so ive been messing around with an arduino uno for the past few weeks trying to build a simple automatic antenna tuner for my end-fed. got the basic idea working where it reads SWR from a bridge circuit and then drives some stepper motors to adjust a variable cap and inductor, but the tuning algorithm is kind of garbage right now — it just sweeps through positions which takes forever.

before i go down the rabbit hole of writing something smarter, has anyone actually built one of these and does it work well enough on SSB where the power is constantly changing? my concern is it'll be chasing its tail every time i talk. also not sure if the arduino is fast enough to do anything useful or if i should just throw a raspberry pi at it and run some actual python. the pi feels like overkill for this but maybe not idk

running about 100w into it on 40m mostly, if that matters for the bridge design

yeah ive done almost exactly this, took me a few iterations to get it not terrible. the sweep approach is fine for initial tune but what you really want is a hill climbing algorithm — basically just nudge the cap or inductor in whichever direction improves SWR and keep going until it gets worse then back off. way faster than a full sweep and the arduino handles it fine, you dont need a pi for the control loop at all.

for SSB the trick is to sample SWR during a pause or use the carrier at the start of a transmission to lock onto a solution, then hold position. if you let it hunt during actual audio it will absolutely chase its tail like you said. i added a simple lockout so once SWR is below like 1.5 it just stops adjusting and waits for the next key-up/key-down transition to re-evaluate. works pretty well, not perfect but way better than retuning by hand every band change

the bridge at 100w is fine just make sure your toroids are rated for it, ive smoked a couple using the cheap ferrite mix stuff at anything over 50w

honestly for something like this i'd probably still just use the arduino, pi is nice but you're adding linux boot time and a whole OS layer to something that really just needs a fast deterministic loop. unless you want to add like wifi logging or a web interface or something then sure the pi makes sense.

one thing i ran into when i built mine — the stepper motor noise was getting into the receiver something awful. had to add filtering on the motor driver lines and run the whole thing off a separate supply. might be worth thinking about early before you get too far into the build