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.
Barry – 2E0IDE