This is a no compromise solution. A robust 1:1 Choke Balun for use with a Doublet or G5RV where ladder-line meets coax - Perhaps just after your ATU. You could also position it at the base of a resonant vertical - to act as a choke/isolator. We don't cut corners: This balun is wound using RG142 coax and the ferrite core is an FT240-31 offering resistive performance between 3.5MHz and 30MHz so a perfect solution for your all-band HF aerial - and it's rated for over 400 watts continuous.
Check out the 2nd picture showing the inside - clear casting-resin for a weather-proof seal!
Baluns - What/Why?
It's good practice to put a Bal(anced)Un(balanced) where coax meets aerial or balanced-feeder. A Balun will help prevent "common-mode current" on the outer of the coaxial braid - This is vital to ensure that RF does not flow down the coax, turn it into part of the antenna system and give you "RF in the Shack". Using a 1:1 Current Balun at the junction of balanced-feeder+coax is preferable, in most cases, to a 4:1 Balun - and certainly better than the internal 4:1 (voltage) balun found in many tuners!