Antenna Tuner Helper
My MFJ Auto Tuner does a really good job of tuning my antenna but I have found a way to help it out. This is the ‘Tuner Helper,’ I hope it helps someone else too. It makes band switching a little easier.
I do this by using a few external components to reduce the range that it must tune. The internal matching components all have to be small enough to fit inside the case so they can’t have the Q or efficiency of an external component.

My vertical antenna wire goes up into a 40 foot tree so I have added a big loading coil for 160 meters at the base near the tuner. The tuner will tune the wire on 160 meters without the external coil but it probably works better with this big coil. It is a 4 inch diameter coil wound with 15 turns of #10 AWG copper wire.

Every band is going to be different so what I do is to find a close match with the external component and let the Auto Tuner do the final trimming to make up the difference. For other bands I sometimes need an external series capacitor. I use HV Mica capacitors with a value that almost tunes the antenna and again let the auto tuner do the final trimming. Some lengths of wire won’t tune at all and external components and/or a balun can solve that problem.
It uses a big ceramic rotary switch to cut these external components in and out of the circuit, but the connections could be made with clip leads. Some bands might require a Balun and that gets switched in and out too.

The values seen in the schematic will vary depending on the length of your antenna wire.

W0RW