR you might not have to compromise so much to
achieve pattern and VSWR bandwidth as you might forced
to do for a fixed element length yagi. It could very well be that
a SteppIR can eek out an extra .5dB of forward gain when
you get rid of the bandwidth constraints. That is the beauty
of the SteppIR, of course. You don't have to stay with a certain
compromise in the design (well except for element spacing)
once the antenna is up in the air. Of course with all the moving
parts long term reliability compared to fixed element designs
remains an open question. So far the customer base seems
pretty happy. Time will tell.

73 de Mike, W4EF................................

----- Original Message -----
From: "Steve London" <n2ic at arrl.net>
To: <towertalk at contesting.com>
Cc: "na5s" <na5s at zianet.com>
Sent: Wednesday, March 16, 2005 1:08 PM
Subject: Re: [TowerTalk] Help in planning a new QTH


> From Dave Hachedorian's (K6LL) posting:
>
>  > Once you do the conversions, the claimed
>  > gain is as follows:
>
>  > Band    4el Steppir    C31XR
>  > 20        9.5dBi        8.1
>  > 17        10.0            -
>  > 15        10.2          8.4
>  > 12        10.4            -
>  > 10        10.6          9.5
>
> Those Steppir gain figures are very questionable.  They are significantly
higher
> than the gain figures for optimized yagi designs in the 20th edition of
the ARRL
> Antenna Book.  While a Steppir may be a fine antenna, it's still just 4
elements
> on each band, and won't be any better than an optimized 4 element beam on
the
> same boom length.
>
> For another comparison:
>
> Band   Optimized 4-element from ARRL Antenna Book
>
> 20            8.5 dBi (26 foot boom)
> 17            8.5 dBi (20 foot boom)
> 15            8.2 dBi (18 foot boom)
> 12            8.5 dBi (15 foot boom)
> 10            8.3 dBi (14 foot boom)
>
> Now, you could argue that the Steppir has the 4 elements on a longer boom,
so
> let's compare to an optimized yagi with approximately the same boom
length:
>
> Band        Optimized N-element yagi from ARRL Antenna Book
>
> 20           9.2 dBi (34 foot boom, 5 elements)
> 17           9.8 dBi (30 foot boom, 5 elements)
> 15           10.8 dBi (36 foot boom, 5 elements)
> 12           10.8 dBi (30 foot boom, 6 elements)
> 10           11.6 dBi (36 foot boom, 6 elements)
>
> I would have to conclude that the Steppir manufacture's gain figures are
> inflated on 20 and 17 meters.  I would also question the higher bands -
when I
> get a chance I'll have to model 4-element optimized yagis for 15, 12 and
10
> meters on 32 foot booms and compare to the Steppir claims.
>
> By the way, I have done my own modeling of the C31XR vs. optimized yagis.
The
> model and results are at http://n2ic.topcities.com/c31xr/c31xr.htm .
>
> 73,
> Steve, N2IC