Several have mentioned potential failure points for the SteppIR antennas. I
haven't heard about many failures. In fact, I can't think of any. There are a
fair number in us by now. How often are failures encountered?
Kim N5OP
"People that make music together cannot be enemies, at least as long as the
music lasts." -- Paul Hindemith
> On Feb 28, 2015, at 13:22, Grant Saviers <grants2@pacbell.net> wrote:
>
> However, stepper motors are notoriously tricky in real mechanical systems
> because of the system dynamics. They impart high frequency energy (think
> square wave Fourier series) and have devilish internal magnetics which lead
> to resonances. Since "servo" usually means a closed loop system, a "stepper
> servo" has to have a separate position reference for feedback position
> accuracy and usually for loop stability. CNC tools with large stepper motors
> are made with various types of position sensors and thus are servo "closed
> loop" controlled. Inexpensive machines have no feedback loop and are open
> loop, risking where the tool is and where the controller thinks it is are
> different. This can lead to ugly/expensive tool crashes.
>
> If a stepper is driven slowly, or the system dynamics are precisely known and
> constant then they work ok for positioning. Slow is the case in a steppIR.
> Note, however, that there is a "recalibrate" button on the steppIR controller
> for when what the microprocesor thinks the tape position is and what it
> really is are different.
>
> Everything is analog except particle physics.
>
> Grant KZ1W
>
>
>> On 2/28/2015 9:02 AM, Patrick Greenlee wrote:
>> That is why it is called a stepper motor. Its motion is stepwise, not
>> continuous, think digital not analog. If the steps are small enough and are
>> taken rapidly enough you can closely simulate the smooth turning of an
>> analog motor. Of course an advantage of the stepper motor is you can keep
>> track of where you are by counting the steps and not need a shaft encoder or
>> other method of tracking position in a system driven by an analog motor.
>> Stepping motors make position servos simpler.
>>
>> Patrick NJ5G
>>
>>> On 2/27/2015 9:09 PM, Dick Green WC1M wrote:
>>> 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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