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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