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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk