Another thing to consider is that with a fixed multi-mono yagi design, all
the gain and F/B specs are at the design frequency. If the design freq is
14200 KHz, then the gain and F/B degrade at 14020 KHz and 14300 KHz. With
the SteppIR, you retune at each frequency to optimize gain and/or F/B.
Also, some of the big multi-mono yagis are considerably heavier with more
wind loading that the SteppIR because they have so many more elements on the
boom.
73,
Steve
N6SJ
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Joe
Subich, W4TV
Sent: Friday, February 27, 2015 7:27 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] SteppIR
> My question: With a SteppIR beam, what is the tradeoff of the fixed >
element spacing on gain and pattern? Especially compared to the >
multi-yagis-on-one-boom high end multiband antennas.
There is no trade-off in gain. Gain is almost entirely a function of
boom length as long as you don't have to few elements. For example,
SteppIR antennas all show more gain on 10/12 meters than the multi- monoband
yagis simply because the SteppIR antennas utilize the entire boom length on
all bands where the multi-monoband antennas typically use 60-70% of the
available boom length on each band.
Where the boom is "short" and the spacing is narrow, you give up bandwidth
but SteppIR compensates by retuning.
When the boom is "long" and the spacing is wide you give up some F/B.
For example, the 3 element SteppIR shows F/B of "only" 15 dB on 12 meters
and 11 dB on 10 meters vs. 25 dB on 20 and 17 meters. You see similar F/B
declines with the 4 element antenna.
With SteppIR the trade off is increased complexity (the stepper motors and
brush contacts) while with the typical overlaid multi- monoband antenna the
trade off is decreased gain for a given boom length. All of this is
verifiable with a few hours spent using a good antenna modelling program.
73,
... Joe, W4TV
On 2015-02-27 9:51 AM, Al Kozakiewicz wrote:
> I was tempted to hijack the Mosley thread, but it should probably be
allowed to die peacefully.
>
> I discovered a few years ago that you can't ask any questions where an
honest answer might be construed as a criticism on the SteppIR forums. The
dialog degenerates into something resembling the useless old alt.advocacy
newsgroups.
>
> My question: With a SteppIR beam, what is the tradeoff of the fixed
element spacing on gain and pattern? Especially compared to the
multi-yagis-on-one-boom high end multiband antennas. You're pretty much in
the same territory price-wise.
>
> Al
> AB2ZY
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
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