I believe the brushes Joe mentioned are the ones that connect the balun to
the copper-beryllium element ribbons. Nothing to do with the stepper motors
but another potential point of failure.
73, Dick WC1M
> -----Original Message-----
> From: Doug Turnbull [mailto:turnbull@net1.ie]
> Sent: Friday, February 27, 2015 4:25 PM
> To: 'Joe Subich, W4TV'; towertalk@contesting.com
> Subject: Re: [TowerTalk] SteppIR
>
> Joe and OMs,
> I do not believe a stepper motor has any brush contacts. It does
not
> create the rotating magnetic field in this manner. There are alternate N
> and S poles on the rotor and the magnetic field on the stator is varied
> N-S-N to cause rotation. Am I wrong in my understanding?
>
> 73 Doug EI2CN
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> Joe Subich, W4TV
> Sent: 27 February 2015 15:27
> 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
> > _______________________________________________
> >
> >
> >
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> > TowerTalk@contesting.com
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> >
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