Analog Updates

published 2025-09-19

By Christopher Howard

I think this THAT analog computer order is going to fall through. When I placed the order, I did not realize that the De Minimis rule, which exempts items $800 or less from tariffs, had been revoked only a few days earlier. Now it looks that there will be an (approx.) $1500 tariff fee, and I know I can't afford that. Personally, I'm a fan of tariffs, and how President Trump is using them, so I'm not upset about that. But it is lame I did not know about the change in the De Minimis rule, which I had researched only a week or two before placing the order.

I am continuing my studies in op amps, and learning some mathematics in the process. I discovered, with great disappointment, that the op amp book I was looking at, the 2nd edition of the Roberge book, is an incomplete project and has only two chapters in it. So I've had to revert to studying from the old scans of the 1st edition.

I've been having fun learning how to solve complex resistor networks, by using the loop method and solving the system of equations. I drew up an arbitrary network, solved it on paper, and then reproduced the network with physical resistors. I was happy to discover that my calculations all matched up with the measurements on the real resistors, so that encouraging.

Recently I read an article in an old copy of QST (January 2024) about ARRL lightning calculators, which were slide-rule like mechanical computation devices that ARRL sold back in the 1930s. There were circular devices printed on cardboard, which had plastic hairlines and dials that rotated around the center. Positioning the dials and hairlines allowed you to solve some computation, like ohms law. There were various models of these calculators for different purposes, such as calculating impedances, or gain.

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