Re: Non Linear Vac Cap?!


Barry - 2E0IDE
 

Thanks for the feedback Immo.

 

I did consider slippage in the steeper. When I first replaced the air cap with a vac cap it had a non- geared stepper(i.e. 1.8 degrees) and I got very similar results. Thinking it was a torque problem I replaced the stepper with 5:1 geared stepper.

I can turn the vac cap by hand but there is quite a lot of resistance, so you could be right that there is still slippage,  even with the increase torque of the 5:1 gearbox.

 

There is a plastic cap on the drive end that looks as though it may be removeable. Perhaps this is where I can re-lubricate. Any thoughts?

 

Attached is a plot of the 20M band after pushing SWR tune and storing,  at each step – it’s linear across the band! But when I went back to 14.000 to check it, the SWR was NFG. So it does indeed look like slippage. Controller stepper settings are 60rpm, 4x, 4, so I don’t think it is a speed problem. Stepper backlash 300.

 

73

 

Barry – 2E0IDE

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