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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>
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