Scales for an Amateur(Ham) Radio Circular Slide Rule

lathechuck's picture

I have a small collection of slide-rules (linear and circular), and I marvel at the precision of their construction. One of the challenges of a circular slide rule is that the disks must be "exactly" concentric, pivoting without any free play, even after multiple uses. (I put quotes around "exactly", because there will always be some error, whether it's measured in thousandths of an inch or millionths of a meter.) Before fussing with logarithmic scales, I'd try a set of linear scales, which would reveal inaccuracy of construction very easily... and could be used for addition. We tend to regard addition as trivial, but that's because we have all the paper and pencils we need. If we had to do our sums on slate with chalk, we might prefer a device.