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Re: [TowerTalk] SteppIR problem

Subject: Re: [TowerTalk] SteppIR problem
From: K4SAV <>
Date: Mon, 11 Jun 2007 01:42:43 -0500
List-post: <>
Roger (K8RI) wrote:

> When it came to accuracy we always had problems with that type of 
> system when things didn't work right.   IOW when the system 
> recalibrates it starts out accurate, but if there is anything that 
> hinders the steps, be it enough drag to prevent the motor from fully 
> stepping,  not enough current, and in some rare instances misshapen or 
> even dropped pulses. The more pulsese to get to the target position 
> that larger the potential error.  I reiterate that this was only when 
> things didn't work right and in the chemical industry we had some 
> strong safety issues with maintaining accuracy so we used output 
> signals much like you find on the large C-Band satellite dish 
> positioners or even on modern radio VFOs. We used magnetic, but they 
> can be optical or even mechanical switches to verify we were 
> really/accurately getting to the positions we expected. Of course this 
> added complexity and cost to the system but we *almost* always knew 
> where the positioners were setting.
> 73
> Roger (K8RI)
> I agree with what you said.  Most systems require some kind of 
> feedback to be assured of position.  In this case the only feedback 
> you have is an SWR indication.  That's not conclusive but it is 
> something.  Retracting the elements for the night is a good practice 
> both from a lightning standpoint and a calibration point. Feedback of 
> position would make resolving problems much simpler.  I guess there is 
> a trade-off to be made between added complexity and cost, versus the 
> number and frequency of occurrence of possible failures.  In this 
> system there is very little friction and mass to be moved, and the 
> only sever failure mode I can think of is an obstruction occurring 
> with the tapes moving outward.
> Jerry, K4SAV


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